The particle-size effect of waste clay brick powder on its pozzolanic activity and properties of blended cement

Abstract

Abstract The manufacture of cement is considered as a high energy consumption and environmental pollution process, and it is necessary to figure out a way to reduce the consumption of cement in construction industry. The waste clay brick is a kind of construction waste with pozzolanic activity, which could be used to prepare blended cement after grinding. However, the particle size of clay brick powder (CBP) will influence its pozzolanic activity and properties of blended cement, which needs to be clarified. Therefore, in this study, the pozzolanic activity of CBP and properties of blended cement containing CBP were investigated. The results show that with the increase of grinding time, the CBP particles tend to be refined and spherical, which will increase the specific surface area and pozzolanic activity of CBP. The decrease of CBP particle size in blended cement paste can accelerate the early-age hydration and decrease the setting time since the ultrafine CBP could become the crystallization nucleus. The compressive strength of mortars with 30% CBP is 10%–35% lower than that without CBP, and the smaller the CBP particle size, the faster the compressive strength grows. Moreover, the hydration products and pore structure results also prove that the CBP with smaller particle size will consume more calcium hydroxide to react, which could make the microstructure denser and obtain stronger compressive strength growth at later ages. Meanwhile, the environmental impact and cost calculations indicate that the energy intensity and CO2 emissions of blended cement are obviously lower than Portland cement. It could be concluded that the pozzolanic activity of CBP will be enhanced with the decrease of particle size, and this research provided the reference for application of waste clay brick to produce green construction materials.