Experimental Investigation of Low-Carbon Concrete Using Biochar as Partial Cement Replacement

Cement is the primary binder in concrete and a major contributor to global CO2 emissions. This experimental study investigates the use of biochar as a partial replacement for cement to develop low-carbon concrete. Material characterisation included particle size distribution, density, and water absorption of biochar and aggregates, followed by tests on setting time, workability, compressive strength, and dry density. The embodied carbon of each mix was also calculated to evaluate the reduction in emissions. Six mixes were produced with 0%, 5%, 15%, 30%, 45%, and 60% biochar replacement by weight of CEM I. Results indicated that biochar has high water absorption and low specific gravity, which reduced workability and strength at higher replacement levels, but significantly decreased the embodied carbon. The findings suggest biochar’s potential use in non-structural, low-strength concrete applications such as concrete blocks.