Work

The Use of Slag, Biochar, and Hydrochar as Potential Concrete Additives: Effects on Compressive Strength and Spalling Resistance Before and After Fire Exposure

Year: 2025

Type: article

Abstract: Cement production is a significant global source of CO2 emissions, leading to a demand for sustainable concrete alternatives. This study investigates the use of various additives to partially replace cement and assesses their effects on compressive strength and fire resistance, particularly spalling. Seven concrete mixes were tested for their initial and post-fire compressive strength, mass loss, and cracking. The cement-only reference mix (R1) achieved the highest initial strength (53.3 MPa) but experienced severe explosive spalling. In contrast, the mix with slag and polypropylene (PP) fibers (R4) offered the best balance, maintaining substantial strength after fire while completely preventing spalling. Biochar additions consistently lowered strength and increased spalling risk, whereas hydrochar notably enhanced spalling resistance, especially at higher replacement levels. The results demonstrate that sustainable additives, such as slag with PP fibers or high-dose hydrochar, can effectively improve fire safety and reduce cement use, though there is an initial trade-off in mechanical performance. Ultimately, choosing the optimal mix depends on whether environmental benefits, fire resistance, or structural strength is the highest priority.

Source: Applied Sciences

DOI: 10.3390/app152413248

Authors: Asaad Almssad, Majid Al-Gburi, A. Viktor, Awaz Mohammadullah

Institutions: Karlstad University, Northern Technical University

Language: English

Topic: Fire effects on concrete materials

Subfield: Civil and Structural Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Responsible consumption and production, Climate action, Industry, innovation and infrastructure

Open Access status: gold

Estimated APC paid: $2,896