Enhancing waterproof performance of alkali-activated slag by optimising pore structure and introducing hydrophobic groups using tetraethoxysilane

In this study, tetraethoxysilane (TEOS) was added into alkali-activated slag (AAS) to enhance water resistance. The products of TEOS hydrolysis and condensation were analysed and characterised. Meanwhile, the influences of TEOS on compressive strength, fluidity, setting time, pore structure, water absorption process, hydration products and water contact angle of AAS were studied. The experimental results demonstrated that the presence of unhydrolysed TEOS slightly enhanced the fluidity and prolonged the setting time of AAS. Additionally, while the incorporation of TEOS slightly reduced the formation of hydration products after 28 days, the nucleation and filling effects of the nano-silicon dioxide particles accelerated the long-term hydration process of AAS. As a result, the compressive strength of the material improved by a maximum of 6.56% after 90 days. By optimising the pore structure and introducing hydrophobic groups into the AAS, the waterproof performance of TEOS-modified AAS has been significantly enhanced. As a result, the water contact angle increased from 20.05° to 64.05°, and capillary water absorption was reduced by 1.79–13.52% with the addition of TEOS.