t AlllDO

NATL INST OF STANDARDS & TECH R.I.C,

A1 11 00992964

Clltton, James R/Polymer Impregnaled har TA435 .U58 V83;1976 C.I NBS-PUB-C 1976 BUILDING SCIENCE SERIES

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

i1 olymer Impregnate

Cement Pastes
The Building Science Series

The Building Sciciur Series disseminutes technical information developed at the National Bureau of Standards on

l)uilfiin<; materials, components, systems, and whole structures. The Series presents research results, test methods, and performance criteria related to the structural and environmental functions and the durability and safety characteristics of building elements and systems. These publications, similar in style and content to the NBS Building Materials and Structures Reports (1938-59),

are directed toward the manufacturing, design, construction, and research segments of the building industry, standards organizations, and officials responsible for building codes. The materia] for this Series originates principally in the Center for Building Technology of the NBS Institute

for Applied Technology. The publications are divided into three general groups: Building Systems and Processes;

Health, Safety and Comfort; and Structures and Materials. For further information regarding these publications

please contact the .Scientific and Professional Liaison Section, Center for Building Technology, Institute for Applied Technology, National Bureau of Standards, Washington, D.C. 20234.

I See mailing list announcement on last |)age j
Polymer Impregnated Hardened Cement

Pastes and Mortars

James R. Clifton, James E. Fearn

and Erik D. Anderson

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

ATIOWAL BDHKAO

or f)TA>n}AIU>8 LrBBABT JUN 2 1976

no. %3

1

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, SecTe\QTy

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assisianf Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued April 1976
Library of Congress Cataloging in Publication Data

Clifton, James R.

Polymer impregnated hardened cement pastes and mortars. (NBS building science series; 83) Bibliography: p. Supt. of Docs, no.: C 13.29:2/83

1. Polymer-impregnated cement—Testing.

2. Polymer-impregnated mortar—Testing. I. Fearn, James E., joint author. II. Anderson, Erik D.. joint author. 111. Title. IV. Series: United States. National Bureau of Standards. Building

science series; 83. TA435.U58 no. 83 [TA435j r590'.021 [666'.94] 76-608072

National Bureau of Standards Building Science Series 83

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 83, 21 pages (Apr. 1976) CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1976

For .sale by the Superintendent of Documents, U.S. Government Printing Office. Washington, D.C. 20402 (Order by SD Catalog No. C13.29/2:83). Price 55 cents. (Add 25 percent additional for other than U.S. mailing).
Contents

Page 1. Introduction 1

1.1. Background 1

1.2. Project Objectives 1

1.3. Approach to Fulfill Objectives 1

2. Materials and Procedures 2

2.1. Cement 2

2.2. Sand 2

2.3. Cement Paste and Mortar 2

2.4. Monomer and Catalysts 2

2.5. Polymer Impregnated Cements and Mortars 2

3. Experimental Methods and Results 3

3.1. Porosity Determinations 3

3.1.1. Mercury Porosimeter Method 3

3.1.2. Nitrogen Capillary Condensation Method 3

3.1.3. Results 4

3.2. Scanning Electron Microscopy 8

3.2.1. Experimental Procedures 8

3.2.2. Results 8

3.3. Fracture Studies 10

3.3.1. Experimental Procedures 10

3.3.2. Results 11

3.4. Strength Properties 12

3.4.1. Experimental Procedures 12

3.4.2. Results 13

4. Discussion 14

4.1. Improvements in Mechanical Properties 14

4.2. Test Methods for Polymer Impregnated Mortars and Concretes 14

5. Summary and Conclusions 15

6". References 15

iii

Polymer Impregnated Hardened Cement Pastes and Mortars

James R. Clifton, James E. Fearn, and Erik D. Anderson

Polymer impregnated hardened cement pastes and mortars have l)een prepared and their properties compared to those of unimpregnated specimens. Specimens were made by impregnating, under pressure, dried and evacuated precast hardened cement pastes and mortars with methyl

methacrylate, which was subsequently thermally polymerized. Tile effects of the microstructure of the cement pastes and mortars on the performanie of jjolymer impregnated cement pastes and

mortars were investigated using specimens with a wide range of porosities which were prepared by

varying the water to cement ratio and the curing times prior lo impregnation.

The properties of impregnated and unimpregnated specimens were investigated by: scanning

electron microscopy; porosity determinations; fracture mechanics studies; and strength deter- minations. The polymer impregnated mortars had compressive and fiexural strengths and fracture toughnesses which were substantially higher than unimpregnated mortars.

Key words: Cement; compressive strength; fiexural strength; fracture mechanics; mortar; polymer

impregnation; polymer impregnated cement; polymer impregnated mortar; porosity; scanning

electron microscopy.

1. Introduction

1.1. Background

A cooperative program was initiated in 1967 by the Brookhaven National Laboratory (BNL), Office of Saline Water (OSW), and the U.S. Department of the

Interior's Bureau of Reclamation (USBR), to improve

the properties of portland cement mortars and concretes by developing concrete-polymer composite materials [1]^ Three distinct types of materials were in- vestigated: (1) polymer-cement concrete (PCC), a pre- mixed mixture of water, portland cement, and aggregate to which monomer or resin is added during mixing and subsequently polymerized; (2) polymer-concrete (PC), consisting of an aggregate mixed with a monomer or resin which is subsequently polymerized:

and (3) polymer-impregnated concrete (PIC), which

consists of a hardened precast portland cement concrete impregnated with a monomer system which is polymerized in situ. To date, the most successful approach to improving the strength and durability

properties of a portland cement concrete has been with

PIC [1-5].

Remarkable improvements in many of the strength

and durability properties of portland cement mortars and concretes have been obtained when their pores have been filled with polymers. For example, the compressive strength of a control concrete was increased

from 5,270 psi (36.3 MN/m^) to 20,260 psi (139.7

MN/m') when the concrete was fully impregnated

with ca. 6 percent by weight of poly [methyl methacrylate] (PMMA) [6]. Similar improvements were measured in tensile strengths of the concrete. The

durabilities of PIC when exposed to freeze-thaw cycling, acids and corrosive salts were also substantially improved compared to the control concretes. The promise of PIC for building and other construction was soon recognized and a number of gov- ernment agencies are now collaborating with BNL and

^ Figures in brackets indicate literature references at the end of the paper.

USBR in investigating specific applications such as bridge decks [7-10], underwater structures [11], concrete sewer pipe [5], improving underground sup- port in mines [12], and prefabricated housing [13].

Since the issuance of a patent on March 2, 1971, to BNL for the PIC process [14], other countries have

commenced its commercial application and are de- veloping a variety of products [15]. Polymer impregnated mortars and concretes appear to have great

potential for use as building materials and in other

areas of civil engineering [16-17], and are potential

substitutes for possibly more expensive building materials, such as steel, glass, aluminum, wood and brick. Most of the previous studies have been directed towards improving the strength and durability of PIC

by optimizing the impregnation and polymerization

processes, and by using different polymer systems.

Only a few studies on the effects of the microstructure

of the inorganic matrix on the performance of the composites have been reported [18-21]. These studies emphasized the relationship between porosity and

strength. This is an area of great importance as the microstructural characteristics of the matrix could

have a strong influence on the ultimate properties of

the composite.

1.2. Project Objectives

The objectives of this project are to identify the important microstructural properties which affect the mechanical properties of polymer impregnated hardened cement pastes and mortars and to investigate

models for interpreting the relationship observed. The

results of this project are intended to contribute to the knowledge of polymer impregnated mortars and concretes.

1.3. Approach to Fulfill Objectives

A range of hardened cement pastes (HCP) and

mortars was prepared which represents a wide range

1
of microstructural features. The microstructural fea- tures which were varied intentionally were the phase

composition and phase distribution of the hydrated cement component and the porosity and pore size distribution of the matrix. Control materials, which

were not impregnated, were characterized by their microstructural features and by selected mechanical

properties. The same properties of companion speci- mens modified by being impregnated with selected polymers were determined.

