Limestone Consolidation: How Much Product is Enough?

This study was aimed at evaluating the performance of four different consolidants (ammonium phosphate, nanolimes, ethyl silicate, acrylic resin) when applied onto a porous limestone (Lecce stone) by different number of brush strokes, with the aim of identifying the optimal product consumption for each consolidant. The results of the study indicate that, in the case of nanolimes and acrylic resin, insufficient mechanical consolidation and resistance to accelerated ageing is achieved even increasing the number of applications, likely because of a scarce penetration depth. In the case of ethyl silicate, increasing the product consumption leads to increasing mechanical effectiveness, which however is linked to significant color change and alteration in water absorption, as well as scarce resistance to freezing-thawing cycles. Ammonium phosphate was able to induce significant consolidation even for the lowest product consumption. By increasing the number of brush strokes, an increase in mechanical effectiveness was registered. For the highest number of applications, the mechanical improvement caused by ammonium phosphate was slightly lower than that caused by ethyl silicate, but ammonium phosphate had the important advantage of not causing any compatibility issue and resisting to freezing-thawing cycles better than all the other alternative consolidants.