Investigation on basic properties and durability of metakaolin based geopolymer modified with silane

Abstract Durability is of great importance property in the sustainable development of green building materials. In this paper, metakaolin based geopolymer was used as control group and modified geopolymer specimens were prepared by adding different dosages (1–4 wt%) of APTES (3‐Aminopropyltriethoxysilane) to study the effect of silane on basic properties and durability of metakaolin based geopolymer. Meanwhile, microscopic tests were used to reveal the mechanism of geopolymer modified with silane on durability performance. Basic properties and durability experiments included fluidity, consistency, mechanical strength, sulfate wet‐dry cycles, and freeze–thaw cycles. Microscopic experiments included SEM, XRD, N₂ adsorption–desorption for characterization. The results showed that 1–2 wt% APTES modified geopolymer specimens improved the fluidity and consistency. However, excessive dosages inhibited fluidity and consistency of specimens. On the other hand, with the increase of APTES contents, mechanical strength under 7th days and 28th days showed a trend of first rise and then fall. Sulfate dry‐wet cycles experiments under 28th days and 56th days indicated that with the increase of APTES dosages, the weight loss of modified geopolymer decreased firstly and then increased compared to the control group, while coefficient of sulfate resistance showed the opposite trend. The 25 times and 50 times freeze–thaw cycles experiments were consistent with the changes of sulfate dry‐wet cycles results. Microscopic experiments were used to characterize the control and modified groups and to reveal the mechanism on basic properties and durability of geopolymer modified with silane.