2. Materials and Procedures

2.1. Cement

Two Portland cements, both meeting the ASTM

specifications for Type 1 portland cement [22], ob- tained from the NBS Cement and Concrete Reference

Laboratory (CCRL) have been used. The portland cement identified as No. I, (CCRL samples No. 30), was used in the early portion of the study but, due

to limited supply, it was replaced by cement No. II

( CCRL sample No. 34). The chemical and compound

compositions of the cements are given in table 1. Tricalcium silicate was obtained from an industrial cement research laboratory.

Table 1. Chemical analysis of portland cements

Cement No. I Cement No. II Constituent Percent Percent

SiO. 20.9 20.9

AloOa 5.0 6.1 Fe=03 2.9 2.3 CaO 63.1 65.0 MgO 2.9 1.1 SO3 2.9 2.6 Loss" 1.6 1.5

Insol." 0.3 0.3 NaS 0.15 0.08 KS 0.67 0.38 Compound Composition'

3 CaO • SiO. 52.0 54.1 2 CaO • SiO» 20.7 19.1 3 CaO • AI2O3 8.3 12.3 4 CaO • ALO3 • Fe..03 8.8 7.0

" Ignition loss. Insoluble residue.

' Calculated by methods in standard specification for Portland Cement ASTM Designation C150-68 [22].

2.2. Sand

The sand was a natural Ottawa silica sand conforming to the requirements of ASTM Designation C109

[23].

2.3. Cement Paste and Mortar

The cement pastes and mortars were prepared by

following the methods given in ASTM Designation

C305 [24], (except that the mixing times were slightly

varied to obtain homogeneously dispersed mixes for mortars with a water to cement ratio of 0.4) using an

epicylic type (0.47m') mixer. All mortars were pre- pared with a cement to sand ratio of 1:2.75 (by

weight) . Specimens were removed from their molds

after 24 hours, and cured under lime water (water

saturated with calcium oxide) until tested or impregnated.

2.4. Monomer and Catalysts

Methyl methacrylate (MMA), inhibited with one ppm hydroquinone was mixed before use with a catalyst consisting of either one percent (by weight)

2,2' azobis [2-methyl-propionitrile] (AMN) or one

percent benzoyl peroxide (BPO). The catalysts were

stored in a refrigerator until used.

2.5. Polymer Impregnated Cements

and Mortars

The impregnation process usually consisted of the following sequence: (1) Specimens were dried at 160

°C for 18 hours; (2) the dried specimens were evacuated for 4 hours in a stainless steel reaction vessel (height of 5 inches, O.D. of 5 inches and wall thickness

of 0.5 inches (12.7 X 12.7 X 1.27 cm) (fig. 1) ; (3) the specimens were soaked in MMA at ambient temperature under a pressure of 30 psi (0.21 MN/m^) of N2(g) (the MMA was transferred to the reaction vessel without breaking the vacuum and then No(g) was

admitted) for 16 hours; when the specimens were removed from the MMA, (4) they were quickly wrapped in aluminum foil enclosed in plastic bags; and

(5) placed in a water bath at 81 °C (to thermally

polymerize the MMA) for 18 hours.

Figure 1. Impregnation vessel and evacuation apparatus.

2
Early in the study it was found that thermal polymerization of MMA with BPO was not complete at 81 °C., whereas apparent complete polymerization was achieved at 81 °C, using AMN as the catalyst.

Strong odors of unpolymerized MMA were detected when specimens of hardened cement paste with sup- posedly polymerized MMA, using BPO as catalyst, were fractured or cut. These specimens also lost weight

corresponding to about 50 percent of the amount of intruded MMA, when heated to 70 °C for several hours. These findings are in agreement with the ob- servations of Auskern of BNL [25].

Difficulties were encountered in producing polymer

impregnated hardened cement paste test specimens

of suitable test size for many of the tests. When heated

to remove evaporable water, the hardened cement

paste specimens cracked badly and, therefore, only a limited number of studies were performed on polymer

impregnated hardened cement pastes. In contrast, excellent polymer impregnated mortar specimens were producd by the above described impregnation process.

3. Experimental Methods and Results

The mechanical properties, fracture characteristics and porosities of polymer impregnated specimens were measured and compared with those of the un- impregnated (control) materials to determine the changes in properties attributable to filling the pores

with a polymer. The experimental methods and ex- perimental results are given in this section.

3.1. Porosity Determinations

A knowledge of the open pore volumes of unimpregnated hardened cement pastes and mortars is important because it is this volume that is available

for polymer intrusion. By measuring the porosity of

the polj'mer impregnated cements and mortars, the

effectiveness of the polymer impregnation process in

filling the pores can be ascertained. Two standard methods were used to estimate porosities, fl) mercury porosimetry and (2) nitrogen

capillary condensation.

3.1.1. Mercury Porosimeter Method

A mercury porosimeter capable of achieving pres- sures up to 60,000 psi (414 MN/m-) was used. Pore

diameters from 100 to 0.003 /xm can be measured with

this type of instrument. The pore diameters were cal- culated by the Washburn [26] equation for cylindrical pores

P =

Cosd

(1)

where

P is the applied pressure, y is the surface tension of mercury, 6 is the contact angle between mercury and

the solid, and d is the smallest diameter of pore through which mercury will advance at pressure P.

A value of 473 dynes per cm was used for y, and 0 was assumed to be 130 degree [27]. Introducing these values into eq 1, and rearranging, the following

relationship is obtained [28] :

d ifim)

d (ju,m) =

175

P (psi)

12.1 X 10' P(N/m-)

(2)

which was used in this study.

Broken fragments, from 1 to 2 grams, of normal and

impregnated cements and mortars were used for the porosity measurements. A specimen of PMMA 1^2- inches (3.7 cm) long and % inch (1.0 cm) in diameter weighing 3.12 grams was also used for the porosity study.

The normal cements and mortars received the same

cure treatments and heat treatments as the impregnated specimens. The specimens were cured under lime water prior to being treated. Corrections for the compressibility of the porosimeter system were made by running blanks. Both pressurization and depressurization studies were performed. In the pressurization study, the applied pressure was increased incrementally and the cumulative volume of intruded mercury was measured

at each incremental increase in pressure (in this context, cumulative volume denotes the summation of the volumes of mercury intruded in all preceeding and the present pressure-increase step). On the basis of these

data, intruded pore volume versus pore diameter dia- grams are constructed, which in turn give an indication of the total volume of mercury intruded, the pore volume in any pore range, and the mode pore diameter (the range of pore diameters corresponding to the region of steepest slope of the pore volume-pore diameter curves). In the depressurization studies, the pres- sure is released and the mercury ejection volume is measured. For a pore structure without bottlenecks,

all the mercury should be ejected. The fraction of mercury retained in the specimen after the pressure has been reduced to atmospheric pressure is termed

the retention factor. High retention factors are indi- cative of a pore system with a significant number of

constructions.

3.1.2. Nitrogen Capillary Condensation Method

A commercial nitrogen absorption instrument was

used for the capillary condensation studies. The capillary condensation method is essentially limited to measuring pore diameters between 0.06 to 0.003 /xm, for the reasons discussed in reference [29].

The pore size distribution information was obtained using a computer program based on the method

of Barrett, Joyner, and Halenda [29].

The pore size distributions of the unimpregnated

and impregnated hardened cement pastes with water

3
to cement ratio of 0.6 were determined by the nitrogen

condensation method. These specimens were taken

from the same sample that had been fractured to obtain specimens for the mercury porosimetry study.

