Slake Durability of Granitic Rocks in Wet and Dry Conditions

Abstract

Weathering processes due to heating and cooling, wetting and drying cycles, salt decay, and acidic rains (atmospheric pollution) can affect the durability and long-term behavior of rock masses and aggregates. The resistance of rocks to weathering can be described using a durability parameter referred to as slake durability index. The main purpose of this study is to evaluate the influence of weathering processes simulated by heating and cooling and wetting and drying on the durability of fine-grained and porphyritic granites rocks from Ado-Ekiti, southwestern Nigeria. Petrographic and physical tests were carried out on the rocks using appropriate international standards. The slake durability test followed the procedure stipulated by ASTM D4644 standard was performed. The test cycles were conducted in wet (with distilled water) and dry (without water) conditions. The granites contain minerals such as quartz, microcline, hornblende, biotite, and muscovite. The fine-grained granite has lower water content, water absorption capacity, and porosity compared to porphyritic granite. The rate of mass loss decreases as the number of slaking cycles increased. This rate of mass loss is found to be higher at the early cycles than the final cycles. The maximum mass loss was observed in samples used for wet slake durability test. Slake durability indices of the granitic rocks decreased as number of slaking cycles increases and is higher in dry test than in wet test. Comparison between the results of dry and wet slake durability tests show that the effect of water on the rate of rock degradation differs in both rocks. The porphyritic granite is sensitive to water in terms of their slake durability compared to fine-grained granite. This may be attributed to the variation in physical properties of the granitic rocks.