Studies indicate that traditional concrete's tensile strength typically falls between 300 and 700 psi, which translates to approximately 2 to 5 MPa.
Unlike its high compressive strength (its ability to resist being crushed), concrete is relatively weak when it comes to resisting pulling or stretching forces, known as tension. Its capacity to withstand these tensile stresses is significantly lower.
Understanding Concrete's Tensile Strength
The tensile strength of concrete is a critical property, especially when considering how structures behave under load. While concrete is excellent at bearing weight that pushes down on it (compression), even moderate pulling forces can cause it to crack.
Based on research, as highlighted by studies:
- Traditional concrete's tensile strength ranges from **300 psi** to **700 psi**.
- In metric units, this is about **2 MPa** to **5 MPa**.
Why is Concrete Weak in Tension?
Concrete is a brittle material. When subjected to tension, small cracks can easily initiate and propagate through the material, leading to failure at relatively low stress levels compared to its compressive strength.
Consider the typical difference:
| Property | Approximate Capacity (Traditional Concrete) | Units |
|---|---|---|
| Tensile Strength | 300 - 700 | psi (2 - 5 MPa) |
| Compressive Strength | 3,000 - 10,000+ | psi (20 - 70+ MPa) |
Note: Compressive strength is vastly higher than tensile strength.
Implications for Concrete Structures
Because of this inherent weakness in tension, concrete structures like beams, slabs, and foundations are almost always reinforced. Steel rebar (reinforcing bar) is commonly embedded within the concrete to carry the tensile forces that the concrete itself cannot effectively withstand. This combination leverages concrete's compressive strength and steel's tensile strength.
Examples of where tension is critical in structures:
- The bottom of a beam supporting a load (it bends, putting the bottom in tension).
- Slabs spanning gaps or openings.
- Walls resisting wind pressure or earth pressure from behind.
Therefore, while concrete *does* have a tension capacity, it's quite low, making it necessary to use reinforcement in most structural applications to handle tensile stresses effectively.
