Impacts of Mg/Al-layered double hydroxide modified with polycarboxylate on the properties of cement paste

Mg/Al-layered double hydroxide (Mg/Al-LDH) has been claimed as a potential hardening accelerator of cementitious materials. The performance of Mg/Al-LDH modified with polycarboxylate (PCE) superplasticizer incorporated into cementitious materials is vitally important, and needs to be completely understood. In this paper, four kinds of Mg/Al-LDH-PCE are incorporated into cement paste. The rheological performance and hydration process of the cement paste are analyzed. The results show that LDH-PCE is advantageous for modifying the rheological performance of fresh cement paste. With increasing content of LDH-PCE, the viscosity and the yield stress of fresh binder decrease gradually. Also, LDH3-PCE contributes to the lowest yield stress. The adoption of LDH-PCE prolongs the introduction period of cement paste, but contributes to an elevated exothermic peak in the acceleration period and enhances cumulative hydration heat flow, indicating enhanced hydration of silicates. Owing to the enhanced cement hydration with the adoption of LDH-PCE, more hydration products form in the matrix, and contribute to improved compressive strength. Among the four kinds of LDH-PCEs, the application of LDH3-PCE leads to the highest compressive strength of cement mortar at 28 days, with a 15.6% increment compared with the blank sample.