The use of coffee waste in bio-foamed concrete brick (B-FCB) to reduce the penetration of carbon dioxide (CO₂) into concrete

Abstract

The aim of this study was to examine the potential of coffee waste (CW) in reducing the carbonation of bio-foamed concrete brick (B-FCB). This study utilised coffee waste (CW) as an alternative material to replace cement, with different concentrations of 1%, 5%, and 10%. Furthermore, the utilisation of Bacillus tequilensis (B. tequilensis) was employed with the objective of achieving self-healing. A 2k factorial design was employed to perform a statistical analysis aiming to optimise the carbonation depth of B-FCB incorporating CW for a duration of 28 days. The experiment consisted of 11 runs. The performance of carbonation depth as response of this study was monitored with three main factors namely the density of concrete (D), coffee waste (CW), and B. tequilensis (B), respectively. The factors were bounded by upper and lower limits of 1300 kg/m3 and 1800 kg/m3, 1% and 10%, and 3x105 cell/ml and 3x107 cell/ml, respectively. The study established that the ideal carbonation depth was 8 mm, based on specific conditions as follow; 1300 kg/m3 of concrete D, 1% of CW and 3×105 cell/ml of B at 28 days. On the other hand, it was observed that the carbonation depth had a value of zero when the cement was replaced with 10% CW in runs 5, 6, 7, and 8. The empirical findings illustrate the effects of (CW) on reducing the level of carbonation in B-FCB, hence promoting its long-term sustainability.