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

Abstract

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 superplasticizer (PCE) adopted into cementitious materials was vitally important, which was urgently necessary to be thoroughly revealed. In this paper, the adoption of four kinds of Mg/Al-LDH-PCE into cement paste has been conducted. The rheological performance and hydration process of cement paste have been analyzed. The results showed that LDH-PCE was advantageous for modifying rheological performance of fresh cement paste. With increased content of LDH-PCE, the viscosity and the yield stress of fresh binder decreased gradually. And LDH3-PCE contributed to the lowest yield stress. The adoption of LDH-PCE prolonged the introduction period of cement paste, but contributed to elevated exothermic peak in the acceleration period and enhanced cumulative hydration heat flow, indicating enhanced hydration of silicates. Due to the enhanced cement hydration with the adoption of LDH-PCE, more hydration products formed in the matrix, and contributed to improved compressive strength. Among the four kinds of LDH-PCEs, the application of LDH3-PCE led to the highest compressive strength of cement mortar at 28d, with 15.6% increment compared with the blank sample.