Yan Dongming, Xie Lingjun, Qian Xiaoqian, Ruan Shaoqin, Zeng Qiang
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China.
Materials (Basel). 2020 Jul 3;13(13):2973. doi: 10.3390/ma13132973.
The understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The pore structure and strength were measured by mercury intrusion porosimetry and compression tests, respectively, which both showed obvious correlations with the material composition. Mass loss, strength loss, visual rate, and microscopic observation were adopted to assess the changes of the material properties and microstructure caused by F-T loads. The results showed that the strength-porosity relationship roughly followed a linear plot. Increases of the Si/Al ratio increased the capillary pore volume, but decreased the gel pore volume and the F-T resistance. Increases of the Na/Al ratio decreased the gel pore, but roughly enhanced the F-T resistance. The MKG mortar at the Na/Al ratio of 1.26 showed the lowest total pore volume and the best F-T resistance. The mechanisms of our experimental observations were that the abundantly distributed air voids connected by the capillary pores facilitated the relaxation of hydraulic pressures induced by the freezing of the pore liquid. The findings of this work help better clarify the compositional dependence of the pore structure, strength, and freezing-thawing resistance of MKG materials and provide fundamental bases for their engineering applications in cold regions.
了解地质聚合物材料的成分依赖性特性和抗冻融（F-T）性能对于其在寒冷地区的应用至关重要。在本研究中，通过控制硅铝比（Si/Al）和钠铝比（Na/Al）制备了偏高岭土基地质聚合物（MKG）砂浆。分别采用压汞法和压缩试验测量了孔隙结构和强度，二者均与材料成分呈现出明显的相关性。采用质量损失、强度损失、外观变化率和微观观察来评估冻融荷载引起的材料性能和微观结构变化。结果表明，强度与孔隙率的关系大致呈线性关系。硅铝比的增加会使毛细孔体积增加，但凝胶孔体积和抗冻融性能降低。钠铝比的增加会使凝胶孔减少，但大致会增强抗冻融性能。钠铝比为1.26的MKG砂浆总孔隙体积最低，抗冻融性能最佳。我们实验观察结果的机制是，由毛细孔连接的大量分布的气孔有助于缓解孔隙液体冻结引起的水压。这项工作的研究结果有助于更好地阐明MKG材料孔隙结构、强度和抗冻融性能的成分依赖性，并为其在寒冷地区的工程应用提供基础依据。
