bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delayed Ettringite Formation at Brewer Stadium, Boone, North Carolina
Authors: Ozol MA , Strand W 
Published: January 2010

Abstract
Brewer Stadium, Appalachian State University, Boone, NC, was constructed in 1962 using steam-cured precast lightweight concrete channel sections for the bleacher seats. Spalling of the bleachers was observed within a few years. By 1995, approximately 375 of 860 precast elements exhibited sufficiently severe cracking and delamination that reconstruction of the stadium was the most economical alternative.
The destructive process causing the cracking and delamination of the 375 units is DEF. The (fibrous, crystalline) ettringite occurs in the concrete intergrown in the paste, in veins and cracks throughout the mortar, filling voids in the mortar, and as rims in the paste around coarse- and fine-aggregate particles. Also observed, in the same spatial relationships as the crystalline ettringite, and commonly intergrown with it, was a clear, gel-like material with low-order, mottled birefringence. This appears to be the same proto-ettringite material as described by Mielenz et al. (1995).
Visibly undistressed members exhibit incipient forms of the same DEF features that are well developed in the distressed members. Sulfate analyses show no difference between distressed and undistressed members.
The physical and chemical circumstances of the failure conform to the model presented by Heinz and Ludwig, whereby cements capable of promoting DEF meet the sulfate limitations of ASTM Specification for Portland Cement (C 150), and DEF occurs due to excessive temperature reached during heat curing of concretes made with cements of a particular sulfate to alumina ratio.
These results support the view that revisions to current standards for portland cement are unnecessary, and that what is necessary is adherence to maximum temperature guidelines during production of heat-cured concrete products.
Petrographic evidence supports the view that expansion due to DEF is caused by swelling of a proto-ettringite gel—by water absorption, similar to alkali-silica gel—that forms in the paste and that later, following expansion and crack formation, crystallizes in the cracks and peripheral separations, forming the familiar veins and rims of fibrous ettringite.
This mechanism speaks to the origin of the expansive force in the general case of sulfate attack, and to why the formation of the delicate, fibrous, ettringite crystals in the cracks is not the mechanism that exerted sufficient force to cause the cracks in which the ettringite occurs.
Autoradiographic Methods for Identifying Alkali-Silica Reaction Gel
Authors: Livingston RA , Aderhold HC , Hover KC , Hobbs SV , Cheng YT 
Published: January 2010

Abstract
The current method for identifying ASR gel uses ultraviolet fluorescence to image the distribution of a uranyl acetate stain that has a high affinity for the silica gel. However, UV fluorescence can also be produced by other minerals. As an alternative, methods based on imaging natural or activated radiation have been investigated. Potassium in the gel can be imaged by both the beta and gamma ray radiation of 40K. The storage photostimulable phosphor imager (SPP) system can have spatial resolution as fine as 50 μm and a dynamic range of &gt;105. Digital images of 40 K distribution in actual concrete cores with K2O% &lt;1% have been acquired with counting times on the order of 24 h. Similarly, using the conventional uranyl acetate stain approach, the distribution of uranium can be imaged by the natural radioactivity of its daughter products, using the SPP plates with counting times on the order of 7 days. Alternatively, the uranium can be imaged by inducing fission and using fission track detectors. Autoradiography can thus be used to survey concrete structures for areas of possible ASR. Further research is necessary to standardize the methods and to evaluate their performance relative to the conventional stain methods.
Determining Elastic Properties of Concrete Using Vibrational Resonance Frequencies of Standard Test Cylinders
Authors: Kolluru SV , Popovics JS , Shah SP 
Published: January 2010

