TEOS modified with PMHS as consolidating coating to improve the strength and hydrophobicity of earthen structures

•The unconfined compressive strength of earthen structures was improved by TEOS and PMHS.•The porosity and compactness of earthen structures were improved.•Modified consolidant could increase hydrophobicity by reducing surface energy.•TEOS and PMHS were connected with soil particles through Si-O-Si(Si-O-Al) bonds after hydrolysis. The surface weathering of earthen structures is a widely encountered and extremely harmful problem. To address this problem, the aim of this study was to evaluate the effect of tetra-ethyl-ortho-silicate (TEOS) modified with various proportions of polymethylhydrosiloxane (PMHS) as a consolidating coating on the strength and hydrophobicity of earthen structures by using the infiltration method. The protective effect of the consolidants was determined using contact angle, water droplet penetration time, unconfined compressive strength, and salt resistance tests. The maximum values of the unconfined compressive strength (7.73 MPa) and hydrophobicity (128.6°) of the earthen samples occurred when the PMHS content in the consolidant was 15%. SEM, XPS, and FTIR results revealed that PMHS-modified TEOS was cured via Si-O-Si bonds or agglomerated with soil particles through Si-O-Al bonds to increase soil strength after hydrolysis and, furthermore, that the methyl group of PMHS imparted a super-hydrophobic characteristic to the sample surface.