Hydrothermal durability of Ca-polyester complexed polymer concrete

Polymer concretes (PC) consisting of an unsaturated polyester (UP)-styrene (St) copolymer binder and a silica-type aggregate possess very poor hydrothermal durability because of the hydrolytic instability of the carboxylic ester existing in the main chains of the UP. It was found that the addition of beta dicalcium silicate (β-C₂S) as a filler in the PC helps to prevent the severe physical degradation of UP-PC which occurs when the hydrolysis reactions take place. This is due to the formation of ionic bonding between the strongly nucleophilic reagent Ca²⁺ ions released from β-C₂S in an aqueous medium and the carboxylate anions (?COO^?) of esters. UP-PC specimens containing Ca²⁺ ion complexed bridge structures of ionic bonding in their main chains display significant improvement in hydrothermal stability at elevated temperatures. In addition, the interaction mechanism of UP with β-C₂S occurring during exposure in an autoclave is also discussed from the results of infrared absorption analysis.