Application of biochar, produced from locally generated wastes, as admixture in cement is a strategy to upcycle biomass waste and produce durable building materials. This research explores the influence of particle size and porosity of biochar, prepared from coconut shell and wood waste, added at 2 wt% of cement, on rheology, setting time, hydration and early age strength of cement mortar. For each biochar type, three particle size gradations are explored – coarser biochar (d₅₀ = 45–50 μm) (obtained by sieving), finer biochar (d₅₀ = 10–18 μm) (obtained by ball milling) and combination of coarser and finer biochar (d₅₀ = 15–25 μm). Experimental findings suggest that combination of coarser and finer biochar improves workability and rheological properties of binder pastes compared to that with (only) coarser biochar. Depending on biochar type, hydration and rate of setting are accelerated compared to control. Inclusion of finer biochar and combination of finer and coarser biochar improve packing density and degree of hydration of pastes compared to coarser biochar and control, leading to 12–19% enhancement in compressive strength at 7-day age. Micro-structural investigations show that the macro-pores of coarser biochar can be filled with dense hydration products, although some macro-pores may remain unfilled. This offsets improvement in strength that can be achieved through enhancement in packing density. The approach of blending coarser and finer biochar reduces the energy demand and cost associated with ball-milling by 23–37% and SGD 2.30–4.80 per ton respectively compared to only finer (ball-milled) biochar per cubic meter of concrete. Overall, the findings from this research demonstrate that blending of biochar of different particle size distributions can enhance physical properties of cement-based materials, while reducing associated energy consumption.

将当地产生的废物生产的生物炭用作水泥的外加剂，是一种升级循环生物质废物和生产耐用建筑材料的策略。本研究探讨了由椰子壳和木材废料制成的生物炭的粒径和孔隙率，添加量为 2 wt% 的水泥，对水泥砂浆的流变性、凝结时间、水化和早期强度的影响。对于每种生物炭类型，探索了三个粒度等级 - 较粗的生物炭（d ₅₀  = 45-50 μm）（通过筛分获得）、较细的生物炭（d ₅₀  = 10-18 μm）（通过球磨获得）和较粗的组合和更精细的 biochar (d ₅₀ = 15–25 微米）。实验结果表明，与（仅）较粗的生物炭相比，较粗和较细的生物炭的组合提高了粘合剂浆料的可加工性和流变性能。根据 biochar 类型，与对照相比，水合作用和凝固速度加快。与较粗的生物炭和对照相比，包含较细的生物炭以及较细和较粗的生物炭的组合提高了糊状物的堆积密度和水合程度，导致 7 天龄时的抗压强度提高 12-19%。微观结构研究表明，较粗的生物炭的大孔可以充满致密的水化产物，尽管一些大孔可能仍未填充。这抵消了可以通过提高填充密度实现的强度提高。与每立方米混凝土仅使用更细（球磨）的生物炭相比，混合更粗和更细的生物炭的方法将与球磨相关的能源需求和成本分别降低了 23-37% 和每吨 2.30-4.80 新加坡元。总体而言，这项研究的结果表明，混合不同粒径分布的生物炭可以增强水泥基材料的物理性能，同时降低相关的能源消耗。