Portland-Cement Concrete Rheology 

and Workability: Final Report

PUBLICATION NO. FHWA-RD-00-025 APRIL 2001

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296
FOREWORD

This report was prepared at the U.S. Army Engineer Research and Development Center (ERDC) for 

the Federal Highway Administration under Funding Document DTFH61-96-Y-30076. The objective 

of the project undertaken by ERDC was to develop and validate a simple, practical test for determining 

the workability of freshly mixed concrete. This report covers the collection of information on existing 

test methods for which the procedures are standardized, techniques or approaches for which certain 

technologies can be employed that were possible candidates for inclusion into the workability test 

program, information on factors influencing the workability of freshly mixed concrete, selection of 

possible candidate procedures, and the test and verification of the selected procedures. This report was 

prepared to provide information to the sponsor on work accomplished during the period of the 

program. The ERDC Team performed a literature search and evaluated methods for determining the 

rheological properties of freshly mixed portland-cement concrete. Different techniques have been 

evaluated and four candidate methods and two types of commercial-off-the-shelf (COTS) pieces of 

equipment have been nominated for further development and evaluation. The evaluation and 

development of a procedure to measure the workability of freshly mixed low-slump concrete is 

described in this report. We were unable to develop a test method that covered the full range of 

concrete mixtures, including high performance concrete (HPC). The method developed is suitable to 

determine rheological properties of low-slump concrete.

NOTICE

This document is disseminated under the sponsorship of the Department of Transportation in the interest 

of information exchange. The United States Government assumes no liability for its contents or use 

thereof. This report does not constitute a standard, specification, or regulation.
1. Report No.

FHWA-RD-00-025

2. Government 

Accession No.

3. Recipient’s Catalog No.

5. Report Date

January 2000

4. Title and Subtitle

PORTLAND-CEMENT CONCRETE RHEOLOGY 

AND WORKABILITY: FINAL REPORT

6. Performing Organization Code: 

CEERD-SC-A

7. Author(s)

G. Sam Wong, A. Michel Alexander, Richard Haskins, 

Toy S. Poole, Phillip G. Malone, Lillian Wakeley

8. Performing Organization Report No. 

ERDC-TR-S-XX-00

9. Performing Organization Name and Address 10. Work Unit No.

Structures Laboratory 

USAE Research and Development Center (ERDC)

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

11. Contract or Grant No.

DTFH61-96-Y-30076

13. Type of Report and Period Covered

Final Report

October 1996 to May 1999

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development

Federal Highway Administration

6300 Georgetown Pike

McLean, VA 22101-2296

14. Sponsoring Agency Code

HNR-20

15. Supplementary Notes

Dr. Stephen Forster, Contacting Officer’s Technical Representative (COTR), HRDI-12

16. Abstract

Methods for determining the workability of freshly mixed portland-cement concrete with slumps less 

than 51 mm (2 in) were investigated. Four potential methods to determine the workability of 

concrete were proposed for evaluation and development. The methods included two moving-object 

methods, one free-orifice method, and a vibrating-slope method. The report outlines modifications to 

these existing techniques and equipment to permit the measurement of rheological properties at two 

or more shear rates. The vibrating-slope apparatus (VSA) was selected for further development. 

(Questions about this report should be addressed to Dr. Paul F. Mlakar, Sr., Chief, Concrete and 

Materials Division, or Mr. G. Sam Wong, Research Geologist, ERDC, Structures Laboratory.)

17. Key Words

Concrete, Rheology, Workability

18. Distribution Statement

No restrictions. This document is available to the public 

through the National Technical Information Service, 

Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this Page)

Unclassified

21. No of Pages

117

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ii
iii

TABLE OF CONTENTS

Section Page

CHAPTER 1: INTRODUCTION.............................................................................................. 1

CHAPTER 2: INFORMATION SEARCH............................................................................... 5

OBJECTIVE..................................................................................................................... 5

DEFINITION OF WORKABILITY................................................................................. 5

INFORMATION SEARCH APPROACH........................................................................ 5

FACTORS INFLUENCING WORKABILITY................................................................ 6

CONSIDERATIONS FOR WORK PLAN ...................................................................... 8

TRENDS IN CONCRETE WORKABILITY MEASUREMENTS................................... 8

Powers and Wiler Apparatus......................................................................................... 11

Two-Point Workability Device....................................................................................... 11

Ready-Mix Truck Hydraulic Device............................................................................... 11

Colebrand Tester........................................................................................................... 11

BML Viscometer........................................................................................................... 12

BTRHEOM Rheometer................................................................................................. 12

Free-Orifice Rheometer................................................................................................. 12

K-Slump Tester............................................................................................................. 12

Delivery-Chute Torque Meter........................................................................................ 13

Delivery-Chute Vane ..................................................................................................... 13

Angles Flow Box........................................................................................................... 13

DIN Flow Table............................................................................................................ 13

Vebe (also V-B) Consistometer..................................................................................... 14

Remolding Test (Powers)............................................................................................... 14

Thaulow Tester.............................................................................................................. 14

Vibrating-Slope Device.................................................................................................. 14

Wigmore Consistometer................................................................................................ 14

Kelly Ball...................................................................................................................... 15

Ring Penetration Test..................................................................................................... 15

Compacting Factor........................................................................................................ 15

Moving-Ball Viscometer................................................................................................ 15

CHAPTER 3: SELECTION OF CANDIDATE TEST PROCEDURES .................................... 17

EVALUATION PROCESS .............................................................................................. 17

Criteria for Selection of Workability Test Methods......................................................... 17

Criterion 1: Practicality............................................................................................. 17

Criterion 2: Costs..................................................................................................... 18

Criterion 3: Applicability to a Wide Range of Concretes............................................ 19

Criterion 4: User-Friendliness and Simplicity............................................................. 20

Criterion 5: Ruggedness............................................................................................ 21

Technical Evaluation by Scientists and Engineers............................................................. 22
iv

TABLE OF CONTENTS

(continued)

Section Page

EVALUATION SUMMARY AND NOMINATION....................................................... 23

CHAPTER 4: LABORATORY EVALUATION OF CANDIDATE 

TEST PROCEDURES........................................................................................................... 27

BTRHEOM DEVICE........................................................................................................ 27

FREE-ORIFICE RHEOMETER....................................................................................... 28

MOVING-OBJECT RHEOMETER................................................................................. 28

VIBRATING-SLOPE VISCOMETER ............................................................................. 31

COLEBRAND TESTER................................................................................................... 31

CHAPTER 5: VIBRATING-SLOPE APPARATUS ................................................................. 35

VIBRATING-SLOPE APPARATUS (VSA) HARDWARE DEVELOPMENT................ 35

VIBRATING-SLOPE DATA-ACQUISITION SOFTWARE........................................... 37

CHAPTER 6: VERIFICATION OF EQUIPMENT PERFORMANCE 

AND FIELD EVALUATION................................................................................................ 39

MATERIALS AND TEST METHODS............................................................................. 39

CONCRETE TEST........................................................................................................... 39

RESULTS AND DISCUSSION....................................................................................... 44

CHAPTER 7: FUTURE DEVELOPMENT............................................................................... 49

EMBEDDED SYSTEM .................................................................................................... 49

DEVELOPMENT PROGRAM......................................................................................... 50

CHAPTER 8: CONCLUSIONS............................................................................................... 53

APPENDIX A: PATENTS PERTINENT TO CONCRETE WORKABILITY.......................... 55

APPENDIX B: SYSTEMS EVALUATION FORMS............................................................... 57

APPENDIX C: HP-VEE DATA-ACQUISITION AND REDUCTION PROGRAM ............... 79

APPENDIX D: VIBRATING-SLOPE APPARATUS TEST METHOD................................... 87

APPENDIX E: DETAILED DRAWINGS OF VSA.................................................................. 91

REFERENCES .......................................................................................................................... 97

BIBLIOGRAPHY......................................................................................................................105
v

LIST OF FIGURES

Figure Page

1 BTRHEOM device............................................................................................................ 28

2 Free-orifice rheometer........................................................................................................ 29

3 Field embodiment of the moving-object rheometer.............................................................. 30

4 Laboratory configuration for testing with moving-object approach....................................... 30

5 Laboratory version of vibrating-slope viscometer................................................................ 31

6 Relation of flow rate to angle of inclination........................................................................... 32

7 Modified Tattersall/Colebrand tester................................................................................... 32

8 Viscosity (slope) of concrete based on use of Colebrand probe

in Tattersall machine ........................................................................................................... 33

9 Relation of predicted slump using Colebrand tester (FCT 101)

to measured slump ............................................................................................................. 34

10 Portable vibrating-slope apparatus...................................................................................... 35

11 Circuit diagram................................................................................................................... 37

12 Data-reduction flow diagram.............................................................................................. 38

13 Two concretes with different workability indices.................................................................. 40

14 Concrete discharge chute ................................................................................................... 41

15 Workability index............................................................................................................... 45

16 Three-point data ................................................................................................................ 46

17 Schematic of embedded system.......................................................................................... 50

18 Hand-held pendant embedded system................................................................................ 52

19 Data-acquisition screen...................................................................................................... 79

20 Data-acquisition program flow diagram and code................................................................ 80
vi

LIST OF FIGURES

(continued)

Figure Page

21 Data-acquisition code......................................................................................................... 82

22 Data-reduction screen........................................................................................................ 83

23 Data-reduction program flow diagram and code.................................................................. 84

24 Data-reduction code .......................................................................................................... 86

25 Vibrating-slope apparatus................................................................................................... 88

26 Details of vibration isolation mounts.................................................................................... 91

27 Dimensions of VBA device................................................................................................. 92

28 Chute walls are isolated from vibration, and the floor of the chute is ribbed 

to minimize slippage ........................................................................................................... 93

29 Rear view of VBA ............................................................................................................. 94

30 Map view of the VBA........................................................................................................ 95
vii

LIST OF TABLES

Table Page

1 Databases searched ........................................................................................................... 6

2 Rating descriptors.............................................................................................................. 23

3 Summary of composite ratings............................................................................................ 24

4 Nominated approaches...................................................................................................... 25

5 Test concrete mixture proportion........................................................................................ 27

6 Concrete mixture proportions for evaluation program.......................................................... 39

7 Batch 990085, 203.2-mm slump........................................................................................ 41

8 Batch 990085, 165.1-mm slump........................................................................................ 42

9 Batch 990086, 95.25-mm slump, 7.8% air......................................................................... 42

10 Batch 990086, 7.8% air..................................................................................................... 42

11 Batch 990087.................................................................................................................... 43

12 Batch 990088.................................................................................................................... 43

13 Batch 990089.................................................................................................................... 43

14 Batch 990090.................................................................................................................... 44
1

CHAPTER 1: INTRODUCTION

The ease with which portland-cement concrete is mixed, transported, placed, and compacted is 

extremely important in executing successful concrete construction. Slump (American Society for Testing 

Materials (ASTM) C 143) (ASTM 1994c) and correlates of slump traditionally have been the 

measures of the flow properties (rheology) of freshly mixed portland-cement concrete. Slump is 

deficient in that it does not represent the full range of workability properties. Research in recent years 

has sought to develop or improve other measurements of fresh concrete properties to improve on this 

condition. Progress has been made in many laboratory tests and approaches. However, as yet, there is 

no test method that will allow this progress to be applied routinely in field practice. The purpose of this 

project was to develop and verify such a method. Since the advent of high-performance concrete 

(HPC), mixtures contain a variety of admixtures that alter the properties of traditional portland-cement 

concrete. The initial research objective was to develop a procedure that encompasses the full range of 

rheological properties encountered in the various concrete mixtures needed in a highway construction 

project. However, it became evident early on that, because of the drastically different properties of 

low- and high-slump concretes, a single procedure would not be sufficient. Therefore, this project 

concentrated on determining methods that could be used to estimate the properties of low-slump 

pavement concretes.

The first step taken by the research team in pursuit of a field-usable approach to measuring concrete 

workability was to gather information on factors affecting concrete workability and on test methods and 

equipment that have existed, been described in the past, or are currently in use. Criteria were 

developed, and methods were screened with regard to their potential for being promoted into use in the 

field and how well they reflect current knowledge of concrete workability principles. A few small 

candidate methods were chosen from this screening and reviewed for current applicability and for 

projected or probable modifications. A plan was written from which prototype instrument and test 

protocols were developed. All of these steps were completed and are described in this final report.

This work modified an existing concept adapting current technology to develop equipment and 

procedures used to determine the workability of low slump plastic concrete. 

Task A. Collect Current Information

1. Form a technical advisory panel consisting of representatives of State Highway Agencies 

(SHAs) and the concrete industry. The purpose of this panel will be to provide input to the 

contractor on current tests and the practicality and useability of any tests and techniques 

considered during the study, as well as provide suggestions for possible projects for the 

field testing portion of the study.

2. Conduct an information search to collect available information on:

a. Factors influencing the workability of plastic concrete and how these factors influence 

workability.
2

b. Tests and potential techniques for measuring workability which reveal the influence on 

workability of the factors which are sensitive to changes in materials and mix design as 

these changes influence workability.

3. Synthesize the available information on each of the areas and develop recommendations for 

those tests and techniques for measuring workability. The recommendations shall be based 

on a number of considerations, including:

a. Practicality

b. Costs, including initial equipment costs and cost per test

c. Ability to predict workability for a variety of concrete mixes, including the factors 

discussed in A.1.

d. User-friendliness/simplicity

e. Ruggedness of the proposed equipment

4. Prepare an interim report documenting the results of the information search and presenting 

and discussing the tests and techniques considered.

5. Revise the interim report in accordance with comments received from the COTR. Make 

final selection of the approaches to be evaluated in the laboratory evaluation.

Task B. Evaluation of Candidate Approaches to Measure Workability

1. Conduct any modification and development work required for the approaches selected in 

A.5, so that all candidate approaches are sufficiently developed to conduct the evaluations.

2. Evaluate the selected approaches.

3. After evaluating the selected approaches hold a meeting of the Advisory Panel and the 

COTR to present the findings of the laboratory evaluation, including the rationale for the 

selection of the approach recommended to measure workability.

Task C. Preparation of the Final Report

1. Prepare an annotated outline of the final report and submit five copies to the COTR and one 

copy to the CO for review. Solicit review comments on this outline from the advisory 

panel.

