Mechanical Property and Microstructure of Cement Mortar with Carbonated Recycled Powder

Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete. In this paper, microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM, the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM, and the strengthening mechanism was analyzed. The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate. It is suggested that the replacement rate of recycled powder should not exceed 20%. The strength index and activity index of carbonated recycled powder mortar were improved, in which the flexural strength was increased by 27.85% and compressive strength was increased by 20% at the maximum. Recycled powder can be quickly and completely carbonated, and the improvement effect of CH pre-soaking carbonation was the best. The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder. Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect, alkaline polycondensation effect and carbonation enhancement effect.