3.1.3. Results

Intruded volume-pore size distribution curves of impregnated and unimpregnated hardened cement

pastes and mortars, based on the mercury penetration

method, are shown in figures 2 and 3. Pressurization

and depressurization curves of mortars and hardened

cement pastes with water to cement ratios of 0.6 are compared in figure 4. The measured porosity of PMMA shown in figure 5, is probably due to its compressibility, because nitrogen absorption studies on polymer impregnated mortars indicated that poly

[methyl methacrylate] was pore free. The adsorption- pore size distribution curve obtained with the nitrogen

condensation study is shown in figure 6 for the un- impregnated hardened cement paste, with a water to cement ratio of 0.6. The adsorption-pore size distribu- tion curve for the impregnated hardened cement paste

is not shown because the nitrogen condensation method

indicated that all the accessible pores of the impregnated hardened cement paste were filled with PMMA

PRESSURE, N/m^

6.9xl0' 6.9x10* 6.9«I05 6.9x10^ 6.9x10^ 6.9«I0^

I I I \ I

POROSITY OF HARDENED CEMENT PASTE (HCP)

WATER TO CEMENT RATIO A PRESSURIZATION OF UNIMPREGNATED HCP — 0.6

B. DEPRESSURIZATION OF UNIMPREGNATED HCP — 0.6

C- PRESSURIZATION OF UNIMPREGNATED HCP —0.4

0 PRESSURIZATION OF IMPREGNATED HCP —0.4

PRESSURE, PSI

Figure 2. Penetration volume curves of impregnated and un- impregnated hardened cement paste, cured for 28 days, meas- ured by the mercury porosimetry method.

PRESSURE, N/m2

69xl0' 6.9x10'' 6.9x10^ 6 9x10^ 6.9x10^ 69xl0'

0 10

A

B

1 1

WATER TO CEMENT RATIO PRESSURIZATION OF UNIMPREGNATED MORTAR 0.6

DEPRESSURIZATION OF UNIMPREGNATED MORTAR 0.6

1 I 1

C PRESSURIZATION OF IMPREGNATED M0R1AR 0.6

D PRESSURIZATION OF UNIMPREGNATED MORTAR 0 4

E PRESSURIZATION OF IMPREGNATED MORTAR 0 4

0 095

B^ ^.^^^^ 0090

D /

A /

C

0025

1

1

I 10 102 10'' lO"* 105 PRESSURE, PSI

Figure 3. Penetration pore volume curves of impregnated and unimpregnated mortars, cured for 28

days, determined by the mercury porosimetry method.

4
PRESSURE, N/m2

Q06

0,05

O04

O03

0.02

0.01

10" 10^ PRESSURE, PSI

Figure 4. Mercury porosimetry pressurization and depressurization curves for polymer-impregnated mortars and hardened cement pastes, cured for 28 days.

PRESSURE, N/m^

6.9M03 6,9M0'* 6.9x10^ 6.9«I06 6.9»i0''' 69«I08

'°| \ \ \

, \

.09 —

.08 —

,07 —

" .06 —

10 100 1,000 10,000 100,000

PRESSURE, PSI

Figure 5. Apparent porosity or compressibility of PMMA, determined by the mercury porosimetry method.

5
Figure 6. Cumulative pore size distribution curve for hardened cement paste with water to cerment ratio of 0.6, determined by the nitrogen condensation method.

Figure 7. Comparison of pore distribution of hardened cement paste (based on the curves in figs. 2 and 4).

in the region of 0.06 to 0.003 fxm. Differential pore

size distributions, based on the mercury intrusion

curves, corrected for the apparent porosity of PMMA,

of the cements and mortars are presented in figures 7 and 8. The resuhs of the mercury porosimeter study

are compiled in table 2. The intruded volume-pore size distribution curves

(fig. 2 and 3) for the two unimpregnated hardened

cement pastes are similar to those previously reported

[30]. The measured porosity (table 2) of the hardened cement paste with a water to cement ratio of 0.4 was 0.154 cmVg as compared to 0.298 cmVg for

a water to cement ratio of 0.6 (fig. 2). The main

difference in capillary pore structure of the two

pastes lies in the region of large pores; the paste with

the water to cement ratio of 0.6 having more pores

6
5 0.03

Q 0.02

PORE SIZE DISTRIBUTION IN MORTAR

WATER TO CEMENT RATIO

A UNIMPREGNATED MORTAR — 0.6

B IMPREGNATED MORTAR —0.6

C UNIMPREGNATED MORTAR — 0 4

D IMPREGNATED MORTAR — 0.4

10"! 10° PORE DIAMETER, jim

Figure 8. Comparison of pore distribution of mortars (based on the curves in fig. 3).

larger than 0.1 /Am than the paste with the water to cement ratio of 0.4. These findings are in agreement

with the study of Powers and Brownyard [31] on the water adsorption of pastes with different water to cement ratios. Consistent with a greater total porosity, the polymer loading for the hardened cement paste

with a water to cement ratio of 0.6 was 25.6 percent,

by weight, compared with a polymer loading of 15.6

percent, by weight, for the paste with the 0.4 water to cement ratio. The porosities of the two pastes were

reduced by about 86 percent when impregnated.

Table 2. Mercury porosimetry studies of specimens

cured for 28 days

Percent Specimen Ratio loading Porosity

(cnrVg)

Retention W/C PMMA factor ° HCP" 0.4 0.154

.4 15.6 .040 Mortar' 0.4 0.095

.4 8.6 .025 HCP 0.6 0.298 0.54

.6 25.6 .055 .88 Mortar 0.6 0.090 0.40

.6 7.4 .027 .67

° Ratio of volume of mercury remaining in the pores of atmospheric pressure to the volume intruded at 60,000 psi (414 MN/m=).

Hardened cement paste.

' Mortars prepared wth cement to sand ratio of 1 :2.75, by

weight.

The total porosities of the two mortars (fig. 3) were

both close to 0.09 cm^/g, in contrast to the larger dif- ferences in porosity for the pastes. However, the pore

size distributions of the two mortars were significantly

different from each other (fig. 8) ; the pore size dis- tribution plot for the mortar with a water to cement

ratio of 0.4 was relatively uniform in the range of 100 to 0.01 /xm. while the pores of the mortar with a water to cement ratio of 0.6 were concentrated in the range of 0.01 to 0.8 /j,m, and tailed-off from either

side. Possibly, the closeness in total porosity of the two mortars can be attributed to observed water

bleeding which could reduce the porosity of the mortar

with the higher water content. The polymer loadings

of the mortars were 8.6 percent for the mortar with

the water to cement ratio of 0.4, and 7.4 percent for

the mortar with the 0.6 water to cement ratio and the reductions in porosity were about 75 percent.

Depressurization studies were performed, following

pressurization to 60,000 psi (414 MN/m^), on the hardened cement paste and mortar with 0.6 water

to cement ratios (fig. 2—4 and table 2). The retention

ratios (ratio of volume to mercury remaining in the pores at atmospheric pressure to the volume intruded

at 60,000 psi (414 MN/m^) ) were 0.54 for the unimpre£;nated hardened cement paste and 0.40 for the unimpregnated mortar. Small retention values are in- dicative of pores with relatively uniform cross sec- tions and large values indicate pores with constric- tions [32], e.g., bottle-shaped pores with narrow

necks [33]. The retention values for the impregnated

7
hardened cement paste and mortar were 0.88 and 0.67,

respectively, suggesting that the polymer is increas- ing the constrictions, i.e., decreasing the pore openings and not completely filling the pores. Studies at Brookhaven have suggested [3] that the MMA monomer fills only about 80 percent of the total cement

pore volume available to the MMA and that on polymerization, there is about a 20 percent shrinkage in volume so only about 64 percent of the pore volume

is actually filled with PMMA. The reduction in porosity

measured in the present study was between 75 to 88 percent suggesting that a number of pores are

sealed-off by a film of PMMA. Such a film could be

either deformed or penetrated at the high pressure

applied in the mercury porosimeter technique. PMMA

is readily compressed or deformed at high pressures,

as is shown in figure 5.

It is evident that the results of mercury porosimetery

studies on polymer impregnated materials must be

carefully analyzed. An example of contradictory in- formation from the two porosity techniques (mercury

intrusion and nitrogen absorption) concerns the pores

smaller than 0.06 /am; the presence of a considerable

volume of pores having diameters below 0.06 ,/xm in the impregnated hardened cement paste (water to cement ratio of 0.6 ) , is suggested by the porosimetry

study (fig. 7) ; however, the total porosity of this impregnated hardened cement paste measured by the nitrogen condensation method was infinitesimal. The nitrogen condensation study also resulted in a

different pore size distribution curve (fig. 6) than the mercury porosimetry study (fig. 2) for the unimpregnated hardened cement paste with a water to cement

ratio of 0.6. The high retention values measured in

this study indicates that the mercury intrusion curves

are probably biased in favor of small pores [32],

which possibly accounts for this discrepancy. Diamond

[34] has also noted that discrepancies exist between

the pore size distributions based on the two methods.

