Compressive strength properties of green bricks cured with hydration and accelerated carbonation curing

Abstract This study was aimed at investigating the potential of lime kiln dust (LKD) and ground granulated blast furnace slag (GGBFS) as alternative cementitious materials, and fine rubber crumbs (FRC) from waste tyres as a partial replacement for sand in brick production. The study focused on determining the design mix that yields optimal strength characteristics when assessing two curing regimens: water curing and accelerated carbonation curing (ACC). After considering various design mixes, two mix designs (1:3 and 1:2) were selected as optimal for the two curing regimens evaluated. For samples produced with the 1:3 (LKD-GGBFS blend: sand) mix design, a water binder ratio of 0.45 was used, and FRC replacement was implemented in increments of 0%, 5%, and 10%. These specimens were subjected to water curing for 7, 14, and 28 days, and subsequently tested. For the 1:2 (LKD-GGBFS blend: sand) mix design, a water binder ratio of 0.4 and FRC replacement in steps of 0%, 5%, and 10% were used. These samples were subjected to ACC using CO 2 for 30, 48 and 72 h, soaked in water for 3 days and thereafter tested. At the end of the investigations, compressive strengths (CS) at 28 days of water curing were 6, 5, and 3 MPa for 0%, 5%, and 10% FRC content, respectively. Furthermore, at 72 h of carbonation, the respective compressive strengths of 7 MPa and 4 MPa were recorded for 0% and 5% FRC content, with a value of less than 3 MPa recorded for the 10% FRC sample. With the results obtained, the bricks produced in this study meet the minimum strength requirements of 5 MPa and 3 MPa for load-bearing and non-load-bearing bricks, respectively, for building small houses. Subsequently, scanning electron microscopy and energy-dispersive X-ray spectroscopy were conducted, highlighting the morphologies and elements responsible for the strength gain in the samples. Lastly, statistical analysis of the data was carried out using multiple linear regression (MLR). Key variables considered in the MLR analysis included curing regimens, curing durations, and FRC contents, all of which significantly influenced the CS of the samples. ACC showed a stronger predictive capability for predicting the strength of the samples, even though different mix designs were considered. According to the study, the 1:2 mix design is recommended in instances where a time constraint exists, as it provides a faster curing method, while the 1:3 mix design is recommended when urgency is not required. Additionally, ACC is a recommended curing option, highlighting it as a faster curing method that is complemented by rapid strength gain and improved sample durability. This promotes a paradigm shift towards a cleaner environment by reducing the carbon footprint through perpetual CO 2 sequestration, while being a promising curing technique that the construction industry can consider.