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Effect of Pyrolysis Temperature on the Performance of Malt Biochar in Cement Mortars

Abstract:

Highlights: What are the main findings? Malt biochar at 500 °C showed improved graphitic structure and fewer defects. Milled BC500 increased compressive strength by up to 20.6%. BC500 reduced water absorption, leading to denser mortars. Superplasticizer + BC500 gave the strongest performance (62 MPa). What are the implications of the main findings? Malt waste valorization supports the circular economy in construction. Biochar enhances strength and durability of cement mortars. Use of BC lowers CO<inf>2</inf> impact compared to conventional binders. Promotes sustainable, high-performance green building materials. This study examines the influence of pyrolysis temperature on the physicochemical characteristics of malt-derived biochar (BC) and its effect on the performance of cement mortars. Malt biomass, a by-product of the brewing industry, was subjected to pyrolysis at 300 °C and 500 °C, followed by high-energy ball milling to produce nanoscale biochar. Characterization using FTIR, Raman spectroscopy, XRD, BET, SEM, and XRF revealed that BC500 possessed higher graphitic ordering, larger specific surface area (110 m<inf>2</inf>/g), and smaller pore size compared to BC300, which exhibited greater hydrophobicity. Incorporation of BC500 into cement mortars at 0.25–1.0 wt.%, with and without superplasticizer, resulted in up to a 20.6% increase in compressive strength and a significant reduction in water absorption. These enhancements are attributed to the internal curing effect of biochar, its refined pore structure, and improved interfacial bonding with hydration products. The findings demonstrate that optimized malt biochar serves as a sustainable additive that improves the mechanical performance and durability of cementitious materials while advancing circular economy principles through the valorization of industrial malt waste and the mitigation of the environmental impact of cement production.