Concrete and Compressive Strength | Tensile Strength of Concrete
What is Compressive Strength
Compressive strength is a measure of how much load a material can withstand before it breaks. Stronger materials have higher compressive strength. Compressive strength is often used for measuring the durability of concrete.
Concrete and Compressive Strength
In residential and commercial structures, the compressive strength of concrete typically ranges from 2500 psi (17 MPa) to 4000 psi (28 MPa) and higher. Several applications also make use of pressures greater than 10,000 psi (70 MPa).
For the concrete to reach this value, it undergoes a process called concrete curing. The curing process is an important step in the building of concrete. It can take up to a week for the concrete to reach its specified strength.
Throughout the curing process, the concrete will continue to harden. As the concrete continues to harden, it will minimize any residual porosity and give the concrete a more durable and lasting material.
Compressive Strength of Concrete with Time
The strength of concrete increases with time during the curing period. The table shows the strength of concrete at different time period in days in comparison with the strength at 28 days after casting.
|% age Strength
Engineers typically specify the needed compressive strength of concrete, which is typically stated in megapascals (MPa) or pounds per square inch (psi).
Because twenty-eight days is a long time to wait to see if required strengths are attained, three-day and seven-day compressive strengths can be used to forecast the ultimate 28-day compressive strength of the concrete.
Tensile Strength of Concrete
Concrete’s tensile strength is its ability to resist cracking or breaking under tension. Although concrete is rarely placed at pure pressure in a construction, measuring the tensile strength is required to comprehend the amount of the potential damage.
Breaking and cracking occur when tensile forces exceed tensile strength.
Traditional concrete has a reasonably high compressive strength compared to ultra-high-performance concrete, but a much lower tensile strength.
This means that any concrete construction that may be subjected to tensile stress must be reinforced with high tensile strength materials such as steel first.
Because of the importance of tensile strength in regulating possible cracking, there is a growing body of understanding on it.
However, determining the tensile strength of concrete is difficult — there is no field test for immediate assessment. However, indirect strategies such as splitting are extremely beneficial.
According to studies, the tensile strength of typical concrete ranges between 300 and 700 psi, or 2 to 5 MPa. This suggests that the tension is around 10% of the compressive strength on average.
Loads applied to concrete members can place them under tension. This is particularly frequent in concrete beams, where a transversely applied load compresses one surface while tensioning the opposite side due to induced bending.
The tensioned piece of the beam may crack. The magnitude of the bending moment and the design of the reinforcing in the beam at the location under consideration determine the size and length of cracks.
Reinforced concrete beams are meant to crack in tension, not compression. This is accomplished by adding reinforcing steel that yields before the concrete fails in compression, allowing for remediation, repair, or, if necessary, evacuation of an unsafe region.
Compressive Strength Vs. Tensile Strength of Concrete
Concrete has a relatively strong compressive strength that prevents it from cracking underweight, but a substantially lower tensile strength that causes it to crack when pulled.
When making concrete, the compressive strength is normally controlled by the water-to-cement ratio, and tensile strength is boosted by additions, often steel, to make reinforced concrete.
In other words, concrete is composed of sand (a fine aggregate), ballast (a coarse aggregate), cement (also known as a binder), and water (which is an additive).
Concrete Strength Influencing Factors
When asked what adds to concrete strength, the answer is almost everything. However, the following are common factors:
- Cement type
- Water proportions
- Cement quantity, quality, or brand
- Variations in shipments
- Curing circumstances
- Accidental cement substitution
- Temperature when Mixing
- The aggregate’s cleanliness and grading
- Concrete age while in form and tested
- Admixture presence or absence
- Methods of handling and placement
At times, extraneous elements find their way into the mix, reducing its power. So, removing the aspects that do not apply and focusing on the important ones is a necessary step in obtaining the required strength. Adequate inspection also ensures that no differences affecting the strength of the concrete occur.