Factors Affecting Strength of Concrete

Factors Affecting Strength of 
Concrete

Factors which affect the strength of concrete:

·    Water – Cement Ratio: Water cement ratio is one of the most important factors which govern the strength of concrete. Water cement ratio is the weight of water in proportion to weight of cement expressed in terms of percentage. Workability increases if more water is added. But if large amount of water is added then paste will become dilute and it will not gain its strength. Adequate amount of water should be added so as to attain high workability and strength.

·         Size of Aggregates Used: For large size aggregates, the surface area is les less cement paste is required to cover the surface area. But if extra-large size aggregates are used then cracks may appear. 

·   Shape of Aggregates: Rounded aggregates give more workability to concrete. Angular or pointed aggregates make concrete harsh.

·         Mix Proportion: High mixes of concrete give more workability to concrete as more cement gives more paste of cement for lubricating the concrete.

·         Admixtures: Presence of admixtures such as pozzolana or plasticizers increases the workability and strength of concrete.

·   Grading of Aggregates: If proper grading of aggregates is done then presence of void is reduced. Therefore aggregates must be properly graded and then used so as to increase the workability and strength of concrete.

·   Surface Texture of Aggregates: Aggregates having irregular or hard surface require more cement to cover them. Hence aggregates must be smooth so as to give proper covering of cement to aggregates and provide workability to concrete.

·     Quality of Aggregates: Good quality aggregates prevents the concrete from creep.

·       Creep: Creep of concrete is the permanent strain induces in concrete due to sustair a long period of time. Poor mix proportion shows more creep and water-cement ratio is the major factor which affects creep in concrete.

·    Age of Concrete: With age of concrete the rate of creep also increases in concrete due to sustained load for a long period of time. 

·      Segregation: Segregation is the separation of constituent materials of concrete. Segregation may appear due to bad quality of aggregates used or due to voids present in cement paste.  

·         Bleeding: Bleeding is a form of segregation in which water comes at top of the concrete. Bleeding is also called water gain and is more problematic in wet mixes.

.    Shrinkage: Concrete shrinks in volume due to loss of water or absorption of water. Major cause of shrinkage is bleeding due to which water from surface evaporates rapidly causing shrinkage cracks or uneven surface finish. Shrinkage can also appear due to hydration reaction. 

regards

prarocks