Effect of Aggregate Size and Gradation on Compressive Strength of Normal Strength Concrete for Rigid Pavement

摘要

In road or most base constructions, uniform size and graded (mixed) aggregates of different sizes have been used without adequate consideration for its implications in terms of compressive strength. This study was carried out to investigate the effect of aggregate size and gradation on the compressive strength of concrete used for rigid pavements. The study investigated four concrete specimens made from aggregate size of 9.5mm, 12.7mm, 19.1mm and graded aggregate specimen made from a combination of 9.5mm, 12.7mm and 19.1mm aggregates. A concrete mix of 1:1.5:3 with a constant water-cement ratio (w/c) of 0.6 was used and tested for slump. Concrete cubes were produced from same mix, cured and tested for compressive strength at 14 and 28 days. The result showed that the concrete made from aggregate sizes of 9.5mm, 12.7mm and 19.1mm recorded slumps of 60mm, 50mm and 30mm respectively, whil e concrete made from the graded aggregates recorded the least slump of 20mm. Also, the concrete made from 9.5mm, 12.7mm, 19.1mm aggregates recorded mean compressive strengths of 18.2N/mm 2 , 20.0N/mm 2 and 20.9N/mm 2 respectively at 28days while concrete made from the graded aggregates recorded mean compressive strength of 17.3N/mm 2 at 28 days. It was concluded that workability (slump) of fresh concrete decreases with increase in aggregate size and that compressive strength increases with increase in aggregate size. The study also noted that grading aggregates using the Cement Treated Aggregate gradation procedure does not necessarily increase compressive strength of concrete for rigid pavements.