Measuring the Effectiveness and Durability of Silicified Sandstones and Conglomerates from Zamora, Spain Subject to Silico-organic Treatments and/or Freezing/Thawing Processes

Abstract

This work was carried out on fresh samples of silicified sandstone and white conglomerate quarry from Zamora, Spain. The stones were treated with conservation treatments (H224, RC70, and RC80) and/or processes of freeze/thaw aging (similar to that of cold areas). The values obtained for the chromatic coordinates (L*, a*, b*) and the ultrasound propagation speed of the samples studied were analyzed and a statistical design was created. In addition, a multivariate technique (Canonical Biplot) was applied to determine the effectiveness of the treatments and the durability of the fresh and treated stones. In most of the cases studied, the ultrasonic propagation speed decreased in both the untreated samples and those treated with the conservation products after carrying out the aging process. Moreover, it was found that the ultrasonic propagation speed was lower with respect to the treated samples. Our results indicate that the treated samples are more durable than the untreated fresh samples and that the most severe changes can be appreciated when the untreated (fresh) samples are compared with their corresponding treated samples. For these samples, the ultrasonic propagation speed increased showing the effectiveness of each of the conservation products. The most effective consolidating treatment used was RC80. Also, the chromatic coordinates of the treated samples, in general, were darker (↓L *), redder (↑a *), and more yellow (↑b *) with respect to the fresh, untreated quarry samples, except in sample Z1 treated with RC80, where redness (↓a *) and yellowness (↓b *) decrease.