碱当量对偏高岭土基地聚物砂浆早期收缩行为影响研究

Effect of Alkali Equivalent on Early Shrinkage of Metakaolin Based Geopolymer Mortars

研究了不同碱当量水玻璃溶液为碱激发剂的偏高岭土基地聚物砂浆的早期收缩和水化放热特性。结合孔隙溶液表面张力和砂浆内部相对湿度计算了地聚物砂浆的毛细管半径及毛细管应力,基于此讨论了地聚物砂浆早期收缩影响机制。结果表明,新拌阶段收缩主要与偏高岭土颗粒形貌及所处的碱性环境有关,碱当量越高,偏高岭土颗粒吸水量越大,浆体收缩越大。地聚物砂浆凝结硬化阶段收缩主要与毛细管应力有关,高碱当量会导致偏高岭土溶解程度增大,砂浆相对湿度降低,孔隙溶液表面张力增大,从而细化砂浆内部毛细管半径,增大毛细管拉应力,导致收缩变大。

The effect of the alkali equivalent of water glass on the characteristics of early shrinkage and hydration heat properties of metakaolin based geopolymer mortars was investigated.Combining the surface tension of pore solution and the inner relative humidity of geopolymer mortars,the capillary radius and capillary stress were calculated.On this basis,the mechanism of early shrinkage of geopolymer mortars was discussed.The results show that the early shrinkage of fresh geopolymer mortars is mainly related to the morphology of metakaolin particles and the corresponding alkaline environment.The higher the alkali equivalent,the higher the water absorption of metakaolin particles and the larger the mortars shrinkage.There is a close correlation between the shrinkage of geopolymer mortars and the capillary stress during the setting-hardening period.High alkali equivalent increases the dissolution of metakaolin,decreases the relative humidity of mortars,and increases the surface tension of pore solution,which refines the inner capillary radius of mortars,increases the tensile stress of capillary,and causes shrinkage to become larger.