Biochar admixtured lightweight, porous and tougher cement mortars: Mechanical, durability and micro computed tomography analysis

摘要

Currently, the global carbon footprint of cement industry is nearly 7 to 8% and this number is expected to grow in the near future given the continued global demand of cement usage in the construction and other sectors. Additionally, extraction of sand from the coastal and riverine environment is detrimental to ecosystem health and also gives rise to sand mafia in many developing countries. Biochar has the potential to sequester CO_2 in cement mortars. The purpose of this study was to valorise a waste biomass (poultry litter) to carbon-rich biochar and utilise as filler material to replace the sand in the range of 10-40% of the total weight in cement. A total of four mix designs each with three replicates at 10%, 20%, and 40% replacement of sand and control (0% biochar addition) were investigated for their mechanical, durability and micro-computed tomography (CT) analysis. The results showed that the flexural strength of the composites at 20% biochar replacement of sand was improved by 26% when compared to control. Biochar addition lowered the thermal conductivity of the cement mortars and was optimised at 10% addition. The density of the mortars decreased ～20% with 40% biochar addition. Micro-CT analysis showed nearly a five-fold increase in the 2-dimensional porosity of the samples, from 2.5% (control) to 12% for samples which had 40% biochar: however, no marked changes were noticed for samples at 20% biochar addition. Taking mortar plastering as an example for 100 m~2 area with standard 12 mm thickness revealed that CO_2 emissions decreased 20% when sand was replaced with 40% biochar as compared to control specimen. It was concluded that biochar has the potential to replace the sand in the mortars for improving toughness, lowering thermal conductivity and density of the cement composites.