Author ORCID Identifier
https://orcid.org/0000-0002-2140-9759
Document Type
Report
Publication Date
6-2023
Abstract
Over the past few decades, Class F fly ash has been widely used in concrete as a supplementary cementitious material (SCM) due, in part, to its ability to mitigate alkali-silica reaction (ASR). However, future availability of fly ash is uncertain as the energy industry shifts towards renewable sources, resulting in the closure of coal-burning power plants. Therefore, there is a growing need to find alternatives to fly ash that are both cost effective and environmentally friendly. This study aimed to evaluate the effectiveness of ground-granulated blast furnace slag (GGBFS), metakaolin, and a locally available natural pozzolan mined from a pumicite deposit near Espanola, NM, USA as potential replacements for fly ash in mitigating ASR. Mortar mixtures were used to assess the ability of each SCM to mitigate ASR, while concrete mixtures were evaluated to assess the effects of the SCMs on rheological properties, compressive and flexural strengths, shrinkage, frost resistance, and chloride ion permeability. Minimum pumicite and metakaolin contents of 25% and 15%, respectively, were needed to mitigate ASR in mixtures with highly reactive aggregates. Mortar mixtures containing pumicite or metakaolin were substantially more effective at mitigating ASR than fly ash mixtures. GGBFS was ineffective for mitigating ASR and was observed to increase ASR expansions such that they surpassed the expansions for the control mixtures containing only cement. The results also showed that replacing fly ash with metakaolin or natural pozzolan had minimal impact on the fresh properties of the concrete mixtures. While all concrete mixtures showed adequate strength values suitable for most concrete applications, metakaolin mixtures had slightly greater 28-day compressive and flexural strengths compared to natural pozzolan mixtures. Using metakaolin, and especially the natural pozzolan, increased shrinkage in concrete mixtures. However, the resulting shrinkage values were acceptable and both SCMs improved frost resistance and decreased chloride ion permeability. Overall, these results support the use of natural pozzolan and metakaolin as reliable alternatives to fly ash in concrete mixtures since they offer satisfactory performance in terms of rheological, mechanical, and durability properties. These findings provide valuable insights for the concrete industry in its search to find sustainable alternatives to fly ash.
Recommended Citation
Newtson, C., Garcia, J. M., & Mousavinezhad, S. (2023). Alkali-Silica Reaction Mitigation using Alternative Supplementary Cementitious Materials. Retrieved from https://repository.lsu.edu/transet_pubs/156
Comments
Tran-SET Project: 22CNMSU19