Effects of elevated temperature on physical and mechanical properties of carbonate rocks in South-Southern Nigeria

Purpose. Limestone and marble are carbonate rocks with several structural and engineering applications. The physical and mechanical properties of the rocks are fundamental as they determine their suitability for various use. Temperature is one of the critical factors that could affect the properties of the rocks and consequently their engineering application. Therefore, a better understanding of how the temperature, especially when it is higher than ambient, will affect the properties of the rocks is essential. In this work, the effects of the elevated temperature on some physical and mechanical properties of the carbonate rocks have been studied. Methods. Cubic samples of the rocks were prepared and heated in a furnace to different temperatures up to 900°C at an interval of 100°C and then cooled to the room temperature for testing. Porosity, dry density and uniaxial compressive strength (UCS) of the samples were determined under the effect of the elevated temperature. The porosity and dry density were determined using the saturation and buoyancy method while the UCS was estimated from the point load index tests performed on the samples. Findings. The results of this work indicate that the elevated temperature has significant effects on the physical and mechanical properties of the rocks. The porosity of the rocks showed an increasing trend as the temperature was increased while the density steadily decreased especially at the temperature above 300°C. The UCS of the rocks also declines with increased temperature but with an intermittent increase in their strength at a specific heating temperature. Originality. Most of the available studies on Nigerian carbonate rocks are focused on the estimation of physical and mechanical properties of the rocks without considering changes in these properties when the rocks are subjected to high temperatures. This study therefore aims to fill the gap by investigating the effects of the elevated temperatures on the physical and mechanical properties of some of the Nigerian carbonate rocks. Practical implications. The results of this study further increase understanding of the effect of high temperature on carbonate rocks, and also help to identify the critical temperature at which the properties of carbonate rocks undergo significant and irreversible changes. This information is very important for restoration of valuable fire-damaged structures made of carbonate rocks.