Reinforcement of ultra-low dosage of polycarboxylate ether (PCE) grafted nano-silica sol to the mechanical and durable properties of cement mortar

How good dispersion of nano-SiO2 (NS) plays a great influence on how strong reinforcing efficiency to cement-based materials. In this study, a novel nanohybrid of polycarboxylate ether (PCE) grafted nano-silica sol (PCE@NSS) was prepared by sol–gel methods to chemically adsorb PCE onto NSS. The developed nanohybrid showed a higher ultraviolet–visible (UV–Vis) absorbance and slower sedimentation in alkaline solutions, indicating the better dispersion and stability of PCE@NSS than that of untreated NSS. By this way, only 0.05 wt.% addition of PCE@NSS was helpful to refine the capillary pore size and reduce the total porosity of cement mortar, which in turn improved the compressive and flexural strength of cement mortar by 18.34% and 10.5% at 28 days, respectively. In addition, a reinforcing index (R index) with the ratio of strength enhancement % to dosage % was proposed, indicating that the R index of PCE@NSS showed 10 times higher than that of other NS-based nanomaterials reported in literatures, addressing the highly reinforcing efficiency of PCE@NSS to cement mortar. Furthermore, water absorption coefficient of cement mortar was therefore reduced by 12.7% with 0.2 wt.% addition of PCE@NSS. In conclusion, such an ultra-low dosage of PCE@NSS with better dispersion and stability exhibited great potential to reinforce cement-based materials with highly efficiency, lower cost and reduced carbon emissions.