Controlling salt weathering of lime mortars by mixed-in additives : a multi-scale analysis

Korte inhoud:Porous building materials, such as lime mortars, play a crucial role in both heritage buildings and modern construction due to their breathability, compatibility with historic structures, and moisture transport properties. However, salt-induced decay remains a major challenge, necessitating research on prevention and mitigation of salt crystallization damage. In this research, the use of mixed-in crystallization inhibitors on the performance of lime mortars against salt damage is evaluated. For this task, accelerated salt crystallization tests were performed at the macro-, meso- and micro-scale on lime mortars with mixed-in crystallization inhibitors (a phosphonate and two polyacrylates) dosed in different amounts. Mechanical and porosity tests showed that the additives increased the mortar strength while increasing their porosity (for pore sizes above 50 µm), except for mortars with a low molecular weight polyacrylate dosed at the highest tested concentration (1000 ppm). This material strengthening was likely given by the incorporation of organic additives as inter- and intra-crystalline occlusions in the CaCO3 crystals formed upon carbonation of Ca(OH)2. Salt crystallization tests confirmed the successful functionalization of the lime mortar substrate through additive incorporation, promoting template-induced crystallization of large euhedral mirabilite crystals in low quantities at low supersaturation levels. This process lowered the effective crystallization stress within the mortars, mitigating damage, especially on mortars with the highest additive dosage. These findings highlight a promising strategy for designing functional building materials with enhanced durability against salt crystallization.

Jaar van publicatie:2025

Toegankelijkheid:Embargoed