3.2. Scanning Electron Microscopy

One of the most sensitive microscopic techniques

available for the study of the microstructural features

of hydrated cements and mortars is the use of the scanning electron microscope (SEM). This technique was used in the present study to ascertain differences

in the fracture modes of unimpregnated and impregnated hardened cement pastes and mortars, and to examine the structures of these materials.

3.2.1. Experimental Procedures

A commercial scanning electron microscope, equipped with a camera and cathode ray tube, was used

to obtain the scanning electron micrographs.

The general method of preparing specimens for the SEM study was to fracture a specimen and, soon as

possible (usually within 10 min.), evaporate a gold or platinum-palladium film on the fresh fracture surface. Most of the specimens were formed in a special mold

similar to those designed by Williamson [35]. These

molds can be opened to expose a fresh fracture surface

and the molds can be placed directly into the SEM.

3.2.2. Results

Scanning electron micrographs of unimpregnated

and impregnated mortars and of hydrated tricalcium

silicate (3Ca0"Si00 pastes are shown in figures 9

to 15. The fracture surface of unimpregnated mortars

usually passes through the cement paste matrix and,

as shown in figure 9, the sand grains remain covered

with a layer of cement paste. A few craters observed

in the fracture surface were caused by sand grains

being pulled loose from the cement paste matrix, but

these sand grains were also observed to be covered

with a layer of paste. An uncoated sand grain was

never observed in the analysis of over 50 micrographs

of the fracture surfaces of mortars. Therefore, the weaker component in the unimpregnated mortar is the cement paste matrix. In contrast, the fracture surface

of the companion polymer impregnated mortar fre- quently passed through the sand grains (fig. 10).

Based on the observation of the fractured sand grains

in the micrograph, it is evident that the strength of

the cement paste matrix was increased to at least the range of strengths of the sand grains. The compressive strength of the unimpregnated mortar was 2450

psi (16.9 MN/m-) and was increased to 19,600 psi

(135 MN/m-) when impregnated with 9.2 percent by

weight, PMMA.

A typical interface between a sand grain and

cement paste in an impregnated specimen is shown in figure 11 at a high magnification. The sand grain

has been fractured and two small cracks extend per- pendicularly to the sand-cement interface. Little, if any, polymer is observable at the sand-cement paste

interface.

Figure 9. Scanning electron micrograph of fracture surface of unimpregnated mortar with water to cement ratio of 0.6 and

cured for 14 days.

8
Figure 10. Scanning electron micrograph of fracture surface

of impregnated mortar with water to cement ratio of 0.6, cured for 14 days, loaded with 9.2 percent PMMA (on a weight basis).

Figure 11. Scanning electron micrograph of interface between sand grain and cement paste matrix of polymer impregnated

mortar (water to cement ratio of 0.5, cured for 28 days, 9.6 percent PMMA on a weight basis).

Hydrated tricalcium silicate pastes were studied to obtain a basic knowledge of the behavior of the most

important cementitious constituent of portland cement.

This was done because micrographs of the hydrated

tricalcium silicate system are easier to interpret than

those of Portland cements which have 4 major components besides varying degrees of impurities [36].

C D

Figure 12. Scanning electron micrographs of fracture surface

of tricalcium silicate paste (water to cement ratio of 0.5 cured for 28 days).

A. Hydration products and some tricalcium silicate. B. Enlargement of central portion of A. C. Enlargement of unliydrated material in B. D. Micro- graph of another area of the specimen showing hydrated material having a

foil-like appearance.

The micrograph of tricalcium silicate paste, water

to cement ratio of 0.5 and cured under lime water for 28 days, is shown in figure 12 where B and C are enlargements of the central portion of A, and D is an enlargement of an area in the upper left side of A. The presence of an unhydrated core of 3CaO • SiOo which has been uncovered is evident in figures 12B

and C. This unhydrated core is encircled by a ring

of inner hydration product, the outer boundary of which is in contact with the outer product columnar

zone (the basis for this interpretation is given in refer- ence [35]). The needle-like structure present in figures

12B and C are crystals of hydration products of 3CaO • SiOo and this structure forms the spiny network

of the hydrating paste [37]. The structure in the center of figure 12D was previously observed in the pres- ent studies and it has a foil-like appearance. Micrographs of tricalcium silicate paste, water to cement ratio of 0.5 and cured for 56 davs, are shown

in figure 13. The spiny network has interlocked and

the hydrated products are more clearly visible than

at 28 days.

The large blocks of solid material in figure 13B and

D are probably calcium hydroxide crystals.

9
D

Figure 13. Scanning electron micrographs of fracture surface

of tricalcium silicate cured for 56 days ( water to cement

ratio of 0.5).

A. Hvdrated tricalcium silicate. B. Enlargement of central area of A, with

well-defined spiny network. C. Enlargement of B, showing the outer hydration products of tricalcium silicate. D. Mixture of hydrated tricalcium

silicate and calcium hydroxide crystals.

Micrographs of the 56 day old tricalcium silicate paste impregnated with PMMA are shown in figures

14 and 15, with the micrographs taken at high magnifications being area enlargements of figure 14A.

The growth of crystals of portlandite (Ca(0H)2) in small cavities can be seen in figures 14B, C, and D. These crystals are identified as portlandite by their

size and fracture pattern and on the basis of the

analysis of Williamson [35]. It has been observed in many micrographs that the polymer seems to obscure

the spiny network of the hydrated paste, for example

as in figure 15A and D. A cavity partially filled with

PMMA is present in figures 15B and C. The polymer

appears to line the walls of the cavity, thereby re- ducing its volume but not completely filling it.

3.3. Fracture Studies

Fracture studies of unimpregnated and impregnated

mortars were performed by making subcritical, crack- growth-rate measurements. These measurements can

lead to an understanding of the mechanisms causing

slow crack growth [38], thereby giving an insight to means of predicting or improving the material's resistance to fracture. Estimates of life times of materials can also be obtained by fracture mechanics

studies [39]. While the fracture toughness of cement

paste has been measured by several investigators [40-

43] and the critical stress intensity factor of PIC

has been briefly studied [43-44], measurements of the subcritical, slow crack growth properties of polymer impregnated cement pastes, or related sys- tems have not been previously reported.

A brief description of the fracture mechanics terms

used in this paper is presented herein. For a crack to grow under static loading, two conditions must be fulfilled: (1) the stress must be sufficiently high to initi- ate fracture; and (2) the energy released by crack

growth must be at least as much as that required to form the new fracture surfaces. The stress field near

the crack then will be proportional to the product of

the stress in the material times the square root of the crack length. This stress field is termed the stress Intensity Factor, K,, i.e.,

K, oc (Tg y/a (3)

where cts is the stress in the material near the crack

and a is the crack length. Usually Kj is related to the

stress applied at a boundary, da, by the equation,

K.^CTaY^ (4)

where F is a dimensionless constant which depends on the geometry of the loading and the crack configuration. Different terminology is used for K, de- pending on the value obtained for the crack velocity;

if the crack velocity is less than 10~^ m/s the stress intensity factor, Kj, is used, but if the velocity is greater than 10"^ m/s then the term "critical stress Intensity Factor", K,c, is used. (The higher velocity indicates that the cracks have grown to the critical size which results in catastrophic failure). In the present study, the double torsion method de- scribed by Williams and Evans [45], was used to measure the stress intensity factor [K,) and the crack

velocity (V). Evans [46] has shown that the stress intensity factor is uniquely related to crack velocity

for brittle materials, and, therefore, the K, versus V

plot is a material property (i.e., the same K, versus V

plot would be obtained regardless of the specimen

size or the loading techniques).

