Effects of curing temperature on mechanical properties of polymer-modified OPC-CA-gypsum repair mortar

Abstract

Portland cement-aluminate cement-gypsum (OPC-CA-gypsum) has the advantages of quick setting, early strength, stable later strength and good shrinkage compensation. It is often used as pavement repair material. However, this cementitious system still has the disadvantages of low toughness and high brittleness, which can be improved by the addition of polymers. At a higher temperature, there is a contradiction between the film-forming effect of the polymer and the stability of the hydration product of this cementitious system. The polymer film is easy to form but the OPC-CA-gypsum hydration products are easy to decompose with the temperature increases. In this paper, the flexural strength, compressive strength, toughness and water absorption of OPC-CA-gypsum modified by styrene-butadiene rubber (SBR) and styrene-acrylic emulsion (SAE) were studied at different curing temperatures. The mechanism was analyzed by XRD and SEM. The results showed that both SBR and SAE can improve the flexural strength and toughness of OPC-CA-gypsum mortar effectively but reduce the compressive strength. The optimal dosages of SBR and SAE were 8% and 12%. SAE has the most obvious effect on improving toughness at high temperature. At 40℃ and 60℃, the toughness of SAE modified OPC-CA-gypsum were 2.7 times and 4.0 times pure OPC-CA-gypsum. The curing temperature can affect polymer-film formation and the morphology and quantity of hydration products, then affect the properties of polymer modified OPC-CA-gypsum.