Compressive strength means the capability of the material or structure to provide resistance against compression. The Compressive strength of a material is based on the capability of the material to withstand failure that appears as cracks and fissure.
With compressive test, the push force enforced on the both faces of concrete specimen and the maximum compression borne by concrete devoid of failure is recorded.
The purpose of concrete testing is to deal with the Compressive strength of concrete as it facilitates to measure the concrete strength to protect gainst Compressive stresses among structures while other stresses like axial stresses and tensile stresses are developed with reinforcement and other means.
In technical term, Compressive Strength of concrete is explained as the Characteristic strength of 150mm size concrete cubes @28 days.
Compressive strength of Concrete and its advantages:-
Concrete is formed by mixing sand, cement, and aggregate. The strength of the concrete is based on several factors which range from individual compressive strength of its materials (Cement, Sand, aggregate), quality of materials applied, air entrainment mix proportions, water-cement ratio, curing methods and temperature effects.
With Compressive strength, the entire strength of the concrete as well as information on the above mentioned factors can be obtained. By initiating this test, it is possible to analyze the concrete strength psi and quality of concrete formed.
The compressive strength of concrete is influenced by the factors given below:-
Coarse aggregate: Concrete becomes uniform by blending aggregates, cement, sand, water and different other admixtures. In spite of perfect mixing, some micro cracks may occur because of variations in thermal and mechanical properties of coarse aggregates and cement matrix, which results in collapsing of concrete structures.
In concrete, the size of aggregate is a key factor for compressive strength. When the size of aggregate is raised, then the compressive strength will also be increased.
But later on, it is discovered that bigger size of aggregates can raise strength in preliminary stage but the strength is decreased greatly. It happens because of the abridged surface area for bond strength among cement matrix and aggregates and lower transition zone.
Air-entrainment: Air entrainment in concrete is a useful feature to avoid damages because of freezing and thawing. Later on, multidimensional benefits of air entrainment lead to improve the workability of concrete at lower water/cement ratio.
When the required workability is attained at lower water content, the concrete contains superior compressive strength which consecutively results in creating light concrete with superior compressive strength.
Water/Cement ratio: Excessive water is injurious to the strength of concrete. Cement is considered as the major binding material in concrete that requires water for hydration process, but the water quantity is constrained to about (0.20 to 0.25) % of cement content. The excess water is useful in case of workability and finishing of concrete.
When the water in the concrete matrix gets dried, it departs large interstitial spaces between aggregate and cement grains. This interstitial space in turn creates primary cracks throughout compressive strength testing of concrete.
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