Study on the use of CO2 to strengthen recycled aggregates and pervious concrete

Abstract

Recycled aggregates (RA) are crushed materials derived from waste concrete or construction debris that play a crucial role in the recycling of construction waste resources. However, RA's irregular particle shape and surface cement paste adhesions limit its potential in pervious concrete applications. To overcome this limitation, the use of carbonation treatment methods to process RA and produce recycled aggregate pervious concrete (RAPC) was investigated. RA was subjected to a pre-carbonation treatment, followed by the production of RAPC mixtures using three slurry-to-aggregate ratios, carbonation curing, and two-step carbonation strengthening, which enhanced the physical and mechanical properties of the specimens. Then, the measurements including permeability coefficient, connected pore fraction, splitting tensile strength, and CT microstructure analysis were performed. A carbon footprint accounting system from "cradle to gate" was conducted to assess the specimens. Our results highlight that an increase in the slurry-to-aggregate ratio in RAPC mixtures results in enhanced mechanical properties but negatively affects permeability performance. By pre-carbonating RA, we significantly increase the pervious concrete's splitting tensile strength, up to 100%, and maintain the compactability while ensuring permeability performance (maximum 3.91% reduction for specimens with slurry-to-aggregate ratio of 0.3). The carbonation treatment method used in our study has ideal environmental effects, as it theoretically sequesters up to 58.12% of the total carbon emissions produced during the production process.