It is known that sand is one of the major constituents of concrete and there is a huge consumption of it especially in developing countries like Ethiopia; where there are many infrastructural projects. The conventional source of sand for these projects is from the bed and banks of rivers, lakes and the like water bodies. This resulted in rapid exhaustion of natural sand from its source and it takes millions of years to be created again. The large amount of depletion of natural sand is also causing a serious threat to the environment. It also results in scarcity of natural sand and the cost is increasing significantly because it is transported from long distances. Because of these and other challenges, it seems vital to find an alternative which can effectively replace natural sand. This research assesses the effect of replacing natural sand with crushed rock fine on the workability, strength and cost of concrete. Initially, natural and crushed rock fine samples to be used in the concrete mixes were collected from a specific source and their physical properties were diagnosed. Based on the results of the diagnosis, a mix design for normal strength concrete (C-25) was made as per ACI 211.1 Standard. As per the mix designs, all constituents were weighed and mixed using a drum mixer. Slump tests were conducted for each batch and the standard cubes were cast and cured in water for 3,7,14 and 28 days and then tested for their compressive strength as per the pertinent standard (BS 1881-108:1983). In addition, comparison of material costs per one cubic meter of concrete for each concrete mix was carried out based on the price of concrete materials collected from different sources within Bahir Dar area. The result of fresh concrete property shows that, partial or full replacement of natural sand with crushed rock fine has a negative (decreasing) effect on the workability of the fresh concrete; but this problem can be eliminated by using the suitable admixture (super plasticizer). In addition, a maximum increase in compressive strength by 14.13% is seen when natural sand is fully (100%) replaced by crushed rock fine without using admixture and 15.79% increase when a 1% superplasticizer is added to the mix. From this, it is concluded that a well graded crushed rock fine if fully replace natural sand plus an admixture, a higher compressive strength concrete can be attained. In addition, the cost analysis shows that, the increase in cost of concrete when replacing natural sand with crushed rock fine and using admixture for enhancing the workability of the mixes is not significant as compared to the increase in the compressive strength of the concrete. The ` ~ iv ~ outcome of the research recommends to use crushed rock fine as a replacement of natural sand with proper admixture for the concrete construction works in and around Bahir Dar.