Abstract
A technique for determining the elastic material constants of a concrete test cylinder from longitudinal resonance frequencies is proposed in this paper. The proposed technique permits calculation of both the material constants (E and μ) from one relatively simple measurement. The formulation is based on an accurate three-dimensional vibration analysis of intermediate length cylinders using the Rayleigh-Ritz method. First, the test procedure is described and an illustrative example is given. The accuracy of the method is then verified through tests on steel and aluminum cylinders. Test results from concrete cylinders are then presented. A favorable comparison between the values of the elastic modulus predicted by the proposed technique, the standard ASTM test procedure and direct mechanical measurement is shown.
Alkali-Silica Reaction in Concrete Caused by Densified Silica Fume Lumps: A Case Study
Authors: Marusin SL , Shotwell LB 
Published: January 2010

Abstract
Petrographic and scanning electron microscopy (SEM) studies of a lightweight aggregate concrete exhibiting severe cracking indicate that a relatively large, nonuniformly distributed and densified formation (lumps) of silica fume (SF) may have substantially contributed to the mechanism of concrete deterioration. The lumps of SF (from 100 to 800 μm in size) were observed to react in a manner similar to reactive aggregates with cement alkalies to form silica gel. Such an alkali-silica reaction (ASR) is often associated with an expansion that leads to cracking of concrete. The poor dispersion of SF also increases the effective water to cement-plus- pozzolan ratio of portions of the concrete, possibly contributing to drying shrinkage cracks. The early drying shrinkage cracks may have led to increased water penetration and subsequent ASR.
Properties of Concrete with Ground Ultrafine Phosphorus Slag
Authors: Feng NQ , Shi YX , Ding JT 
Published: January 2010

Abstract
Ultrafine phosphorus slag (UFPS) with surface area greater than 6000 cm2/g is a vitreous powder similar to granulated blast-furnace slag (GBFS). The comparative investigation of UFPS and GBFS in this paper showed that UFPS could improve the fluidity, strength, and durability of concrete at partial replacement of cement. With 275 kg/m3 compound UFPS, 27 5 kg/m3 Grade 525# ordinary portland cement, 0.26 water-binder ratio, and 9.7 kg/m3 high-range water-reducing admixture (HRWRA), a concrete had been prepared with a slump of 240 mm, 28-day compressive strength 101 MPa, and a diffusion coefficient of Cl about one third lower than that of the control portland cement concrete.
A Kinetic-Based Method for Interpreting ASTM C 1260
Authors: Johnston D , Stokes D , Surdahl R 
Published: January 2010

Abstract
A proposed kinetic-based method for interpreting ASTM C 1260 test results is introduced that appears capable of overcoming some of the shortcomings currently encountered using a percent expansion criterion for defining potentially reactive aggregate. The method is based on nucleation and growth or phase transformation reaction kinetics where the percent expansion is exponentially related to a power of time. Solving the logarithmic form of the kinetic equation by a least-squares fit yields two parameters, lnk and M, where lnk is the intercept and M is the slope of the regression line, which can be used to determine potential reactivity. A plot of M versus lnk yields two separate domains—one containing reactive aggregate and one containing innocuous aggregate. Values of lnk &lt; -6 are associated with innocuous aggregate. The method successfully differentiated between several reactive aggregates with 14-day expansions of less than 0.1% as reactive and indicated that one aggregate with a 14-day expansion of 0.278% was innocuous. The method also appears promising with regard to determining effective levels of pozzolans and other admixtures for mitigation of ASR reactive aggregate.
Evaluation of the Potential of Densified Silica Fume to Cause Alkali-Silica Reaction in Cementitious Matrices Using a Modified ASTM C 1260 Test Procedure
Authors: Rangaraju PR , Olek J 
Published: January 2010

