Promotion on self-healing of cracked cement paste by triethanolamine in a marine environment

Abstract

In order to hinder ingress of aggressive ions from sea water via cracks efficiently, it is of great significance to realize rapid self-healing in concrete. In this study, the feasibility to promote self-healing of cracked cement paste in sea water by using triethanolamine (TEA) was investigated. To enlarge the effects of TEA, 0.5–2% (by mass of cement) TEA was added into cement pastes and it was found that TEA can dramatically enhance the self-healing efficiency in sea water conditions. In cement pastes with TEA more than 1% (by the mass of cement), the crack closure ratio can reach 100% at a healing period of 1 d in sea water, 20 times faster than a cement paste without TEA. The permeability of cracked specimen with TEA decreased by about 90% after a healing period of 2 days. At the early stage of self-healing promoted by TEA, large amounts of Mg(OH)2 was formed, accounting for about 70 wt% of the reaction products of self-healing. It is well known that TEA can not chelate with Mg2+ ions. Therefore, the large amounts of Mg(OH)2 leading to complete self-healing of cracks in a short time indicates that the promotion on self-healing by TEA was not mainly caused by the chelating action. Experimental results show that in sea water with the high concentration of Mg2+, the property of TEA to increase its surrounding OH− concentration induces the formation of Mg(OH)2. This is the main mechanism of the promotion on self-healing of cracks by TEA in cement paste in sea water.