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Michael D A Thomas - One of the best experts on this subject based on the ideXlab platform.
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Alkali-Silica Reaction: Current understanding of the Reaction mechanisms and the knowledge gaps
Cement and Concrete Research, 2015Co-Authors: Farshad Rajabipour, Eric Giannini, Cyrille Dunant, Jason H. Ideker, Michael D A ThomasAbstract:Alkali-Silica Reaction (ASR) is a major concrete durability problem, resulting in significant maintenance and reconstruction costs to concrete infrastructures all over the world. Despite decades of study, the underlying chemical and physical Reaction mechanisms remain poorly understood, especially at molecular to micro-scale levels, and this has resulted in the inability to efficiently assess the risk, predict the service life, and mitigate deterioration in ASR-susceptible structures. This paper intends to summarize the current state of understanding and the existing knowledge gaps with respect to Reaction mechanisms and the roles of aggregate properties (e.g., composition, mineralogy, size, and surface characteristics), pore solution composition (e.g., pH, alkalis, calcium, aluminum), and exposure conditions (e.g., temperature, humidity) on the rate and magnitude of ASR. In addition, the current state of computer modeling as an alternative or supplement to physical testing for prediction of ASR performance is discussed.
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alkali Silica Reaction asr performance testing influence of specimen pre treatment exposure conditions and prism size on alkali leaching and prism expansion
Cement and Concrete Research, 2013Co-Authors: Jan Lindgard, Michael D A Thomas, E J Sellevold, Bard Pedersen, Ozge Andiccakir, Harald Justnes, Terje F RonningAbstract:Alkali-Silica Reaction (ASR) -performance testing : Influence of specimen pre-treatment, exposure conditions and prism size on alkali leaching and prism expansion
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the effect of supplementary cementing materials on alkali Silica Reaction a review
Cement and Concrete Research, 2011Co-Authors: Michael D A ThomasAbstract:Abstract This paper reviews studies on the effect of supplementary cementing materials (SCM) on alkali-Silica Reaction (ASR). SCMs control expansion due to ASR by binding alkalis and limiting their availability for Reaction with alkali-Silica reactive aggregate. The efficacy of the SCM is dependent on the composition of the SCM. Increased amounts of SCM are required to control ASR as its calcium and alkali content increase, as its Silica content decreases, as the alkali contributed by the Portland cement increases and as the reactivity of the aggregate increases. There is evidence that the alumina content of the SCM also affects its alkali-binding capacity, however, the precise role and contribution of the alumina is not clear.
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effect of fly ash on the expansion of concrete due to alkali Silica Reaction exposure site studies
Cement & Concrete Composites, 2011Co-Authors: Michael D A Thomas, P J Nixon, Andrew Dunster, Barry BlackwellAbstract:Abstract In this study 45 concrete blocks (915 × 915 × 815 mm or 350 mm cubes) containing alkali-Silica reactive aggregates, and various levels of high-alkali cement and fly ash were placed on an outdoor exposure site in S.E. England for a period of up to 18 years to determine the efficacy of fly ash in controlling damaging alkali-Silica Reaction (ASR). The reactive aggregates used included a variety of flint sands and a crushed greywacke combined coarse and fine aggregate. Length-change measurements were conducted periodically throughout this period. All concrete blocks without fly ash showed excessive expansion and cracking within 5–10 years of production and in many cases the ultimate expansion exceeded 1.0% after 15–18 years. Fly ash used at replacement levels of 25% and 40% was effective in significantly reducing expansion and cracking with all three flint aggregates at all levels of alkali. Of the 27 blocks containing fly ash and flint sand only two blocks showed evidence of damage after 16–18 years. The expansion of these blocks was significantly lower than similar blocks with the same Portland cement content without fly ash. None of the blocks with greywacke aggregate and fly ash exhibited cracking (expansion data were not available for these blocks). Collectively the data confirm that fly ash, when used at levels of 25–40%, does not effectively contribute alkalis to the alkali-Silica Reaction.
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effect of environmental conditions on expansion in concrete due to alkali Silica Reaction asr
Materials Characterization, 2009Co-Authors: Benoit Fournier, Jason H. Ideker, Michael D A Thomas, Kevin J. Folliard, Pierre Claver Nkinamubanzi, Ray ChevrierAbstract:Abstract The environmental conditions to which a concrete element incorporating alkali–Silica reactive aggregates is exposed play a major role in dictating the progression and manifestation of the Reaction. This paper reports and analyses the results of research programs investigating the comparative evaluation of the effect of environmental conditions on the development of alkali–Silica Reaction (ASR) in concrete specimens stored in outdoor exposure at the authors' respective laboratories. This data is compared to samples subjected to laboratory testing (controlled environmental conditions). Concrete mixtures that incorporate reactive aggregates with varying reactivity levels are compared. The focus of this paper is on control concretes e.g. 100% opc + reactive aggregate (coarse or fine).
