Data-driven evaluation of supplementary cementitious materials for cement-based repair mortars: A statistical literature review

The growing demand for repairing deteriorating concrete structures across Europe has led to the increased use of cement-based repair mortars with high clinker content. This induces a high environmental impact. Moreover, it compromises long-term durability, as they are prone to cracking, e.g. induced by restrained autogenous shrinkage, resulting in debonding. This premature failure negatively affects service life and hence, sustainability. As a more sustainable solution, Supplementary Cementitious Materials (SCMs) have gained attention for their ability to reduce clinker content and the environmental impact of repair mortars. This review examines 23 SCMs derived from virgin materials, industrial by-products, and waste streams. It focuses on their availability, key material characteristics influencing reactivity, and performance. To evaluate their technical potential, a comprehensive literature review was conducted, resulting in a database comprising 364 publications. The fresh, mechanical, physical, and transport-related properties, including bond strength, of SCM-based cementitious materials were analysed. These were statistically compared to conventional clinker-rich cementitious materials using boxplots, regression analysis, and the Wilcoxon signed-rank test. This enabled a data-driven comparison across varying replacement levels. The results indicate that certain SCMs (e.g. biochar, LC3, rice husk ash) enhance durability and strength, while others (e.g. steel slag, sewage sludge ash) require careful consideration depending on treatment and dosage. Overall, the study highlights the importance of selecting SCMs statistically based on performance and availability, and advocates for a shift from a “deemed-to-satisfy” strategy towards a “design for durability and sustainability” approach. Although bond strength remains underrepresented in current literature, its role in repair success warrants further investigation.