2. Prepare a draft final report based on the annotated outline and detailing the work carried 
3

out, and including the interim report. The draft final report shall include a discussion of the 

conclusions and recommendations derived from the performance of the contract.

Accompanying the draft final report shall be a set of slides and narrative to be used in 

presentations to transfer the results of this study to the industry and field practitioners. This 

technology transfer package shall convey the steps involved in the conduct of the 

workability test and the benefits to be derived from using the test.

3. Revise the draft final report, technical summary and technology transfer package in 

accordance with comments received from the COTR and resubmit for approval.
4

CHAPTER 2: INFORMATION SEARCH

OBJECTIVE

Workability of concrete shares with durability the distinction of being a property that every concrete 

should have but that cannot be measured directly. That is, there is no direct test method, standard or 

otherwise, for durability or workability of concrete. Instead, each of these properties is indicated by 

measurements of other properties that are considered to be correlated somehow to the behavior that 

must be controlled and that can be quantified by standardized methods.

The objective of this project was to develop a test method for concrete workability that can measure 

workability directly or is an improved indicator of workability through measurements of correlated 

properties. Further, this method must be usable in field practice and capable of becoming a standard 

method. When this project was undertaken, it was unclear whether such a method already existed in 

another form and needed only to be modified to become widely used in the field, or if it would be 

necessary to develop a new method, possibly beginning with extensive modification of some older 

technology. Thus, the first task of this project was a review of historical and current test methods for 

correlates of workability, an essential step toward the project objective. 

DEFINITION OF WORKABILITY

American Concrete Institute (ACI) Standard 116R-90 (ACI 1990b) defines workability as “that 

property of freshly mixed concrete which determines the ease and homogeneity with which it can be 

mixed, placed, consolidated, and finished.” For this study, workability is considered to increase or 

improve as the ease of placement, consolidation, and finishing of a concrete increase. In common 

practice, an assumption is made that the standard test for slump of concrete (ASTM C 143) (ASTM 

1994c) indicates workability. In fact, it correlates well with one component of workability: the yield 

stress of the concrete. Plastic viscosity also is an essential component of concrete workability but is not 

indicated by slump. The standard slump test is a static test and is not a measurement of workability. 

However, it might be used along with some dynamic test to define the essential components of 

workability. This possibility was considered in the review phase of the project, described in the 

following pages.

INFORMATION SEARCH APPROACH

The principal tool used in the literature review was the search of electronic databases. Keywords used 

in the search were “concrete,” “workability,” and “rheology.” Databases searched are listed in table 1. 

 Other references were identified from a review of monographs on the subject and from other 

documents available at the U.S. Army Engineer Research and Development Center (ERDC). The 

complete list of reference sources is provided in the reference and bibliography sections of this report.
5

Table 1. Databases searched

Database Positive Result 1

NTIS *

EI Compendex *

Mechanical Engineering Abstracts

SciSearch *

Dissertation Abstracts *

SPIN *

TRIS *

GPO Monthly

Conference Papers Index

Engineered Materials Abstracts

Chemical Abstracts *

LCMARC Books

Books in Print

British Books in Print

1

 Databases were searched in sequence as listed.

* Asterisk indicates a positive result.

Patents on equipment and methods to measure concrete workability were identified by searching the 

U.S. Patent Database using a search program provided by the Center for Networked Information 

Discovery and Retrieval. This database covers patents issued from 1976 through February 1997. 

Keywords used in the search were concrete and slump, concrete and rheology, and concrete and 

workability. Seventeen patents were identified and are listed in appendix A. 

A number of books and major reviews that have been published in the last 30 years address the issue of 

measuring workability in a general way. These issues are addressed by Ferraris (1996), Scanlon 

(1994), Dewar and Anderson (1992), Banfill (1991), Tattersall (1991), Tattersall and Banfill (1983), 

and Powers (1968). Symposia on the subject are presented by Bartos (1993b), Dhir (1975), and 

Bombled et al. (1973).

FACTORS INFLUENCING WORKABILITY

Workability is affected by every component of concrete and essentially every condition under which 

concrete is made. A list of factors includes the properties and the amount of the cement; grading, 

shape, angularity and surface texture of fine and coarse aggregates; proportion of aggregates; amount of 

air entrained; type and amount of pozzolan; types and amounts of chemical admixtures; temperature of 

the concrete; mixing time and method; and time since water and cement made contact. These factors 

interact so that changing the proportion of one component to produce a specific characteristic requires 

that other factors be adjusted to maintain workability. These interactions are discussed extensively in 
6

texts and reviews on the subject (see Scanlon 1994, Bartos 1993a and b, Bartos 1992, Neville and 

Brooks 1987, and Mindess and Young 1981). Individual factors are discussed in the following text.

In most mixture-proportioning procedures, the water content is assumed to be a factor directly related 

to the consistency of the concrete for a given maximum size of coarse aggregate (Falade 1994, Hobbs 

1993, and Popovics 1962). If the water content and the content of cementitious materials are fixed, 

workability is largely governed by the maximum coarse aggregate size, aggregate shape angularity, 

texture, and grading. The coarse-aggregate grading that produces the most workable concrete for one 

water-cement ratio (w/c) may not produce the most workable concrete for another w/c. As a general 

rule, the higher the w/c, the finer the aggregate grading required to produce appropriate flow without 

segregation.

Three factors in concrete are involved in determining the consistency of the concrete: water-cement 

ratio, aggregate-cement ratio, and water content. Only two of the three factors are independent. If the 

aggregate-cement ratio is reduced, the water content must increase for the w/c to remain constant. The 

water required to maintain a constant consistency will increase as the w/c is increased or decreased.

The increase in fine aggregate/coarse aggregate ratio generally increases the water content required to 

produce a given workability. If finer aggregate is substituted in a mixture, the water content typically 

must be increased to maintain the same workability (Glanville, Collins, and Mathews 1947). Similarly, 

water content must be increased to maintain workability if angular aggregate is substituted for rounded 

aggregate. Crushed aggregates having numerous flat or elongated particles will produce less workable 

concrete that requires a higher mortar content and possibly a higher paste content. Aggregates with high 

absorption present a special case because, if they are batched with a large unsatisfied absorption, they 

can remove water from the final concrete mixture and, hence, reduce workability. 

The size and shape of particles in the fine aggregate affect the workability. For example, the use of very 

fine sand requires that more water be added to achieve the workability that a coarser sand would 

provide. Angular fine aggregate particles interlock and reduce the freedom of movement of particles in 

the fresh concrete. Using angular fine aggregate (e.g., manufactured sand) increases the amount of fine 

aggregate that must be used for a given amount of coarse aggregate and generally requires that more 

water be added to achieve the workability obtained with a rounded sand (Scanlon 1994).

Lowering the cement content of concrete with a given water content typically will lower workability. A 

high proportion of cement will produce excellent cohesiveness but may be too sticky to be finished 

conveniently. An increase in cement fineness decreases workability and produces excessive bleeding, 

especially when the surface area (Blaine) is less than 280 m

2

/kg. A cement with a high fineness will 

cause a concrete mixture to lose workability more rapidly because of its rapid hydration 

(U.S. Department of the Interior 1975).

The workability of concrete mixtures commonly is improved by using air-entraining and water-reducing 

admixtures (Malek and Roy 1992, Cordon 1955). Air entrainment typically increases paste volume 

and improves the consistency of the concrete while reducing bleeding and segregation. Water-reducing 

admixtures disperse cement particles and improve workability, increasing the consistency and reducing 
7

segregation (Scanlon 1994, Mehta 1986). Small changes in the amounts of chemical admixtures used in 

a concrete can profoundly affect workability. Some chemical admixtures interact in adverse ways with 

some portland cements, resulting in accelerated hydration of the portland cement. 

Mineral admixtures or pozzolans are used to improve strength, durability, and workability in concrete 

(Paya, Monzo, and Gonzalez-Lopez 1996; Punkki, Golaszewski, and Gprv 1996; Krstulovic 1994; 

Mora, Paya, and Manzo 1993; Bayasi 1992; Ikpong 1992; Naik and Ramme 1990). Freshly mixed 

concretes are generally more workable when a portion of the cementitious material is fly ash, in part 

because of the spherical shape of fly ash particles. Smoother mixtures are typically produced if the 

mineral admixture is substituted for sand rather than cement, but highly reactive or cementitious 

pozzolans can cause loss of workability through early hydration (Scanlon 1994, Mehta 1986). Very 

finely divided mineral admixtures, such as silica fume, can have a very strong negative effect on water 

demand and hence workability, unless high-range water-reducing admixtures are used (Kucharska and 

Moczko 1994, Male 1993).

Freshly mixed concrete loses workability with time. The reduction in workability is generally attributed 

to loss of water absorbed into aggregate or by evaporation, or from chemical reaction with the 

cementitious materials in early hydration reactions. Elevated temperatures increase the rate of water 

loss in all of the modes mentioned above. The workability of air-entrained concretes is reported to be 

more easily reduced by elevated temperature than workability in similarly proportioned nonair-entrained 

concretes (U.S. Department of the Interior 1981).

CONSIDERATIONS FOR WORK PLAN

The factors summarized here were confirmed in many other published studies and in Corps of Engineers 

experience. They were considered in devising a work plan for the candidate workability approaches, as 

presented in chapter 6 of this report. In particular, the work plan includes consideration of water 

content, aggregate size, and one common mineral admixture used in concretes for pavements.

TRENDS IN CONCRETE WORKABILITY MEASUREMENTS

Hydraulic-cement concrete has been used in the United States since the mid-1800's. Apparently, in 

these early years, it was common practice to proportion concrete with just enough water to allow it to 

be rammed into place (Powers 1968). No references were found for test methods used to measure this 

property. Trautwine (1904) described mixture proportioning which resulted in sufficient mortar of 

appropriate consistency (“just sufficient to make a plastic paste”) to fill voids in compacted coarse 

aggregate and noted “Ramming adds about 50 percent to the strength.” The rammers are like those 

used in street paving world, 152 to 203 mm (6 to 8 in) in diameter, 1.2 m (4 ft) long, shod with iron, 

weight about 15.9 kg (35 lb), and let fall 152 or 203 mm (6 or 8 in). The earliest published test method 

found is for the slump-cone method. This was first published by the ASTM in 1922 as ASTM D 138-

22T (currently ASTM C 143 (1994c)). 
8

Powers (1932) recognized some of the deficiencies of the slump test and developed the “remolding 

test.” Unlike the slump test, which is based largely on static forces, the remolding test allows for 

measuring the dynamic component of workability. Comparative work indicated that the remolding test 

better represented important features of the workability of air-entrained concreted than did the slump 

test (Cordon 1955).

Other test methods were developed based on the basic principle of the remolding test. These included 

the Vebe consistometer (Bahrner 1940), the Wigmore consistometer (Wigmore 1948), and the 

Thaulow tester (Thaulow 1952). The Vebe consistometer was developed into standard test methods 

by ASTM C 1170 (ASTM 1994h) and by the U.S. Army Corps of Engineers (USACE) (CRD C-53) 

(U.S. Army Engineer Waterways Experiment Station 1949). The compaction factor test, which is 

currently a standard test method in British Standard 1881 (BSA 1984, 1993), also includes a dynamic 

component, but in the configuration of a falling mass of concrete (Mather 1962). 

In another approach to developing a technology that would measure the dynamic component of 

workability, Powers and Wiler (1941) published a description of a coaxial-cylinder rotational 

viscometer. Concrete was placed between the two cylinders. The outer cylinder was rotated, and the 

amount of force necessary to prevent the rotation of the inner cylinder was measured. This device was 

never developed into a standard test apparatus (Powers 1968), but it does represent the first effort to 

apply a rotational viscometer to concrete.

Other test methods were developed that used vibration as a means of imparting the dynamic component 

of the test. These include a vibrating slope method (Saucier 1966), and the Angles flow box (Angles 

1974). Two recent (1994 and 1995) references were found in the Japanese literature to vibrating flowtype devices (Kurokawa et al. 1994 and 1995). The DIN flow table is a similar device used in 

Germany.

In spite of the limitations inherent in trying to characterize workability by measuring slump, several 

devices and test methods have been developed to facilitate the determination of slump by measuring 

some correlate of that property. These include the Kelly-Ball method, ASTM C 360 (ASTM 1994f) 

(originally published in 1955), and the K-slump tester (Nasser and Biswas 1996) patented in 1995.

Three patents were found for devices with valves that are regarded as indicative of slump as test results 

obtained from a ready-mix truck or from data collected during discharge of a ready-mix truck. One 

such device is a meter that measures the hydraulic pressure required to turn the drum of a ready-mix 

truck (patent 4,356,723 (1982)). This device apparently is commercially available and in use by some 

ready-mix operations. Patents 4,332,158 (1982) and 4,578,989 (1986) describe devices that mount 

in the delivery chute of a ready-mix truck and measure a slump correlate during delivery. Because these 

devices are correlates of slump, they still do not measure or indicate the dynamic component of 

workability.

Tattersall and Banfill (1983) analyzed the state of the art for workability of concrete test methods. They 

classified the technologies into two groups: empirical and rigorously defined. Most of the test methods 
9

existing then were empirical, giving results that were interpretable only in the context of the test method. 

 Consequently, results obtained by different test methods could not be compared. Another deficiency 

of most empirical tests is that they are single-point tests, i.e., they represent only a single operating 

condition. Rigorously defined methods are those that give results in fundamental units of measure. 

Tattersall and Banfill (1983) argue strongly that workability should be measured by rigorously defined 

methods. The focus of their considerable body of literature is to develop the application of standard 

rheological principles to the measure of workability of concrete (Tattersall 1982, 1983, 1991; Tattersall 

and Baker 1989; Tattersall and Bloomer 1979; Tattersall and Banfill 1983; Banfill 1990, 1991, 1994; 

British Society of Rheology 1991). The approach of Tattersall and Banfill has been to use the Bingham 

model for fluid flow to represent the rheological behavior of fresh concrete. This is a relatively simple 

linear mathematical model that relates shear rate and stress applied to fresh concrete. This model is 

characterized by two constants: the yield stress and the plastic viscosity. Application of this model to 

concrete rheology is an approximation, but it appears to work reasonably well at relatively low shear 

rates. The objective of state-of-the-art technology in recent years is to estimate Bingham constants and 

to correlate changes in these values to changes in concrete workability.