3.3.1. Experimental Procedures

The test specimens were 4V8-inches long, 2^/4- inches wide and approximately l/^-inch thick (10.5

X 5.7 X 0.63 cm). They were grooved along their length with a thin diamond saw to about half their thickness, and then notched at one end of the groove

to help initiate the crack (fig. 16) . The load was ap- plied at two points spaced at equal distances from

the crack initiating notch, using an electromechanical

testing machine. Both Ki and V were measured by

the load-relaxation method [45]. A value of 0.22 was

assumed for Poisson's ratio of both the unimpreg10
C D

Figure 14. Scanning electron micrographs of the fracture sur- face of polymer impregnated tricalcium silicate ( water to cement ratio of 0.5, cured for 56 days).

A. Low magnification micrograph of surface. B. Area enlargement of A,

sfiowing fractured crystals, probably calcium hydroxide crystals. The spiny network, shown in figure 13B, is apparently obscured by the PMMA. C

and D are close-ups of the fractured crystals observed in B. Note lack of

detail of the hydration products of tricalcium silicate as compared to figure 13.

nated and impregnated mortars on the basis of the work at Brookhaven National Laboratory [5], and the value of E calculated from resonance frequency meas- urements (ASTM Designation C215 [47]) were used.

3.3.2. Results

Data of V versus K, are plotted in figures 17-19,

for unimpregnated and impregnated mortars with water to cement ratios of 0.4, 0.5, and 0.6, cured for

either 14 or 28 days. Compared to other studies, the variability in data for the unimpregnated speci- mens from the same mix was small. The data for the impregnated mortars were more scattered, possibly

due to differences in the internal distribution of the polymer between supposedly identical specimens.

The unimpregnated mortars all have K, values below 1.0 MN/m^/", compared to the impregnated

mortars which have much higher values of Ki. This

indicates that the latter are much tougher materials

and will withstand greater stresses before failing. This

conclusion is consistent with the higher K,c value measured in this study for the impregnated mortars

(table 3), than for the unimpregnated mortars. CerFlCURE 15. Enlargements of sectors shown in micrograph of

figure 14A.

A. Hydrated tricalcium silicate particles apparently covered with PMMA.

B. Cavity partially filled with PMMA. C. Enlargement of cavity in B. in- dicating that the polymer seems to line the walls of the cavity. D. Close-up

of A, showing PMMA deposited on the spiny network.

6

ro

ID

Figure 16. Double torsion specimen for fracture mechanics measurement.

Table 3. Critical stress intensity factor, Kic, for motors'^

w/c Ratio Age (days) Percent polymer loading Kic (MN/mV=)

0.4 28 0 0.83

0.5 28 11.2 2.56

0.6 14 10.1 2.49

" Cement to sand ratio of 1 :2.75, by weight. Percent by weight.

11
Figure 17. Subcritical crack-growth data for unimpregnated

and impregnated mortars of water to cement ratio of 0.4.

Kj values below 1.0 MN/m^/- are for the unimpregnated mortar.

I0"5

>

I0"8

1

1

1 11

' " 1' /

' /I / / u / / ','/'

r

1 14 DAY

1 28 DAY

1 1 1 1

KT(MN/m3^2)

Figure 18. Subcritical crack-growth data for unimpregnated and impregnated mortars of water to cement ratio of 0.5. Kj values below 1.0 MN/mV" are for the unimpregnated mortar.

Figure 19. Subcritical crack-growth data for unimpregnated and impregnated mortars with water to cement ratio of 0.6.

Kj values below 1.0 MN/m^ aj-g fQj. the unimpregnated mortar.

tainly, at identical stress levels, the polymer impregnated mortars will resist failure for much longer times

than the unimpregnated mortars. Changes in either the water to cement ratio or the curing age did not have a significant effect on the frac- ture properties of the unimpregnated and impregnated

mortars. Possibly the cement to sand ratio of the mortars and the strength of the sand are more important variables and should be investigated.

3.4. Strength Properties

The compressive, tensile-splitting, and flexural strengths of unimpregnated and impregnated mortars and hardened cement pastes were measured by the appropriate ASTM methods for two purposes: (1) to serve as a rapid means of monitoring the efficiency of the impregnation process; and (2) to determine

the effects of changes in microstructural features on

these mechanical properties. Filling the pores of the cement matrix with PMMA can be expected to result in substantially increased compressive strengths [48],

and an approximately three-fold increase in strength

is quite reasonable in the case of mortars [49].

3.4.1. Experimental Procedures

The compressive and splitting-tensile strengths of 2 inch cubes (5.1 cm cubes) were measured by follow- ing the methods outlined in ASTM Designation C109

[23] and ASTM Designation C496 [501], respectively.

Flexural strengths of 1.58 X 1-58 X 6.3 inch (4.0

X 4.0 X 16 cm) bars were measured using a 3-point

loading arrangement by the method outlined in ASTM

Designation C348 [51].

12
3.4.2. Results

Values of the measured strength properties are hsted in table 4 for unimpregnated and impregnated

materials. The standard deviation in percent polymer

loadings was about 0.6 percent within each series of impregnated specimens. The coefficient of variation of the strength values for the unimpregnated specimens was about 10 percent of the listed averages, and

about 5 percent of the listed averages for the impregnated specimens. The average ratios of the strengths

of the impregnated specimens compared to the unimpregnated specimens were: compressive strength, 4.0, and flexural strength, 5.8. Changes in the compressive strengths of the polymer

impregnated mortars (table 5) did not appear to be

closely related to changes in water to cement ratios and curing ages. However, two interesting trends developed when considering the flexural and splitting

tensile strengths of the impregnated specimens, which

were: the flexural strengths at a given water to cement

ratio decreased as the curing age increased; and also the splitting tensile strengths for the mortar with a water to cement ratio of 0.5 decreased as the age

increased. These trends are possibly associated with

different amounts of MMA intruded into the pores of

the mortars because of changes in the porosity of the cement paste matrices, and indicate that increased

amounts of intruded MMA increase the flexural and

tensile strengths of the composites.

Table 4. Strength properties of impregnated " and unimpregnated mortars and hardened cement paste

Laboratory desig- nations of specimens '' Cement

No. w/

Age

(days)

Percent

loading

Compressive

strength " Splittingtensile strength ' Flexuralstrength ^ PMMA psi (MN/m^) psi (MN/m=) PSI (MN/m=)

20-M I 0.4 47 10.0L12]'' 18300[2] (126) 3450[2] (23.8)

.4 47 none 6900L2] (47.5) 30-HCP I 0.5 35 17.7[10] 18900[3] (130) 2460E1] (16.9)

.5 35 none 7100[2] (48.8) 850E1] (5.86) 35-M I 0.6 14 9.2111] 19600 [2] (135)

.6 14 none 2450L2] (16.9) 36-M 11 0.5 7 9.5[13] 25480 [5] (176) 3068f5l (21.1)

.5 14 9.4L12] 24500[5] (170) 302015] (20.8) 4560E2] (31.4)

.5 14 none 3120[3] (21.5) 781 [4] (5.38)

.5 28 8.3[14] 24300[1] (167) 2420 [5] (16.9) 4041 [2] (28.5)

.5 28 none 5250[2] (36.1) 792L5] (5.46) 37-M II 0.6 14 9.1L13] 22960[3] (158) 4768[4] (32.8)

.6 14 none 3900 [3] (26.9) 831E5] (5.72)

.6 28 8.0[12] 22650[3] (156) 3866 [5] (26.6)

.6 28 none 5110[3] (35.2) 828 [5] (5.70) 38-M II 0.4 14 9.0113] 22600 [2] (156) 4842 [1] (33.4)

.4 28 none 3470[2] (23.9) 885 [4] (6.10)

.4 28 7.8[8] 24140L5] (166) 4253[3] (29.3)

' Impregnated under pressure of 30 psi (0.21 MN/m^) of N2(g).

M indicates mortar specimens, while HCP identifies hardened cement paste specimens.

' Water to cement ratio.

^ Percent by weight.

'ASTM Designation C109 [23]. 'ASTM Designation C496 [50]. ^ASTM Designation C348 [51].

