Evaluates a new method to quantify soluble alkalis in supplementary cementitious materials, indicating important implications for concrete durability.
Supplementary cementitious materials (SCMs) are often used in concrete to reduce the risk of alkali-silica reaction (ASR), primarily through alkali dilution and binding. However, the effectiveness of SCMs with high alkali content (e.g., Na 2 O eq > 3.0 wt.%) in ASR mitigation is of concern, as these alkalis may dissolve in concrete’s pore solution and elevate its pH. This study proposes and preliminarily evaluates a test method to quantify the soluble alkalis in SCMs. The method was applied to 14 SCMs, including natural pozzolans, coal ashes, and ground glass, to monitor their alkali release over a 180-day period. The test involves measuring soluble sodium in 1 M KOH host solution and soluble potassium in 1 M NaOH solution. Thermodynamic modeling confirmed that most released alkalis remain in solution, with minimal solid precipitation and alkali binding. Findings revealed that a significant portion of alkalis in SCMs is soluble, often exceeding the level identified by ASTM C311 Available Alkali Test.
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Sharbaf et al. (2026) studied this question.
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