Properties of Concrete
These tables show the structural properties of concrete
Compressive Strength
The most important property of structural concrete is the compressive strength at 28 days (f'c). Common compressive strengths of structural concrete range from 25-85MPa (3500-12000psi). Ultra-high-performance concretes can exceed 85MPa, but they are not widely used on typical structures. Most building codes use the compressive strength as a benchmark and provide empirical relations for stiffness and tensile strength.
Unit Conversion
Concrete properties are usually measured in units of pressure. In Canada, concrete is typically specified in MPa. In the US, it is typically specified in psi or ksi. 1 MPa is approximately 145 psi or 0.145 ksi
Modulus of Elasticity
The stiffness of concrete material is determined using the Modulus of Elasticity (Young's Modulus). It can be directly measured, but most building codes provide an empirical equation that relates compressive strength to modulus of elasticity.
CSA A23.3
The table below shows the modulus of elasticity for various concretes.
| f'c | (3300√fc+6900)(yc/2300)1.5 cl. 8.6.2.2 | 4500√fc cl. 8.6.2.3 |
|---|---|---|
| 25 MPa | 24943 MPa = 3618 ksi | 22500 MPa = 3263 ksi |
| 30 MPa | 26621 MPa = 3861 ksi | 24648 MPa = 3575 ksi |
| 35 MPa | 28165 MPa = 4085 ksi | 26622 MPa = 3861 ksi |
| 40 MPa | 29602 MPa = 4293 ksi | 28460 MPa = 4128 ksi |
| 45 MPa | 30951 MPa = 4489 ksi | 30187 MPa = 4378 ksi |
| 50 MPa | 32228 MPa = 4674 ksi | 31820 MPa = 4615 ksi |
| 55 MPa | 33442 MPa = 4850 ksi | 33373 MPa = 4840 ksi |
| 60 MPa | 34602 MPa = 5019 ksi | 34857 MPa = 5056 ksi |
| 65 MPa | 35714 MPa = 5180 ksi | 36280 MPa = 5262 ksi |
| 70 MPa | 36785 MPa = 5335 ksi | 37650 MPa = 5461 ksi |
| 75 MPa | 37818 MPa = 5485 ksi | 38971 MPa = 5652 ksi |
| 80 MPa | 38817 MPa = 5630 ksi | 40249 MPa = 5838 ksi |
| 85 MPa | 39785 MPa = 5770 ksi | 41488 MPa = 6017 ksi |
| 90 MPa | 40725 MPa = 5907 ksi | 42691 MPa = 6192 ksi |
ACI 318 and LATBSDC 2020
The table below shows the modulus of elasticity for various concretes.
| f'c | 57000√fc | 40000√fc+106 |
|---|---|---|
| 4000 psi | 3605 ksi | 3530 ksi |
| 4500 psi | 3824 ksi | 3683 ksi |
| 5000 psi | 4031 ksi | 3828 ksi |
| 5500 psi | 4227 ksi | 3966 ksi |
| 6000 psi | 4415 ksi | 4098 ksi |
| 6500 psi | 4595 ksi | 4225 ksi |
| 7000 psi | 4769 ksi | 4347 ksi |
| 7500 psi | 4936 ksi | 4464 ksi |
| 8000 psi | 5098 ksi | 4578 ksi |
| 8500 psi | 5255 ksi | 4688 ksi |
| 9000 psi | 5407 ksi | 4795 ksi |
| 9500 psi | 5556 ksi | 4899 ksi |
| 10000 psi | 5700 ksi | 5000 ksi |
| 10500 psi | 5841 ksi | 5099 ksi |
Concrete strength guide
Low strength (5-20MPa or 1000-3000psi)
Low strength concrete typically has a strength under 20MPa. It is widely available from ready-mix suppliers and bagged products. Low strength concrete has limited structural value for buildings but may be used in applications such as rat slabs and nonstructural slabs-on-grade, soil enhancement, and small misc footings.
Normal strength (25-45MPa or 3500-6500psi)
Normal strength concrete typically has a strength in the range of 25-45MPa. This concrete is widely available from ready mix suppliers and bagged products. Normal strength concretes are typically used for flatwork such as slabs and footings, as well as beams, columns, and walls in shorter buildings.
High strength (45-85MPa or 6500-12000psi)
High strength concrete typically has a strength in the range of 45-85MPa, although strengths above 65MPa may be difficult to obtain in some markets. This concrete is tyipcally used for vertical elements in tall buildings such as columns and shear walls.
Ultra high strength (more than 85MPa or 12000psi)
Ultra-high performance concrete with strength exceeding 85MPa is typically reserved for special uses and structures. It is not economical to use in most typical buildings.
Calcs.app