Pore Solution-Based Performance Approach for Utilization of Conventional and Alternative SCMs for ASR Mitigation

The current performance-based approach to determine the optimal supplementary cementitious materials (SCM) dosage for alkali-silica reaction (ASR) prevention in concrete requires testing at multiple replacement levels, which is time-consuming and inefficient. Moreover, the effects of soluble alkalis from certain supplementary cementitious materials (SCMs) on ASR remain undetected because of the alkali-boosted test conditions of the current tests. Thus, a chemical screening tool (CST) was developed to predict optimum SCM dosage for ASR prevention by establishing concrete pore solution alkalinity (PSA) and aggregate threshold alkalinity (THA) based criteria. The TTI Model-1, a pore solution model, was developed within CST to estimate concrete PSA, considering the combined soluble alkali effects from cement and SCMs. Soluble alkali contributions from SCMs were assessed using quantitative X-ray diffraction and water-soluble alkali methods, followed by PSA estimation through the TTI Model-1. AASHTO TP142 and ASTM C1567 tests were used to validate CST’s dosage predictions. The current study shows that CST reliably predicted dosages for both conventional (Class C & F ashes) and unconventional (blended/reclaimed ashes and natural pozzolans) SCMs within 1–2 days. The CST effectively highlighted the shortcomings of the rapid ASTM C1567 test for certain SCMs and identified SCMs that require further validation by reliable but long-term concrete ASR testing like TP 142 (90 days) and C1293 (2 years).