Activation of phosphorous slag by chemical activators and quality improvers

Nowadays, partial or full replacement of Portland cement with industrial slags exhibiting latent hydraulic or pozzolanic properties is considered as an effective way of reducing energy consumption and environmental pollutions. Different methods of activation, such as chemical, can be used to activate the slag and to enhance its hydraulic properties. This work is devoted to chemical activation of phosphorous slag. Based on 28- and 60-day compressive strengths, an optimum mixture consisting of 80% phosphorous slag, 10% type II Portland cement, and 10% a compound additive has been considered for being activated and improved with chemical activators and quality improvers, respectively. A number of different chemical activators with two different quality improvers including Triethanolamine and Triisopropanolamine were used individually and in combinations. Based on the measured compressive strengths, addition of 1% NH4NO3 along with 0.04% Triethanolamine was the most effective combination. The 28- and 60-day compressive strengths of the activated cement mixture were increased to 77 and 105 MPa showing 15 and 25% growths compared to control values, respectively. Studies by X-ray diffractometry on 60-day cured hardened paste of the activated mixture have revealed that the microstructure is composed of an amorphous matrix.