The typical ratio to mix cement is approximately 10 to 15 percent cement, 60 to 75 percent aggregate, and 15 to 29 percent water. In many concrete mixes, entrained air may take up another 5 to 8 percent.
The cement and water components form a paste that coats each particle of the aggregate (stone and sand). The strength of this paste depends on the mix of cement and water, which in turn determines the strength of the concrete. The water-cement ratio is the weight of the mixing water divided by the weight of the cement. Builders sometimes include small amounts of entrained air to enhance durability.