Factor effecting the strength of concrete

Through this presentation you can know about the factors which effects the strength of concrete.
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1. L O GO FACTOR EFFECTING THE STRENGTH OF CONCRETE

2.   Water/cement ratio: this is defined as the mass of water divided by the mass of cement in a mix. For example, a concrete mix containing 400 kg cement and 240 litres (=240 kg) of water will have a water/cement ratio of 240/400=0.6. The water/cement ratio may be abbreviated to 'w/c ratio' or just 'w/c'. In mixes where the w/c is greater than approximately 0.4, all the cement can, in theory, react with water to form cement hydration products. At higher w/c ratios it follows that the space occupied by the additional water above w/c=0.4 will remain as pore space filled with water, or with air if the concrete dries out. Consequently, as the w/c ratio increases, the porosity of the cement paste in the concrete also increases. As the porosity increases, the compressive strength of the concrete will decrease. Factors affecting concrete strength

3. Soundness of aggregate: it will be obvious that if the aggregate in concrete is weak, the concrete will also be weak. Rocks with low intrinsic strength, such as chalk, are clearly unsuitable for use as aggregate. Aggregate-paste bond: the integrity of the bond between the paste and the aggregate is critical. If there is no bond, the aggregate effectively represents a void; as discussed above, voids are a source of weakness in concrete. Factors affecting concrete strength

4. Effect Of Temperature Low temperature decreases the early strength development. High temperature at early stage : Increase the early strength Decrease the ultimate strength

5. Effect of Humidity Moisture creates the ideal conditions for the growth of mold, mildew and bacteria. When mold and bacteria grow and reproduce within concrete, they affect its strength. When relative humidity levels increase, the compressive strength of concrete decreases, affecting its durability.

6. Effect of compaction Compaction of concrete is very important in developing qualities like strength, durability. Imperviousness by making the concrete dense and free from voids. It is done by vibrator mostly. If full compaction is not achieved , porous and honey-combed concrete will produced resulting in loss of strength.

7. Curing Positive effects : Protects concrete surface from sun and wind. The presence of water is essential to cause the chemical action which accompanies the setting of concrete. Resistance of concrete to abrasion is increased. By proper curing durability is increased and shrinkage is reduced.

8. Curing Negative effects : Compressive strength is reduced. Cracks will be formed due to shrinkage. Durability decreases Frost and weathering resistance are decreased. Rate of carbonation increases