Experimental Research on the Microstructure and Strength Characteristics of Tailings Paste Containing Wate Reducer

Abstract

In order to study the effect of polycarboxylate superplasticizer (PCE) on the microstructure and strength characteristics of tailings paste, a total of 6 tailings paste combinations including 2 cement-sand ratios (20%, 40%) and 3 water reducer dosages (0, 0.40%, 0.80%) were investigated based on the indoor microstructure test (porosity measurement, XRD test, and SEM observation) and mechanical properties method. The strength of test blocks at different ages was obtained by numerical simulation. The results showed that: 1) The water reducer can effectively reduce the porosity of the tailings paste, and the reduction effect was more significant in the condition of high cement-sand ratios. Meanwhile, high cement-sand ratio is conductive to generate more beneficial hydrates such as portlandite; 2) Compared with the significant effect of cementitious agent on the tensile strength σt of the paste, the effect of water reducer on σt is weak. Accordingly, the σt of the tailings paste is much more sensitive to cementitious agent than water reduce; 3) SEM images show that the better ratio of slurry containing polycarboxylic acid superplasticizer has more C-S-H cementitious content, smaller pore size and shorter molecular chain between particles, indicating that the particles are more encapsulated and the early strength is improved. 4) The incorporation of water reducer enhancement was particularly significant under the condition of triaxial compression. However, the presence of water reducer did not change its deformation characteristics, when the confining pressure is low, the strain softening appears; and when the confining pressure is high, it transforms to strain hardening. The peak strain ε0 and the confining pressure σ3 had a linear relationship; 5) The strength of the paste was significantly affected by the confining pressure σ3 under different conditions. The peak intensity σ1 and the confining pressure σ3 satisfied a linear relationship, while the residual strength σr and the confining pressure σ3 satisfied a quadratic polynomial fitting relationship. The strength parameters cohesion c and internal friction angle ϕ were both positively correlated with the water reducer dosage.