Microwave Treatment of Stone Surfaces for the Devitalization of Biodeteriogens

Abstract

The experimental work described in this paper is aimed at evaluating the possibility of applying microwave heating to a restoration project. The technique involves the application of microwaves to stone surfaces affected by biodeterioration. Results showed that the pests were completely devitalised. The materials chosen for the survey were yellow and grey tuff. Samples of both tuffs were taken in the area of agro nocerino-sarnese and samples of lime mortar and brick were taken from a ruin located in Saint Eustachio (AV). The methodology consists of two phases: in the first, samples of material are placed in a reverberation chamber and treated by varying the parameters of power and exposure time; in the second, they underwent chemical-physical analysis aimed at establishing whether the treatment had induced aesthetic and/or structural alterations. The procedure was performed both on intact samples and on powdered samples for further analysis. Specifically selected and treated samples were subjected to colorimetric analysis, thermogravimetric analysis, of x-ray diffraction, infrared spectroscopy, SEM, and analysis of transport properties and compressive strength. Results from the chemical and structural analyses relating to the samples treated with the protocol showed no differences between the treated and untreated material. The only difference between the two types of material used related to the absorption capacity of water after treatment. From this, it can be deduced that the heating of stone materials using microwaves devitalizes pests, while leaving the substrate unaltered and the microstructure unaffected by any change.