We all know that on mixing cement with sand, stone/aggregates and water, a paste will form which can be used to bind the building materials together. This paste is also called as concrete. The strength of this concrete mix is determined by the proportion on which these cement, sand, stones or aggregates are mixed. There are various grades of concrete available in the market based on these ratios. Concrete mix ratios Some of them are M10, M20, M30, M35, etc. So, what really does M10 or M20 mean or represent.