Assessment and Evaluation of Volcanic Rocks Used as Construction Materials in the City of Addis Ababa

Addis Ababa capital city of Ethiopia at an elevation of about 2000 m above mean sea level is entirely covered with volcanic rocks, basalt, trachyte, ignimbrite and rhyolite. Construction industry makes use these rocks extensively and indiscriminately for structural loading, pavements, wall cladding, fencing, as cobblestone and masonry stones. The suitability of these rocks and their petrographic and physico-mechanical properties evaluation becomes important for their aforementioned applications. So, field observation and sample collection for laboratory investigations were conducted on six selected target areas of the city periphery. In doing so, the compressive strength, open porosity, water absorption and density of various volcanic rocks were studied in the central laboratory of the Geological Survey of Ethiopia. Based on the physico-mechanical test results, some layers of ignimbrites and rhyolites are found to be the best for use in the construction industry. Out of the six target areas, two areas located on the south and south eastern periphery of the Addis Ababa city were selected for possible dimension stone production. Therefore, these areas could be developed for dimension stone quarry and exploitation of these rocks could be as rough unprocessed building stone or better polished natural stones for a variety of uses.