This research investigated the effects of aggregate gradation on the cement optimization and assessed the strength of concrete sample cubes in Bahir Dar. The researcher prepared different sample cubes of concrete in laboratory to determine the actual cement content needed for C-25 and C-30 concrete strength. Lack of knowledge, negligence and inspection in the production, use and implementation of aggregate gradation can be some of the causes of the problem using more cement in concrete mixes. Literatures indicate that using un optimized cement content leads to use more proportion of cement in concrete beyond the normal requirement. This leads to an increment in production of Portland cement as a result; it causes 5-7% of world CO2 production, which affects the global warming and its consequences. Snowball sampling method was used to collect fourteen fresh concrete samples for RAM test to know the amount of cement in freshly mixed concrete. In the other sampling, forty-five cube samples were collected to know the existing compressive strength of concrete produced in Bahir Dar city and thirty- six cube samples were prepared by using local aggregate source and concrete strength tests were conducted using the optimum amount of cement in BiT-BDU laboratory. As the RAM result showed, the average cement consumption of Bahir Dar Concrete was 376.7 kg/m3 and according to ACI recommendation the cement content for C-25 concrete production should be between 315 and 357kg/m3 hence 50% of samples were within the standard, 29% was below the standard and 21% were above the standard set by ACI. The fortyfive samples collected from Bahir Dar construction site were tested for 3rd, 7th, and 28th day compressive strength and as a result, the minimum 28th day compressive strength for C-25 concrete category was 13.5 MPa and the maximum was 27 MPa, which did not full fill the compliance criteria set by EBCS. The laboratory test results showed, for C-25 the average 28th day strength 18.77 MPa and 28.85 MPa were recorded with 270kg/m3 and 320 kg/m3 cement amount respectively. For C-30 average strength, 20.38MPa and 30.51 MPa were recorded with 300kg/m3 and 350kg/m3 cement, respectively. Even though none of the control samples prepared passed, the compliance criteria set by Ethiopian Standard (EBCS-2, 1995), the samples did have better concrete strength with optimum cement content than Bahir Dar city concrete sample results.