The effect of metakaolin on alkali–silica reaction in concrete

Ramlochan, T; Gruber, Karen A.

doi:10.1016/s0008-8846(99)00261-6

Cited by 200 publications

(91 citation statements)

References 2 publications

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“…The literature lists a wide range of pressures applied to cement pastes and mortars to obtain a suitable amount of pore solution for the test procedure. Accordingly, the pressures applied to cement pastes varied between 345 MPa and 560 MPa, although it was not specified by all of the authors (33)(34)(35)(36). Similar figures may be observed in the literature on the pressures applied to obtain pore solutions from mortars, which generally ranged between 200 MPa and 1,100 MPa (37)(38)(39)(40)(41).…”

Section: Ph-meterssupporting

confidence: 55%

A review of sample preparation and its influence on pH determination in concrete samples

Manso

Aguado

2017

Mater. construcc.

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SUMMARY:If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field. RESUMEN:Revisión sobre la preparación de muestras de hormigón y su influencia sobre la determinación del pH. Determinar el pH de la fase acuosa de los poros de pastas de cemento, morteros y hormigones tiene gran importancia en el monitoreo de los procesos químicos que tienen lugar en los materiales cementiceos. Sin embargo, no existe una normativa que regule el método de preparación de la muestra para la determinación de su pH. Este artículo presenta un estado del conocimiento de diferentes metodologías para la determinación del pH de materiales cementiceos y la influencia del método de preparación según el objetivo. Además, se presenta una campaña experimental comparando tres técnicas diferentes. Dicha campaña contribuye a establecer un criterio simple que ayude al investigador en la selección del método más adecuado dependiendo del objeto de studio. Este artículo tiene por objetivo ser una herramienta sencilla para seleccionar la metodología más fácil y económica para determiner el pH dependiendo del objetivo, especialmente para investigadores noveles o aquellos con escasa experiencia.

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Section: Ph-meterssupporting

confidence: 55%

A review of sample preparation and its influence on pH determination in concrete samples

Manso

Aguado

2017

Mater. construcc.

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“…The replacement levels presented are chosen such that they contain the optimums for mechanical strengths that are prevalent in the literature (10-20%). In addition, the range was chosen to include higher replacements because durability tends to increase systematically with replacement level [12,[23][24][25][26][27]. This concept of an 'optimum' replacement level is evoked because of the need to maximize performance and minimize cost.…”

Section: Objectivementioning

confidence: 99%

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

et al. 2018

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Abstract:Metakaolin is the only major natural pozzolan to be specified for use as a supplementary cementitious material in the United States. As a result, the metakaolin market for concrete has grown dramatically in the past 20 years. As of now, the specifications of up to 16 state departments of transportation allow for the use of commercially-available and high-reactivity metakaolin products. However, to the best of the authors' knowledge, no study has been performed to evaluate whether these products are comparable in their performance. Three commercially-available (U.S.) metakaolin products, each replacing 10%, 15%, and 20% of the cement content in concrete and mortar mixtures are studied. Concrete mixtures contained a cementitious content of 422 kg/m 3 , a coarse aggregate fraction of 985 kg/m 3 , and a water-to-cementitious ratio equal to 0.43. Varying levels of a superplasticizer were used to maintain a uniform workability between mixtures. Each mixture was subjected to the following tests: compression, split-cylinder tension, modulus of rupture, dynamic elastic modulus, rapid chloride-ion penetrability, alkali-silica reactivity, sulfate resistance, the coefficient of thermal expansion, and drying shrinkage. Benefits from the inclusion of metakaolin were highly product-dependent and include increases in mechanical strength. All metakaolin supplemented concrete mixtures benefitted from decreased permeability and increased resistance to chemical attacks, with the exception of the sulfate resistance of mortars including a metakaolin product with high fineness. The inclusion of any metakaolin at any replacement level increased the coefficient of thermal expansion of concrete specimens. Reasons for difference in performance between products are discussed, and predictors of quality are recommended.

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“…Metakaolin has a high aluminum oxide content (typically around 45%) (Kosmatka, Kerkhoff et al, 2008). The introduction of alumina causes the C-S-H structure to form C-A-S-H (calcium alumino silicate hydrate), which has an even greater capacity to bind alkalis than C-S-H (Ramlochan, Thomas et al, 2000;Thomas, 2011). C-S-H is formed during cement hydration and C-A-S-H can be formed as a result of the pozzolonic reaction produced using fly ash provided sufficient alumina is present in the fly ash (Thomas, 2011), thus further reducing alkali-silica reactivity.…”

Section: Mitigation Studymentioning

confidence: 99%

Durability Assessment of Recycled Concrete Aggregates for Use in New Concrete Phase II

Ideker¹

2014

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Type of Report and Period Covered14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract: This Phase II investigation into the durability of new concrete incorporating recycled concrete aggregates (RCA) focused on several goals: 1) Provide corroboration of results obtained in Phase I for a multi-laboratory study related to assessing alkali-silica reactivity (ASR) of RCA in accelerated laboratory tests; 2) Investigate the efficacy of mitigation methods to control ASR in concrete containing potentially reactive RCA; 3) Establish long-term data through placement of concrete blocks containing RCA in an outdoor exposure site in Laramie, WY; and 4) Survey state DOTs and other transportation agencies about their perceptions and usage of RCA ASR in concrete within their agency and how that may be improved through the use of a database tracking tool. From Phase II the following main conclusions were drawn: 1) The coefficient of variation limits in ASTM C 1260-07 do not apply to concrete mortar bars incorporating RCA. It is recommended that further testing, using different RCA and more laboratories (at least six), should be completed before a new standard for RCA and/or incorporation of RCA into the current ASTM C 1260 test may be allowed. 2) Generally, as the replacement level of RCA was reduced, the amount of SCM needed to control deleterious ASR also decreased for the RCA sources investigated in this study. 3) Ternary blends containing metakaolin resulted in the most significant decrease in expansions compared to the mixtures with no SCMs.The results of the transportation agency survey showed the following: 1) A vast majority of agencies believed that sustainability was important to their agency and that it was addressed in a clear and meaningful way. 2) A majority, 54%, of agencies believed they had specific guidance for the use of RCA in new concrete; however, only 15% believed that there was strong information from the federal level about the use of RCA in new construction. 3) Of all respondents, 77% indicated their agency was concerned about alkali-silica reaction in concrete in general for their agency. 4) The biggest barriers to using RCA were noted as concerns about quality, a lack of standards and specifications, and unclear guidance on the testing of RCA. 5) The biggest concerns specific to a source of RCA when considering it for use in new construction were increased shrinkage concerns, ASR and residual chlorides. 6) The most sought-after information about a potential RCA source when considering it for use were the existing condition of the RCA when it was taken out of service, the reason it was taken out of service, whether repairs were performed to the structural element taken out of service, and the age of the RCA. 17.

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The effect of metakaolin on alkali–silica reaction in concrete

Cited by 200 publications

References 2 publications

A review of sample preparation and its influence on pH determination in concrete samples

A review of sample preparation and its influence on pH determination in concrete samples

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

Durability Assessment of Recycled Concrete Aggregates for Use in New Concrete Phase II

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