Evaluation of Workability and Mechanical Properties in Cement Mortar after Compounding Igneous Rock Powder and Silica Fume

Abstract

In order to investigate the influence of igneous rock powder and silica fume on the performance of cement mortar, facilitate the application of igneous rock powder in engineering, and promote the greening of the cement industry, this study examined the pozzolanic activity of three different types of igneous rock powders: granite, andesite, and tuff. It explored the workability and mechanical properties of both binary systems (igneous rock–cement) and ternary systems (igneous rock–silica fume–cement). Microscopic techniques including X-ray diffraction (XRD), thermogravimetric analysis–differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and nitrogen adsorption were used to investigate the mechanisms of how different types of igneous rock and silica fume affect the cementitious systems. The results showed that the pozzolanic activity of igneous rock powders was relatively weak, and their inclusion at levels below 20% had minimal impact on the flowability of cement mortar. In fact, within the 20% inclusion range, andesite powder even increased the flowability. Co-blending igneous rock powders with silica fume promoted the early hydration of cement, resulting in reduced calcium hydroxide (CH) content in the hydration products. The most significant increase in strength of the cement mortar system was observed when 5% to 10% (by mass) of igneous rock powder and 5% to 10% of silica fume were used as replacements for cement. The highest cement mortar strength was achieved when 10% andesite and 10% silica fume were used as replacements, resulting in a compressive strength of 52.2 MPa.