Compressive strength and composite pore structure parameters of iron ore tailings ball concrete

Abstract

• Concrete with iron tailings ball as coarse aggregate is studied. • Compressive strength and pore structure of tailings ball concrete are analyzed. • The new fractal model well reflects the pore structure of tailings ball concrete. • The sensitive pore size is 0–160 µm for tailings ball concrete. • Composite pore structure parameter (P) for compressive strength is found. To investigate the relation between the pore structure and compressive strength of tailings ball concrete, compressive strength tests were subjected to normal concrete and different groups of tailings ball concrete (masterbatch and natural sand admixture as variables). The pore structure characteristics parameters of concrete were obtained with Rapidair457 concrete pore structure analyzer. The fractal dimension was calculated to analyze the intrinsic connection between the fractal dimension and pore structure of concrete, which were divided into three ranges to find sensitive pore size ranges. The results show that the compressive strength of tailings ball concrete increases and then decreases with increasing sand admixture. The masterbatch optimizes the pore structure and thus improves the compressive strength. Compared with other fractal calculation models, the solid mass fractal correction model takes into account not only coarse aggregates do not participate in the fractal, but also the influence of pores and solids, which better reflects the complexity of the internal structure of concrete. The small pore size in the range of 0 ∼ 160 µm is most influential to the compressive strength of tailings ball concrete. The composite pore structure parameter P is defined based on the three parameters of modified solid fractal dimension, air content at sensitive pore size range and specific surface area. The compressive strength and the parameter P satisfy a quadratic function relationship, and it can better characterize the compressive strength of tailings ball concrete with both these three factors considered.