Barbara Lothenbach - One of the best experts on this subject based on the ideXlab platform.
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synthesis of alkali Silica Reaction product structurally identical to that formed in field concrete
Materials & Design, 2020Co-Authors: Zhenguo Shi, Andreas Leemann, Daniel Rentsch, Barbara LothenbachAbstract:Abstract Alkali-Silica Reaction (ASR) can cause expansion and cracking of concrete. Despite significant progress over the past 80 years, the molecular structures of the ASR products remain poorly understood. These Reaction products are present in very small amounts within concrete aggregates, which severely limit their chemical and physical characterizations. In this study, synthesis of an ASR product structurally identical to that formed in field concrete is achieved in large quantities at 40 °C. The temperature is found to affect the formation of different types of crystalline ASR products: 12.0 A (
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synthesis characterization and water uptake property of alkali Silica Reaction products
Cement and Concrete Research, 2019Co-Authors: Zhenguo Shi, Andreas Leemann, Barbara Lothenbach, Guoqing GengAbstract:Abstract The Reaction mechanism of alkali-Silica Reaction (ASR) is poorly understood due to the difficulties to directly characterize ASR products in concrete. In this study, ASR products with initial Ca/Si of 0.25 and (K + Na)/Si ratio 0.5 with different K/Na ratios are synthesized at 80 °C. The synthesized ASR products are characterized by different techniques, also the solution chemistry is analyzed and saturation indices are calculated. The results show that crystalline and nano-crystalline phases are formed in the presence of both alkalis and calcium. No ASR product is present in the absence of calcium. All synthesized crystalline ASR products highly resembles the crystal structure of shlykovite, indicating that a substitution of K in shlykovite by Na can occur. Its Silicate sheet structure has strong similarity to the ASR products formed in concrete according to Raman spectra, while some differences are observed in their morphologies and basal peak of the XRD patterns.
Andreas Leemann - One of the best experts on this subject based on the ideXlab platform.
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synthesis of alkali Silica Reaction product structurally identical to that formed in field concrete
Materials & Design, 2020Co-Authors: Zhenguo Shi, Andreas Leemann, Daniel Rentsch, Barbara LothenbachAbstract:Abstract Alkali-Silica Reaction (ASR) can cause expansion and cracking of concrete. Despite significant progress over the past 80 years, the molecular structures of the ASR products remain poorly understood. These Reaction products are present in very small amounts within concrete aggregates, which severely limit their chemical and physical characterizations. In this study, synthesis of an ASR product structurally identical to that formed in field concrete is achieved in large quantities at 40 °C. The temperature is found to affect the formation of different types of crystalline ASR products: 12.0 A (
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synthesis characterization and water uptake property of alkali Silica Reaction products
Cement and Concrete Research, 2019Co-Authors: Zhenguo Shi, Andreas Leemann, Barbara Lothenbach, Guoqing GengAbstract:Abstract The Reaction mechanism of alkali-Silica Reaction (ASR) is poorly understood due to the difficulties to directly characterize ASR products in concrete. In this study, ASR products with initial Ca/Si of 0.25 and (K + Na)/Si ratio 0.5 with different K/Na ratios are synthesized at 80 °C. The synthesized ASR products are characterized by different techniques, also the solution chemistry is analyzed and saturation indices are calculated. The results show that crystalline and nano-crystalline phases are formed in the presence of both alkalis and calcium. No ASR product is present in the absence of calcium. All synthesized crystalline ASR products highly resembles the crystal structure of shlykovite, indicating that a substitution of K in shlykovite by Na can occur. Its Silicate sheet structure has strong similarity to the ASR products formed in concrete according to Raman spectra, while some differences are observed in their morphologies and basal peak of the XRD patterns.
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Raman microscopy of alkali-Silica Reaction (ASR) products formed in concrete
Cement and Concrete Research, 2017Co-Authors: Andreas LeemannAbstract:Abstract Recently, the structure of the crystalline alkali-Silica Reaction (ASR) product formed in affected concrete has been identified based on μ-XRD measurements. However, the data were obtained from a single aggregate. In this study, Raman microscopy is applied on crystalline ASR products formed in several aggregates and concrete mixtures, enabling a comparison of their spectra and with it their structure. In a first step, samples from the same concrete used for μ-XRD measurements are analyzed and compared. In a second step, samples from a second structure and from a concrete prism test are measured. In addition to Raman microscopy, SEM with EDX is used to characterize the microstructure. The Raman spectra of the crystalline ASR product are practically identical in all studied aggregates and concrete mixtures, showing it is the same phase. This conclusion is further supported by the microstructural data.
