Developing Low Cost Eco-friendly Restoration Mortars for Historic Lime-based Stucco and Building Materials

In this work, three formulations based on hydrated lime and eco-friendly additives of powdered brick, fly ash and silica fume were designed to improve repair mortars for historic lime-based stucco and building materials. The microscopic features, physical-mechanical behavior and the microstructure of the prepared mortars were evaluated before and after artificial ageing (by humidity/drying cycles and salt weathering). However, a significant mechanical enhancement was reported for the studied mixes, but the silica fume mix showed a notable failure after salt ageing. The fly ash mix revealed the highest bulk density ratio (1.172 g/cm3) compared to the lime and silica fume mixes. The silica fume mix recorded the lowest percentage of water absorption (35.56%) and apparent porosity (28.11%). Further, the silica fume mix yielded the highest dry compressive strength value (22.19 kg/cm2), with an increase reached 31% when compared to the standard lime mix. The results demonstrated that the fly ash mortar is more compatible for sustainable restoration procedures of historic lime-based structures in respect of the physical-mechanical properties.