Mechanical properties and microstructure of cement-fly ash-dacite powder composite cementitious system

Abstract

This study used the indexes of fineness, pozzolanic activity, hydration heat, mortar fluidity and strength, and circular cracking degree, and combined the techniques of SEM, EDS, XRD, MIP, and TG-DSC. We investigated the effect of different finenesses and contents of dacite powder on the mechanical properties and microstructure of the composite cementitious system. The results showed that the median diameter of 12 μm of dacite powder has better basic properties, and can be used together with cement and fly ash as cementitious materials in mortar systems. The addition of dacite powder can effectively improve the crack resistance of the composite cementitious system. The microscopic test found that dacite powder has the ''filling role'' and ''nucleation role'' in the system, which is reflected in the optimization of the pore structure, improves the interfacial adhesion, reduces the evaporation of free and adsorbed water, and reduces the rate of quality loss.

Keywords

• Green building material
• Dacite powder
• Composite cementitious system
• Mechanical properties
• Microstructure