Geopolymers have attracted attention as green building materials with low carbon dioxide emissions and excellent mechanical properties. Due to their hydrophilicity and porous structure, geopolymers can be infiltrated by water involving harmful ions. In this study, the effects of polydimethylsiloxane (PDMS) as an additive on the wettability, mechanical properties and microstructure of metakaolin-based geopolymer were investigated. The microstructure was characterized by MIP, μ-XCT, SEM, EDX, TIM, XRD, FTIR and ²⁹Si NMR test. As the PDMS content increased, the geopolymer became hydrophobic, increasing its contact angle to approximately 140°. This hydrophobicity mainly results from the chemical modification and the increased roughness of the matrix. PDMS, with the content over 1.5 mL/L, can raise the porosity and pore size of the geopolymer, and promote the transformation of small gel pores into transitional and capillary pores. The fluffy pore structures and cured hybrids jointly created nano-scale and micron-scale roughness structures. No new crystalline phases will be generated by adding PDMS. The compressive strength increased with the addition of a small amount of PDMS, while it began to decrease when the PDMS content exceeded 10 mL/L. The effect of PDMS with different contents on the pore and silicate structure of geopolymers leads to changes of mechanical properties. The hybridization mechanism of PDMS molecules and N-A-S-H was summarized based on microstructure analysis.

地质聚合物作为具有低二氧化碳排放量和优异机械性能的绿色建筑材料备受关注。由于其亲水性和多孔结构，地质聚合物可以被含有有害离子的水渗透。在这项研究中，研究了聚二甲基硅氧烷 (PDMS) 作为添加剂对偏高岭土基地质聚合物的润湿性、力学性能和微观结构的影响。通过 MIP、μ-XCT、SEM、EDX、TIM、XRD、FTIR 和²⁹硅核磁共振测试。随着 PDMS 含量的增加，地质聚合物变得疏水，其接触角增加到大约 140°。这种疏水性主要是由于化学改性和基质粗糙度的增加。PDMS含量超过1.5 mL/L时，可以提高地聚合物的孔隙率和孔径，促进凝胶小孔向过渡孔和毛细孔的转化。蓬松的孔隙结构和固化的混合体共同创造了纳米级和微米级的粗糙度结构。添加 PDMS 不会产生新的结晶相。抗压强度随着少量PDMS的加入而增加，而当PDMS含量超过10 mL/L时，抗压强度开始下降。不同含量的PDMS对地质聚合物的孔隙和硅酸盐结构的影响导致其力学性能发生变化。基于微观结构分析总结了PDMS分子与NASH的杂交机制。