Effects of a novel amide-alcohol bearing admixture on the hydration, microstructure and strength of Portland cement

Grinding aids and hydration accelerators (GA-HAs) are important admixtures for reducing energy consumption and enhancing cement performance, however, widely used alkanolamine GA-HAs have the drawback of only enhancing early strength while contributing little to the later strength development. In this study, a new amide-alcohol bearing admixture named Diethanolamine-Citrate (DC) was synthesized by using diethanolamine (DEA) and citric acid (CA). The addition of DC improved the particle size distribution of cement, delayed the initial setting time and shortened the final setting time of cement, and enhanced the fluidity of cement. The 28d compressive strengths of cement mortar added with DC were 16.4 % and 11.4 % higher than that of control group and cement mortar added with TEA, respectively. The incorporation of DC promoted the dissolution of cement, accelerated the overall hydration process of cement, increased the production of C-S-H and AFm, reduced the pore size and porosity, produced smaller (Sub-micron grains and nano-grains), tightly accumulated and partially amorphous CH. Moreover, CA is cheap and readily available industrial product that can reduce the cost of GA-HAs as synthetic feedstock. This study represents a breakthrough in preparing organic cement GA-HAs and provides a new approach to developing a novel type of amide-alcohol cement admixtures.