New selective dissolution process to quantify reaction extent and product stability in metakaolin-based geopolymers
New selective dissolution process to quantify reaction extent and product stability in metakaolin-based geopolymers
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DOI：
10.1016/j.compositesb.2019.107172
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发表时间：
2019-11-01
影响因子：
13.1
通讯作者：
Wang, Hao
中科院分区：
文献类型：
--
作者：
Longhi, Marlon A.;Walkley, Brant;Wang, Hao
开发了一种选择性溶解方法，该方法可以量化基于偏高岭土的地质聚合物体系中可溶性材料、地质聚合物凝胶和残余未反应前体的量，并确定原料和地质聚合物凝胶组分的纳米结构特征。在地质聚合过程中产生的碱性铝硅酸盐水合物型凝胶（N-A-S-H）的碱可溶解性的敏感性尚未完全了解。从微观结构、美学和性能的角度来看，这种现象导致了有害的过程。使用不同含量和类型的碱（M/Al=0.50-0.83，其中M表示Na或K）、活化剂中不同含量的可溶性二氧化硅（表示为SiO2/M2 O比为1.0、0.5和0.0）和固化温度（25和50 ℃）合成地质聚合物。选择性溶解过程基于在pH 7下的中性溶解以提取可溶性材料，以及使用pH 0下的强酸的酸溶解以溶解地质聚合物凝胶，这首次提供了定量地质聚合物中的（i）可溶性材料、（ii）地质聚合物凝胶和（iii）未反应材料的方法。可溶性材料提供了在中性pH环境中可从地质聚合物中去除的材料的可靠指示，因此提供了浸出和风化的可能性，这对于耐久性预测和使用寿命是有用的。残余的未反应的偏高岭土的定量确定了前体的反应性，并评估了不同合成条件对不同应用的适用性。因此，这项工作提供了一种新的和广泛适用的方法来确定地质聚合物材料的浸出敏感性。
A selective dissolution process is developed that can quantify the amount of soluble material, geopolymer gel and remnant unreacted precursor in metakaolin-based geopolymer systems and determine the nanostructural features of the raw materials and geopolymer gel components. The susceptibility of alkalis leachability from the alkaline aluminosilicate hydrate-type gel (N-A-S-H) produced during the geopolymerization is not fully understood. This phenomenon led to deleterious processes from a microstructural, aesthetic and performance point of view. Geopolymers were synthesised using different contents and types of alkalis (M/Al=0.50-0.83, where M represents Na or K), different contents of soluble silica in the activator (expressed as SiO2/M2O ratio of 1.0, 0.5 and 0.0), and curing temperatures (25 and 50 degrees C). The selective dissolution process is based on neutral dissolution at pH 7 to extract the soluble materials and acid dissolution using a strong acid at pH 0 to dissolve the geopolymer gel, which provides for the first time a method to quantify the (i) soluble material, (ii) geopolymer gel and (iii) unreacted material in geopolymers. The soluble material provides a reliable indication of the materials that can be removed from the geopolymers in a neutral pH environment and hence the potential for leaching and efflorescence, which is useful for durability prediction and service life. Quantification of remnant unreacted metakaolin determines the reactivity of the precursor and assesses the suitability of different synthesis conditions for varied applications. This work therefore provides a novel and widely applicable approach to determine the susceptibility of geopolymer materials to leaching.