Carbonation treatment to repair the damage of repeatedly recycled coarse aggregate from recycled concrete suffering from coupling action of high stress and freeze-thaw cycles

Abstract

• It is feasible to recycle waste RAC in harsh environments by carbonation treatment. • Accelerated carbonation shows excellent repair effect on the damage of RRCA. • Producing C-RRCA per ton can capture 38.3 kg CO 2 with great environmental benefits. • RRAC with C-RRCA (content ≥ 6 %) shows good chloride ion permeability resistance. The recycling of waste recycled concrete (RC) has become a focus of many scholars. But the repeatedly recycling of RC used in harsh environments is still a difficult issue, due to the poorer quality of repeatedly recycled aggregate. This paper studied the repair effect of accelerated carbonation treatment on repeatedly recycled coarse aggregate (RRCA), which was collected from the failed parent recycled concrete via coupling action of high stress and freeze-thaw (F-T) cycles. Then the properties of carbonated repeatedly recycled aggregate concrete (C-RRAC) containing 0 %, 25 %, 50 %, 75 % and 100 % carbonated RRCA (C-RRCA) were evaluated. And the recycling potential of C-RRCA was explored, finally. The results suggested that accelerated carbonation treatment had excellent ability on repairing coupling damage of high stress and F-T in RRCA. Compared with RRCA, the apparent density of C-RRCA increased by 5.5 %, and water absorption, crushing value and soundness (mass loss) decreased by 26.6 %, 23.7 % and 19.9 %, respectively. The quality of C-RRCA was improved from type III to type II. With the growth of C-RRCA replacement rate, the water absorption, porosity, and chloride ion permeability coefficient of C-RRAC decreased by 34.4 %, 48 % and 55.6 %, respectively, and the compressive strength increased by 34.2 %. In addition, the C-RRAC could satisfied requirement of 100 years design service life of concrete structures in the E-type chloride environment, totally. According to the numerical fitting analysis, the minimum content of C-RRCA is 6 % under the condition that the compressive strength and chloride ion permeability of recycled aggregate concrete are met. It is feasible to recycle waste or even failed RC in high stress and F-T environment so as to reuse it in chloride environment, which provides a data support for effective utilization of waste RC under freeze-thaw environment.