Estimation of mechanical properties of stones is very important because their measurements are cost and timeconsuming. The purpose of this paper is to investigate the relationship between compressive strength and the modulus of rupture of three types of stones as Granite, Calcite and Travertine groups of Iran. In this project all tests were carried out according to ASTM (American society testing of material) standard in laboratory, The obtained results show that the relationship of both properties of direct and is very little between correlation coefficients of linear equations and also nonlinear equations of all stone groups in most of zones of Iran By reason, it is preferred to use of linear equations based on their simplicity and easy application.
Unconfined compression has the most frequent use of the strength test of rocks, however it properly is not simple to perform, and its results can vary by a factor of more than 2. ASTMC 170–90 is used to measure compressive strength of buildings and decorative stones. The compressive strength c is expressed as the ratio of peak load w to initial cross-sectional area A: c %w/A (1) The flexural strength or "modulus of rupture" is the maximum tensile stress on the bottom of the rock beam corresponding to the peak load. It is calculated from simple beam theory assuming elastic conditions. The flexural strength is found to be two to three times as great as the direct tensile strength. For three points bending of cylindrical rock specimens, with loads applied at L/2 from each end and reactions at the ends, the modulus of rupture is: R=3 w. L /2b.d2 (2) R is modulus of rupture Psi (M Pa),w is the maximum load lbf (N), L is the length specimen, and d is the thickness of the specimen in(or mm) b is width of specimen in(or mm). This paper considers relationship between the compressive strength and the modulus of rupture on three types of stones as Granite group, Calcite and Travertine groups in Iran.
Taken samples from the quarries have been cut in cutting workshops and sent to the laboratories for the tests. ASTM standard is considered during sampling as shown in table1. Based on standard codes, physical and mechanical tests should be done on each sample and mean value of tests should not be more than 10%.
To prevent various names of stones, which use in different classifications, determination of the Dunhan System is applied for notation of sedimentary stones, and regarding the volcanic stones, it is also considered the main and subsidiary materials names and also the tissue name of the stones. Based on obtained results from these tests all decorative stones can be divided into four groups as follows:
Granite is a volcanic rock, which consists mainly of quartz and feldspar grains. Granite color varies from pink to gray with homogeneous texture. Usually, one or several mafic minerals associated with granite.
