Compressive strength
Definition and meaning of compressive strength
The fundamentals of civil engineering start with knowing the compressive strength of the construction material. This is essential to ensuring the structure’s stability, durability, and safety. Before we discuss this in more detail, let’s first understand what it is and its role in civil engineering.
In literal terms, compressive strength implies the ability of the construction material to withhold the load to the extent that it crushes or deforms the material. An extensive amount of force is applied to the material at the top and bottom to test this. This force is implied until the material either shatters or loses its shape. By doing so, engineers test the threshold limit of the material to understand its durability and load-bearing capacity.
In some cases, where the material is ductile, deformation may occur. However, materials like rock or concrete may withhold pressure and prove successful in these tests to a certain extent. After this, a fracture may happen. Materials like steel and iron have excellent compressive strength.
Material response to compressive strength testing
Different materials react in various ways when put under test. Here is the material classification and their behaviour:
- Concrete: When force is applied to concrete, it tends to get shattered or brittle. As the load increases, it starts to deform, and as it reaches its peak load-bearing capacity, it changes shape and shatters into many pieces. Because of its brittle behaviour, engineers often use metal reinforcement to provide extra support for durability and safety. Metal reinforcement provides flexibility to the concrete and allows the structure to stay in shape without any deformity or failure, hence proving itself to be the highest compressive strength material.
- Steel: Steel is a more ductile material than concrete. Under extreme pressure, steel starts to deform permanently. Once the deformation happens, it cannot return to its original shape. The deformation leads to more energy absorption, making it the best choice for engineers to choose during deflection. Circumstantially, if the load imposed crosses the bearing limit, the steel will eventually bend and lose its shape.
- Rock: Natural rocks are available in different sizes and compositions. Each type composes a different compressive strength. The stronger the rock, the more brittle its response. For instance, when exposed to extreme pressure, granite brittles and shatters into pieces. On the contrary, the lighter the rock, the more ductile its response. For instance, shale, a lighter rock, exhibits a more ductile response under extreme pressure. But before understanding this in deep detail, it is also very essential to know rocks geographical history, including its composition, time of formation, and availability.
Difference between compressive strength and tensile strength
These 2 terms are quite different from each other, conceptually and practically. Here are some factors that differentiate between the two:
| S.No | Basis | compressive strength | Tensile strength |
| 1. | Focus area | Primarily focuses on enduring pushing forces | Mainly focuses on withstanding the pulling forces |
| 2. | Force | Pushing | Pulling |
| 3. | Material behaviour | Crushing, possible shattering or brittle | Rupture and eventual elongation |
| 4. | Applied on | Foundations, walls or columns | Cables, trusses or beams |
| 5. | Examples of high-strength material | Steel, concrete and masonry | Steel, wood and polymer |
Application of compressive strength in engineering and construction
Compressive strength plays a significant role in the engineering and construction industry. Here are some key applications:
- The materials required to build the foundation should necessarily have high compressive strength as the foundation is the primary level for bearing the extreme load of the structure.
- The next important area that requires good compressive strength of material is columns. These are the vertical parts of the structure that distribute the load from the hammer beams to the foundation, where metallic materials or concrete are highly recommended.
- Walls are another important area where engineers make sure to use materials with comparatively high compressive strength.
- Slabs or blocks are a structure’s support system. Hence, the material should combine good tensile strength with compressive strength.
Calculating compressive strength
It is calculated by evaluating the concrete mix. Engineers test the concrete using a small sample in a concrete testing machine.
The formula which is used for calculating the compressive strength of the material is:
F= P/A
Where,
F = The compressive strength
P = Maximum load applied to the sample
A = Cross-sectional area of the sample resisting the load
In a nutshell, a material’s compressive strength is essential to the construction industry. Knowing this, engineers can make an informed decision while selecting the construction material for a project, which can also help avoid accidents and failures.