Sequestration and utilization of carbon dioxide to improve engineering properties of cement-based construction materials with recycled brick powder: a pathway for cleaner construction

The research explores the possibility of utilizing carbon dioxide to modify the properties of recycled brick powder (RBP) and enhance the engineering performances of RBP-mortar. The RBP, crushed to the size range of 0.075 to 4 mm, is carbonated by exposing to 5% CO2 for 4 h and characterized for phase composition, porosity and micro-structure. The non-carbonated RBP (RBP) and pre-carbonated RBP (Carb-RBP) are applied to replace 25% and 75% of manufactured sand (M-sand) in cement mortars maintained at similar flow level (110 - 113%), which are then cured under three conditions - (i) ambient condition (N), (ii) 4 h of steam curing followed by moist and dry curing (STC), and (iii) accelerated CO2 curing (5% CO2 of 99% purity) for 4 h followed by moist curing and dry curing (CC). Physico-chemical characterizations suggest that Carb-RBP has higher micro-pore volume and surface area contributed by pores in the size range of 1 nm to 3 nm than RBP. After carbonation, the reactivity of RBP in alkaline environment is increased due to CO2-induced breakdown of calcium and alumino-silicate minerals into calcium carbonate and silica gel. Due to addition of 25% and 75% RBP and CarbRBP, hydration kinetics is accelerated by 4 - 4.50 h compared to control due to nucleation of hydration products on the surfaces of RBP. Faster precipitation of hydration products, more micro-pore sites in RBP and higher porosity due to increased water demand enhance the carbon sequestration in RBP-mortars and Carb-RBP mortars by 30-82% compared to control (0% RBP). Use of Carb-RBP to replace 25% of M-sand offer similar compressive strength as control and 19 - 21% higher strength than mortars with RBP (non-carbonated). CO2 curing also reduces the total shrinkage of mortars with recycled brick powder by 12 - 17% compared to ambient curing and steam curing due to densification by calcium carbonate crystals. The findings from this research strongly suggests a significant reduction in embodied carbon of Portland cement-based construction materials by utilizing a combined approach of carbon sequestration and replacement of fine aggregates by recycled brick powder.

Automated summary

This research explores the possibility of using carbon dioxide to modify the properties of recycled brick powder (RBP) and enhance the engineering performances of RBP-mortar. The study suggests that carbonated RBP has higher micro-pore volume and surface area, leading to increased carbon sequestration and higher strength in RBP-mortars. The findings strongly recommend a combined approach of carbon sequestration and replacement of fine aggregates by recycled brick powder to reduce the embodied carbon of Portland cement-based construction materials.