Abstract
Numerous research and field studies in the past have shown the ability of silica fume to improve the mechanical and durability properties of concrete. Despite these beneficial effects, some recent studies have raised concerns about the dispersibility of a few commercial dry densified silica fumes and the potential for development of alkali-silica reaction associated with the presence of undispersed agglomerates of silica fume in cement matrices.
In light of these developments, the present investigation focuses on determining the potential of undispersed silica fume agglomerates to participate in the alkali-silica reaction and the influence of such factors as size and morphology of the agglomerates on the extent of this reaction. An experimental program consisting of a modified ASTM C 1260 test procedure was used to identify and study distress associated with the presence of undispersed silica fume in cementitious pastes and mortars.
Results of this investigation indicate that undispersed silica fume agglomerates in cementitious pastes actively participate in alkali-silica reaction. The nature and the magnitude of the observed distress were found to be distinctly dependent on factors such as the size of the agglomerates, their morphology, and the water-binder ratio of the cementitious matrix. In addition, this paper presents suggested modifications to the ASTM C 1260 procedure to test for the reactivity of silica fume agglomerates.
Proportioning Concrete Mixes with Quarry Wastes
Authors: Nataraja MC , Nagaraj TS , Reddy A 
Published: January 2010

Abstract
An integral part of concrete mix proportioning is the preparation of trial mixes and making adjustments to such trials striking a balance between the requirements of placement, strength, and durability. When coarse aggregate characteristic strength is lower than the levels of strength of the concrete desired, different methods, viz., British, ACI, and the country's standard code, cannot be used directly. In this paper a generalized method is advanced to proportion concrete using quarry wastes, namely, cuddapah and marble in concrete, as coarse aggregate. Concrete is regarded as a composite of cement mortar matrix and coarse aggregate. The basic principle of the method is to assess the characteristic strength of coarse aggregate from compressive strength data of concrete failed by aggregate fracture and from that characteristic strength to assess the cement mortar strength required so as to ensure the development of the required strength of concrete. To arrive at the exact water-cement ratio of mortar matrix, the generalized Abrams' law is used.
Analysis of the Granular Structures of Aggregates Using Solid Volume Measurement of Elementary Fractions
Authors: Lecomte A , Mechling JM 
Published: January 2010

Abstract
This article deals with the measurement of the solid volumes and hence the packing density of elementary fractions of aggregates, a parameter used in modern methods for the optimization of granular mixtures. After reviewing methods for measuring solid volumes, two examples are presented to illustrate the relevance of the proposed method in elucidating the internal structures of aggregates, their morphological properties, and the state of the surfaces of their grains. The solid volumes data not only enhance standard characterization of aggregates but also underline the need to closely relate aggregate identification data with the geological history of the site where aggregates are extracted.
Use of Copper Slag and Cement By-Pass Dust as Cementitious Materials
Authors: Al-Jabri K , Taha R , Al-Ghassani M 
Published: January 2010

Abstract
Copper slag (CS) and cement by-pass dust (CBPD) are by-products of the production of copper and cement, respectively. In the Sultanate of Oman, large quantities of copper slag (60,000 tons/year) and cement by-pass dust (25,000 tons/year) are produced every year, most of which is not effectively utilized and disposed on-site without any reuse. The main objective of this research is to investigate the potential use of copper slag and cement by-pass dust in concrete as partial replacements for Portland cement. The physical and chemical properties of both slag and cement by-pass dust were determined. Mortar samples were prepared using different proportions of slag, cement by-pass dust and lime, which was used as an activating material. Proportions up to 15% of Portland cement replacement were used. In addition, a control mixture containing 100% Portland cement was prepared for comparison. Results obtained indicated that the increase in the proportions of copper slag and cement by-pass dust alone resulted in a decrease in the compressive strength of mortars compared with the control mix. The highest compressive strength was achieved in samples containing 5% CBPD + 95% cement, which was 41.7 MPa after 90 days. The optimum copper slag and cement by-pass dust to be used is 5%. In addition, it was determined that using cement bypass dust as an activating material will work better than using lime. Additional studies should investigate the strength and durability when copper slag and cement by-pass dust are used in concrete mixes.
Laboratory Assessment of the Potential Rate of ASR Expansion of Field Concrete
Authors: Berube M-A , Frenette J , Pedneault A , Rivest M 
Published: January 2010

