Synergy between cellulose nanocrystals and calcium silicate hydrate-polycarboxylate ether enhances the strength and carbonation resistance of cement pastes

To promote both strength development and durability of cement, a new nanoscale cement additive (CCP) was designed and synthesized via a one-pot coprecipitation approach. CCP mainly comprised cellulose nanocrystals (CNCs), calcium silicate hydrate (C-S-H), and polycarboxylate ether (PCE). The crosslinking network of CNCs and surface attachment with PCE considerably increased the stability of the nano-C-S-H suspension, in which no precipitation was observed even after 180 days of storage. The addition of C-S-H nanoparticles in CCP considerably promoted cement hydration in the early stage of hydration, reducing the time required to reach the peak of hydration heat flow by 3.7 h. Therefore, CCP considerably increased the early flexural strength and compressive strength of cement pastes by 48.4 % and 82.7 %, respectively (vs. blank control, 16 h), and, due to the short circuit diffusion of CNCs, it still maintained a 12.3 % enhancement effect in flexural strength after 28 days. Notably, the addition of CCP improved the pore structure of cement pastes and decreased the carbonation depth by 43.9 %. Results indicate that CNCs and C-S-H nanoparticles synergistically enhance both the strength and carbonation resistance of cement pastes. This study contributes to the field of construction by using renewable biomass as a resource, accelerating the construction process, enhancing cement performance, and avoiding frequent maintenance.