Concrete is a mixture of water, sand, stones and cement. It hardens to a stone like mass within a few days. Concrete is highly strong and durable with a life span of about 50yrs.
Concrete is a major constituent of modern building structures. Many houses, roads,bridges, skyscrapers are constructed using concrete.
Grade of Concrete
Grade of concrete refers to the strength and quality of concrete. The grade of concrete typically depends on;
- The type of constituent materials used for making the concrete.
- Mixing ratio of the materials; the amount of cement being a very important factor.
Concrete grades are usually designated with the letter C followed by its typical strength at 28 days.
For instance, a Concrete grade mix of C7.5 means that it has a strength of 7.5 N/mm2 after 28days. This type of concrete is only useful for light weight loading.
On the other hand a concrete grade mix of 25N/mm2 is a heavy duty concrete containing dense aggregate. This grade of concrete is what is acceptable for reinforced concrete works. The mix for this grade is 1 part of cement to 2 parts of fine aggregates (sand) to 4 parts of coarse (stone) aggregates. Mix ratio 1:2:4