Tattersall developed the “Two-Point Workability Apparatus” (Tattersall 1971) for estimating Bingham 

constants. This instrument is a large version of the rotational viscometers used to measure the viscosity 

of Newtonian fluids but modified to accommodate the heterogeneous nature of concrete. It is similar in 

concept to the instrument designed by Powers and Wiler (1941). The instrument has been revised over 

the years (Tattersall 1991) and is commercially available. Other forms of rotational viscometers have 

been developed in recent years for application to concrete and are commercially available.

Other types of viscometers have been investigated but have not received as much research effort as 

have the rotational viscometers. Therefore, they are relatively unknown in concrete technology. 

These include a moving ball viscometer, described by Powers (1968) and a free-orifice viscometer, 

described by Bartos (1978). In principle, these instruments can also yield estimates of the Bingham 

constants.

The information search identified a total of 21 methods related to measuring workability. Most of these 

methods do not actually measure workability, because they measure only the static component or are 

otherwise limited. Most of them correlate with slump at low shear rates. The key to characterizing 

workability may be to impart a shear rate high enough that it could be used in combination with another 

test, and the results of the combination might define both the static and dynamic components of 

workability.

To organize the discussion, methods are grouped according to how they impart energy to the concrete: 

by rotation, flow, vibration, penetration, drop, or linear movement. There is some overlap among these 

groups, and some methods arguably could be in a category different from the one in which they have 

been placed. Each method is described in the following text.
10

Powers and Wiler Apparatus

The Powers and Wiler apparatus (Powers and Wiler 1941, Orchard 1979) uses the principle of the 

Couette or McMicheal viscometer (coaxial cylinder). A closed inner drum is suspended in the center of 

a larger drum containing fresh concrete. The outer drum rotates back and forth through a small preset 

angle. The torque exerted on the inner drum is measured. 

 

The Powers and Wiler apparatus only measures through small fractions of a revolution because, after 

shear failure of the fresh concrete, slippage occurs within about 3.175 mm (1/8 in) of the inner drum. 

This device, called a “plastometer” by Powers, is capable of generating stress-strain curves. However, 

varying the strain rate produces negligible output changes in the torque readings. Development of this 

device is said to have stopped around the time of World War II. A coaxial-cylinder viscometer that 

does not suffer from the slippage problem is better developed in the BML device which is discussed 

below.

Two-Point Workability Device

The two-point workability device, also known as the Tattersall device, measures the torque required to 

turn an impeller submerged in a sample container at various speeds. The use of a planetary mixer is said 

to increase testing capability in the low-slump range. The planetary system also uses a different form of 

impeller blades (Tattersall 1971, 1983; Tattersall and Bloomer 1979).

Ready-Mix Truck Hydraulic Device

The patented ready-mix truck hydraulic approach (patent 4,356,723 (1982)) allows an operator to 

monitor the torque required to turn the mixer on a truck. The inventor claims that the required torque 

can be correlated to the slump of the mixture.

Turning the mixer at different rates would generate varying shear rates in the concrete. The influence of 

factors such as concrete slippage, density of the mixture, fullness of the truck, and incline of the tank are 

not addressed in the patent documentation. Additionally, slippage, flow effects from the mixing vanes, 

and variations in mixer-truck characteristics make the system rheologically complex. Polatty (1949) 

described a device called “Plastograph,” invented by Glenway Maxon and used by the U.S. Army 

Corps of Engineers at Allatoona Dam, that measures flow of concrete in the mixer on a meter. 

According to the Plastograph, 3.9 was a “good dry” 25.4-mm (1-in) slump; 5.3 was a “good” 

63.5 mm (2-1/2-in) slump; and 6.1 was a “wet” 107.95-mm (4-1/4-in) slump.

Colebrand Tester

The Colebrand tester is a small portable mechanism similar to a drill that rotates an impeller with two 

small hemispheres in the concrete under test. The analyzing and control electronics are contained within 

the device housing. This device is similar in concept to the two-point workability (Tattersall) test. The 

product literature gives information on slump measurement only. The embedded design of this device 
11

may complicate the modifications that would be needed to make viscosity measurements. It appears 

that measurement averaging is used to reduce error effects created by relatively large aggregate to 

sensor size ratios.

BML Viscometer

The BML viscometer (Wallevik 1996) is based on the coaxial-cylinder viscometer. Blades are used 

instead of smooth cylinders to prevent concrete slippage. Four sets of inner and outer blades allow 

aggregates of different sizes to be tested. A computer is used to automate control, measurement, and 

data reduction. The output can be presented in Tattersall or rheological units. This is one of the more 

developed instruments available for measuring concrete viscosity. The manufacturer’s field system is a 

slightly smaller device mounted to a frame resembling a large wheelbarrow.

BTRHEOM Rheometer

The BTRHEOM rheometer is a rotational viscometer similar to the Tatersall. Instead of bladed 

impeller, the device rotates a bladed disc. A second bladed disc in the bottom of device also helps 

prevent concrete slippage. The torque required for rotation is measured. A computer is used to 

automate control, measurement, and data reduction. A commercial unit is available from France (de 

Larrard et al. 1993; Hu et al. 1995, 1996; and Hu and de Larrard 1996).

Free-Orifice Rheometer

The free-orifice rheometer (Tattersall and Baker 1989, Bartos 1978) consists of a simple tube that is 

beveled at the bottom to create a slightly smaller diameter than the rest of the tube. The purpose of the 

bevel is to force the concrete to flow and not just slide out of the tube. A vibrator is required to sustain 

movement of a low-slump concrete. The flow rate out of the tube is measured and correlated to the 

concrete slump.

In its stated form, the free-orifice rheometer operates at only one shear rate. A forcing mechanism, such 

as a mass on the concrete column, could be used to generate additional shear rates for viscosity 

determination. Another likely problem with this technique is that different size tubes would be needed 

for varying aggregate size and concrete slump. The use of vibrators, as required when testing lowslump concrete with this device, distorts the shape of the viscosity curve at low to medium shear rates as 

well as offsetting the curve across all shear rates.

K-slump Tester

The K-slump tester is composed of a perforated tube and a float-level measuring rod. The perforated 

tube is inserted into the concrete and paste flows in through the perforations. The amount of paste that 

flows in is indicated on on the float level. This device measures to some degree the static yield of the 

paste. Test results have shown a high degree of scatter when correlated to slump readings. Because 

the tube perforations are small, aggregate influence is not assessed by this test. Application is also 
12

limited to high-slump concrete, unless the probe insertion depth is increased significantly. (Scanlon 

1994; Nasser and Biswas 1996; and patent 5,437,181 (1995)).

Delivery-Chute Torque Meter

The delivery-chute torque meter (patent 4,332,158 (1982)) is designed to test the concrete as it is being 

removed from a mixer. Two spring-loaded torque sensors are held in the flowing concrete and 

measure the resulting torque, which is then correlated to slump. No information was found on 

measuring viscosity with this device. It should be possible to generate multiple shear rates by changing 

the incline angle of the chute. Additional difficulties may result from level variations in the chute. A 

statement was made in the patent that this device compensates for different flow rates. It is not clear 

how this is being achieved, but it could be an obstacle for viscosity measurement.

Delivery-Chute Vane

The delivery-chute vane (patent 4,578,989 (1986)) is a simple slump-measuring device. Concrete 

flows down the chute, which is set at a predefined angle. The flow is then stopped, and the vane is 

inserted into the concrete in the chute. The slump measurement is made from a scale on the side of the 

vane. There does not appear to be a way to obtain multiple shear rates; therefore, it could be an 

obstacle for viscosity measurement.

Angles Flow Box

The Angles flow box (Angles 1974, Scanlon 1994) is a box that has two removable partitions in the 

center. The first partition is simply to hold the fresh concrete on one side of the box until the test is 

started. The second partition is a grate of cylindrical bars spaced so that the aggregate can flow 

between them. Testing is performed by vibrating the box on a table vibrator, or possibly with a hand 

vibrator, and measuring the time it takes for the concrete to level itself on both sides of the box. Details 

for determining the cylindrical bar size and spacing as well as the details for using a hand vibrator were 

not included in the description of this device. Test data or technical discussion of this approach were 

not found during the literature search. No method of generating different shear rates (except perhaps 

changing the incline angle) is apparent.

DIN Flow Table

The DIN flow table (Scanlon 1994, Mor and Ravina 1986, Orchard 1979, Dimond and Bloomer 

1977) technique is similar to many of the remolding techniques. A mass of molded concrete is placed 

on a hinged drop board or a cam-operated drop table and jolted a specific number of times. The 

average radius of the reshaped concrete is then measured as an indicator of workability. This technique 

is applicable only for high-slump concrete. Additionally, it is a single-point measurement and therefore 

not suited to measuring flow at different shear rates.
13

Vebe (also V-B) Consistometer

The V-B consistometer (Scanlon 1994, Orchard 1979, Balaguru and Ramakrishnan 1987) is a 

vibrator-based remolding test. A sample of concrete is molded with the slump cone, inside a larger 

cylinder. A large clear disc rests on top of the molded concrete. The vibration time required for the 

slump mold to remold into the larger cylinder is measured. This test is suitable only for dry concrete 

(50.8-mm (<2-in) slump). While the results of this test are related to viscosity, the relationship is not 

direct, and multiple shear rates are not easily obtained. The influence of vibration would also distort the 

viscosity curve if it were obtainable.

Remolding Test (Powers)

The remolding test (Scanlon 1994, Powers 1932, Orchard 1979) developed by Powers is very similar 

to the V-B consistometer. The primary difference is the use of a drop table instead of an electric 

vibrator. The number of drops required to remold the slump cone mold into a large-diameter cylinder is 

the measured quantity. This is a single-point test. The drop table creates an initial high shear rate that 

decreases quickly to zero. Rheologically, this technique suffers from combining a range of shear rates 

along with the static yield into the measurement. Ideally, a single constant shear rate is desired either 

from terminal conditions or control.

Thaulow Tester

The Thaulow tester (Scanlon 1994, Orchard 1979) is very similar to the remolding test and the V-B 

consistometer. For high-slump concrete, a handle on the container is dropped as the vibration source. 

For a lower-slump concrete, a drop table is used. This device suffers from the same problems as the 

other vibration-based remolding methods, and vibration would distort the viscosity curve.

Vibrating-Slope Device

Use of the vibrating-slope device is described by Saucier (1966). A known mass of concrete is placed 

in an inclined trough on a vibrating table. The vibrating table is switched on, and the time required for 

half of the concrete to flow into the catch container is measured. The catch container can be placed on 

a large scale to allow determination of the stop point. While the testing of this technique has focused on 

slump cone correlation, it may be possible to use different incline angles and produce a series of shear 

rate measurements suitable for viscosity determination.

Wigmore Consistometer

The Wigmore consistometer (Scanlon 1994, Orchard 1979, Wigmore 1948, Anonymous 1949) 

consists of a concrete container, a drop table, and a small metal sphere attached to a graduated rod. 

The sample of concrete is vibrated with the drop table, and the number of drops required for the sphere 

to fall a specific distance is measured. In its defined state, this is a single-point measurement. It may be 

possible to use spheres of different mass to produce different maximum shear rates.
14

Kelly Ball

The Kelly ball is a large, heavy, ball-shaped steel probe that is gently set on the concrete surface. A 

graduated scale allows the operator to measure how deep the ball settles into the concrete. (See 

ASTM 1994f, Scanlon 1994, Kelly and Polivka 1955, Howard and Leavitt 1952, and Orchard 1979).

Ring Penetration Test

This method consists of a steel ring that is allowed to sink into fresh concrete under its own mass and 

the sinking velocity is measured (Kurokawa et al. 1995, Teranishs et al. 1994). When used to measure 

concrete, masses are added to the apparatus, and the minimum load needed for penetration is closely 

related to the yield value. The method is applicable to grouts and may be applicable to fluid concretes. 

It apparently is not applicable to low-slump concretes.

Compacting Factor

The compacting factor test involves dropping concrete through multiple heights and measuring the 

degree to which it compacts (Scanlon 1994; Orchard 1979; Mather 1962, 1965; Mather and Saucier

1963). The density of the dropped concrete is compared to the density of vibrator-consolidated 

concrete. This test is a standard test method in BS 1881 (BSA 1984, 1993). This test measures the 

energy needed to obtain a certain degree of compaction. Results of this test cannot be related to 

viscosity or yield stress.

Moving-Ball Viscometer

The moving-ball viscometer is based on the classical falling-sphere viscometer. A sealed linear actuator, 

load cell, and a small vibrator are the primary components. The actuator pushes and/or pulls an object 

such as a sphere through the concrete, and the load cell measures the resulting terminal forces. The 

vibrator is used to reconsolidate the concrete for the next run and is briefly used to initiate movement at 

low force levels. The physics are well defined for this approach and include correction calculations for 

boundary influences such as sample container. (See Odar 1967; Shepard et al. 1995; Dinsdale and 

Moore 1962; Gilmont 1964; Powers 1968).
15

CHAPTER 3: SELECTION OF CANDIDATE TEST PROCEDURES

EVALUATION PROCESS

Criteria for Selection of Workability Test Methods

The criteria for measuring performance of a workability testing apparatus as listed in Task A.3 of the 

prospectus are practicality, costs, applicability to wide range of concretes, user-friendliness and 

simplicity, and ruggedness of the equipment. This section defines these five criteria and discusses many 

of the questions associated with each criterion. Most of the questions could not be answered from 

published information during initial screening and will be addressed fully only for the candidate methods 

chosen for further evaluation as a result of this initial screening. Even though many of the 21 methods 

measured only one component of workability or were not direct measurement devices, they were 

included in the initial screening for completeness and because they still might have the potential to be 

used in combination with another method.

Criterion 1: Practicality

Practicality includes measures of how practical the equipment and procedure are, that is, how feasible 

or possible it is to use the equipment for measuring workability and how well the equipment serves its 

intended purpose. Some of the issues to be considered when rating practicality of each device are the 

following:

1. Does the method require that a sample be taken of the concrete? Or can a test be made 

within a batch or in the form or in the mixer? 

2. If a sample of concrete must be taken, how large a sample is required? Does it lead to 

long sampling delays and wasted concrete?

