The construction industry is one of the biggest contributors to global carbon emissions. The carbon neutral or negative nature of biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More is, therefore, being capitalised to develop cementitious composites with it as an additive. Additionally, the other unique and inherent properties of biochar, such as a porous structure, surface functional groups, have the potential to improve the performance and durability of cementitious composites. In particular, the use of biochar in self-healing and self-sensing cementitious composites has the potential to significantly lower maintenance needs and extend the service life, which, in turn, can lead to higher sustainability and can create a paradigm shift in the design and monitoring of concrete structures. 

Self-healing cementitious systems have an innate ability to seal cracks and reduce permeability thereby, conserving its mechanical performance without extra and external interventions. On the other hand, self-sensing mortars (i.e., cementitious systems without coarse aggregates) can covert acting mechanical stresses into detectable and measurable electrical signals. These two aforementioned systems, thus, can significantly lower the need for extensive repairs and enhance durability, which are directly proportional to low embodied carbon and consequently, high sustainability (Dong et al., 2021; Deeba and Ammasi, 2024). Interestingly, in self-sensing cementitious systems, biochar can create conductive pathways, especially when used in conjunction with other highly conductive additives such as carbon fibres or carbon black. These ‘hybrid’ systems have been reported to exhibit higher signal stability and sensitivity under cyclic loading or low-strain conditions as compared to mixes having only biochar (Kang et al., 2024). Additionally, a recent study from LTU demonstrated that biochar can promote internal curing by enhancing the degree of hydration and helps late-age strength development (Wang et al., 2025). These effects can also positively affect the reproducibility of the sensing response. The dual ability of biochar to regulate moisture and electrical contribution sets it apart from other conventional carbon-based fillers. Self-sensing mortars employing a microbial process with biochar as an additive is gaining academic traction. The inherently porous structure of biochar acts as an ideal ‘home’ for CaCO₃precipitating bacteria, protecting them from the harsh alkaline cement environment (Lin et al., 2025; Anoop and Palanisamy, 2025). Biochar, which is also a reservoir for water and nutrients, encourages microbial activity, which in turn, aids in effective crack sealing. 

Despite the aforementioned potential of biochar in self-healing and self-sensing cementitious systems, numerous challenges related to biochar need to be addressed before it becomes an accepted additive. One of the biggest issues is that no biochar is created equal, meaning, that its specific surface area, porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More/carbon content, electrical conductivity, etc, can be inconsistent. These properties highly depend on the feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More type and thermo-chemical reaction conditions (e.g., highest treatment temperature, residence timeResidence time refers to the duration that the biomass is heated during the pyrolysis process. The residence time can influence the properties of the biochar produced.   More, etc.) (Das et al., 2021; Gabhi et al., 2020; Ottani et al., 2023). Biochar, without any further pre-treatment lack the performance of engineered nanomaterials and must rely on hybridisation to achieve the required electrical sensitivity. Biochar may not remain uniformly distributed in the cementitious matrix leading to agglomerations, non-uniform conductive paths, and thus unstable sensing signals (Mobili et al., 2021; Jeong et al., 2022). Overtime, biochar’s properties might change owing to carbonation, oxidation, and moisture, which could render the electrical behaviour uncertain during the lifetime of the structure (Liu et al., 2024; Ziegler et al., 2017).  The issues with biochar property inconsistencies also negatively affect its capacity to self-heal in cementitious systems. Such property variability can create incompatibility with microbial colonies and not all biochars are able to host a common bacterium (i.e., Bacillus pumilus) that is used to heal cementitious systems (Anoop and Palanisamy, 2025).

In summary, although biochar has a strong potential to spearhead the development of low-carbon, intelligent, and resilient infrastructure, the production and utilisation of biochar must be optimised to reduce property variation. This can be done employing a standardised protocol of biochar characterisation, which is lacking, as well as ‘purpose-built’ biochar production and processing. In other words, researchers must comprehend what properties of biochar are important for developing cementitious composites and how these properties affect the overall performance, both in short and long terms. It is recommended that future research involving biochar-added cementitious composites should conduct long-term durability testing, develop property-based design guidelines for biochar production, and investigate biochar’s interactions with both cement hydration and microbial healing mechanisms. These can enable biochar to become a mainstay additive of multifunctional and sustainable construction materials.

