Biochar-based cement pastes and mortars with enhanced mechanical properties

Abstract

Nowadays, the environmental impact of cementitious material industry and more generally of building activities is matter of concern, especially in terms of their effects on climate change and consumption of natural resources. Within this context, the aim of this paper is the investigation of the role of biochar, a solid carbonaceous by-product material resulting from biomass pyrolysis/gasification of residual biomass, as a sustainable ingredient for the production of cementitious materials, combining carbon sink properties with enhanced mechanical properties. Although biochar is mainly investigated as agricultural amendment, there is also evidence that biochar may be a eco-friendly material to enhance the sustainable performance of cementitious materials. As outlined in literature, biochar can be used as filler to modify the nanogranular nature of cement matrix, or as substitute of clinker to reduce the emissions of greenhouse gases related to cement production. In this work, biochar is added as micro-nano particles in different cementitious composites, i.e. cement pastes and mortars, as a function of filler or partial substitute of cement. The main mechanical properties of biochar-based materials are then investigated to determine the optimal percentage of biochar addition.

Combined effects of biochar and recycled plastic aggregates on mechanical behavior of concrete

“…13,17,21 This was also confirmed by the water absorption value of the used biochar, which was experimentally determined according to the method described in Ref. 40 and resulted equal to 2.08 ± 0.06 g of water per gram of biochar.…”

“…Biochar particles are characterized by a high surface area and demonstrate great compatibility with the cement matrix, as also highlighted by SEM analyses, (Figure 9c). The abovementioned beneficial effects of biochar particles on fracture are indeed known in the literature, 40,59,60 but become even more relevant with the combined use of plastic aggregates. Biochar improves the adhesion of the components in concrete: it is able to fill the additional voids in the cement matrix due to poor compatibility between the plastic grains and the cement matrix, as well as to soak up the water not absorbed by the plastic grains thanks to its high water absorption capability (Figure 12a).…”

Toward Carbon-Neutral Concrete through Biochar–Cement–Calcium Carbonate Composites: A Critical Review

“…At elevated temperatures, addition of 1-2 wt% of this biochar leads to lower damage to the concrete microstructure and a 22-25% higher residual strength and water tightness compared to the control mix. Sirico et al [9] described how, for wood waste biochar made at 700 • C, the addition of 2 wt% biochar was the most suitable for use as filler in cement paste mixtures, improving flexural strength and fracture energy by acting as a micro-reinforcement in the cement paste that deflects the trajectory of fractures and creates multiple fractures instead. Additionally, for mortars, 2.5 wt% biochar was found to be optimal; anything more hindered the casting process and required more superplasticizer than recommended.…”

“…The application of both biochar and calcium carbonate in cement has been explored. For the application of biochar in cement, two conclusions can be drawn from the many research findings available [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. First, biochar can be effectively used as an additive and as a replacement for cement in cement mortars.…”

Feasibility of Using Biochar as an Eco-Friendly Microfiller in Polymer Concretes

“…Its properties and effectiveness as a material for carbon sequestration also make it potentially interesting for use as a component of concretes. Research examining the use of biochar as an additive in cementitious materials has been conducted and have shown very promising outcomes [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Biochar has also been considered as an alternative, eco-friendly microfiber reinforcement in polymer composites [ 36 , 37 ] because it is more beneficial than natural fibers.…”