AbstractIn-situ monitoring of concrete deformations and movements is the best way to assess the current expansion of concrete members affected by alkali-silica reactivity (ASR). However, laboratory tests on cores are less expensive and more rapid, and are commonly used to assess the potential for further expansion due to ASR. The risk of expansion and damage due to ASR can be reasonably assessed in the laboratory from: (1), the inherent expansivity of the concrete under study, which is determined by testing core samples in air at 100% RH and 38°C; (2), the residual absolute reactivity of the aggregates present in the concrete under study, which can be determined by testing core samples in 1N NaOH solution at 38°C or, even better for coarse aggregates, by testing aggregates extracted from cores through the concrete prism test CSA A23.2-14A or ASTM C 1293; (3), the amount of alkalies that are still active in the concrete, i.e. in the pore solution, which is estimated by a hot-water extraction method on ground concrete, and (4), humidity, (5), temperature, and (6), stress conditions (confinement, reinforcement, pretensioning, postensioning) in service. The individual risk indices corresponding to each of the above parameters are combined to determine the potential rate of ASR expansion of concrete members in service, either already affected by ASR or not.
Measurement of the Alkali Content of Concrete Using Hot-Water Extraction
Authors: Bérubé M-A , Frenette J , Rivest M , Vézina D 
Published: January 2010

AbstractThe knowledge of the active- or soluble-alkali content of concrete is useful in the diagnosis and prognosis of alkali-aggregate reactivity (AAR). A method often used for determining this content is hot-water extraction from ground concrete samples. This method was applied to 17 aggregates and 8 concretes incorporating aggregates presenting different degrees of alkali-silica or alkali-carbonate reactivity. The following conclusions can be drawn: (1) a correction must be made to take account for the alkalies released by the aggregates in the test; (2) using cold water rather than hot water has no significant effect on the results; (3) grinding to &lt;160 μm appears more appropriate than &lt;80 μm (lower amount of alkalies released by the aggregates); (4) the soluble-alkali content progressively decreases as alkali-silica reaction (ASR) progresses, which indicates that a significant part of alkalies, progressively incorporated in the reaction products from ASR, is not leached in the test; (5) the repeatability from one series of tests to another and the reproducibility from one laboratory to another appear relatively poor; (6) the use of a control concrete with a known soluble-alkali content may greatly improve the repeatability and the reproducibility of the method.
Review of the Thermodynamic Stability of Ettringite
Authors: Constantiner D , Farrington SA 
Published: January 2010

Abstract
A critical review of published solubility and thermodynamic data for ettringite is presented. Today, the data reported in the literature have variability and uncertainty that could affect the outcome of thermodynamic models. One major uncertainty arises from the fact that Kspett and ΔGfrm° for ettringite have been calculated assuming congruent dissolution even when the data indicates incongruent dissolution. Another uncertainty is the effect of the activity of water. This is an issue that exists when dealing with concentrated solutions, and has not been addressed thus far in ettringite thermodynamic studies. Proper modeling requires that the issues presented in this paper be considered to insure reliable results.
Evaluation of the Potential for Internal Sulfate Attack Through Adaptation of ASTM C 342 and the Duggan Test
Authors: Lane DS , Ozyildirim HC 
Published: January 2010

