Abstract

This study aims to compare the compressive strength of concrete produced from locally sourced coarse aggregates in Imo State and with a view to determine their suitability for construction. Objectives is to discuss and characterize the coarse aggregates found within the study area, to determine the compressive strength of concrete produced using these aggregates, identify the factors affecting the compressive strength of concrete produced within the study area. In achieving this, experiments conducted were the sieve analysis, specific gravity and water absorption test, slump test and compressive strength test. The sieve analysis result shows that, when sieve sizes of 20, 12.5, 10, 4.75, 2.36 and 1.25 were used, the cumulative percentage weight retained for the coarse aggregates obtained in Obinze, Okigwe and Njaba were; 0, 2.11, 39.36, 79.65, 97.48, 100 percent; 0, 0.059, 32.26, 82.92, 97.7 and 0, 0.91, 33.61, 82.34, 97.98, 100% respectively. Result obtained from the specific gravity and water absorption tests shows that the average specific gravity and average water absorption rate of coarse aggregates obtained from Obinze, Okigwe, Njaba are 2.80 and 0.57%; 2.76 and 0.55%; 2.78 and 0.69% respectively, which is between 2.5- 3 specific gravity, and with water absorption rate less than 3%. Result of the slump test showed that the slump values of concrete produced using Obinze stone, Okigwe stone and Njaba stone are 66mm, 81.5mm and 77mm respectively, which is within 50-100mm (medium) degree of workability. Result from the compressive strength of concrete shows that the average compressive strength of concrete produced using coarse aggregate from Obinze, Okigwe and Njaba, at 3days, 14days, 21days and 28days were as follows; 17.26 N/mm2, 19.04 N/mm2, 26.96 N/mm2 and 29.26 N/mm2 for Obinze aggregates, 16.59 N/mm2, 18.81 N/mm2, 22.30 N/mm2 and 25.85N/mm2 for Okigwe aggregate and 17.26 N/mm2, 21.72 N/mm2, 23.73 N/mm2 and 26.30 N/mm2for Njaba Aggregate. The hypothesis was tested with ANOVA method at a 5% significant level to test for the variation among the compressive strength of concrete produced from the selected locations in Imo state. The study concludes that there is no significant variation in the compressive strength of concretes produced from coarse aggregates obtained from selected locations in Imo in a ratio of 1:2:4 and were all above 25N/mm2 at 28 days of curing which exceeds the minimum required compressive strength for M25 grade targeted. The Okigwe gravel of Okigwe local government area performed best with a compressive strength of 29.26N/mm2 after 28days of curing. Followed by the Njaba aggregates with a compressive strength of 26.30N/mm2 and then the least performed was the Obinze gravel with compressive strength of 25.85N/mm2 after 28days of curing. The study recommends Okigwe gravel for standard concrete grade design of between 25 and 29N/mm2. Although the concrete made from the other two aggregates were above 25N/mm2 which could be attributed to adequate curing in the concrete lab and which may not be available on in-situ concrete.