Preparation Technology and Properties of Carbon-Reinforced Recycled Aggregate Concrete and Mortar

Abstract

Crushing the demolished waste concrete as aggregate to prepare fresh concrete may cause aggregate internal damage leading to strength reduction. To counter this issue, in the current study, the recycled aggregate is mixed with nano-calcium oxide in a vacuum reactor, and then a high concentration of carbon dioxide is introduced to fill the internal damages of the recycled aggregate. A layer of hydrophilic alkaline substance is formed on the surface of recycled aggregate to absorb carbon dioxide, which improves the strength of recycled aggregate particles and the bonding performance of aggregate-cement interface area. The test results show that the mechanical properties of recycled aggregate particles are improved after vacuum carbon strengthening, and the vacuum carbon strengthening effect of recycled aggregate with large particle size is more obvious. Compression strength of concrete and mortar prepared by vacuum carbon-reinforced aggregate is observed to be 13.6% and 30% higher than ordinary recycled concrete, respectively. Also, the proposed recycled aggregate improvement method manifests a 21.1% reduction in carbon emissions. These findings offer crucial parameters for the engineering use of recycled concrete, promote new ideas to reduce carbon emissions caused by fresh concrete production, and provide an important reference for the sustainable recycling of waste concrete.