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

Abstract

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 Carb-RBP, 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.