Effect of microcapsules on the self-repairing ability of limestone calcined clay cement (LC3) mortar at different temperatures

Abstract

The fundamental principle of sustainable civil engineering revolves around minimizing energy and resource consumption throughout the entire life cycle of a structure, including raw material production, construction, and maintenance. To achieve this, efficient utilization of raw materials is crucial. LC3, a novel low carbon cementitious material, offers sustainability advantages. In this paper, LC3 mortar was prepared by incorporating limestone, calcined clay and gypsum as supplementary cementitious materials, thereby replacing 50% of ordinary Portland cement (OPC). Additionally, microcapsules, comprising 4% of the total mass of cementitious materials, were introduced. This reduction in OPC content not only decreases energy consumption and CO2 emissions during cement preparation but also capitalizes on the self-repairing ability of microcapsules to mend microcracks that occur within the cement-based material during its service life. Consequently, the durability of cement-based materials is enhanced. To evaluate the effects of self-repairing on mechanical properties, permeability, and maximum amplitude at different temperatures, a comparison was made between OPC mortars and LC3 mortars. Furthermore, the self-repairing ability of surface cracks in microencapsulated mortar was assessed. The findings demonstrate that the mechanical and permeability properties of LC3 mortar (designated as CA2) exhibit no significant deviation from those of OPC mortar (designated as CA0). Moreover, under the same conditions, LC3 mortar containing microcapsules (designated as CA3) displays superior self-repairing ability compared to OPC mortar containing microcapsules (designated as CA1). Additionally, the self-repairing characteristics of microcapsules in LC3 mortar improve with increasing temperature. The self-repair process involving epoxy resin (repairing agent) and 2-ethyl-4-methylimidazole (curing agent) follows a quasi-second-order reaction kinetic model. Surface cracks with an initial width exceeding 0.4 mm in CA3 were entirely repaired within a 72-hour period.