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Efflorescence mitigation in construction and demolition waste (CDW) based geopolymer
Journal of Building Engineering ( IF 6.4 ) Pub Date : 2022-07-30 , DOI: 10.1016/j.jobe.2022.105001
Jiawei Tan, Özlem Cizer, Brecht Vandevyvere, Jentel De Vlieger, Hancheng Dan, Jiabin Li

Using construction and demolition waste (CDW) as a raw material in geopolymer synthesis is gaining a growing interest owing to the dwindling availability of traditional aluminosilicate sources. However, CDW-based geopolymer (CDWG) is more prone to efflorescence due to the relatively low reactivity of CDW. Up till now, the efflorescence mitigation in CDWG has not been well documented. This study compared the effect of Al-rich admixtures, i.e., metakaolin (MK), and Ca-rich admixtures, i.e., ground granulated blast furnace slag (GGBS), on the efflorescence mitigation in CDWG. Results showed that both MK and GGBS addition significantly reduced the efflorescence formation of CDWG, but were based on different mechanisms. MK addition significantly decreased the number of excessive alkalis (from 24.5 to 10.2 mol%) through Al species introduction and N-A-S-H gels formation. Although GGBS addition only marginally reduced the excessive alkalis (from 24.5 to 19.9 mol%), it reduced the porosity and capillary water absorption of the geopolymer samples through C-A-S-H gels formation, hereby impeding the migration of alkalis and reducing the efflorescence extent. However, considering the risk of crystallization pressure and cracks induced by internal efflorescence in GGBS-containing samples, adding Al-rich materials (e.g., MK) is a better choice to mitigate efflorescence in CDWG. These findings also bring insights into efflorescence mitigation schemes and mechanisms of geopolymer sourced from other materials.



中文翻译:

基于建筑和拆除废物 (CDW) 的地质聚合物的风化缓解

由于传统铝硅酸盐来源的可用性不断减少,使用建筑和拆除废物 (CDW) 作为地质聚合物合成的原材料正引起越来越多的关注。然而,基于 CDW 的地质聚合物 (CDWG) 由于 CDW 的反应性相对较低,因此更容易风化。到目前为止,CDWG 中的风化缓解还没有得到很好的记录。本研究比较了富铝外加剂(即偏高岭土 (MK))和富钙外加剂(即磨碎的粒状高炉矿渣)的效果(GGBS),关于 CDWG 中的风化缓解。结果表明,MK和GGBS的添加都显着减少了CDWG的风化形成,但基于不同的机制。MK 添加通过 Al 物种的引入和 NASH 凝胶的形成显着减少了过量碱的数量(从 24.5 到 10.2 mol%)。虽然 GGBS 的添加仅略微减少了过量的碱(从 24.5 到 19.9 mol%),但它通过 CASH 凝胶的形成降低了地质聚合物样品的孔隙率和毛细管吸水率,从而阻碍了碱的迁移并降低了风化程度。然而,考虑到在含 GGBS 的样品中由内部风化引起的结晶压力和裂纹的风险,添加富铝材料(例如,MK)是减轻 CDWG 风化的更好选择。

更新日期:2022-07-30
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