钙基膨润土对碱激发复合砂浆干燥收缩性能影响

Effect of Calcium Bentonite on Drying Shrinkage Properties of Alkali Activated Composite Mortar

为改善碱激发矿渣胶凝材料(AAS)干燥收缩率较大的问题,将钙基膨润土(CB)作为胶凝材料,水玻璃(WG)作为碱性激发剂制备膨润土复合砂浆,通过在AAS中掺入CB,对其性能进行宏观和微观试验,分析了不同CB掺量对AAS性能的影响及机理。试验结果表明,掺入CB的AAS第一、二阶段干燥收缩均有不同程度的改善,抗压强度呈现随CB掺量增大而提升的趋势。3.75%碱掺量、15%CB掺量为最佳配比,有利于提升AAS的抗压强度和减缩性能,最大抗压强度提升率为20%,最高减缩率为49%。CB可吸附体系中自由水,减少水分蒸发。反应后期,蒙脱石在碱性条件下溶解,同时在反应产物中发现水钙沸石相生成。说明溶解后的CB参与了AAS的水化反应,且溶解沉淀后的CB可有效填充水化孔隙,使水化结构更加致密,减少了裂缝的产生。

To improve the problem of the large drying shrinkage of alkali-activated slag cementitious material(AAS),calciumbentonite(CB)was used as cementitious material mixed with water glass(WG)to prepare bentonite composite mortar.Incorporating CB into AAS,test was carried out to analyze the impact and mechanism of different CB content on AAS’s performance.The test results show that the drying shrinkage of AAS was improved at the first and second stages,and the compressive strength was enhanced with the increase of CB admixture.3.75%WG and 15%CB was the optimal mixing ratio.It is beneficial to improve the compressive strength and reduce the drying shrinkage of AAS,the compressive strength improvement rate is 20%,and the drying shrinkage reduction rate is 49%.The CB could adsorb free water in the system and reduce water evaporation.Montmorillonite was dissolved under alkaline conditions at the later stage of the reaction,while the aqueous calcium hydrocalcite phase was found to be generated in the reaction products.It indicated that CB was involved in the hydration reaction of AAS.The dissolved precipitated CB could effectively fill the hydration pores,lead to a dense hydration structure and reduce the generation of cracks.