The comparison of the compressive strength of rock in view of requirements according to selected civil engineering standards

This study is aimed at analysing the requirements for compressive strength values of rocks used in the universally understood construction industry as stone materials. The compressive strength value obtained in laboratory tests may prove significantly different from the actual compressive strength of a given rock, depending on its application. According to PN-EN 1342:2013, lower expected value must be declared for paving block stone, normalised value for wall components, as per PN-EN 1996-1-1:2023 and PN-EN 771-6:2015, while with respect to stone for hydrotechnical works – structural integrity acc. to PN-EN 13383-1:2003. Despite testing samples in the same manner, e.g. acc. to PN-EN 1926:2007, all these parameters differ with the declared value and, in many cases, significantly differ from the most frequently used average compressive strength value. The analysis involved the results of compressive strength tests performed as per PN-EN 1926:2007, for samples of sandstone, granite, and limestone. The tests were performed for the aforementioned rocks in the air-dry condition, after saturation, and after the frost resistance test. On average, for all rock types, the lower expected value vs. average value was lower: in the air-dry condition by 25%, after saturation by 29%, and after frost resistance test by 37%. Furthermore, in most analysed cases, lower expected value did not exceed minimum compressive strength value. Normalised value in the air-dry condition was by approximately 15% lower than the average value, while after saturation totalled from 10% to 25%, depending on rock type.