3. What volume of concrete is needed for test?

4. How long does it take to test the concrete? Does this cause delays in placement, or delays 

in acceptance decisions for each batch or truck?

5. How quickly is the answer available? If data processing after testing is a lengthy step, such 

a method may not be practical in the field where acceptance decisions must be made 

quickly.

6. Is the concrete tested before, during, or after placement? Time of testing may impact the 

timing and sequence of placement.
16

7. How portable is the equipment? In situ or rapid testing during paving operations may 

require that the test equipment move in conjunction with the paving operations or 

continuously.

8. Does the equipment have special power requirements? Considerations here are availability of 

120- or 220-V electrical supplies, field generators, line stabilizers, or other special sources or modifiers.

9. Size, bulk, and mass of the equipment may affect many aspects of testing.

10. Is the concrete tested directly, or is there some special pretreatment requirement? 

Examples of possible pretreatment are aggregate screening, temperature measurements, or 

filling some specialty sample container.

Criterion 2: Costs

Any equipment for testing workability will have many associated costs in addition to its initial purchase 

price. Some of the costs to be considered are as follows:

1. Initial purchase price of equipment.

2. Availability of equipment commercially in the United States. If it is not already available, 

the costs of modification or equipment development are a factor.

3. Costs associated with promotion of general acceptance and widespread application of the 

equipment. These may include publication of manuals, training, advertising, or other 

promotion costs.

4. Actual per-test cost. This may vary widely depending on the practicality considerations 

(criterion 1), the number of people required to operate the equipment, and most of the 

factors listed in criterion 2.

5. Frequency of testing required. Does the test regimen defined by use of the equipment 

follow existing ASTM or other standard guidelines? Or does it require development of 

new testing guidelines or standard practices?

6. New test methods--exotic or complicated, and cost of training qualified operators.

7. Supplies needed for method or equipment. Are disposable supplies required that must be 

purchased frequently? Do any required materials have a shelf life, thus imposing new 

inventories?

8. Calibration or verification of the equipment. What costs are associated with quality 

assurance?
17

9. Equipment repair or parts replacement. What spare parts should be stocked, and what 

delays occur if parts are not available?

10. Need for a back-up system.

11. Value of posttest concrete sample. How much wastage is associated with the required 

testing?

12. Time delays as a result of testing during paving or placement operations. 

13. Impact on placement operations of equipment downtime for verification, service, routine 

maintenance, or other required delays between tests (cool-down cycle).

14. Peripheral equipment required, in addition to the test equipment itself, for full performance 

of the method.

Criterion 3: Applicability to a Wide Range of Concretes

The range of aggregate sizes that must be accommodated by the workability device of choice is fairly 

well defined by the range of aggregates in standard use in U.S. paving operations. For example, the 

apparatus need not accommodate the boulder-size aggregates of mass concretes. Still, aggregates will 

range from fine sand sizes up to almost 37.5 mm (1-1/2 in), and will cover all common aggregate 

shapes. The widespread use of both mineral and chemical admixtures in concrete pavements 

necessitates that the device must be usable over large ranges of fluidity, harshness, and ultimately, 

workability. Special considerations for applicability include the following:

1. Can the test be used for rapid-setting concretes? Fast-track paving, rapid-setting repair 

materials for minimum downtime of roadways, and many other concretes have a working 

time short enough to pose problems for many potential tests. If the equipment or method 

selected must be applicable to concretes with very short working times, that will eliminate 

many options.

2. Can the equipment be used for very stiff (no-slump or very-low-slump) concretes, such as 

those used in slip-form paving or roller compacting?

3. Is it effective for measuring workability of harsh concretes with highly angular aggregates or 

finely ground mineral admixtures?

4. Can it handle special aggregates for skid resistance, or unconventional materials such as 

ground or chipped recycled rubber?
18

5. Do existing ASTM or other standard testing methods or practices for stiff or harsh 

concretes apply to testing with this equipment, or must new standard practices be 

developed?

Criterion 4: User-Friendliness and Simplicity

Some of these are closely related issues that were considered with criterion 1, Practicality. However, 

user-friendliness or simplicity centers around the person or people required to conduct the test and 

produce useful test results:

1. How many people are required to handle the equipment, conduct the test, and produce 

useful results?

2. Is the equipment portable enough to move easily with paving operations?

3. How frequently and how much time is required for knockdown, packing, transport, 

unpacking, setup, verification, etc? Relative to an entire paving job, are these times 

acceptable?

4. Is maintenance and verification truly routine, or are additional specialists required?

5. What is the time delay between testing and output of useful results? Can the equipment 

provide information rapidly enough to be the basis of acceptance decisions?

6. Is the equipment output immediately useful, or does it require extensive calculation to 

transfer output data into useful information?

7. Are data acquired directly, or must they be transcribed or entered into software before 

processing?

8. Does or can the equipment provide directly readable outputs that are useful in the field; that 

is, does it report in real time?

9. Will operators need computer training or more training than is required for measuring 

slump?

10. Can the equipment be used readily by multiple operators? Truly user-friendly equipment 

can generate an answer within specified acceptable tolerances reliably and repeatedly 

when operated by a standard practice, no matter what trained person is operating it.

11. What is the reuse interval? Does the reset, cool-down, or reinitiate procedure cause a 

delay and waste operator time?
19

Criterion 5: Ruggedness

Some considerations for equipment ruggedness affected criterion 4. Here, they apply to the actual 

physical sampling, testing equipment, and ancillary hardware, rather than to operators or job sequencing:

1. Frequency of parts replacement, spare parts inventory, back-up equipment, support 

materials with a short shelf life, downtime for repair, cool-down or reset time, calibration 

and verification requirements all are part of ruggedness.

2. Ease in maintaining the equipment and checking for compliance with equipment 

specifications such as those in an ASTM Test Method? Calibration and equipment 

tolerances must not be altered.

3. Special protection required for the equipment for long periods of time and use in field 

conditions? Special protection may include dust control, temperature control, power-surge 

control, humidity barriers, or other physical means. 

4. Versatility of equipment to continue to function as needed and specified after multiple 

operators.

As stated previously, not all of these questions could be considered for every method screened. There 

was no information available on some subjects. Some questions applied to only a few methods. To 

create a workable matrix for the first evaluation process, based only on published information, these 

criteria were simplified into more specific requirements.

The practicality factor was simplified into three standards relating to implementation: sample testing, in 

situ testing, and testing in equipment such as pavers, hoppers, pumps, and mixers. Most of the rated 

approaches are focused on testing of removed samples. The techniques applicable to in situ testing can 

typically be applied to sample testing without modification.

The cost factor was broken down into four standards: equipment cost, testing time and labor, 

maintenance and serviceability, and availability. In many cases, estimates were used based on the 

complexity of the hardware and test procedure. Maintenance and serviceability were rated based on 

how likely it seemed that a component might fail, if that component was available off the shelf, and if a 

technician could make the repair. Some devices were considered to be available if their construction 

was extremely simple or if they have been standardized somewhere. 

Applicability was broken down into three standards: ability to generate multiple shear rates, ability to 

test a wide variety of concrete mixtures, and rheological simplicity.

A complete workability test should quantify not only the static yield (or slump) but also the dynamic 

viscous behavior of plastic concrete. Over practical shear rates, concrete behavior is approximated by 

the Bingham model. An acceptable approach should be capable of producing measurements across or 
20

at different shear rates. This allows quantification of the offset and slope of this linear model. It is 

beneficial for the approach instruments to test at shear rates approximating real concrete operations. It 

is also considered beneficial if the shear rate is constant and not transitional, allowing terminal conditions 

to be measured. Many of the rated workability techniques focused only on slump measurements. 

When apparent, simple modifications of these techniques were considered, possibly allowing them to 

generate or test at multiple shear rates.

A simple rheological approach increases that ability of the test method to prove that the desired 

parameters are being measured. Simple rheology refers to the simplicity of the physics influencing the 

measurement operation. The coaxial cylinder rheometer is an example of a simple rheological 

approach. Approaches that incorporate vibrators or drop tables into their measurements are 

considered more rheologically complex. An approach is also more complex if it combines a transitional 

range of shear rates and static yield instead of a single shear rate. 

User-friendliness and simplicity were restated as automation and simplicity. Typically, a simple device is 

not very automated, and an automated device is not very simple. This trade-off is a function of the level 

of development and characteristics of the approach. If an approach was highly automated but not 

necessarily simple, it received a good rating. If a device was simple and could lend itself well to 

automation or does not require automation, it also received a good rating.

Ruggedness was broken down into the standards of vulnerable components and sensitivity to elements 

and handling. Consideration of these categories was based on the number and size of moving parts, 

vulnerability of these parts to concrete, ability of the equipment to withstand shock, and the effect rain or 

dust might have on the equipment. Larger devices with computer components received better ratings if 

the computer could easily be disconnected and removed.

Technical Evaluation by Scientists and Engineers

Each approach was evaluated technically in the aforementioned categories. A rating of good, fair, or 

poor was given to each. Categories for which information was either not found or not published were 

noted. Approaches that had a poor rating and some that were rated fair were also rated on the risk of 

improving the device in that category through additional development and/or modifications.

The 21 candidate methods described in the previous section were evaluated by the 6 scientists and 

engineers listed as authors of this report. The preliminary screening was a qualitative process, drawing 

on the extensive research and field experience of this group. The group evaluation process included 

identifying whether the method measured a static or a dynamic component of workability, and 

considered the potential for using tests in combination to characterize workability. Thus, no test was 

eliminated outright on the basis of lacking completeness. Dynamic tests were considered for their 

potential to be combined with the familiar and standard test for concrete slump to quantify workability. 

Each of the methods was rated for technical merit as well as the risk of fielding the particular method, 

using the descriptors shown in table 2.
21

The following pages provide a brief description of each technique along with some details from the 

reviewers’ comments.

Table 2. Rating descriptors.

Technical

Good Meets standard as reviewed or is able to meet standards with 

minimal modification

Fair Can be made to meet standard with some modifications

Poor Cannot be made to meet standard without special emphasis

Risk

Low Minimal effort is required to bring product to meet standard

Medium Major effort is required to meet the standards

High The standard cannot be met within the funding and time constraints

EVALUATION SUMMARY AND NOMINATION

Of the 21 approaches that were evaluated, 9 received a rating of good or fair based on only simplified 

considerations of the 5 performance requirements. The remaining 12 were rated poor and considered 

of high risk with regard to development for producing meaningful results for this project. Each evaluator 

brought certain expertise to his evaluation of the methods considered. The evaluators met as a group to 

discuss their ratings and to collectively rate the methods. This collective rating is summarized in table 3.

Three of the four methods that were rated technically “good” used closely related technologies; that is, 

they all are rotational viscometers and are complex devices designed for laboratory use as opposed to 

routine field use. The evaluators considered that it was not in the best interest of the project to 

concentrate all future efforts on these “good” devices, given their similarity, cost, and complexity. 

Another factor not specifically listed in the screening is that the review group tried to select candidate 

methods that represented several different technical approaches to measuring workability, rather than to 

select methods that were different versions of the same technology. The four candidate methods with a 

fair to good technical rating and medium developmental risk were selected as having promise as 

fieldable techniques and warranting further testing represent one device each from the flow, moving 

object, vibration, and rotation type techniques. Thus, they are the best available candidates from 

several different technologies.

Many of the systems considered are poorly suited to determining workability because they focus solely 

on the static yield or slump measurements. Some of the reviewed techniques combine a result obtained 

from transitional shear rates and the yield stress. The drop-table methods and the Kelly ball are 
22

examples of such systems. These techniques are ill suited because the shear rates or the stresses are not 

steady state and the results are also weighted toward the static yield measurement. Other systems 

incorporate vibrators to induce flow of stiff concretes.

Table 3. Summary of composite ratings.

No. Approach Technical Risk

1 Powers and Wiler Apparatus Poor High

2 Two-Point Workability (Tatersall) Good Med

3 Ready-Mix Truck Hydraulic Fair High

4 Colebrand Fair Med

5 BML Viscometer Good Med

6 BTRHEOM Rheometer Good Med

7 Free Orifice Fair Med

8 K-Slump Poor High

9 Delivery-Chute Torque Meter Fair High

10 Delivery-Chute Vane Poor High

11 Angles Flow Box Poor High

12 DIN Flow Table Poor High

13 V-B consistometer Poor High

14 Remolding Test (Powers) Poor High

15 Thaulow Tester Poor High

16 Vibrating Slope Fair Med

17 Kelly Ball Poor High

18 Wigmore Consistometer Poor Med

19 Ring-Penetration Test Poor High

20 Compacting Factor Poor High

21 Moving Object Good Med

The approaches listed in table 4 are nominated for consideration for development and evaluation as 

potentially capable of measuring workability for concretes applicable to pavement construction. All of 

the nominated approaches have weaknesses. The major concerns for each nominated approach are 

described in the modification, development, and acquisition plan sections of this report (Chapters 4 

and 5). This first screening involved a simplified consideration of the five performance criteria. 
23

Evaluation of the best candidate approach required answering many of the questions given at the 

beginning of this chapter. The four approaches in table 4 were considered for actual field 

measurements. In addition to these candidates, the laboratory-grade rotational viscometer 

(BTHROEM) was used as a laboratory reference device.

Table 4. Nominated approaches.

1 Free-orifice rheometer

2 Moving-object rheometer

3 Vibrating slope

4 Colebrand tester

The following paragraphs summarize the technical concerns expressed during evaluation of the 

candidate devices. Detailed evaluation forms are provided as appendix B.

Free-orifice rheometer—This classical method for rheological measurement does not normally 

operate at multiple shear rates. To obtain different flow rates, different diameter orifices would 

be used. The method may be more useful when combining measurements made using this 

technique with a static measurement (such as slump) to describe the rheological properties of a 

concrete mixture. To prevent blockage of the orifice, the opening should be a minimum of three 

times the maximum-size coarse aggregate particle. Even with the large openings, the evaluators 

did not believe that this technique would be workable without the use of vibration. This device 

would be used strictly for testing of sampled concrete. It would not be useful for testing of 

in situ concrete or for testing of concrete while the concrete is still in the mixer or a paving 

machine.

