Abstract

Concrete is the most popular construction material worldwide. More than 50% of construction worldwide use concrete materials, mainly because of its versatility and economy compared to steel in relation to total height of building. The final output of the concrete material is, however, affected by factors including the rock type and its attendant physio-mechanical properties. This paper seeks to investigate the effect of the physio-mechanical properties of three rock types (quartz, sandstone, and quartzite) on the compressive strength of the constituent concrete product, with a maximum rock size of 25 mm. A concrete mix design of C25 was used with a nominal mix of 1:2:4 calculated by absolute weight method and water cement ratio of 0.4. Cube test results show that concrete produced from quartz aggregates produced the highest at all-time strength of 25.6 kN, 0.2% above the expected strength at the end of the 28 day period. Thus concrete produced from quartz rocks revealed a superior strength of 13 and 31% above that of crushed sand stone and quartzite, respectively. Again crush quartz (igneous) rock revealed the highest workability in concrete. The poor compressive test results in strength of the crushed quartzite may be attributed to the week properties such as high porosity, moisture content, permeability and lack of toughness. It is obvious that engineers, practitioners and the local authority should take keen interest in these results in the wake of the recent buildings collapse in Accra.

Key words: Strength properties, compressive strength, concrete, slump, workability, aggregates.