Highly dispersed and thermally stable PCE-LDH and its application as hardening accelerator for mortar

Abstract

Layered double hydroxide (LDH), has recently been proposed as a potential concrete hardening accelerator. In this study, polycarboxylic superplasticizer-layered double hydroxides (PCE-LDH) nanoparticles were synthesized by modifying LDH nanosheets with PCE in an aqueous solution. The nanoparticles exhibited good dispersion as well as thermal stability in an aqueous solution with PCE absorbed on the surface of LDH nanosheets. As indicated by the isothermal calorimetry test, the addition of PCE-LDH can accelerate the hydration of Portland cement. The strength of acceleration was quantified by a previously proposed scale factor model and similar linear relationships were obtained between the scale factor and the PCE-LDH dosage at all temperatures tested. However, induction time was reduced by the addition of PCE-LDH at 20 °C and 15 °C but not at 25 °C. Specimens containing PCE-LDH showed increases in compressive strength by 69.1% at 16 h and 30.6% at 24 h, respectively, compared to the control ones. It was speculated that the surfaces of PCE-LDH nanoparticles may act as the nucleation sites for cement hydration products and thereby stimulate nucleation reactions. Considering its facile preparation, good dispersion and high thermal stability, the obtained PCE-LDH has great potential to be used as a hardening accelerator for mortar.