Effect of the accelerated carbonation treatment on the recycled sand physicochemical characteristics through the rolling carbonation process

Abstract

Accelerated carbonation was employed to improve the physicochemical properties of the recycled sand through CO2 sequestration by a method called rolling carbonation. The carbonation process was fully evaluated by varying some parameters such (i) moisture of the sand, (ii) rotation speed, (iii) recycled sand amount in the reactor, (iv) initial internal pressure, and (v) partial CO2 pressure.The rolling speed, initial moisture content, and mass amount played an important role in CO2 sequestration. The best rolling carbonation condition (at atmospheric pressure and 7 h) was at 4% of moisture, 500 g, and 100 rpm, under such conditions an increasing mass of 23.0 mg/g was reached while at the static condition was 5.0 mg/g. However, when the internal pressure increases from 1.014 to 1.4 bar an increase of more than double in the CO2 sequestration was reached, from 23.0 to 47.5 mgCO2 per gram of recycled sand. Phenolphthalein test indicated that rolling carbonation efficiently carbonated the entire aggregates with at least 6.0 mm of particle size.The rolling system yielded rounded aggregates with less rough-textured surfaces which can provide better workability when used in producing new concrete. The water absorption capacity in the carbonated samples was lower than that of non-carbonated while the densities were higher in the carbonated samples.The results showed that rolling carbonation is an interesting method for improving recycled sand physicochemical properties.