Experimental study on selection of early-strength agent for low-strength cementitious materials prepared with manganese tailings

The early-strength characteristics and mechanism of eight kinds of early-strength agents in low-strength cementitious materials prepared with manganese tailings were studied, and then the optimum mixing amount was obtained by means of progressing and superimposing optimization. The phase composition and morphology of hydration products were characterized through X-ray diffraction and scanning electron microscopy. The results indicated that there existed good superimposing effect among triethanolamine, ferric chloride and lithium carbonate. When the mixing amount of triethanolamine, ferric chloride and lithium carbonate were 0.04, 0.3 and 0.7%, the compressive strength of 3- and 7-day net paste samples increased by 105.5 and 34.5%, while the porosity of 3- and 7-day decreased by 8.3 and 7.4%, respectively. The initial setting time shortened from 130 to 65 min. Therefore, the combination of early-strength agents could accelerate the dissolution of tailings, shorten hydration cycle, increase the amount of ettringite and calcium silicate hydrate, compact the internal structure further, reduce the porosity, which could achieve the compressive strength improved in short time.