^ Numbers in brackets give the number of specimens tested.

13
Table 5. Effect of water to cement ratio and curng ages on mechanical properties of polymer impregnated mortars

w/c

Ratio " Age

{ days)

Polymer

I perceni iyLi\i\} Compressive strength " Flexural strength * Splitting tensile strength *

Psi (MN/m=) Psi (MN/m") Psi (MN/m=)

0.4 14 9.0 22600 (156) 4842 (33.4) 7 ft 24140 (166) 4253 (29.3) — —

0.5 7 9.5 25480 (176) 3068 (21.1) 14 9.4 24500 (170) 4560 (31.4) 3020 (20.8) 28 8.3 24300 (167) 4041 (27.8) 2450 (16.9)

0.6 14 9.1 22960 (158) 4768 (32.8) 28 8.0 22650 (156) 3866 (26.6)

" Water to cement ratio. Percent by weight.

''ASTM Designation C109 [23]. "ASTM Designation C496 [50]. •ASTM Designation C348 [51].

4. Discussion

Polymer impregnated mortars and concretes are a new class of materials which require further study to delineate the relationships between material composition and structure, and performance. In this context, strength improvements, areas for future studies and

test methods are discussed in the following.

4.1. Improvements in Mechanical Properties

The fracture toughness (sec. 3.3) and strength

properties, (sec. 3.4) of mortars have been found

in this study to be increased by over 300 percent by

the incorporation of PMMA. A model has been de- veloped by Auskern [52] to explain the improvements

in the mechanical properties of mortars and concretes when their pores are filled with a polymer. He

related the improvements to a decrease in porosity

of the cement matrix and to increased bonding be- tween the cement matrix and aggregate. The present

study confirmed that the porosity of the cement matrix

is substantially reduced by more than a factor of three

(table 2), by the incorporation of PMMA. However,

no evidence for increased bonding between the cement

matrix and aggregate was obtained from scanning

electron microscopic studies of fractured surfaces

(sec. 3.2). Failure of the unimpregnated mortars took

place by fracturing of the cement matrix; the sand

grains were left loaded with a layer of cement paste

indicating that the matrix aggregate bond was not

the source of failure. The fracture surface of the impregnated mortar passed through both the cement

matrix and sand grains. Based on these findings, it can only be concluded that the strength of the cement

matrix was increased to the strength level of the sand

grains by the impregnation with, and the subsequent

polymerization of MMA.

The effect of the polymer on the mechanical properties of mortars and concretes can also be rational- ized by consideration based on the fracture mechanics

approach of Griffith [53]. In this approach when

cracks in a brittle material reach a critical size catastrophic failure takes place. The polymer, by filling the pores of the cement matrix as well as voids and

microcracks, reduces the size and numbers of cracks

and flaws, etc., which can grow to critical size under

stress. This results in an increase in the stress re- quired to induce failure. Therefore, larger stresses are required to cause the failure of polymer impregnated

materials than the unimpregnated materials.

4.2. Test Methods for Polymer Impregnated

Mortars and Concretes

Polymer impregnated mortars and concretes will probably have two main uses for which different test methods are possibly applicable: (1) where high

strength/weight ratios are important; and (2) where

durability to aggressive environments is required.

These different uses will require different test methods.

The strength properties of mortars and concretes most often measured, and upon which criteria are

established, are the compressive and tensile strengths.

It is apparent that properly prepared polymer-impregnated mortars and concretes will have strength properties many times higher (3 to 6 fold improvement)

than the unimpregnated materials. Possibly the frac- ture mechanics approach can be used as a supplement to the conventional strength measuring tech- niques and, therefore, should be more thoroughly

investigated.

When polymer impregnated materials are used

because of the increased resistance to aggressive en- vironments, the relationships between durability and

the microstructure of the material should be investi- gated. Possibly, the traditional type of long-term

durability testing (i.e., freeze-thaw cycling, resistance,

weather exposure, etc. ) can be partially supplanted by

porosity determinations, once the relationships be- tween pore structure and durability are determined.

14
5. Summary and Conclusions

The objectives of this project were to identify the important microstructural properties which possibly

could affect the mechanical properties of polymer

impregnated hardened cement pastes and mortars, and

to identify models to interpret the relationships observed. Results of this study indicate that the microstructural properties such as porosity and phase composition, of the mortars, prior to impregnation, have little effect on the compressive strength and fracture mechanic properties of the polymer impregnated mortar. However, when the porosity of a mortar of a specific water to cement ratio was decreased by increasing the curing times, then a definite decrease was measured

for the flexural and tensile strengths of the polymer

impregnated mortar specimens. These strength de- creases can be attributed to a decreased amount of intruded MMA into the specimens. If the highest at- tainable flexural or tensile strengths are desired, the specimens should be impregnated at early ages. The porosities of hardened cement paste and

mortars were reduced by at least a factor of three by

impregnation with MMA. Mercury intrusion studies

of polymer impregnated hardened cement paste and

mortars are difficult to interpret because of the ap- parent compressibility of PMMA at high intrusion

pressures. However, high mercury retention factors indicate that the residual pores in the impregnated

materials have constricted entrances, i.e., bottle neck

or ink spot shapes.

The fracture characteristics of mortars changed

when they were impregnated with MMA. Unimpregnated mortar specimens failed by fracture through the cement paste matrix, with the sand grains left cov- ered with a layer of cement. The fracture surface of

the impregnated specimens pass through both the cement paste matrix and sand grains. No evidence for increased bonding between the cement paste matrix

and aggregate, often attributed to polymer impregnation of mortars and concretes, was obtained in this study.

The authors thank Anthony Evans for experimental

assistance in the fracture mechanics studies and Harry

Anderson, NBS, and Jan Skalny, Martin Marietta

Laboratories, for their respective contributions of the Portland cements and tricalcium silicate.

6. References

[1] Steinberg, M., Dikeou, J. T., Kukacka, L. E., Backstrom,

J. E., Columbo, P., Rubenstein, S., Kelsch, J. J., and

Manowitz, B., Concrete-Polymer Materials, First Topical Report. BNL 50134 (T-509) and USER General Report No. 41, Dec. 1968.

[2] Steinberg, M., Dikeou, J. T., Kukacka, L. E., Backstrom,

J. E., Columbo, P., Hickey, K. B., Auskern, A., Rubenstein S., Manowitz, B., and Jones, C. W., Concrete- Polymer Materials, Second Topical Report, BNL

50218 (T-560) and USBR REC-ICE-70-1, Dec. 1969.

[3] Dikeou, J. T. Steinberg, M., Cowan, W. C, Kukacks,

L. E., DePuy, G. W., Auskern, A., Smoak, W. G., Columbo, P., Wallace, G. B., Hendrie, J. M., and Manowitz, B., Concrete-Polymer Materials, Third Topical

Report, NSBR REC-ERC-71-6 and BNL 50275 (T-

(602) Jan. 1971.

[41 Dikeou, J. T., Steinberg, M., Cowan, W. C, Kukacks, L.

E., Depuy, G. W., Auskern, A., Smoak, W. G., Colombo,

P., Wallace, G. B., Hendrie, J. M., and Manowitz, B., Concrete-Polymer Materials, Fourth Topical Report, USBR REC-ERC-72010 and BNL 50328. Jan. 1972.

[5] Kukacka, L. E., DePuy G. W., Auskern, A., Causey, F.

E., Columbo, P., Cowan, W. C, Romano, A., Lockman,, W. T., Steinberg, M., and Smoak, W. G., Concrete-Poly- mer Materials. Fifth Topical Report, BNL 50390 and USBR REC-ERC-73-12, Dec. 1973.

[6] Table 16, p. 32, Concrete-Polymer Materials, Fourth

Topical Report, ibid. [7] Steinberg, M., Kukacka, L. E., Columbo, P., Auskern, A., Reich, M., and Pike, R., Concrete-Polymer Materials for Highway Applications, Progress Report No. 1, BNL

15395, Sept. 1970.

