On the importance of specimen’s geometric shape effects on the slake-durability index of limestones and grain size distribution of the sediment particles obtained during the test

Abstract

The slake-durability test is one of vital test method used in engineering geological studies for evaluating resistant of rocks against wetting–drying cycles in humid environments. The result of the test is related to many parameters specially specimen’s geometric shape. In the present research, eight limestone samples used as common building stones in Iran have been selected and their mineralogical and physical properties have been measured in the laboratory. In order to determine the effect of specimen’s shape on the slake-durability index of the stones, laboratory specimens were prepared in seven various shapes including lump, rounded lump, cube, sphere, square prism, square-base plate, and rectangular cube which have different shape parameters. After performing the slake-durability tests, the samples were classified as very durable rocks according to Gamble and Franklin-Chandra classifications. The results indicated that specimen’s shape has essential effects on both rock durability and grain size distribution of the obtained sediment particles, so that the spherical and lump specimens shown the highest and lowest values of the slake-durability index, respectively. This means that more unregular dimensions, nonsphericity, and angularity of the specimens lead to decrease the slake-durability index which is highly correlated to the roundness (Rc) values of the specimens. The granulation parameters (D10, D30, D60, Cu, and Cc) of the obtained sediment particles were different for the tested samples. These parameters were recognized related to the specimen’s shape so that, the D60 and Cu are also highly correlated to the roundness (Rc) values of the specimens used in the slake-durability test.