Cementtoaggregate

Cement-to-aggregate describes the proportion of cementitious binder to aggregate in cement-based composites, most notably concrete and mortar. It refers to the relative amounts of cement and aggregates (both fine and coarse) used to bind particles together.

In ordinary weight concrete, cement content is commonly about 300–450 kg per cubic meter, while aggregate content ranges from about 1,200–1,800 kg/m3. As a result, the cement-to-aggregate ratio by mass typically falls roughly in the range of 1:4 to 1:6. Mortar mixes use a higher proportion of cement relative to sand, commonly around 1:2 to 1:3.

The ratio influences several properties: higher cement relative to aggregate generally increases compressive strength, reduces permeability, and improves bonding, but raises cost and heat of hydration and shrinkage; too much cement can cause cracking and long-term durability issues, while too little can lead to weak bonding and early failure.

In mix design, engineers select a cement-to-aggregate ratio based on target strength, workability, exposure conditions, and environmental considerations. Trial batches, slump tests for workability, and strength testing on cured specimens guide final proportions. Admixtures and supplementary cementitious materials can modify performance without dramatically changing the ratio.

Aggregate quality and gradation, particle shape, moisture content, and compatibility with cement type affect the effective ratio and performance. Cement-to-aggregate balance must account for absorption and surface area.

Sustainability considerations include reducing cement content through supplementary cementitious materials, using recycled or locally sourced aggregates, and optimizing mix designs to minimize embodied energy.