Abstract
The potential for distress resulting from internal sulfate attack in mortars was evaluated using a test method adapted from ASTM Test Method (C 342) and the Duggan test. While these test procedures were originally developed to evaluate the potential for cement-aggregate combinations to undergo deleterious alkali-aggregate reactions, the test scheme of temperature and moisture cycling may simulate conditions that are conducive to internal sulfate deterioration.
Length change bars were fabricated from mortars composed of various combinations of a Type I cement: the Type I cement with Class F fly ash; and a Type I/II cement. The aggregate was alkali-silica reactive. The bars were moist cured for seven days after molding at 23°C. Afterward, the bars were subjected to wet-dry, hot-cool cycles over a period of 24 days; one group subjected to a maximum temperature of 55°C and the other to a maximum of 80°C. Two additional groups received the thermal cycling to 55 or 80°C, and a final group was stored continually wet at 23°C. Following the moisture- thermal cycling period, the bars were stored immersed in water for a period of up to one year, and periodically measured for length change. Excessive expansions were noted only with the Type I cement mortars cycled to 80°C, with expansion developing more rapidly in specimens subjected to a drying cycle. Optical microscopic and scanning electron microscopic examinations of specimens indicate that the paste in expansive specimens expanded relative to aggregate particles.
Curing Practices and Internal Sulfate Attack—The European Experience
Authors: Skalny J , Locher FW 
Published: January 2010

Abstract
The relationships between concrete curing procedures, materials composition, and internal sulfate attack damage will be discussed in view of the experience obtained in Europe in the 1970s and 1980s. The heat-treatment procedures that were introduced and specified to eliminate or minimize the damage will be highlighted and suggestions will be made as to the needed adjustments in curing practices.
Mineralogy and Performance of Cement Based on High Sulfate Clinker
Authors: Herfort D , Rasmussen S , Jøns E , Osbæck B 
Published: January 2010

Abstract
The question of whether or not the release of sulfates from the clinker phases in portland cement can result in late or renewed ettringite formation has been addressed through a series of physical tests and by mineralogical examination. The cements tested contained clinker with SO3 contents ranging up to 3%, including high belite contents and sufficiently low alkali contents to ensure the presence of anhydrite. The physical testing consisted of expansion tests of mortars cured and stored at 20°C, in addition to compressive strength determinations. The mineralogical examination consisted of monitoring the consumption of anhydrous phases by X-ray diffraction and microscopy on the SEM. Linear expansion at 10 months was negligible for all cements with no significant loss in strength. No significant late, or renewed development of ettringite was observed. Calculations based on the distribution of elements between phases in the clinker included in the investigation show that the potential for late ettringite formation from the unreacted clinker is negligible, even when making the most pessimistic assumptions.
Evaluation and Mitigating Measures for Premature Concrete Distress in Texas Department of Transportation Concrete Elements
Authors: Lawrence BL , Moody ED , Guillemette RN , Carrasquillo RL 
Published: January 2010

Abstract
Concrete for both cast-in-place and precast construction plays a vital role in the development of the highway infrastructure in Texas. Historically, Texas has enjoyed a consistent supply of quality concrete because of the availability of economical and high-quality aggregates and cementious materials. However, recent discoveries by the Texas Department of Transportation (TxDOT) of premature concrete distress in concrete elements has raised significant concerns regarding current standards and specifications for concrete materials and construction practices.
In late 1995, 69 precast concrete box beams fabricated in San Marcos, TX became the subject of a comprehensive concrete evaluation effort to determine the cause of premature concrete distress in 56 of the 69 beams. This was TxDOT's first experience with the distress mechanism referred to as delayed ettringite formation. As a result of the investigation, the 56 distressed beams were rendered unsuitable for use.
Since the box beam case study, TxDOT has identified a number of other structures exhibiting similar signs of distress. Four of these structures have been evaluated petrographically. In each case, the distress was attributed to DEF. The increase in the number of structures with this problem has prompted TxDOT to expand its investigation. This includes conducting an extensive in-house research program, sponsoring a round-robin investigation of the box beam concrete, and funding research. As a result of the initial findings, TxDOT is presently considering changes to the cement, aggregate, and construction specifications for mitigation of this problem.
This paper addresses the key elements of TxDOT's continuing investigation and research efforts regarding the problem of premature concrete distress in Texas. Emphasis is placed on the growing nature of the problem in Texas, technological advances in evaluation techniques, and mitigating measures presently under consideration by TxDOT.