Moving-object rheometer—The moving object (moving-ball viscometer) is a classical 

rheological technique. Theoretically, one can construct a device that will operate at multiple 

shear rates and will work across a broad range of concrete mixtures. It is anticipated that the 

device could be made portable for use in testing concrete sampled from a batch as well as 

in situ concrete and concrete in mixers. No such device is currently available for use in 

determining rheological properties of concrete. Construction of a test device should be rather 

simple for laboratory testing of this technology. 

Vibrating slope—Since vibrating slope at one fixed angle develops a single shear rate, it is 

anticipated that testing the concrete mixture at several slope angles would give multiple shear 

rates for a concrete mixture. Vibration field adds to complexity for determination of shear and 

classical rheology calculation. Instead, an index number determined by the change in the 

discharge rate versus angle of discharge will be used as a correlation to concrete workability. 
24

Colebrand tester—Torque is measured as two hemispheres mounted at the end of a shaft are 

rotated. Measured torque is correlated to slump and w/c. This device is commercially available 

and is designed for field use. It works with concrete mixtures with a slump greater than 70 mm 

and mixtures with coarse aggregates having a nominal maximum size of less than 32 mm. 

Portability of the device allows its use for in situ testing of concrete mixtures that have been 

placed, testing of concrete mixtures while still in a truck or paving machine, and also in concrete 

sampled from a concrete batch. This tester uses a battery that is internal to the device and 

rechargeable; it can be recharged using normal 120-v current with the accompanying charger. 

The device is lightweight and requires only a single operator. The current device does not allow 

for multiple shear rates. Ten data points are collected and then averaged at 1 fixed shear rate. 

The time to collect the data using this device is similar to the time required to perform a slump 

test.
25

CHAPTER 4: LABORATORY EVALUATION OF CANDIDATE

TEST PROCEDURES

The laboratory evaluation included selection of a commercial off-the-shelf rheometer to use as a 

standardization tool in testing, modifying, developing, and verifying the performance of the four 

potentially fieldable candidate approaches. The two rheometers that were considered as reference tools 

were the BML and the BTRHEOM. (The items in table 4 are workability techniques recommended for 

further consideration as fieldable devices.) A BTRHEOM was purchased for this program because of 

its size and portability. The following sections describe the status of the research rheometer and the four 

techniques that were considered. Topics discussed include the technical difficulties with each technique, 

as anticipated by the research team, and approaches and modifications to improve performance.

Low-slump concrete mixtures were used in developing and testing the candidate methods. To minimize 

the effects of hydration and the necessity of continuing to make new batches of concrete, the test 

mixture consisted only of fly ash, water, fine aggregate, and coarse aggregate. The slump changed as 

the water evaporated from the mixture, and water was added to maintain slump during testing. The fly 

ash mixture proportions were as shown in table 5.

Table 5. Test concrete mixture proportion.

Materials Batch, m3

Cement, kg -

Fly ash, kg 356

Water, kg Variable

Fine aggregate, kg 534

Coarse aggregate, kg 1,424

Water was added to the test mixture adjusting the workability to obtain mixtures with slumps of near 

zero and 50.8 mm (2 in). Slumps was measured for each test according to ASTM C 143, “Standard 

Test Method for Slump of Hydraulic Cement Concrete,” (ASTM 1994c) prior to using the mixture in 

testing the devices. Higher-slump mixtures were made by the addition of more water.

BTRHEOM DEVICE

The laboratory version of the BTRHEOM device is shown in figure 1. This device uses rotating discs to 

measure viscosity. The discs are fabricated to prevent slippage of the concrete. A field system, which 

uses a portable computer is available for this device. 

The BTRHEOM is commercially available from France. The research team was able to obtain the use 

of the equipment. The BTRHEOM is limited to testing concrete with a slump of more than 50 mm.
26

Figure 1. BTRHEOM device.

When the device was evaluated using the low-slump mixture, no steady-state measurements could be 

made, even when vibration was added. Either the system did not rotate or, when rotation was possible, 

it tended to be sporadic in rotational speed. This apparatus is not capable of handling the low-slump 

mixture, even with vibration.

FREE-ORIFICE RHEOMETER

The free-orifice rheometer is shown in figure 2. This device measures the flow rate produced by the 

gravitational force of the concrete and the opposing viscous force produced at the smaller exit orifice. 

Modification of this approach to generate multiple shear rates involved incorporating some sort of 

variable external force, such as a linear actuator or external weights. A linear actuator as described in 

the development section of the moving object approach was used to generate high applied forces for 

testing low-slump mixtures without external vibration. External vibration was necessary for low-slump 

concrete. 

One reported problem with this technique it that the orifice size is a function of the maximum aggregate 

size and the concrete slump. Laboratory testing with this device revealed that, even with several orifice 

sizes, flow through the device was not possible within the practical range of the device and concrete 

mixtures used in the program.

MOVING-OBJECT RHEOMETER

In 1850, Sir George Stokes first developed an equation for calculating the absolute viscosity of a metal 

sphere falling through a fluid. Still today, falling- and drawn-object viscometers are used extensively for 

laboratory and field materials testing. The physical equations are well defined and include provisions for 

influences such as container boundary effects.
27

Lead Weight and Disc 

Steel Tube (4 in I.D.)

Soft Rubber Exit Orifice

 (3-1/2 in I.D.)

Catch Pan

Load Cells

Poker 

Vibrator

Supports

Foam Rubber

Hose Clamps

Figure 2. FREE-orifice rheometer.

L’Hermite and Tournon (1993) performed workability experiments in the late 1940’s by controlling the 

force and measuring the rate at which a steel sphere moved through vibrated concrete. They confirmed 

the application of Stokes law to vibrated concrete and use of the drawn sphere.

The moving-object rheometer in a conceptual final form is shown in figure 3. The data acquisition and 

control operations could be performed by a notebook computer or an embedded system. A movingobject rheometer in a limited laboratory form is shown in figure 4. This laboratory system uses pulleys 

in various configurations to create the different shear rates needed to describe viscosity. 

This procedure was evaluated using both a constant-force and a constant-velocity system. The 

laboratory unit for the moving-object device used an overhead crane as a constant-speed device. 

Pulleys were used to achieve four speeds from the two-speed crane. While the data series from these 

tests had consistent patterns, a steady-state force value was not always clear.

Data collected using a constant-force device were somewhat more difficult to interpret, because the 

maximum force required is not known prior to testing. To reduce the force required for the test to a 

practical level, a vibration field was applied to the concrete test sample.

Dilatation of the concrete during object movement through the concrete mass required that a large 

amount of concrete must be tested. Restraint imparted by the dilatation of the concrete
28

Conceptual Field System 

Figure 3. Field embodiment of the moving-object rheometer.

Displacement

Y o - y o

Pulley

Load Cell

Two-Speed 

Electric Ceiling Crane

 Moving Object 

Stiff Rod

Concrete 

Container

Displacement

Y o -y o

Pulley

Load Cell

 Moving Object 

Stiff Rod

Concrete 

Container

weight 

basket

note: tests were also performed with a large vibrator attached to the concrete container

Constant Rate Measurement Constant Force Measurement

Figure 4. Laboratory configuration for testing with moving-object approach.
29

increased the force necessary to move the object through the concrete, as well as causing increased 

velocity as the object neared the free surface of the sample being tested.

VIBRATING-SLOPE VISCOMETER

The vibrating-slope viscometer, in its laboratory form, is shown in figure 5. For this initial approach, the 

time required to vibrate half of the concrete out of the chute is measured as an indication of workability. 

 The modification for this approach involved changing the angle of incline to generate multiple shear rates 

and measure maximum discharge rate. This device performed well in the laboratory phase, and a more 

field-applicable device was developed and is recommended for further testing.

 

Load Cells (2)

Vibrator

Table

Catch Pan

Chute With Mesh Bottom

Angle 

Selector

Figure 5. Laboratory version of vibrating-slope viscometer.

Discharge rate was determined for some low-slump concrete as shown in figure 6. Mixtures were 

tested at slopes of 10 and 15 deg. There was an increase in the discharge rate with increase in slope 

angle. No problems were encountered with handling of either the fluid mixture or the low-slump 

mixture. Fluid concrete mixtures flowed from the chute without vibration, where as the low-slump 

concrete required vibration to discharge the concrete. Maximum vibration was used for all tests 

performed. This method does not lend itself to the measurement of fluid concrete, as the concrete 

begins to discharge soon after the gate to the chute is opened. Concrete mixture with a one-inch slump 

showed slight decrease in discharge rate with an increase in discharge angle this was due to aging of the 

concrete mixture during testing. Higher-slope angles may be necessary for low-slump concrete.

COLEBRAND TESTER

A modified Colebrand tester is shown in figure 7. In its current form, the device makes a dynamic 

measurement that is correlated to slump. This embedded system does not display in the output 

information the rotational speed or resulting drag force. Hemispherical probes similar to those used in 

the Colebrand tester were fabricated and were used in conjunction with a two-point test device instead 

of the impellers normally used, and the ability of this type of device to 
30

Figure 6. Relation of flow rate to angle of inclination.

Tattersall Unit

Scaled up Colebrand

 Impeller

Accumulator 

(Added to Reduce

Hydraulic Gauge Pressure

Oscillations)

 side top

view view

Figure 7. Modified Tattersall/Colebrand tester.

angle of inclination (deg)

 flow rate (lb/sec)

8 9 10 11 12 13 14 15 16

0

2

4

6

8

7-1/2 in. 

3-3/4-in. 

2-1/2 in.

1-in

slump
31

measure additional shear rate was evaluated. Low-slump concrete tested using this device showed 

channeling of the concrete by the probe after one revolution. The indicated viscosity of the concrete 

(slope of lines in figure 8) remained the same or dropped, revealing problems using this device for highshear determination in low-slump concrete mixtures.

Figure 8. Viscosity (slope) of concrete based on use of Colebrand probe in

Tattersall machine.

The Colebrand tester was tested separately with several concrete mixtures. These measurements 

correlated with slump as shown in figure 9.

Three of the candidate methods had physical limitations that were difficult to overcome. Flow through 

the free-orifice device was intermittent, and consistent flow measurements could not be obtained for the 

size of device tested. The moving-object rheometer required a large sample and container size to avoid 

dilation of sample and influence of container size on the measurements. The Colebrand only gave results 

that correlated with slump. However, when the probe was used with low-slump concrete to determine 

shear stress at different shear rates, the probe would make a channel through the concrete upon its first 

pass and subsequent passes through the concrete gave results that were not useful.

The vibrating-slope apparatus was the only method that could measure some relevant properties of lowslump concrete. It was selected for additional testing and development.

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2.5"

3.75"

7.5"

8.25"

Torque (Nm)

Colebrand velocity 

Velocity (m/s)
32

Figure 9. Relation of predicted slump using Colebrand tester (FCT 101)

to measured slump.

Colebrand FCT 101: Predicted Slump vs Measured Slump

Predicted Slump, mm

0 20 40 60 80 100 120 140 160 180 200

Measured Slump, mm

0

20

40

60

80

100

120

140

160

180

200
33

CHAPTER 5: VIBRATING-SLOPE APPARATUS

The initial laboratory system from which the portable vibrating-slope apparatus (VSA) (figure 10) was 

designed using a vibrating table, an attached chute, and an external electronic scale. The scale was used 

to measure the mass of the deposited concrete as a function of time. The following sections document 

the development of a device to meet the requirements of portability, compactness, and ruggedness for 

field use, as well as the software for data acquisition and data processing.

Figure 10. Portable vibrating-slope apparatus.

VIBRATING-SLOPE APPARATUS (VSA) HARDWARE DEVELOPMENT

The VSA measures the rate at which vibrated concrete flows from a chute. One of the key 

modifications was the incorporation of the load-cells into the device chassis so that an external massdetermining apparatus was not needed. To accurately measure the concrete mass while under vibration, 

three things are done. First, vibration isolators are used between the load-cell and chassis and between 

the chassis and vibrating chute. Second, an analog-summing amplifier is used to combine the output 

from three load-cells into one signal. Since the instantaneous vibration component at each load-cell is 

different, summing the load-cells helps average out vibration noise. The third step used to reduce 

vibration noise is signal averaging. This is accomplished in the data-acquisition program. Sequential 

signals are averaged over a time interval small enough so that the concrete mass does not significantly 

change, but long enough to span several vibration cycles. Since the vibration phase varies in each signal, 

averaging is effective in reducing the vibration noise.

During testing of the laboratory system, the appearance of vibration nodes and antinodes in the chute 

was noted. As a result, the concrete was not being uniformly vibrated in the chute. Concrete at a node 

would undergo minimal vibration, while concrete at the antinodes would experience more vibration. 

Vibration

mount
34

Because the concrete that was under more vibration flowed more freely than the concrete at a node, a 

hump would tend to form near the node (near the center of the chute). To overcome this problem in the 

VSA, the vibrator was mounted directly on a large stiff plate of 12.7-mm (1/2-in) steel, which forms the 

bottom of the chute. In addition, the walls of the chute are isolated from the bottom by rubber strips 

and grommet vibration mounts. This helps to minimize vibration nodes in the chute walls and reduces 

the overall vibration of chute walls, producing a more uniform vibration field in the concrete.

The bottom of the chute is covered with staggered transverse metal strips about 12.7 mm (1/2 in) in 

height. These strips prevent the concrete from sliding out of the chute. A quick lift gate is used at the 

front of the device to hold the concrete in the chute during filling, leveling, transport, etc. A manual 

screw-jack on the back of the chute allows various incline angles to be set. The incline angle is 

determined with an angle indicator magnetically affixed to the chute. This indicator gives the true angle 

of incline regardless of the ground surface incline or smoothness.

There are eight vibration dampers to isolate vibration on the VSA. Six of these are the type used on 

vibration tables and other heavy-vibration applications. Three of the six dampers are mounted directly to 

the top of the load-cells to help prevent chassis vibrations from traveling through the load-cells to the 

pedestal or wheels. If excessive vibration reached these supports, the system would hop on the ground, 

and measurement data very likely would be lost. Two additional vibration dampers are used to connect 

the front of the chute to two heavy-duty hinges located on the chassis.

