Autogenous self-healing induced by compressive fatigue in carbonated hydraulic lime mortars

Abstract

This study investigates the autogenous self-healing mechanisms in carbonated natural hydraulic lime mortar exposed to cyclic compressive loads. We sought to explain the observed 40% surge in residual compressive strength compared to the quasi-static compressive strength following fatigue testing at frequencies of 5 Hz, 0.5 Hz, and 0.05 Hz [Theoretical and Applied Fracture Mechanics 118 (2022) 103201]. Central to our investigation is the hypothesis that cyclic loads mobilize the embedded water in the mortar, catalyzing chemical reactions that foster autogenous self-healing. To substantiate this, intact and post-compressive fatigue specimens were analyzed using differential thermal analysis (DTA), thermogravimetric assessments (TGA), mercury intrusion porosimetry (MIP), and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). The TGA-DTA highlighted the evolution of new hydration pathways, characterized by C–S–H gel and portlandite formation. The MIP results indicated a decline in pore volume, particularly in fine pores, affirming the synthesis of novel hydration compounds. The SEM-EDX analysis further authenticated the composition of these emergent microstructures. This work, therefore, presents a comprehensive understanding of the factors influencing autogenous self-healing in lime mortar systems.