[8] Kukacka, L. E., Romano, A. J., Reich, M., Auskern, A., Colombo, P., Klamut, C. J., Pike, R. G., and Stein- berg, M., Concrete-Polymer Materials for Highway

Applications, Progress Report No. 2, Federal Highway

Administration RD-73-7, April 1972.

[9] Reich, M., and Koplik, B., Analysis of Bridge Decks

Using Polymer Impregnated Concrete, Polymers in Concrete SP-40, pp. 247-281, American Concrete Institute, Detroit (1973).

[10] Fowler, D. W., Houston, J. T., and Paul, D. R., PolymerImpregnated Concrete Surface Treatments for High- way Bridge Decks, Polymers in Concrete SP^O, pp. 93-117, American Concrete Institute, Detroit (1973).

[11] Albedtsen, N., and Haynes, H. H., Polymer-Impregnated

Concrete Shepherical Hulls for Seafloor Structures, Polymers in Concrete SP^O, pp. 119-148, American

Concrete Institute, Detroit (1973).

[12] Waide, C. H., Reich, M., Colombo P., Klamut, C. J., Beller, M., and Steinberg, M., Mine Safety and Under- ground Support Structures, Rock Impregnation and Pumpable Rockbolt Development, First Annual Report, Informal Report BNL 16187, Sept. 1971. [13] Birkimer, D. L., and Lott, J. R., Polymerized Light-Weight

Structural Elements, Report No. 37, presented at conference on Radiation and Isotope Techniques in

Civil Engineering, Brussels, October 20-30, 1970. [14] Steinberg, M., Colombo, P., Kukacka, L. E., and Manowitz, B., Method for Production Plastic Impregnated

Concrete, assigned to U. S. Atomic Energv Commission,

United States Patent, 3,567,496, March 2, 1971. [15] Lizzio, A. M., Status of concrete-polymer composites

in the United States and Abroad, Public Roads, 37,

No. 4, 129 (1973).

[16] Depuy, G. W., and Dikeou, J. T., Development of Polymer-Impregnated Concrete as a Construction Materials for Engineering Projects, Polymers in Concrete SP

40, pp. 35-56, American Concrete Institute, Detroit (1973).

[17] Chen, W. F., and Dahl-Jorgensen, E., Polymer-Impregnated

Concrete as a Structural Material, Mag. Cone. Res. 26

[86], 16 (1974).

[18] Auskern, A., and Horn, W., Some properties of polymerimpregnated cements and concretes, J. Am. Ceram.

Soc. 54, 282 (1971).

[19] Gebauer, J., and Coughlin, R. W., Preparation, Properties and corrosion resistance of composites of cement mortar and organic polymers. Cement and Concrete Research 1, [20] Manning, D. G., and Hope, B. B., The effect of porosity on the compressive strength and elastic modulus of polymer-impregnated concrete. Cement and Concrete

187 (1971).

15
[21] Manning, D. G., and Hope, B. B., The Influence of Porosity and Partial Drying on Properties of Polymer

Impregnated Mortar, Polymers in Concrete SP 40, pp. 191-203, American Concrete Institute, Detroit (1973).

[22] Standard Specification for Portland Cement. ASTM

Designation C150-68, ASTM Standards Part No. 9 (1969).

[23] Standard Method of Test for Compressive Strength of Hydraulic Cement Mortars (using 2 in. cube speci- mens). ASTM Designation C 109-64.

[24] Standard Method for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency.

ASTM Designation C 305-65.

[25] Private discussion at Brookhaven National Laboratory,

Dec. 19, 1973.

[26] Washburn, E. W., Proceedings of the National Academy

of Sciences 7, 115 (1921).

[27] Winslow, N. W., and Shapiro, J. J., An Instrument for the Measurement of Pore-Size Distribution by Mercury

Penetration, ASTM Bulletin No. 236, p. 39 (Feb.

1959).

[28] Ulmer, G. C, and Smothers, W. J., Application of mercury porosimetry to refractory materials. Am.

Ceram. Soc. Bull. 46 ( 6), 649 (1967).

[29] Barrett, E. P., Joyner, L. G., and Halenda, P. 0., The

determination of pore volume and area distribution in porous substances. I. Computation from nitrogen

isotherms, J. Amer. Chem. Soc. 73, 373 (1951).

[30] Auskern, A., and Horn, W., Capillary porosity in hard- ened cement paste J. Testing and Evaluation 1 (1), 74 (1973).

[31] Povifers, T. C, and Brownyard, T. L., Studies of the Physical Properties of Hardened Portland Cement

Pastes, Bulletin, Portland Cement Association (1948).

[32] Hill, R. D., An improved method of interpreting mercury

penetration data. Trans. Brit. Ceram. Soc. 59, 198

(1960).

[33] de Boer, J. H., The Shape of Capillaries, in the Structure and Properties of Porous Materials, D. H. Everett and F. S. Stone, Eds. pp. 68-94 ( Butterworths Scientific Publications, London, 1958).

[34] Diamond, S., A critical comparison of mercury porosimetry and capillary condensation pore size distributions

of Portland cement pastes. Cement and Concrete Research I, 531 (1971).

[35] Williamson, R. B., Solidification of Portland Cement,

Report No. UCSESM 70-23, Structural Engineering

Laboratory, University of California, Available from NTIS, Order No. AD 720-755.

[36] Lea, F. M., The Chemistry of Cement and Concrete,

third edition. Chemical Publishing Company, N.Y., (1971).

[37] Diamond, S., Applications of Scanning Electron Microscopy to the Study of Hydrated Cement, IIT Res. Inst., Chicago, III, pp. 385-92 (1970).

[38] Wiederhorn, S. M., Subcritical Crack Growth in Ceramics,

in Fracture Mechanics of Ceramics, Vol. 2, R. C. Bradt, D.P.H. Hasselman, and F. F Lange, Ed.s, pp 613-646 (Plenum Press, N. Y., 1974).

[39] Lange, F. F., Origin and Use of Fracture Mechanics, in Fracture Mechanics of Ceramics, Vol. 1, R. C. Bradt, D.P.H. Hasselman, and F. F. Lange, Eds., pp. 1-15 (Plenum Press, N.Y., 1974).

[40] Brown, J. H., Measuring the fracture toughness of cement paste, Mag. Conor. Res. 24 [81], 185 (1962).

[41] Moavenzadeh, F., and Kuguel, R., Fracture of concrete,

J. Mater. 4 [3] 497 (1969).

[42] Nadeau, J. S., Mindess, S., and Hay, J. M., Slow crack growth in cement paste, J. Amer. Ceram. Soc. 57 [2], 51 (1974).

[43] Aleszka, J. C. and Beaumont, P.W.R., The Fracture Behavior of Plain, Polymer-Impregnated and Fiber- Reinforced Concrete, Master's Thesis, UCLA-ENG7396, Materials Dept., School of Engineering and Applied Science, UCLA. Los Angeles (1973).

[44] Glucklich, J., The Reinforcement of Concrete by Poly- mers, Final Report, TDM 74-14, Technion-Israel Insti- tute of Technology (1974).

[45] Williams, D. P., and Evans, A. G., A simple method for studying slow crack growth, J. Testing and Evaluation,

1, [4], 264 (1973).

[46] Evans, A. G., Fracture Mechanics Determinations, in Fracture Mechanics of Ceramics, Vol. 1, R. D. Bradt, D.P.H. Hasselman, and F. F. Lange, Eds., pp. 17-48 (Plenum Press, N.Y., 1974).

[47] Standard Method of Test for Fundamental Transverse, Longitudinal, and Torsional Frequencies of Concrete Specimens, ASTM Designation C215-60.

[481 Auskern, A., A Model for the Strenth of Cement-Polymer

and Concrete Polymer Systems, BNL 13493 R-3,

Radiation Processing Section, Brookhaven National

Laboratory, Upton, N.Y. (1970).

[49] Auskern, A., The Strength of Concrete-Polymer Systems,

BNL 12890, Radiation Processing Section, Brookhaven

National Laboratory, Upton, N.Y. (1968).

