Each year, approximately 22 billion tons of concrete is poured for projects around the world. This critical material dams rivers, supports buildings, and surfaces sidewalks.
But not all concrete is created equal. Concrete grades help identify which concrete mix is most appropriate for a particular job to ensure structural integrity.
Let’s look at the different grades, how they relate to concrete strength, and where to use them.
Understanding Concrete Grades
Your choice of concrete for a project is dictated by the grade you need. Grading lets you know the compressive strength of a specific concrete mix after it has dried and cured for 28 days.
Grades are presented as a letter-number set where the letter identifies the particular mix and the number tells you the compressive strength in MPa. For example, a concrete listed as a C30 mix would have a compressive strength of 30 MPa and be of mix design C. The strengths can range from 5 MPa to 70 MPa, depending on the mix and use.
Mix designs involve the unique proportions of the standard components in concrete as well as any additives included. The mix is shown as a ratio of cement, sand, and coarse aggregate.
Mixes come in two types — nominal mix or design mix. Nominal mixes are generally used for smaller-scale construction projects that use less concrete. Design mix involves ratios set by lab tests to provide good quality control for large projects.
While the letter/number set is commonly used, you will see concrete grades listed as a number in the thousands. This is the standard used by the American Concrete Institute. In this case, the number is the compressive strength listed in psi rather than MPa.
Uses of Concrete Grades
Standard-strength concrete grades run up to M25, while grades above that are considered high-performance strength and suitable for commercial use. Some common applications for the various grades are as follows:
- C10 – trench fills, floor binding, and drainage
- C15 – foundations for smaller walls, concrete steps, and residential flooring
- C20 – lightweight foundations, driveways, and garages
- C25 – foundations, footings, and large mass fills
- C30 – pavement, light external projects, driveways, and walkways
- C35 – larger foundations for commercial buildings, warehouses, and agricultural storage
- C40 – industrial support beams, roadwork, and agricultural yards
Of these, C10 and C25 are among the most versatile concrete mixes as they can handle a lot of different applications. You’ll find C15 used for plain cement concrete projects, while C20 is the minimum grade used for reinforced concrete construction.
C35 frequently has special additives added to help it handle freezing temps and reduce the formation of air bubbles.
Ready to Pour?
Concrete is one of the most versatile and ubiquitous construction materials available. Knowing the properties of the various concrete grades ensures whatever you build will stand up to its purpose.
If you have a concrete project on the horizon, contact us to discuss how our experienced team can help you make it a reality. We specialize in high-quality concrete work for everything from homes to tunnels.
