Читать книгу Monument Future - Siegfried Siegesmund - Страница 248

Drilling Resistance Measurement System (DRMS) measures the force that the tested material opposes to perforation, keeping constant penetration rate (ν) and rotational speed (ω). The first applications of this technique date back to the beginning of 20th century to study the weak points of stone surfaces (Pamplona et al. 2007). Nowadays drilling resistance instrument is used both for natural and artificial stones, particularly for mortars, even if the application on heterogeneous materials is still a discussed and studied argument from many researchers (Costa et al. 2010, Del Monte et al. 2008, Delgado Rodrigues et al. 2016, Dumitrescu et al. 2017). Recent devices were developed by SINT Technology, and DRMS Cordless became quite widespread. In such instruments, drill bit diameter can vary between 3 and 10 mm, the penetration rate (ν) between 1 and 80 mm/min, the rotational speed (ω) between 20 and 1000 rpm, and the maximum achievable load is 100 N.

In this study ancient mortars were examined, and drilling tests were performed both in situ on bedding mortars and in laboratory on drilling core samples extracted from some Tuscan monuments (see Case Studies paragraph). The used instrument is a Cordless Drilling Resistance Measurement System by SINT Technologies S. r. l. (Italy). On the base of preliminary tests, the chosen parameters were 300 rpm/20 mm/min for in situ measures and 150 rpm/20 mm/min for tests on core samples. Three holes were performed on each area in situ, while two holes were made on each core sample. A 5 mm diameter Fischer SDD widia drill bit was used.