Synergetic effect of magnesium oxide expansion additive and biochar on deformation and mechanical properties of concrete

The combined effects of magnesium oxide expansion additive (MEA) and biochar (BC) on concrete properties were explored, focusing on drying shrinkage, autogenous shrinkage, internal humidity and mechanical strength. Concrete mixtures with various dosages of MEA (0, 6, 8 and 10%) and BC (0, 2 and 4%) were evaluated to determine the synergistic impact of the additives. It was found that the addition BC of increased the drying shrinkage, but the concurrent use of MEA and BC mitigated this effect. MEA was found to reduce autogenous shrinkage more effectively than BC. An optimal MEA–BC blend was identified as more efficacious in controlling this deformation than MEA alone. This combination was also found to improve the early compressive strength of concrete, although excessive amounts of either additive could impair long-term strength development. This study highlights the potential of using MEA and BC to enhance concrete’s performance through careful dosage optimisation.