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e modulus of the alkali Silica Reaction product determined by micro indentation
Construction and Building Materials, 2013Co-Authors: Andreas Leemann, Pietro LuraAbstract:Abstract The effects of expansion on concrete structures induced by alkali–Silica Reaction (ASR) are complex. Numerous attempts have been made to model them. Some of these models assume an E -modulus for the ASR product, as no experimental data exist up to now. In this study, Vickers hardness, indentation and E -modulus are determined by micro-indentation tests on undried, polished concrete samples taken from a structure damaged by ASR. Both the indentation tests and the chemical analysis by EDX performed on the ASR product in different aggregates indicate that it is relatively homogenous. Vickers hardness ranges between 10 and 19 and E -modulus between 7 and 9 GPa. Towards the edge of the aggregates the ASR product takes up calcium and the values for Vickers hardness and E -modulus increase.
Karen Scrivener - One of the best experts on this subject based on the ideXlab platform.
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alkali Silica Reaction and sulfate attack expansion of limestone calcined clay cement
2018Co-Authors: Aurelie Favier, Karen ScrivenerAbstract:In this paper, two durability issues: Alkali Silica Reaction (ASR) and external sulfate attack were studied. The results of expansion were presented for a Normal Portland cement and a blended cement LC3 containing calcined clay and limestone as supplementary cementitious materials (SCMs). The systems containing SCMs did not expand after several years of exposure showing a high resistance to ASR and sulfate attack.
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micro mechanical modelling of alkali Silica Reaction induced degradation using the amie framework
Cement and Concrete Research, 2010Co-Authors: Cyrille F Dunant, Karen ScrivenerAbstract:AMIE, a finite element/extended finite element framework, has been designed to provide the tools to run detailed microstructural simulations; this paper demonstrates the possibility of simulating the mechanisms underlying the alkali-Silica-Reaction (ASR). The numerical model presented provides a better understanding of experimental observations. Macroscopic free expansion and degradation of mechanical properties have been previously linked to the extent of Reaction. The connection between microscopic and macroscopic measurements, simulated by the model, supports the hypothesis that damage is induced by growing gel pockets in the aggregates.
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relation of expansion due to alkali Silica Reaction to the degree of Reaction measured by sem image analysis
Cement and Concrete Research, 2007Co-Authors: Ben M Haha, Emmanuel Gallucci, Amor Guidoum, Karen ScrivenerAbstract:Scanning Electron Microscopy Image Analysis (SEM-IA) was used to quantify the degree of alkali Silica Reaction in affected microbars, mortar and concrete prisms. It was found that the degree of Reaction gave a unique correlation with the macroscopic expansion for three different aggregates, stored at three temperatures and with two levels of alkali. The relationships found for the concretes and the mortars overlap when normalised by the aggregate content. This relationship seems to be linear up to a critical Reaction degree which coincides with crack initiation within the reactive aggregates.
Paulo J.m. Monteiro - One of the best experts on this subject based on the ideXlab platform.
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relationship between degree of deformation in quartz and Silica dissolution for the development of alkali Silica Reaction in concrete
Materials, 2017Co-Authors: Francieli Tiecher, Denise Carpena Coitinho Dal Molin, Marcia Elisa Boscato Gomes, Nicole P Hasparyk, Paulo J.m. MonteiroAbstract:This paper presents research on the influence of quartz deformation in aggregates for the development of the alkali-Silica Reaction in concrete and its relationship with Silica dissolution. The study also compares these characteristics with the field behavior of such rocks in concrete. The paper proposes parameters to classify the different degrees of deformation of quartz. Transmission electron microscopy showed the presence of walls even in slightly deformed quartz, which indicate the presence of the internal paths available to react with the alkaline concrete pore solutions and point to the potential development of an alkali-Silica Reaction. The presence of the deformation bands in the quartz grains leads to the alkali aggregate Reaction occurring more rapidly. The visible spectrophotometer test was performed to evaluate the dissolution potential of the different samples of deformed quartz, which confirmed that the reactivity of the quartz increases as the deformation of the crystalline structure increases. The parameters established in the present study could be verified by analyzing the behavior of reactive and innocuous aggregates from the buildings.
