Corrosion and fracture in reinforced mortars with limestone calcined clay cement

Licentiatavhandling, 2026

Low-carbon substitutes for conventional cementitious binders, such as Limestone Calcined Clay Cement (LC³), represent a promising pathway toward more sustainable infrastructure. However, their use in steel-reinforced concrete requires confidence in their long-term resistance to corrosion-related damage. This study examines the relationship between corrosion-induced cracking, mechanical behavior, and binder composition in mortars made with Ordinary Portland Cement (OPC) and LC³, each represented by two strength classes.
Corrosion was accelerated using an impressed current technique. To evaluate the corrosion level leading to cracking, the applied electrical current was identical and constant for all specimens, and the resulting time-to-cracking, t_crack, was determined. The results were analyzed in relation to compressive strength, tensile strength, fracture energy, and the chloride migration coefficient.
LC³ mortars exhibited a lower capacity to accommodate the expansive stresses generated by corrosion products, leading to earlier cracking than OPC mortars. This behavior is consistent with the measured fracture energy, which was lower for LC³ mixes, indicating a reduced resistance to crack propagation despite comparable strength levels.
Nonlinear finite element analyses were performed using the measured material properties and a corrosion model based on radial expansion at the steel-concrete interface to support and interpret the experimental observations. The simulations reproduced the relative cracking trends among the mortars, although cracking was predicted later than observed experimentally. Nevertheless, normalized results captured the ranking of the mixtures, supporting the modeling approach while indicating the need for improved calibration of the corrosion expansion properties.
Overall, the results suggest a potential mechanical drawback of LC³ mortars in reinforced systems. However, this may be partly compensated by their enhanced resistance to chloride ingress and delayed corrosion initiation under natural exposure conditions. These findings emphasize the importance of comprehensive durability assessments that extend beyond corrosion initiation to include the mechanical consequences of corrosion propagation, particularly cracking resistance.