Effect of Biochar Dosage and Fineness on the Mechanical Properties and Durability of Concrete

Abstract

Biochar (BC), a byproduct of agricultural waste pyrolysis, shows potential as a sustainable substitute material for ordinary silicate cement (OPC) in concrete production, providing opportunities for environmental sustainability and resource conservation in the construction industry. However, the optimal biochar dosage and fineness for enhancing concrete performance are still unclear. This study investigated the impact of these two factors on the mechanical and durability properties of biochar concrete. Compressive and flexural strength, carbonation resistance, and chloride ion penetration resistance were evaluated by varying biochar dosages (0%, 1%, 3%, 5%, 10%) and fineness dimensions (44.70, 73.28, 750, 1020 μm), with the 0% dosage serving as the control group (CK). The results showed that the addition of 1–3 wt% of biochar could effectively reduce the rapid carbonation depth and chloride diffusion coefficient of concrete. The compressive and flexural strength of BC concrete initially increased and then decreased with the increase in biocarbon content, BC with a fineness of 73.28 μm having the most significant effect on the mechanical strength of concrete. At the dosage of 3 wt%, BC was found to promote the hydration degree of cement, improving the formation of cement hydration products. These findings provide valuable insights for the development of sustainable and high-performance cement-based materials with the appropriate use of biochar as an additive.

Analysis of Electromagnetic Shielding Properties of Cement-Based Composites with Biochar and PVC as Fillers

“…In [33], an increase was observed in the flexural strength, indicating an improvement in the fracture energy. A similar mechanical property enhancement with respect to the control group was described in [34]. The compressive strength and flexural strength increase with moderate biochar addition.…”

Enhancing Biochar Impact on the Mechanical Properties of Cement-Based Mortar: An Optimization Study Using Response Surface Methodology for Particle Size and Content

“…Additionally, the finer particles likely contributed to reduced void spaces within the mortar, leading to enhanced density and strength. The study by Ling et al [25] also proved that the BC particle size of about 40-70 µm has the most significant effect on the mechanical strength of cement-based materials. However, Choi et al [41] showed that finer BC particles will increase the viscosity of the mortar, resulting in a decrease in fluidity.…”

“…Additionally, it is also observed that there is a discernible presence of BC particles on the surface of the cement mortar. This morphological change underscores the role of finer BC particles as micro-fillers, effectively reducing voids and cracks within the cement matrix and at the interfacial transition zone [25,35]. Consequently, this contributes to the creation of a more compact colloidal matrix.…”

“…To meet specific application requirements, BC produced via slow pyrolysis is typically subjected to milling and sieving, resulting in particle sizes ranging from 0.044 to 20 mm [22]. BC with a finer particle size boasts a larger specific surface area and an increased number of active sites, making it advantageous for applications such as soil remediation and heavy metal adsorption [23][24][25]. However, it is essential to determine whether fine particle size BC similarly benefits cementitious materials.…”

Enhancing Cement Paste Properties with Biochar: Mechanical and Rheological Insights

“…In comparison with the used cement powder's particle size distribution, a significant portion of the biochar's particles are finer than the cement's ones. The low dimension of biochar can allow the biochar to be dispersed between the cement powder particle, thus biochar can act as a nucleation point of the hydrated phase of cement, as demonstrated by Ling et al [41].…”