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fiber reinforced mortar affected by alkali Silica Reaction a study by synchrotron microtomography
Cement & Concrete Composites, 2016Co-Authors: Daniel Hernandezcruz, Craig W. Hargis, Jolee M Dominowski, Michael J Radler, Paulo J.m. MonteiroAbstract:Abstract Alkali-Silica Reaction (ASR) is a physicochemical process that can deteriorate concrete and is a recurring engineering problem. In this study three different cylindrical samples affected by ASR were prepared: a plain mortar and two composite mortars containing fibers (polypropylene and a polymer hybrid), which were analyzed at the microtomography (μCT) beamline 8.3.2 at the Advanced Light Source (ALS). In general, three different features were observed during the 136 day observation period: (1) aggregate dissolution, (2) crack propagation from inside the aggregate, through the cement matrix, and at the ITZ, and (3) the alkali-Silica gel filling cracks and voids. In addition, accelerated mortar bar tests were utilized to observe ASR's expansive effect in the plain and composite mortars, and the fibers' ability to restrain expansion due to ASR.
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Aggregate Passivation: Lithium Hydroxide Aggregate Treatment to Suppress Alkali-Silica Reaction
ACI Materials Journal, 2013Co-Authors: Craig W. Hargis, Maria C. G. Juenger, Paulo J.m. MonteiroAbstract:Alkali-Silica Reaction (ASR) continues to be a concrete durability problem despite the many physical and chemical mitigation techniques known to successfully prevent it. The research presented herein tested a new method to limit ASR: aggregate passivation. A lithium Silicate layer was created on reactive natural siliceous aggregate surfaces by treating the aggregates in a lithium hydroxide solution prior to use. A 4 M LiOH treatment was found to be superior to a 2 M LiOH treatment in producing a lithium Silicate passivation layer and in reducing expansion due to ASR. The use of passivated aggregates greatly reduced expansion in accelerated mortar bar tests compared to nonpassivated aggregates and lithium-based admixtures.
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effect of lithium nitrate on the alkali Silica Reaction gel
Journal of the American Ceramic Society, 2008Co-Authors: Jose Fabian Schneider, Nicole P Hasparyk, Denise A Silva, Paulo J.m. MonteiroAbstract:Lithium nitrate has been used to prevent and to mediate the expansion caused by alkali-Silica Reaction (ASR). However, there is limited information on how it affects the existing Reaction products caused by ASR. The aim of the present work is to determine the modifications caused by the LiNO3 treatment on the structure of the gel produced by ASR. ASR gel samples obtained from a concrete dam were exposed to an aqueous solution of lithium nitrate and sodium hydroxide with molar LiNO3/ NaOH=0.74, and the resulting products were analyzed by X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance of 29Si, 23Na, and 7Li. The treatment of the gel samples produces significant structural modifications in ASR products. A new amorphous Silicate compound incorporating Li+ ions is formed, with an average Silicate network that can be described as linear in contrast with the layered structure of the original gel. This elimination of the layered structure after the Li-based treatments may be related to the reduction of the tendency of the gel to expand. Also, several crystalline compounds containing potassium indicate the release of this species from the original ASR gel.
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study of the structure of alkali Silica Reaction gel by high resolution nmr spectroscopy
Journal of Non-crystalline Solids, 2006Co-Authors: C E Tambelli, Nicole P Hasparyk, Jose Fabian Schneider, Paulo J.m. MonteiroAbstract:The alkali-Silica Reaction is a deleterious chemical process that can occur in concrete. The product of the Reaction is an amorphous Silicate material with gel characteristics, whose high expansion properties may cause cracking in the matrix and in the discrete aggregate of particles, leading to severe deterioration of the concrete structure. Structural information of this gel at the atomic scale can provide critical information on how to develop appropriate repair of the affected structure. Samples of this gel, produced under in-service conditions in a large concrete dam, were studied by 29 Si and 23 Na high-resolution nuclear magnetic resonance spectroscopy, triple quantum magic angle spinning 23 Na nuclear magnetic resonance, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The short-range atomic structure of the compound was determined as an amorphous potassium-hydroxide-Silicate glass, with a Q 3 -like dominant Silicate connectivity, having a Silicate speciation highly disproportioned when compared with potassium-Silicate glasses with the same K 2 O content. Sodium ions are mostly segregated from the bulk amorphous Silicate network, forming crystal domains attributed to the trona compound (sodium sesquicarbonate, Na 2 CO 3 ·NaHCO 3 ·2H 2 O). The structural picture at atomic scale obtained in this study gives support for double-layer models of the expansive properties of the alkali-Silica Reaction gel.