Characterization of Uniaxial Compressive Strength and Point Load Index and Their Correlation in Compact and Porous Building Stones: Insights from the Effects of Stone Heterogeneity

The point load index (PLI) is a low-cost and rapid test widely used for the indirect evaluation of uniaxial compressive strength (UCS). However, its accuracy in predicting UCS may differ between compact and porous stones. This study investigated the performance of the PLI for UCS prediction in these two stone types. Granite and travertine samples were selected as representatives of compact and porous stones, respectively. The UCS and PLI of the samples were determined through laboratory testing. For both stone types, the average (AVE), standard deviation (SD), and coefficient of variation (CV) of UCS and the PLI were calculated. Next, correlation equations between UCS and the PLI were developed for granites and travertines using regression analyses, and several statistical indices were calculated to evaluate their performance. The results showed that travertines exhibited higher CV values for both UCS and PLI than granites, indicating greater dispersion in their data. The statistical indices demonstrated that PLI performed better in predicting the UCS of granites, representing compact stones, than that of travertines, representing porous stones. However, due to high dispersion of the UCS and PLI data of travertine (assessed by CV), the PLI was a less suitable parameter in predicting the UCS of this stone type.