EFFECT OFCOARSE AGGREGATE SIZES ON THE COMPRESSIVE STRENGTH OF CONCRETE

The common phenomenoms on the most Nigeria structures in recent times are engineering problems. The main purpose of this research project is to investigate the influence of coarse aggregate sizes on the comprehensive strength of concrete. In order to find lasting solution to this engineering problem, with respect to the strength and economy. The project is aimed to investigate the effects of coarse aggregatesizes, that will eliminate the problem relating to structural failures. In order to achieve the purpose,Coarse aggregates, which is the interest of this project, make the difference. Three different sizes of coarse aggregates, with 20mm maximum size, employed in this investigation, these are; 12mm, 16mm, and 20mm. The grading and compressive strength of the aggregates were studied. The mix ratio and water/cement ratio adopted for the study was 1:2:4 and 0.55 respectively. Two concrete cubes (150mm x 150mm x 150mm) were cast for each coarse aggregate size of which they were crushed at each curing age namely; 7, 14, 21, and 28 days. The 28 day strengths of the concretes made with 20mm, 16mm, and 12mm were 26.20N/mm2 , 24.02N/mm2. and 22.03N/mm2 respectively, The 21 day strengths of the concretes made with 20mm, 16mm, and 12mm were 23.23N/mm2 , 21.85N/mm2 , and 18.17N/mm2 respectively, The 14 day strengths of the concretes made with 20mm, 16mm, and 12mm were 21.24N/mm2 , 20.03N/mm2 , and 17.47N/mm2 respectively and The 7 day strengths of the concretes made with 20mm, 16mm, and 12mm were 19.34N/mm2 , 17.55N/mm2 , and 15.53N/mm2 respectively. Therefore, result shows that as the aggregate size increases, the compressive strength increases also with increasing curing days.