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<p>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<sub>2</sub>O<sub>eq</sub> &gt; 3.0&#xa0;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&#xa0;M KOH host solution and soluble potassium in 1&#xa0;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.</p>

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Towards a test method for measuring soluble alkalis in supplementary cementitious materials

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月25日

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  • Moe Sharbaf,
  • Zhanzhao Li,
  • Jan Olek,
  • Sulapha Peethamparan,
  • Farshad Rajabipour

摘要

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., Na2Oeq > 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.