Effect of Grain Size on Strength of Crystalline Building Stones

Grain size distribution as an important micro property is of a considerable effect on rock properties including strength. Determining grain size is a difficult task in practice and a flawless approach has yet to be introduced. The method adopted in this research is precise and basically simple where grain size is directly determined from thin sections. It has found successful applications for crystalline marble stones of Neiriz, Baghat, and Maroon in Iran, with the results reflecting the prominent effect of grain size on rock peak strength. Microscopic observations project grains of the marbles as identical and homological, whereas T-Test results evince significant discrepancies. The mean and the standard deviation for particles radii (mm) for Neiriz, Maroon, and Baghat were calculated as 0.648±0.317, 0.706±0.465, and 1.477±0.757 respectively. Moreover, the respective gauged strengths from triaxial tests were 52.30MPa, 56.68MPa, and 75.35MPa. The results indicate a positive correlation between particles radius and sample strength.