Alkali-activated materials (AAMs) are increasingly being researched to reduce the reliance on conventional cements as building materials. However, expensive and energy-intensive alkaline activators curtail the usage of AAMs. Waste-derived alkaline activators are effective in mitigating the environmental concerns for alkaline activators, but their synthesis process and the transport properties of AAM concrete are yet to be fully understood. This paper presents comprehensive results of syntheses of alternative sodium silicates (SSs) from rice husk ash (RHA) using a hydrothermal process. The effect of mixing duration, temperature, and RHA/NaOH ratio on the availability and structure of silicate species in the extracted RHA SSs were investigated. Compressive strength, water absorption, sorptivity, and chloride resistance tests were carried out to assess the performance of RHA SS in AAM concrete. The results showed that all RHA SSs contain monomer, dimer, trimer, and tetramer silicate oligomers but their respective proportion primarily depends on the temperature and RHA/NaOH ratio. The recommended hydrothermal process in this study was 1 h of mixing at 80 °C. The 28-day compressive strength of AAM concrete made of RHA SS was only up to 5 % lower than the one made of commercial SS. In addition, the transport properties of AAM concrete made of RHA and commercial SSs were comparable, proving the feasibility of RHA-derived activators (filtered and unfiltered).

中文翻译：

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稻壳灰水热合成水玻璃：合成对碱激活混凝土硅酸盐结构和传输性能的影响

人们越来越多地研究碱活化材料（AAM），以减少对传统水泥作为建筑材料的依赖。然而，昂贵且耗能的碱性活化剂限制了 AAM 的使用。废物衍生的碱性活化剂可有效减轻碱性活化剂的环境问题，但其合成过程和 AAM 混凝土的传输性能尚未完全了解。本文介绍了利用水热工艺从稻壳灰 (RHA) 合成替代硅酸钠 (SS) 的综合结果。研究了混合时间、温度和 RHA/NaOH 比例对提取的 RHA SS 中硅酸盐物质的可用性和结构的影响。进行了抗压强度、吸水率、吸附性和抗氯性测试，以评估 RHA SS 在 AAM 混凝土中的性能。结果表明，所有 RHA SS 均含有单体、二聚体、三聚体和四聚体硅酸盐低聚物，但它们各自的比例主要取决于温度和 RHA/NaOH 比例。本研究中推荐的水热过程是在 80 °C 下混合 1 小时。由 RHA SS 制成的 AAM 混凝土的 28 天抗压强度仅比商用 SS 制成的混凝土低 5%。此外，由 RHA 和商业 SS 制成的 AAM 混凝土的传输性能相当，证明了 RHA 衍生活化剂（过滤和未过滤）的可行性。