A novel cellulose ether cross-linking modification and its effect mechanism on the properties of cementitious materials

Cellulose ether (CE) is a very important functional component of building materials, which can significantly improve the cohesiveness and water retention of mortar. However, the air entrainment of cellulose ether in cement-based materials would increase porosity and reduce their mechanical properties. In this study, a new cellulose ether modification technology was successfully invented based on the principle of cross-linking of boric acid and glyoxal to improve the comprehensive performance of mortar. The influence of modified cellulose ether on the working and mechanical properties of mortar was systematically studied. The mechanism of the modified cellulose ether on the performance of mortar was revealed. The results show that the cellulose ether hydroxyl groups were successfully cross-linked with boric acid and aldehyde groups by the novel cellulose ether modification technique. A three-dimensional spatial network structure was formed on a cellulose ether molecular chain. The modified cellulose ether significantly improved the water retention and thickening properties of cementitious materials. Cellulose ether doping of 0.09 % has the best performance, and the water retention of mortar after boric acid modification increased by 17 %. The viscosity of the modified mortar was increased and the fluidity was decreased. In addition, the cellulose ether modified by glyoxal improved the mechanical properties of mortar. The flexural strength and compressive strength at 7 d increased by 14.05 % and 7.12 %, compared with the control group. Through scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) experiments, it was shown that the aldehyde group and boric acid of modified cellulose ether strengthen the intertwining of the molecular chain and increase the flexibility of the polymer chain. As a result, the comprehensive performance of the mortar is significantly improved.