The Influence of CO2-Cured Boiler Cinder on the Mechanical Strength of RPC Exposed to NaCl Erosion

Abstract

Boiler cinder is a kind of mining waste that may cause environmental pollution. Based on this reason, a processing method needs to be carried out. In this study, the influence of CO2-cured boiler cinder on the compressive and flexural strengths of reactive powder cement concrete (RPC) under NaCl actions is investigated. The mass loss rates (MLR) and the relative dynamic modulus of elasticity (RDME) are measured to reflect the resistance of NaCl erosion. The thermogravimetric analysis (TGA), scanning electron microscope (SEM), and X-ray diffraction (XRD) spectrum are obtained for revealing the mechanism of the macro performance. Results show that the relationship between the MLR and the mass ratio of CO2-cured boiler cinder fits the quadratic function with NaCl erosion. Meanwhile, the MLR during NaCl action are decreased by increasing the amount of CO2-cured boiler cinder. The MLR range from 0% to 5.3% during NaCl action, and the decreasing rate of MLR by CO2 curing on boiler cinder is 0%–51.3%. The function of RDME and the mass ratio of CO2-cured boiler cinder accords with the positive correlation quadratic function. The mechanical strengths decrease when NaCl erosion is encountered. The mechanical strengths’ decreasing rates of RPC are elevated with the increasing number of NaCl freeze–thaw cycles and the NaCl dry–wet alternations. The increasing rates of flexural and compressive strengths of RPC by 13.1%–36.3% and 11.2%–50.4% are achieved by adding CO2-cured boiler cinder. As observed from the TGA and SEM’s results, the addition of CO2-cured boiler cinder can increase the thermogravimetric value and the compactness of hydration products.