Recycled mineral admixtures based on recycled clay brick

Abstract

The utilization of construction demolition waste as recycled mineral admixtures can simultaneously reduce cement consumption and the environmental impact on the construction industry. Thus, recycled mineral admixtures based on recycled clay brick powder (CBP) were prepared and circulating fluidized bed combustion (CFBC) fly ash was introduced as the activity compensation and sulfate excitation component. The effects of the hydration of recycled mineral admixtures on the mechanical performance and drying shrinkage of mortar were investigated. The results indicated that the incorporation of CFBC fly ash into the blended cement paste accelerated the hydration of C3S and shortened the induction period. The fly ash also promoted the secondary hydration of C3A and the conversion of ettringite to the monosulfate phase. The CBP consumed portlandite to form a calcium–silicate–hydrate gel at a later age, whereas CFBC fly ash promoted the pozzolanic reaction to occur earlier. The incorporation of the CBP and CFBC fly ash increased the porosity and pore volume of the blended paste.