Effect of PDMS on the waterproofing performance and corrosion resistance of cement mortar

The currently used cement hydrophobic additives are either expensive or damageable during use, limiting their large-scale application on concrete. In this study, low-cost and commercially available polydimethylsiloxane (PDMS) is proposed as a cement admixture for the hydrophobic modification of cement mortar. The uniform distribution of PDMS in hardened cement mortar (HCM) attributes integral hydrophobicity to HCM. The PDMS modified HCM (M-HCM) surface exhibits superhydrophobicity, with a contact angle of 157.3° and a sliding angle of 8.7°. The superhydrophobic M-HCM is mechanically robust after being abraded for 110 m distance. In addition, the water absorption of the M-HCM reduced approximately 92.51%, and the corrosion resistance of the M-HCM obviously improved. The compressive strength and flexural strength of the M-HCM reduced by 30.9% and 18.1%, respectively, while the toughness of the M-HCM improved. Furthermore, the durability of the M-HCM against weathering, sulfate attack, and leaching significantly improved in comparison with the U-HCM. This type of mechanically robust superhydrophobic M-HCM material can be used in the waterproof concrete and anti-corrosive concrete.