Two custom dampers and one standard damper are used to connect between the jack, chute, and 

chassis. These custom dampers allow for the rotational freedom needed to connect the screw-jack 

between the chassis and chute while also reducing vibration transmission into the chassis. They were 

constructed from a hollow pipe, large, thick, rubber washers, threaded rod, nuts, and steel washers.

The VSA is moved by lifting up on the chassis handle, allowing it to roll on the front wheels, like a 

wheelbarrow. Large-diameter, hard, rubber wheels are used so that the device can be more easily 

transported over rough and uneven surfaces. The front wheels share a common axle that is braced to 

the rear supporting leg. This bracing helps provide the rigidity needed to compensate for the softness 

and flexibility of the vibration mounts. 

The load-cells are fatigue-rated transducers of the pancake-type capable of measuring both tension and 

compression to 226.8 kgf (500 lbf). A custom electronic circuit was constructed to provide regulated 

and temperature-compensated load-cell excitation as well as to condition the output signals. The 120-

ohm load-cells are excited with a bipolar direct current of 20 v. All of the amplifiers in the circuit are 

excited with a regulated bipolar direct current of 30 v. This sets the output limits to ±15 v. In the signalconditioning circuitry, the differential outputs from the three load-cells are converted to single-ended 

outputs by means of three high-performance differential operational amplifiers (op-amps). These singleended signals are then summed and scaled with a summing op-amp network. An optional six-pole lowpass filter output is also provided by means of a specialized integrated circuit (figure 11).
35

Power Supply

120 V AC

 to

18 V DC

converter

common

5.1 volt zener diode

precision resistor 1/2 watt

1

2

3

4

load cell (X3)

1

3

5

6

7

Signal Conditioning

2

4

5

7

6 (ref)

G1

G1

G1

G1 set by external resistance ~200

G2

6

+15V

regulator

-15V

regulator

20 V D.C.

(max)

DE

SE

DACQ

1. Differential to single ended

2. Amplification

3. Summation

Figure 11. Circuit diagram.

The VSA is powered by a standard 120-v alternating current. Battery power of the entire system is not 

feasible because of the power requirements of the vibrator. This system was built with a variable-speed 

vibrator to allow maximum testing flexibility. Currently the system is being evaluated with the vibrator 

operating at maximum speed and its off-center mass set to a force level of 136.07 kgf (300 lbf).

VIBRATING-SLOPE DATA-ACQUISITION SOFTWARE

The software that is used to perform the data collection, display, and processing for the vibrating slope 

device is written in Hewlett Packard’s Virtual Engineering Environment (HP-VEE) (appendix C). This 

software interfaces a Data Translation PC Card. This card is a 12-bit 200,000-sample per second 

analog-to-digital converter. The software is comprised of two programs. The first program collects and 

averages the raw data and stores this information, as well as the incline angle and test description. This 

program also processes and displays the flow-rate information, although this information is not stored. 

The second program reads, processes, and displays the data files generated by the first program. 

Discharge rate decreases as the chute empties, so a maximum flow rate is calculated for that incline 

angle. After all test data have been read in, a linear fit is applied to the data, which relates the maximum 

flow rate in kilograms per second (pounds per second) to incline angle. 

The data collection program allows the user to change data-acquisition parameters including angle of 

inclination, test description, data file, and length of test. However, for the majority of concrete mixtures, 

the default configuration should be used. When the user clicks the start button, the software activates a 

timer that keeps up with the elapsed test time. This start button also begins the data acquisition. During 

data acquisition, 4,096 samples are collected at a rate of 100,000 samples/s and then averaged to 

generate each data point. This sampling process is repeated until the stop button is pressed. A multiplier 
36

and offset are used to apply a calibration to the data. Periodic calibration is performed using dead 

weights. The output data file contains test comments, incline angle, elapsed time, and the previously 

described data. Additional processing is performed on the data so that the user can preview the test 

results. These processing operations are described below. During a test, a real-time graph of the 

collected mass data is displayed on the screen as well as a numeric display of the instantaneous weight. 

After the collection of data is stopped by the user, the mass flow-rate data are calculated and displayed.

The second program, which performs the data-reduction tasks (figure 12), allows the user to load 

multiple data files created by the previously described program. The elapsed test time and measured 

amplitude data array, which are both contained in the stored data file, are used to construct a wave form 

that relates amplitude as a function of elapsed time. A seventh-order polynomial fit is then applied to the 

data as a type of low-pass filter. A first-order derivative is then applied to the data to convert them from 

mass to mass flow rate. The maximum mass flow rate that occurs in the first half of the data is then 

extracted. This value is stored in an array along with the angle at which the test was run. A composite 

graph is also updated with this result. This process is repeated for as many test data files (for a given 

mixture) as desired. Each time a test data file is loaded, the extracted angle and flow-rate information 

are added to the final array. When the user has loaded all of the desired test data, the “Go” button is 

pressed and the software calculates the best linear fit of the data as well as a correlation coefficient or 

quality indicator. At least two different measurement angles must be loaded to calculate a fit, but there 

is no restriction on loading multiple tests performed at the same angle.

6 th

Order 

Polynomial

Fit

Derivative

Open Data File

Extract: 

Number of points

Elapsed Time

Incline Angle

Data Values

Reconstruct 

Time Series

Extract

Peak 

Flow 

Rate

Generate

Composite

(rate vs angle)

Repeat 

for next

datapoint

( 2 pts . min.)

Calculate 

Linear 

Coefficients

and 

Fit Quality

Figure 12. Data-reduction flow diagram.
37

CHAPTER 6: VERIFICATION OF EQUIPMENT PERFORMANCE

AND FIELD EVALUATION

MATERIALS AND TEST METHODS

Materials Company, a Class F fly ash, natural rounded fine aggregate, and two coarse aggregates, (a 

washed gravel meeting ASTM C 33 (ASTM 1994a) nominal size No. 67 from Mississippi Materials 

Company and a limestone coarse aggregate with a 19.05 mm (3/4-in) maximum size from in-house 

standard stock).

The candidate technology was examined in an evaluation program that purposed to determine needed 

modifications to hardware and operational details. Several concrete mixtures were used in this step. 

Mixture 1 is the only one to contain a high-range WRA (water-reducing admixture). Air entraining 

admixture (AEA) was used in two mixtures. Other mixtures varied in the fly ash content and the amount of 

cement in the mixture. Mixtures are described in the following table:

Table 6. Concrete mixture proportions for evaluation program.

Mixtures

Material 990085199008619900872990088299008929900902

Cement, kg (lb) 331 (729) 152 (335) 185 (406) 231 (508) 145 (319) 192 (423)

Fly ash, kg (lb) 46 (102) 47 (104)

Fine aggregate, 

kg (lb)

480 (1,057) 609 (1,341) 540 (1,188) 598 (1,316) 534 (1,176) 535 (1,176)

Coarse aggregate, 

kg (lb)

767 (1,690) 824 (1,815) 883 (1,943) 845 (1,860) 948 (2,089) 948 (2,089)

AEA, ml (fl oz) 367 (12.4) 59 (2.0) 132 (4.5) 441 (15)

WRA, ml (fl oz) 863 (29.2) 88 (3)

Water, kg (lb) 116 (255) 99 (218) 110 (243) 110 (243) 83 (182) 83 (182)

1Natural chert coarse aggregate.

2Crushed limestone coarse aggregate.

CONCRETE TEST

For all mixtures, the following standards were applied: for slump, ASTM C 143 (ASTM 1994c), 

“Standard Test Method for Slump of Hydraulic-Cement Concrete”; for air content, ASTM C 231 

(ASTM 1994e), “Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method”; 

and for temperature, ASTM C 1064 (ASTM 1994g), “Test Method for Temperature of Freshly Mixed 

Portland Cement Concrete.”
38

A sample of freshly mixed concrete (approximately 0.1 m3) is placed and compacted by vibrating in the 

chute. The chute is raised to a predefined angle and vibrated to allow the concrete to flow out of the 

chute. The rate of discharge is measured and recorded. A second sample is prepared in the same 

manner and tested at a predefined angle different from that used in the first measurement. The 

workability is defined as the slope of the line defining the two discharge rates versus the angle of the 

discharge chute.

A draft method of the VSA procedure is presented in appendix D. The maximum discharge rate is 

determined for a minimum of two discharge angles. The discharge rate will increase relative to the 

discharge angle and the effort necessary to move the concrete. Concrete that is easily moved will have 

a higher discharge rate than those stiffer and less workable concrete. The discharge rate for concrete 

having a lower workability will show a smaller increase relative to the increase in the discharge angle. 

Figure 13 illustrates two concretes having different workability indices. The concrete represented by 

series 1 has a workability index of 0.20 and concrete series 2 has a workability index of 0.13. More 

work effort is required to move the concrete represented by series 2 than is necessary to move the 

concrete in series 1.

Figure 13. Two concretes with different workability indices.

The general procedure for testing using the VSA is described below. More angles were included for 

additional information.

The bottom of the chute was leveled and then dampened and allowed to drain so that no standing water 

remained in the chute. The concrete was placed into the chute in a single lift, bringing the level of the 

concrete 100 mm (4 in) above the bottom of the chute (figure 14). The vibrator attached to the 

apparatus was then used to vibrate the concrete to rid the system of “tracks” and voids. This took 

approximately 5 s, depending on the stiffness of the concrete. 

Workability Index

y = 0.1957x - 0.4286

y = 0.1267x + 0.3333

0

1

2

3

4

5

0 1 0 2 0 3 0

Discharge angle, deg

Series1

Series2
39

The angle of the chute was raised to 10 deg, the gate was opened, and the data-acquisition system and 

the vibration were started.

Following the test, residual concrete from the chute was removed and the chute was releveled. A 

second sample of concrete was placed into the chute to the same height and treated as in the case of 

sample one. After consolidation, the chute was raised to an angle of 15 deg and the test was repeated. 

 The process was also investigated using 5-, 10-, and 25-deg angles.

Figure 14. Concrete discharge chute.

a. Discharge chute is cleaned and drained prior 

to use.

b. Concrete remains in the chute when the gate is 

removed.
40

Tables 7 through 14 summarize the testing of the VSA.

Table 7. Batch 990085, 203.2-mm (8-in) slump.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 10 2.601 (5.729)

B 10 2.054 (4.525)

C 10 2.498 (5.503)

D 15 2.959 (6.518)

E 15 2.969 (6.54)

F 15 3.556 (7.832)

G 25 4.672 (10.29)

H 25 5.689 (12.53)

I 25 3.392 (7.472)

J 15 3.578 (7.881)

K 5 1.693 (3.728)

L 5 1.722 (3.793)

M 5 1.910 (4.208)

Table 8. Batch 990085, 165.1-mm (6.5-in) slump.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

N 10 2.536 (5.585)

O 15 6.401 (14.1)

P 25 8.717 (19.2)

Q 10 2.281 (5.024)

R 15 3.597 (7.923)

S 25 4.069 (8.962)
41

Table 9. Batch 990086, 95.25-mm (3-3/4-in) slump, 7.8% air.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 15 2.432 (5.357)

B 15 2.023 (4.455)

C 15 2.283 (5.029)

D 25 10.056 (22.15) Bad data

E 25 3.196 (7.04)

F 25 2.808 (6.186)

G 10 1.172 (2.581)

H 10 0.977 (2.153)

I 10 1.286 (2.833)

Table 10. Batch 990086, 7.8% air.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

J 10 1.738 (3.828)

K 15 3.213 (7.076)

L 25 3.726 (8.207)

101.6-mm (4-in) slump

M 10 1.882 (4.145)

N 15 2.570 (5.661)

O 25 4.065 (8.954)

76.2-mm (3-in) slump

P 10 2.119 (4.667) 63.5-mm (2.5-in) slump

Q 15 1.781 (3.922) Bad data

R 25 3.168 (6.979)

Table 11. Batch 990087.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 10 1.629 (3.589)

B 15 1.559 (3.433)

C 25 2.606 (5.74)

76.2-mm (3-in) slump

J 10 1.615 (3.557)

K 15 2.364 (5.207)

L 25 4.465 (9.835)

101.6-mm (4-in) slump

M 10 1.846 (4.067)

N 15 2.684 (5.912)

O 25 3.631 (7.998)

101.6-mm (4-in) slump
42

Table 12. Batch 990088.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 10 1.491 (3.284)

B 15 2.517 (5.543)

C 25 3.441 (7.58)

127-mm (5-in) slump

D 10 1.915 (4.219)

E 15 2.07 (4.559)

F 25 3.802 (8.374)

101.6-mm (4-in) slump

G 10 1.622 (3.573)

H 15 2.10 (4.625)

I 25 2.783 (6.131)

57.2-mm (2-1/4-in) slump

J 10 1.286 (2.833)

K 15 1.611 (3.549)

L 25 3.410 (7.512)

44.5-mm (1-3/4-in) slump

Table 13. Batch 990089.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 10 0.565 (1.245)

B 15 1.168 (2.572)

C 25 1.658 (3.651)

31.8-mm (1-1/4-in) slump

D 10 0.716 (1.577)

E 15 0.841 (1.852)

F 25 1.446 (3.186)

6.4-mm (1/4-in) slump

Table 14. Batch 990090.

Measurement Angle, deg Max Discharge rate, kg/s (lb/s) Comments

A 10 1.307 (2.879)

B 15 2.041 (4.496)

C 25 2.339 (5.151)

50.80 mm (2-in) slump

D 10 1.183 (2.605)

E 15 1.145 (2.523)

F 25 1.884 (4.149)

31.8 mm (1-1⁄4-in) slump
43

RESULTS AND DISCUSSION

Since each construction operation using concrete operates under a specific shear rate, it requires a 

different amount of force to work the concrete for a given mixture for a given operation. There is only 

one shear rate for the static case, and that is zero. However, there is an infinite number of shear rates 

for the dynamic case, and hence there is an infinite number of required stresses or work values. Since 

the work function is a straight line, at least for low shear rates, we do not have to measure an infinite 

number of points. Only two sets of coordinates are measured to develop the linear function for the 

work curve. Only two parameters are necessary to define the curve—the yield stress and viscosity. 

The yield stress is the y-intercept, and the dynamic viscosity is the slope. By plotting the data with the 

angle on the x-axis and the discharge rate on the y-axis, we can use the equation of a straight line to 

describe the workability of the concrete.