[50] Standard Method of Test for Splitting Tensile Strength

of Cylindrical Concrete Specimens, ASTM Designation: C496-69.

[51] Tentative Method of Test for Flexural Strength of Hydraulic Cement Mortars, ASTM Designation: C348-

63. [52] Auskern, A., A Model for the Strength of Cement- Polymer and Concrete-Polymer Systems. BNL 13493

R-3, Radiation Processing Section, Brookhaven National Laboratory, Upton, N.Y. (1970).

[53] Griffith, A. A., The phenomena of rupture and flow in

solids, Phil. Trans. Roy. Soc. (London), A221, 163

(1921).

*U. S. GOVERNMENT PRINTING OFFICE: 1976 —210-801/208

16
U.5.. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. public;ation or report no. NBS BSS-832. Gov 'i Accession

No.

3. K( ( ipicnt *s Acc<;sMon No.

4. TITLE AND SUBTITLE

Polymer Impregnated Hardened Cement Pastes and Mortars

5. Publication Date April 1976

6. Performing Organization Code

7. AUTHOR(S)

James F. Clifton, James E. Fearn, and Erik D. Anderson

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

National Bureau of Standards

Department of Commerce

Washington, DC 20234

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Number: 76-608072

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Polymer impregnated hardened cement pastes and mortars have been prepared and their

properties compared to those of control specimens. Specimens were made by impregnating

dried and evacuated precast hardened cement pastes and mortars with methyl

methacrylate, under pressure, which was thermally polymerized. The effects of the

micros tructure of the cement pastes and mortars on the performance of polymer

impregnated mortars were determined by preparing specimens with a wide range of

porosities by varying the water to cement ratio and the curing times prior to impregnation

The properties of impregnated and control specimens were investigated by: scanning

electron microscopy; porosity determinations; fracture mechanics studies; and strength

determinations. The polymer impregnated materials had compressive and flexural

strengths, moduli of elasticity, and fracture toughnesses which were substantially

higher than unimpregnated materials.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons ) Cement; compressive strength; flexural strength; fracture

mechanics; polymer impregnated cement; polymer impregnated mortar; porosity; scanning

electron microscopy

18. AVAILABILITY InT Unlimited

1

' For Official Distribution. Do Not Release to NTIS

|-y--bOrder From Sup. of Doc, U.S. Government Printing Office ^^Washineton. D.C. 20402. SD Cat. No. C13. 29/Zr83

1 ! Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

21. NO. OF PAGES

21

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

$0.55

USCOMM-DC 29042-P74

ANNOUNCEMENT OF NEW PUBLICATIONS IN

BUILDING SCIENCE SERIES

Superintendent of Documents,

Government Printing Office,

Washington, D.C., 20402

Dear Sir:

Please add my name to the announcement list of new publications to be

issued in the series: National Bureau of Standards Building Science Series.

Name

Company

Address

City State Zip Code

(Notification key N-339)

NBS TECHNICAL PUBLICATIONS

PERIODICALS JOURNAL OF RESEARCH reports National Bureau

of Standards research and development in physics,

mathematics, and chemistry. It is published in two sections, available separately:

• Physics and Chemistry (Section A)

Papers of interest primarily to scientists working in these fields. This section covers a broad range of physical and chemical research, with major emphasis on

standards of physical measurement, fundamental constants, and properties of matter. Issued six times a year. Annual subscription: Domestic, $17.00; Foreign,

$21.25.

• Mathematical Sciences (Section B)

Studies and compilations designed mainly for the mathematician and theoretical physicist. Topics in mathematical statistics, theory of experiment design, numerical analysis, theoretical physics and chemistry, logical

design and programming of computers and computer

systems. Short numerical tables. Issued quarterly. Annual subscription: Domestic, $9.00; Foreign, $11.25. DIMENSIONS/NBS (formerly Technical News Bulletin) —This monthly magazine is published to inform

scientists, engineers, businessmen, industry, teachers,

students, and consumers of the latest advances in science and technology, with primary emphasis on the work at NBS. The magazine highlights and reviews such

issues as energy research, fire protection, building tech- nology, metric conversion, pollution abatement, health and safety, and consumer product performance. In addition, it reports the results of Bureau programs in measurement standards and techniques, properties of matter and materials, engineering standards and services, instrumentation, and automatic data processing.

Annual subscription: Domestic, $9.45; Foreign, $11.85.

NONPERIODICALS Monographs—Major contributions to the technical liter- ature on various subjects related to the Bureau's scientific and technical activities. Handbooks—Recommended codes of engineering and

industrial practice (including safety codes) developed

in cooperation with interested industries, professional

organizations, and regulatory bodies.

Special Publications—Include proceedings of confer- ences sponsored by NBS, NBS annual reports, and other

special publications appropriate to this grouping such

as wall charts, pocket cards, and bibliographies.

Applied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists,

engineers, chemists, biologists, mathematicians, computer programmers, and others engaged in scientific and technical work.

National Standard Reference Data Series—Provides

quantitative data on the physical and chemical properties of materials, compiled from the world's literature and critically evaluated. Developed under a world-wide

program coordinated by NBS. Program under authority

of National Standard Data Act (Public Law 90-396). NOTE: At present the principal publication outlet for these data is the Journal of Physical and Chemical

Reference Data (JPCRD) published quarterly for NBS

by the American Chemical Society (ACS) and the American Institute of Physics (AIP). Subscriptions, reprints, and supplements available from ACS, 1155 Sixteenth

St. N. W., Wash. D. C. 20056.

Building Science Series—Disseminates technical infor- mation developed at the Bureau on building materials,

components, systems, and whole structures. The series presents research results, test methods, and performance criteria related to the structural and environmental functions and the durability and safety characteristics of building elements and systems.

Technical Notes—Studies or reports which are complete

in themselves but restrictive in their treatment of a

subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often serve as a vehicle for final reports of work performed at NBS under the sponsorship of other' government agencies.

Voluntary Product Standards—Developed under pro- cedures published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations.

The purpose of the standards is to establish nationally

recognized requirements for products, and to provide

all concerned interests with a basis for common understanding of the characteristics of the products. NBS

administers this program as a supplement to the activities of the private sector standardizing organizations. Federal Information Processing Standards Publications (FIPS PUBS)—Publications in this series collectively constitute the Federal Information Processing Standards Register. Register serves as the official source of information in the Federal Government regarding stand- ards issued by NBS pursuant to the Federal Property and Administrative Services Act of 1949 as amended,

Public Law 89-306 (79 Stat. 1127), and as implemented

by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal

Regulations).

Consumer Information Series—Practical information, based on NBS research and experience, covering areas

of interest to the consumer. Easily understandable language and illustrations provide useful background

knowledge for shopping in today's technological

marketplace.

NBS Interagency Reports (NBSIR)—A special series of interim or final reports on work performed by NBS for

outside sponsors (both government and non-government). In general, initial distribution is handled by the sponsor; public distribution is by the National Technical Information Service (Springfield, Va. 22161) in paper

copy or microfiche form.

Order NBS publications (except NBSIR's and Biblio- graphic Subscription Services) from: Superintendent of Documents, Government Printing Office, Washington,

D.C. 20402. BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-mwareness and literature-survey

bibliographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service A literature survey issued biweekly. Annual subscription: Domestic, $20.00; foreign, $25.00.

Liquefied Natural Gas. A literature survey issued quarterly. Annual subscription: $20.00. Superconducting Devices and Materials. A literature

survey issued quarterly. Annual subscription : $20.00.

Send subscription orders and remittances for the preceding bibliogi-aphic services to National Bureau of Standards, Cryogenic Data Center (275.02)

Boulder, Colorado 80302. Electromagnetic Metrology Current Awareness Service Issued monthly. Annual subscription: $24.00. Send

subscription order and remittance to Electromagnetics

Division, National Bureau of Standards, Boulder,

Colo. 80302.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. D C. 20234

OFFICIAL BUSINESS

Penalty for Private Use. $300

POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE COM-2 1 5 U.S.MAIL

SPECIAL FOURTH-CLASS RATE BOOK

YEARS

1901 IMBS- 137B