Fabricating hydrophobic silica fume to improve mechanical strength and anti-corrosion of integral hydrophobic cement mortar and its carbon emission assessment

Integral hydrophobic concrete possesses superior waterproof performance and can prevent internal concrete and steel bar from erosive ions attacking in marine environment. However, the low mechanical strength limits its application. Silica fume (SF) and stearic acid (SA) were used to prepare hydrophobic SF by ball milling. Further, the prepared hydrophobic SF was added to cement mortar to fabricate integral hydrophobic cement mortar. Effects of hydrophobic SF on compressive strength, water resistance and anti -corrosion performance of integral hydrophobic cement mortar were investigated. Besides, the cement hydration products and morphology were analyzed after the addition of hydrophobic SF. The results showed the compressive strength of integral hydrophobic cement mortar reached 48.3 MPa. The contact angle of integral hydrophobic cement mortar surface arrived 151.5-152.7. The capillary absorption coefficient also reduced by 93.06 %-93.67 % compared with the control group. Electrochemical test results showed the integral hydrophobic cement mortar provided a long-term protection for the embedded steel bar. The hydrophobicity and pozzolanic effect of the hydrophobic SF made cement mortar a high strength, good water resistance and corrosion resistance. Additionally, the global warming potential (GWP) of hydrophobic cement mortar was calculated based on life cycle assessment (LCA). It showed that the GWP and environmental impacts of hydrophobic cement mortar reduced.