Pore Solution-Based Innovative Approach for Evaluating the Effectiveness of Conventional and Alternative SCMs to Mitigate ASR

Pore Solution-Based Innovative Approach for Evaluating the Effectiveness of Conventional and Alternative SCMs to Mitigate ASR

Grand Rapids, Michigan

Pore Solution-Based Innovative Approach for Evaluating the Effectiveness of Conventional and Alternative SCMs to Mitigate ASR Authors Prof. Anol Mukhopadhyay - United States - Texas A&M University Abstract Current ASR tests such as ASTM C 1293 and C 1567 are not sensitive to detecting FA soluble alkali's effect on ASR expansion due to alkali boosting test conditions. Moreover, the current empirical prediction models (e.g., chemical index and extended chemical index) to determine the fly ash dosage for mitigating ASR ignore the role of fly ash soluble alkali contribution on ASR evaluation. The main objective of this study was to develop a performance-based approach using an emerging accelerated concrete cylinder test (ACCT, AASHTO TP142) method and estimation of concrete pore solution alkalinity (PSA) to evaluate the effectiveness of the fly ashes and other potential alternative SCMs to mitigate ASR. A rapid chemical screening tool (CST) was developed to determine the optimum fly ash dosage (within 2 days) to mitigate ASR in concrete mixes based on the aggregate threshold alkalinity (THA) - PSA relationship. A pore solution model called TTI Model-1 was developed as a part of the CST to estimate concrete PSA based on the combined effects of soluble alkali from cement and water-soluble alkali (WSA) from fly ashes in pore solution. The relationship between aggregate ASR reactivity and THA determined by AASHTO T364-17 was found to be effective in assigning THA for an aggregate with known reactivity. The ACCT method was very effective in validating the dosages predicted by the CST method for conventional and selective alternative SCMs within 75-90 days. The CST can be used to verify the contents determined by ASTM C1567 (14 days testing duration) in one hand and identify the ashes (i.e., mismatch ashes based on CST vs ASTM C1567 comparison) that need further validation testing by the ACCT method on the other hand.