Durability Assessment of Hydraulic Lime Grouts Incorporating Cappadocia Waste Earth Under Selected Environmental Exposures

Hydraulic lime grouts are widely used for masonry consolidation, yet their environmental durability remains insufficiently understood. This study evaluated natural hydraulic lime (NHL) grouts incorporating Cappadocia Waste Earth (CWE) at CWE/NHL mass ratios of 0–0.50, while maintaining constant total binder mass and water-to-binder ratio, under freeze–thaw cycling, accelerated sodium sulphate exposure, and a comparative mortar-cup drying assessment. Newly generated mass-variation, ultrasonic pulse velocity (UPV), visual, and post-exposure scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS) data were interpreted together with previously published pre-exposure pore and moisture-transport characteristics. After 15 freeze–thaw cycles, all CWE-containing formulations showed significantly greater mass loss than REF, whereas CWE30, CWE40, and CWE50 did not differ significantly. UPV reduction correlated positively with mass loss (r = 0.781). Under accelerated sodium sulphate exposure, all CWE-containing formulations disintegrated by the twelfth cycle, although CWE30 deteriorated less severely than CWE40 and CWE50. Higher CWE/NHL ratios also produced more pronounced visible cracking during mortar-cup drying. SEM–EDS revealed Ca–Al–S-bearing needle-like products consistent with possible ettringite-like phases, without definitive phase identification. Overall, CWE30 showed the most favourable response among the CWE-containing formulations and is considered the most promising candidate for further conservation-oriented validation, but not an established optimum or recommended dosage.