Effect of modified lignosulfonates additive on properties of cement mortar

In order to improve the compressive strength and seepage resistance of cement mortar, the modified lignosulfonate additive GCL1-M was prepared, with the calcium lignosulfonate (CLS) from the black liquor of paper-making as the main material. The physical and mechanical properties as well as the microstructure of the mortar were then investigated. The results indicate that, with the addition of GCL1-M, the water-reducing ratio of the mortar reaches 30%, and the 28-day compressive strength and seepage pressure of the mortar with 0.30% of GCL1-M are respectively raised by 20% and 230%. The nitrogen adsorption and SEM measurements show that the addition of GCL1-M decreases the heat-releasing rate of cement hydration and the pore size of the mortar, but increases the seepage resistance of the mortar. Moreover, the results of adsorption performance test and environmental scanning electron microscopy reveal that the GCL1-M may be absorbed on the cement surface in a network form. Thus, the static repelling force between cement particles increases and the dispersive and water-retention performances of GCL1-M on the mortar improve, which may result in the improvement of the seepage resistance and the compressive strength of the mortar.