Durability of Lime Mortars Treated with Ammonium Phosphate

The present paper aims at comparing diammonium hydrogen phosphate (DAP) and nanolimes (NL) as consolidants for the preservation of lime mortars. The durability of the two consolidants was evaluated in terms of resistance to freezing thawing and salt crystallization cycles. The results of the study point out that, compared to the untreated reference and NL-treated samples, DAP-treated mortars showed much improved resistance to freezing-thawing cycles. A lower benefit was found in the case of salt crystallization cycles, as DAP-treated samples exhibited a behavior substantially similar to untreated and NL-treated ones. The different improvement in durability observed for the two weathering processes could be ascribed, on the one hand, to the slight modification of the pore size distribution after treatment (which may lead to increased crystallization pressure) and, on the other hand, to the severity of the salt weathering test (involving the use of a saturated Na2SO4·10H2O solution). All things considered, the potential of the DAP treatment for the conservation of lime-based mortars is confirmed.