References

Anoop, P. P., & Palanisamy, T. (2025). Non-reactive biochar and Bacillus pumilus RSB17-based healing powder: A sustainable solution for enhanced bacterial viability in self-healing mortar. Science of The Total Environment, 965, 178635. https://doi.org/10.1016/j.scitotenv.2025.178635

Das, O., Mensah, R.A., George, G., Jiang, L., Xu, Q., Neisiany, R.E., Umeki, K., Phounglamcheik, A., Hedenqvist, M.S., Restás, Á. and Sas, G. (2021). Flammability and mechanical properties of biochars made in different pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More reactors. BiomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More and Bioenergy, 152, p.106197. https://doi.org/10.1016/j.biombioe.2021.106197

Deeba, S., & Ammasi, A. K. (2024). State-of-the-art review on self-healing in mortar, concrete, and composites. Case Studies in Construction Materials, 20, e03298.

Dong, W, Li, W., Zhu, X., Sheng, D., & Shah, S. P. (2021). Multifunctional cementitious composites with integrated self-sensing and hydrophobic capacities toward smart structural health monitoring. Cement and Concrete Composites, 118, 103962.

Gabhi, R., Basile, L., Kirk, D. W., Giorcelli, M., Tagliaferro, A., & Jia, C. Q. (2020). Electrical conductivity of wood biochar monoliths and its dependence on pyrolysis temperature. Biochar, 2, 369–378.

Jeong, J., Jeon, G., Ryu, S., & Lee, J. H. (2022). Ecofriendly and electrically conductive cementitious composites using melamine-functionalized biochar from waste coffee beans. Crystals, 12(820). https://doi.org/10.3390/cryst12060820

Kang, Z., Yang, Y., Zhang, J., & Li, N. (2025). Synergistic effects of biochar and carbon black on conductive cement composites: Mechanical and conductive properties. Construction and Building Materials, 470, 140579.

Lin, X., Nguyen, Q. D., Castel, A., Li, P., Tam, V. W. Y., & Li, W. (2025). Self-healing efficiency of sustainable biochar-cement composites incorporating crystalline admixtures. Construction and Building Materials, 458, 139542. https://doi.org/10.1016/j.conbuildmat.2024.139542

Liu, C., Ye, J., Lin, Y., et al. (2024). Effect of natural aging on biochar physicochemical property and mobility of Cd(II). Scientific Reports, 14, 22214. https://doi.org/10.1038/s41598-024-72771-8

Mobili, A., Giosuè, C., Bellezze, T., Revel, G. M., & Tittarelli, F. (2021). GasificationGasification is a high-temperature, thermochemical process that converts carbon-based materials into a gaseous fuel called syngas and solid by-products. It takes place in an oxygen-deficient environment at temperatures typically above 750°C. Unlike combustion, which fully burns material to produce heat and carbon dioxide (CO2​), gasification More char and used foundry sand as alternative fillers to graphene nanoplatelets for electrically conductive mortars with and without virgin/recycled carbon fibres. Applied Sciences, 11, 50. https://doi.org/10.3390/app11010050

Ottani, F., Morselli, N., De Luca, A., Puglia, M., Pedrazzi, S., & Allesina, G. (2023). The conductivity dilemma: How biochar grain’s chemical composition and morphology hinder the direct measurement of its electrical conductivity. Measurement, 222, 113662. https://doi.org/10.1016/j.measurement.2023.113662

Wang, D., Jantwal, A., Kaynak, E., Sas, G. and Das, O. (2025). Promoting internal curing in concrete by replacing sand with sustainable biochar. Case Studies in Construction Materials, 22, p.e04542. https://doi.org/10.1016/j.cscm.2025.e04542

Ziegler, D., Palmero, P., Giorcelli, M., Tagliaferro, A., & Tulliani, J.-M. (2017). Biochars as innovative humidity sensing materials. Chemosensors, 5(35). https://doi.org/10.3390/chemosensors5040035