Problems arising from limited coarse aggregate sizes where by coarse aggregates are gotten from long distance quarry sites which have led to high cost of coarse aggregates and in turn resulted to high cost of construction. A synergistic combination of three sizes of coarse aggregates for concrete works was investigated in this research. For the purpose of this work, three sizes of coarse aggregates, 10mm, 14mm, and 20mm were used. Each of the sizes were cast which served as the control. The three aggregate sizes were also combined based on percentage proportion and cast. For each combined sizes of coarse aggregates, 21cubes (150×150mm) were cast to allow the compressive strength to be monitored at 7, 14 and 28 days respectively. Results showed that third test of the combined coarse aggregates which contained 30% 10mm, 20% 14mm and 50% 20mm had the highest compressive strength of 25N/mm2. Statistical T-Test analysis was introduced in this research to compare each of the control mixes with the concrete made with combined aggregates. It was seen from the analysis that, the value obtained which is 12.12 and
4.51 is greater than the T critical (4.303 at 5% level of significance) which also indicated that the third test of the combined aggregate had the highest compressive strength of concrete.