The workability index “W” is calculated as the slope of the line between two points determined using 

the discharge rate at two discharge angles. The following equation was used to make the calculations:

R = WA + C

R = rate of discharge, mass/unit time

A = angle of discharge, degrees

W = workability index

C = calculated yield offset

W = (R2 – R1)/(A2 – A1)

C = R – WA

Workability index trends were calculated for the two mixtures having similar slumps but differing 

compositions. Mixtures 990089 and 990090 were mixtures having the same ingredients, varying only 

that in Mixture 990089 some of the cement was replaced by fly ash. Mixture 990089 shows lower 

slumps and discharge rates for both fly ash mixtures than those of 990090 without fly ash (figure 15). 

Where the slumps of 990089 and 990090 were the same, the mixture with fly ash had a larger 

workability index, i.e., a steeper slope.
44

Figure 15. Workability index.

The workability index was calculated using averages of three points at three angles (10-, 15-, and 25-

deg) and was also calculated using the averages of two points at 10- and 25-deg angles. The results 

showed that there is little difference in developing the third point. The workability index calculated 

based on the averages of three data points for Mixture 990085 was y = 0.322x + 2.07 and, when 

calculated using two angles, was y = 0.3233x + 2.01.

The data are sometimes scattered, as shown in figure 16. This sample was tested three times. As the 

sample aged, changes in its workability were observed. The slope of the regression curve ranged from 

0.1211 for the initial sample (line a) to 0.0799 in sample c (with sample b at 0.1314).

The VSA was rolled onto the ramp of a small utility trailer and was taken to a local ready-mixed 

concrete plant for evaluation and test. The plant provided an area normally used for testing, which 

contained a source of both water and 110-v electric current. Although the notebook computer is 

capable of operating on batteries, it was operated using a common AC supply used by the vibrator on 

the VSA.

Workability index

y = 0.0688x + 0.6202

y = 0.0468x + 0.7162

y = 0.0729x - 0.1632

y = 0.0488x + 0.2292

0.000

0.500

1.000

1.500

2.000

2.500

0 5 10 15 20 25 30

Discharge Angle, deg

990090, 51 mm

990090, 32 mm

990090, 32 mm

990089, 6 mm
45

Figure 16. Three-point data.

The plant adjusted its mixture proportion and produced concrete with three slumps by adjusting the w/c. 

 Mixtures had slumps of 222.3, 12.7, and 165.1 mm (8-3/4, 1/2, and 6-1/2 in). The truck discharged 

the sample into a wheelbarrow from which concrete samples for the slump and VSA tests were 

obtained. The amount of concrete in the wheelbarrow was no more than the amount taken normally 

during quality testing in the field.

Time required to set up was reasonable. Power necessary for the operation is generally available at 

concrete-batching facilities. Once the VSA was set up, numerous measurements could be made with 

relative ease.

Measurements were made automatically with no data collection or calculations made by the technicians 

running the test. The maximum rate of discharge was determined by the data-reduction program. (See 

appendix D for details of the data acquisition and reduction program.)

Cleanup can be done with a scrub brush and a 19-L (5-gal) pail of water. This was aided somewhat by 

presence of an available external water source, also readily available at batching facilities.

Initial setup problems included the need for a place to put the notebook computer, glare from sunlight 

which made it difficult to read the computer screen, and inability to obtain a signal from the load-cells to 

the data-acquisition program. The working surface problem was solved by turning over a 19-L (5-gal) 

plastic bucket and using the bottom surface to hold the computer. Glare on the computer screens 

continued to be a problem during the course of the field test. The connection between the cables and a 

Workability Index

y(a) = 0.1211x + 0.8775

y(b) = 0.1314x + 0.5831

y(c) = 0.0799x + 1.0271

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

4.500

0 5 10 15 20 25 30

Angle, deg

Discharge rate, Kg/s

a

b

c
46

data-translation PC card is not rugged and tends to come loose when moved. Care was taken to make 

sure there was good connection to the PC card prior to running each test.

An 222.3-mm (8-3/4-in) slump concrete was tested using the VSA. During the testing, vibration 

caused the concrete to splatter from the chute. Items not cleaned with water should be covered (i.e., 

the notebook computer and controllers on the VSA.)

Miscellaneous apparatus items needed for the VSA test are similar to those needed the determination of 

slump (ASTM C 143 (ASTM 1994c)) or for air content determination (ASTM C 231 (ASTM 

1994e)). Items include a scoop or shovel to load concrete into the VSA, a trowel or other device such 

as a square-nose shovel to level the concrete, a scrub brush to aid in cleaning the unit after testing, a 

19-L (5-gal) plastic bucket to carry water, waste concrete, and gloves.
47

CHAPTER 7: FUTURE DEVELOPMENT

The current program was limited to the development of a method for determining the workability of 

concrete. Several concrete mixtures were tested during this program to verify the ability of the system 

to obtain these measurements. The limits of resolution or the ability of the VSA to resolve the effort 

necessary to move certain concrete was not determined. Continued effort is necessary to correlate the 

information gained from the VSA and how to use the information in specifications and in proportioning 

mixtures. Future research and development should include the development of correlation of concrete 

properties with VSA index numbers in addition to increasing the portability of the VSA software and 

hardware. Currently, our testing has shown that using vibrating slopes with angles of 10 and 25 deg can 

resolve differences in concrete having similar slumps. It is assumed that the workability index decreases 

as the effort required to move the concrete increases. If the calculated workability index of 0.2 goes to 

0.1, more effort is required to move the concrete with the workability index of 0.1.

The VSA was configured with flexibility in mind so that tests could be run at different slope angles, using 

varying amounts of material, collecting data at different rates and displaying data for analysis. The unit 

currently has a mass of about 158 kg (350 lb) and consists of the test device and a notebook computer 

for data acquisition. Detailed drawings of the VSA device are presented in appendix E. The computer 

uses HP-VEE software to perform the data collection, processing, analysis, and storage. The dataacquisition card is a PC-card that plugs into the notebook computer. This configuration is very 

beneficial during system development, because it provides a great deal of flexibility and signalprocessing capability. This flexibility has caused the equipment to be bulky and cumbersome.

A reduction in overall mass of the device can be achieved by using components of lower mass where 

possible and in reducing the dimensions of the chute. 

EMBEDDED SYSTEM

An embedded system for data acquisition and processing can replace the notebook computer. In the 

sunlight, the computer screen was difficult to view. Also, it was difficult to keep the computer clean and 

free of debris. Additional work area was necessary for placement of the computer, and the computer is 

not rugged enough for everyday use in the field. 

An embedded system would be compact and mounted on the vibrating slope apparatus, and depending 

on the desired output, it should provide the same data-acquisition and processing capability of the 

current system at a much-reduced production cost. The system would have limited output capabilities, 

providing a discharge rate from which a workability index is calculated. The embedded system would 

be easier to use, with fewer input options and an automatic output. The embedded system should have 

increased stability and reliability.

Once the signal-processing, data-acquisition, and other test-method parameters are chosen, the 

embedded system can be designed. Embedded systems can be built from scratch or set up using 
48

multifunction-type kits. These kits provide a more economical solution for moderate production levels. 

Typically these kits contain data-acquisition components, a programmable microprocessor, ROM, 

RAM, and various binary and/or analog outputs on a single circuit board (figure 17). 

Measurement speed and resolution, as well as computational performance, are dependent on the 

parameters of the embedded system. 

load 

cell 1

load 

cell 2

load 

cell 3

Amp Amp

Amp

summation

Low - Pass

Filter

A / D

CPU

RAM

memory

Display

ROM

memory

Start

Test

2.1 LB/S

Vibrator Activation

Relay

Vibrate

Figure 17. Schematic of embedded system.

DEVELOPMENT PROGRAM

Several sophisticated signal-processing functions are currently implemented in the VSA. A 

development program should consist of additional performance studies of the parameters of these 

functions parameters as well as similar functions that may have implementation benefits. As an example, 

a polynomial curve fitted to the averaged data was found to be the most robust of several possible 

filtering techniques. However, there are many other filtering techniques (including adaptive and nonlinear 

methods) that were not explored. Because embedded systems are generally not flexible, it is important 

to invest a portion of the initial development effort into the research and design of what is being 

implemented. The goal of this phase should be to increase the reliability, accuracy, speed, and 

robustness of the final implementation.

Once a design has been selected, the implementation can follow many possible routes. As mentioned 

previously, the VSA is likely to have low-to-moderate production levels. Thus, a multifunction 

embedded-system kit will likely be the most economical solution. 

Circuit-simulation software will be used to model the analog and, to a lesser extent, the digital portion of 

the embedded system. These simulators are highly developed and include such things as controlled 

modeling of temperature and noise effects. As an example, the existing load-cell signal-conditioning 

consists of a regulated power supply, differential buffer amplifiers, a summer amplifier, and an optional 

sixth-order low-pass filter. Simulation Program with Integrated Circuit Emphasis (SPICE) models of 

these components are freely available from manufacturers. The models allow designers to simulate and 
49

test the components in a complete circuit. This modeling is important for “what-if” testing. For 

example, what if the power supply exceeds its output rating, or what if the ambient temperature is 

40.55 °C (105 °F)? This modeling also allows optimization of passive component values (e.g., 

resistors, capacitors, diodes).

A processor-based embedded system will consist of some low-level programming. Most of the more 

developed kits use interpreted languages such as BASIC (beginners all purpose symbolic instruction 

code) or some form of compiler. A Motorola or Intel processor in its raw state would be programmed 

in 1’s and 0’s. At this level the programmer must specify every detail, such as where in memory to get 

an input value and where to put a result. The bulk of the programming effort will likely consist of 

implementing the signal-processing and data-handling functions.

Most embedded systems have both analog and digital components. Some of the initial design effort will 

focus on selecting the most appropriate form of implementation. Each type of implementation has its 

own benefits and drawbacks depending on what is being implemented. Noise immunity, speed, circuit 

complexity, design complexity, and stability are factors that should be evaluated when choosing between 

an analog or digital implementation. 

At least one prototype should be constructed prior to constructing the final system. Various lessons and 

improvements from the prototype would be incorporated into the final system. End-user needs would 

determine the form of the final output. This could range from a scalar value displayed on a liquid crystal 

display (LCD) to onboard storage of data for serial or wireless downloads. The embedded system 

should be laid out with sufficient detail for accurate reproduction. This would include board level tuning, 

calibration, and evaluation procedures. 

The final system would be packaged in a hand-held pendant form (figure 18). This pendant would have 

(as a minimum) membrane (waterproof) buttons for user input and an LCD for displaying test results. 

The pendant and internal components would be designed to resist damage from temperature, shock, 

and moisture.
50

Embedded System

Figure 18. Hand-held pendant embedded system.
51

CHAPTER 8: CONCLUSIONS

The development of the VSA was intended to provide additional information on workability of lowslump fresh concrete. Where the slump measures as static yield stress, workability is a function of effort 

required to move the concrete under applied force especially required in the placement of low-slump 

concrete. It was concluded that the VSA test could be used as a measure of workability of concrete 

having low slump. The use of vibration to impart energy to the concrete makes the calculation for 

determining basic rheological values challenging. In practice, vibration is used to consolidate concrete, 

so that values derived in this manner actually simulate field practices.

The following conclusions were made during this investigation:

1. Low-slump concrete acts more like a plastic than a fluid. Vibration is necessary to make 

the concrete fluid for the measurements made using the VSA. The design of the VSA 

encompasses the use of vibration in its design.

2. The VSA is capable of determining the workability of low-slump concrete. Due to some 

scatter in the data, and the lack of a method that currently can measure fundamental 

parameters of rheological properties of low-slump concrete, additional testing of all 

concrete mixtures that might be used by the highway department are needed to refine the 

limits of the device for distinguishing small differences in mixture proportions.

3. The workability of a concrete mixture can be described using two points. For mixtures 

there is a straight-line relationship between the discharge rate and the angle of the chute. 

4. The VSA can be handled easily by a single operator. The device as constructed has a 

mass of about 136.1 kg (300 lb). The effect of mass of the VSA was minimized by 

mounting the unit on wheels and using mechanical advantage offered by extended handles. 

Some reduction in mass may be feasible, but much of the mass is in the vibrator and the 

support needed to evenly distribute the energy of the vibrator throughout the sample.
52

APPENDIX A: PATENTS PERTINENT TO 

CONCRETE WORKABILITY

Patent No. Year Name Inventor

3935726 1976 Apparatus for measuring viscosity of liquids Heinz

3967934 1976 Prothrombin timer Seitz, Bowen

4062225 1977 Rotational viscometer and plastometer Murphy and Ortm

4148215 1979 Apparatus for making rheological measurements Hofstetter

4299119 1981 Incremental rotary viscometer Figzgerald, Matusik, Nelson

4332158 1982 Slump testing device Osborne

4356723 1982 Process and apparatus for continuously measuring slump Fay

4388823 1983 Apparatus for automatically measuring viscosity of liquids Garnaud, Bouhier

4535621 1985 Proc. & app. for meas. rheol. props. of semi-solid bodies by

harmonic shear in rotation

Gervais, Vermeire, Cerf, 

Toux

4578989 1986 Concrete slump measuring device Scott

4879897 1989 Method and apparatus for determination of viscosity Booth, Edwards, Wrigley, 

Orth

5203203 1993 Viscometer for in situ monitoring Bryan, Bryan

5240225 1993 Plastic slump cone Workman, Fitzgerald

5321974 1994 Method and device for determining rheological properties Hemmings

5357785 1994 Method and device for determining rheological properties Hemmings

5359881 1994 Viscometer for sanitary applications Kalotay, Van Cleve

5437181 1995 Concrete slump testing Nasser
53

APPENDIX B: SYSTEMS EVALUATION FORMS

Powers and Wiler Apparatus Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High Measures shear failure

Works across a broad range of mixes Poor High Small aggregate size

Rheological simplicity Poor High

Practicality:

Sample testing Fair

In situ testing Poor Med

Equipment testing (pump, paver, etc.) Poor Med

Cost:

Equipment cost Fair Med

Testing time and labor Fair Med

Maintenance and serviceability 1

Availability Poor Med

User Friendliness and Simplicity:

Automation and simplicity Poor Med

Ruggedness:

Ruggedness of components Fair Low

Immunity to elements and handling Poor Low

1

 Unpublished or unacquired information.
54

Two-point Workability Technical Risk Comments

Ability:

Operates at multiple shear rates Good

Works across a broad range of mixes Fair High > 1-in slump w/ planetary 

drive

Rheological simplicity Fair Poor w/ planetary drive

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor Med

Cost:

Equipment cost Fair High

Testing time and labor Fair Med

Maintenance and serviceability Good

Availability Good Commercialized

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Fair

Immunity to elements and handling Poor Low
55

Ready-mix Truck Hydraulic Technical Risk Comments

Ability:

Operates at multiple shear rates Fair High Slippage may be a problem

Works across a broad range of mixes Fair

Rheological simplicity Poor High Sensitive to weight, load, 

etc

Practicality:

Sample testing Poor High

In situ testing Poor High

Equipment testing (pump, paver, etc.) Fair High Only mix-truck

Cost:

Equipment cost Fair Low

Testing time and labor Good

Maintenance and serviceability Good

Availability Good

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
56

Colebrand Tester Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Low

Works across a broad range of mixes Fair High >7-mm slump, <32-mm 

aggregate

Rheological simplicity Fair

Practicality:

Sample testing Good

In situ testing Good

Equipment testing (pump, paver, etc.) Fair Med

Cost:

Equipment cost Fair

Testing time and labor Good

Maintenance and serviceability 1

Availability Good Commercialized

User Friendliness and Simplicity:

Automation and simplicity Good

Ruggedness:

Ruggedness of components Fair

Immunity to elements and handling Good

1

 Unpublished or unacquired information.
57

BML Viscometer Technical Risk Comments

Ability:

Operates at multiple shear rates Good 0.0022-0.85 rps

Works across a broad range of mixes Fair >80-mm slump, <32-mm 

aggregate

Rheological simplicity Good 4 config, Coaxial cylinder

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Poor High

Testing time and labor Good

Maintenance and serviceability 1 Commercialized

Availability Good Commercialized

User Friendliness and Simplicity:

Automation and simplicity Good

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling 1

1

 Unpublished or unacquired information.
58

Moving Ball Viscometer Technical Risk Comments

Ability:

Operates at multiple shear rates Good

Works across a broad range of mixes Good Theoretically

Rheological simplicity Good Classic rheological technique

Practicality:

Sample testing Good

In situ testing Good

Equipment testing (pump, paver, etc.) Good

Cost:

Equipment cost Fair Med

Testing time and labor Fair Med

Maintenance and serviceability 1

Availability Poor Low

User Friendliness and Simplicity:

Automation and simplicity Good

Ruggedness:

Ruggedness of components 1

Immunity to elements and handling 1

1

 Unpublished or unacquired information.
59

Free Orifice Rheometer Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Med

Works across a broad range of mixes Fair High Different tubes required

Rheological simplicity Fair Med Without vibration

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Fair Med Specialized vibrator required

Testing time and labor Fair

Maintenance and serviceability Good

Availability 1

User Friendliness and Simplicity:

Automation and simplicity Poor Med

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good

1

 Unpublished or unacquired information.
60

Angles Flow Box Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor High

Rheological simplicity Poor High Mostly conceptual

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Good

Testing time and labor Fair

Maintenance and serviceability Good

Availability Poor Low

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
61

DIN Flow Table Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor High

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability Good ASTM1 standard

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good

1 American Society for Testing and Materials.
62

V-B Consistometer Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor High <2-in slump

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Good

Testing time and labor Fair

Maintenance and serviceability Good

Availability Good British Standard

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Fair
63

Compacting Factor Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Fair

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Good

Testing time and labor Fair

Maintenance and serviceability Good

Availability Good British Standard

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
64

K-slump Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor High Better for high slump

Rheological simplicity Poor High Does not test aggregate infl.

Practicality:

Sample testing Good

In situ testing Good Low Only measures near surface

Equipment testing (pump, paver, etc.) Med High

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability Good ASTM

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
65

Delivery Chute Torque Meter Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Low

Works across a broad range of mixes 1

Rheological simplicity Poor High

Practicality:

Sample testing Poor Med

In situ testing Poor High

Equipment testing (pump, paver, etc.) Good Delivery chute

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability 1Patented

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good

1

 Unpublished or unacquired information.
66

Delivery Chute Vane Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Low

Works across a broad range of mixes 1

Rheological simplicity Poor High

Practicality:

Sample testing Poor Med

In situ testing Poor High

Equipment testing (pump, paver, etc.) Good Delivery chute

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability Fair Patented

User Friendliness and Simplicity:

Automation and simplicity Poor Med

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good

1

 Unpublished or unacquired information.
67

Remolding Test (Powers) Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor Med

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Fair

Testing time and labor Fair High

Maintenance and serviceability Good

Availability Fair

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
68

Thaulow Tester Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Poor High Different test for high slump

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Fair

Testing time and labor Poor Med

Maintenance and serviceability Good

Availability Fair

User Friendliness and Simplicity:

Automation and simplicity Poor Med

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
69

Vibrating Slope Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Low

Works across a broad range of mixes Fair

Rheological simplicity Poor Med Complicated by vibrator

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor Med 

Cost:

Equipment cost Fair

Testing time and labor Fair Med

Maintenance and serviceability Good

Availability Good

User Friendliness and Simplicity:

Automation and simplicity Poor Low

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
70

Kelly Ball Technical Risk Comments

Ability:

Operates at multiple shear rates Poor High

Works across a broad range of mixes Fair

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Good

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability Good

User Friendliness and Simplicity:

Automation and simplicity Good

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
71

Wigmore Consistometer Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Low

Works across a broad range of mixes Poor Med Disturbed by large aggregate

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Poor Med

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Fair

Testing time and labor Fair

Maintenance and serviceability Good

Availability Good

User Friendliness and Simplicity:

Automation and simplicity Fair

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
72

BTRHEOM Rheometer Technical Risk Comments

Ability:

Operates at multiple shear rates Good

Works across a broad range of mixes Fair Med >2-in slump, >50-mm 

aggregate

Rheological simplicity Good

Practicality:

Sample testing Good

In situ testing Poor High

Equipment testing (pump, paver, etc.) Poor High

Cost:

Equipment cost Poor High

Testing time and labor Good

Maintenance and serviceability Fair

Availability Fair Commercialized (France)

User Friendliness and Simplicity:

Automation and simplicity Good

Ruggedness:

Ruggedness of components Fair

Immunity to elements and handling Fair
73

Ring Penetration Test Technical Risk Comments

Ability:

Operates at multiple shear rates Poor Med

Works across a broad range of mixes Poor High For fluid concrete

Rheological simplicity Poor High

Practicality:

Sample testing Good

In situ testing Good

Equipment testing (pump, paver, etc.) Poor Med

Cost:

Equipment cost Good

Testing time and labor Good

Maintenance and serviceability Good

Availability Fair

User Friendliness and Simplicity:

Automation and simplicity

Ruggedness:

Ruggedness of components Good

Immunity to elements and handling Good
74

APPENDIX C: HP-VEE DATA-ACQUISITION AND REDUCTION PROGRAM

Figure 19. Data-acquisition screen.
75

Figure 20. Data-acquisition program flow diagram and code (Sheet 1 of 2).
76

Figure 20. Data-acquisition program flow diagram and code (Sheet 2 of 2).
77

Figure 21. Data-acquisition code.
78

Figure 22. Data-reduction screen.
79

Figure 23. Data-reduction program flow diagram and code (Sheet 1 of 2).
80

Figure 23. Data-reduction program flow diagram and code (Sheet 2 of 2).
81

Figure 24. Data-reduction code.
82

APPENDIX D: VIBRATING-SLOPE APPARATUS TEST METHOD

Standard Test Method for Determining Workability of Freshly Mixed Hydraulic-Cement 

Concrete Using the Vibrating-Slope Apparatus 1

1. This test method covers determination of workability of low-slump hydraulic-cement concrete, 

both in the laboratory and in the field, using the vibrating-slope apparatus.

1.1 The values stated in SI units are to be regarded as standard. 

1.2 This standard does not purport to address all of the safety concerns, if any, associated 

with its use. It is the responsibility of the user of this standard to establish appropriate 

safety and health practices and determine the applicability of regulatory limitations 

prior to use.

1.3 The text of this standard references notes and footnotes which provide explanatory material. 

These notes and footnotes (excluding those in tables and figures) shall not be considered as 

requirements of the standard.

2. Reference Document

2.1 ASTM StandardC 172-Practice for Sampling Freshly Mixed Concrete (ASTM 1994d)

C 143/C 143M-Standard Test Method for Slump of Hydraulic-Cement Concrete (ASTM 

(1994c)

3. Summary of Test Method

3.1 A sample consisting of approximately 0.1 m3 sample of freshly mixed concrete is placed and 

compacted by vibrating in the chute. The chute is raised to predefined angle and vibrated to 

allow the concrete to flow out of the chute. The rate of discharge is measured and recorded. 

A second sample is prepared in the same manner and tested at a predefined angle different 

than that which was used in the first measurement. The workability is defined as the slope of 

the line defining the two discharge rates versus the angle of the discharge chute. 

____________________________________________________________________________

1

 American Society for Testing and Materials (ASTM). Reference information is found on page 97 at 

end of main text.
83

4. Significance and Use

4.1 This test method is intended to provide the user with a procedure to determine workability of 

freshly mixed hydraulic-cement concrete.

4.2 This test method is considered applicable to freshly mixed concrete having coarse aggregate 

of not greater than 37.5 mm in nominal maximum size

4.3 This test method is considered applicable to cohesive and noncohesive concrete.

Note 1—This test method may not adequately test concrete having slumps greater than 50 mm.

5. Apparatus

5.1 Angle indicator shall be a device with one flat edge that can be used to measure the angle of 

the floor of the chute when elevated to different angles.

5.2 Vibrating slope apparatus shall consist of chute measuring 0.6 m long by 229 mm wide (2 ft 

by 9 in) by 300 mm high (12 in). It shall be mounted with a vibrator such as to consolidate 

the sample as well as to cause the concrete to move during the testing. The vibrator shall have 

a 227.79-kg (500-lb) force capacity running at 4,000 RPM. The apparatus shall have the 

ability to raise the chute to different angles prior to initiating the test. The apparatus shall have 

a method by which the rate at which concrete is discharged from the chute can be determined. 

 One method as described in figure 25 is to mount the chute on load cells which can be used 

to continuously monitor the amount remaining in the chute, thus a calculation can be made to 

determine the rate concrete is discharged from the chute. Load-cells shall contain a 120-ohm 

bridge, 20-v maximum excitation (+/- 10 v implemented), and have a 227.78-kg (500-lb) 

tension/compression fatigue rating.

Figure 25. Vibrating-slope apparatus.

Vibration

mount
84

5.3 The data-collection program allows the user to change data-acquisition parameters (angle of 

incline, test description, data file and length of test). The length of time for the test can be set 

and the chute angle can be entered into the data. The time of test is usually set at 60 sec or 

less, and the test is usually stopped at less than 45 sec, depending on the chute angle and the 

workability of the concrete. When the user clicks the start button, the software activates a 

timer that keeps up with the elapsed test time. This start button also begins the data 

acquisition. During acquisition, 4,096 samples are collected at a rate of 100,000 

samples/second and then averaged to generate each data point. This sampling process is 

repeated until the stop button is pressed. A multiplier and offset are used to apply a 

calibration to the data. Periodic calibration is performed using dead weights.

5.4 Data files are used to construct a wave form that relates amplitude as a function of elapsed 

time. A seventh-order polynomial fit is applied to the data as a type of low-pass filter. A 

first-order derivative is then applied to the data to convert it from mass to mass flow rate. 

The maximum mass flow rate (R) that occurs in the first half of the data is then extracted.

6. Sample

6.1 The sample of concrete from which test specimens are made shall be representative of the 

entire batch and obtained in accordance with Practice C 172 (ASTM 1994d).

7. Procedure

7.1 Level the bottom of the chute. Dampen the chute and let drain so that no standing water 

remains in the chute. Place the concrete into the chute in a single lift, bringing the level of the 

concrete 4 in (10 cm) above the bottom of the chute. Using the vibrator attached to the 

apparatus, vibrate the concrete to consolidate the concrete. This should take approximately 5 

sec, depending on the stiffness of the concrete. 

7.2 Raise the angle of the chute to 10 deg, open the gate, and begin data acquisition and vibration.

7.3 Clean the residual concrete from the chute and relevel chute. Place a second sample of 

concrete into the chute to the same height and treat sample as in paragraph 7.1. After 

consolidation, raise the chute angle to 25 deg and repeat the test as described above.

8. Calculation

Calculate the workability index as follows: 

R = WA + C

R = rate of discharge, mass/unit time

A = angle of discharge, degrees

W = workability index

C = calculated yield offset
85

W = (R2 – R1)/(A2 – A1)

C = R –WA

9. Report

9.1 Report the angle of discharge chute and the discharge rate for each sequence.

9.2 Report W, C, and slump. The resistance of the concrete to move is a function of workability 

W and yield stress C as calculated or slump as measured by ASTM C 143 (ASTM 1994c).

10. Precision and Bias

10.1 No precision or bias information are available for this test method.

11. Keywords

11.1 Concrete; consistency; plasticity; slump; workability.
86

APPENDIX E: DETAILED DRAWINGS OF VSA Custom rotational vibration damper (Front View) (Side View) Rubber Bearing rubber Vibration Mounts

Vibration Mount Details

Figure 26. Details of vibration isolation mounts.
87

Portable Vibrating-Slope Device

12.7 mm (1/2 in)square tubing1/8 wall thickness

139.7

 63.5 

127 

138.7 

 50.8

203.2 

406.4 

 609.6 

 1244.6 

381.00 

203.2 

304.8 

Figure 27. Dimensions of VBA device.
88

50.8

Portable Vibrating-Slope Chute

 12.7 12.7 

101.6

12.7 L-iron

RubberMat

(Front View)

(Side View)

(Top View)

152.4

292.1

Figure 28. Chute walls are isolated from vibration, and the floor of the chute is ribbed to minimize slippage.
89

 101.6

666.8

15.9

31.75 

 25.4

50.8

 101.6

2

Figure 29. Rear view of VBA.
90

25.4

63.5

 203.2 

101.6

368.3

939.8

Figure 30. Map view of the VBA.
91

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