The effect of nano-biochar produced from various raw materials on flow and mechanical properties of mortar

Abstract

ObjectivesThe objectives of this study are to determine the effects of nano-biochar produced from waste sludge (industrial and municipal) and a hybrid combination of municipal sewage sludge biochar and lignocellulosic biochar (apricot kernel shell) on the fresh state (flow) and mechanical properties (compressive strength, flexural strength, and fracture energy) of mortar. MethodologyAs methodology, the biochar was produced by a pyrolysis process at 500 °C and ground to 200 nm average particle size by ball milling. Detailed characterization of biochars with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), X-ray diffraction (XRD), BET (Brunauer-Emmett-Teller) analysis, and the strength activity index test was conducted. Mortar mixtures were designed by adding single and hybrid nano-biochar with different volume percentages (between 0.04–0.15%). Flow, flexural strength and compressive strength tests were performed on mortar samples along with microstructural SEM investigations. FindingsAs major findings, the addition of 0.06% municipal sewage sludge nano-biochar (BCSS) resulted in an increase in flexural strength by 23% while an increase in fracture energy by 100% compared to the control mortar. The addition of 0.12% BCSS increased the compressive strength by 17% and the compressive fracture energy by 28%. The hybrid nano-biochar additions also improved the strength and ductility. Sewage sludge nano-biochar and hybrid combinations have the potential to enhance the performance of the cement composites. The mechanisms governing the nano-biochar effect on mortar were enlightened as: pore filler effect, crack bridging and divergence, hydration initiation cite, internal curing of mortar. NoveltyNovelty of this work are: the use of nanoscale biochar in cement composite; the use of nano-biochar derived from sewage and industrial sludge in cement composite; the investigation of the effect of a hybrid nano-biochar on the properties of cement composites. The use of nano-biochars in cement composites can enable waste recycling while improving environment protecting and the mechanical properties of cement composites.