Factors affecting properties of hardened concrete

For producing desired properties of hardened concrete, we first should know which factors affect the properties of hardened concrete. Controlling those factors properly we can produce strongest and most durable concrete.

Below are the factors mostly affecting the properties of hardened concrete:-

  • Water-cement ratio
  • Type and amount of cement
  • Type and amount of aggregate
  • Weather condition



Water-Cement ratio:
Water-Cement ration is defined as the weight of water divided by the weight of cement in concrete mix. The water-cement ratio is abbreviated to w/c ratio or just w/c. For normal concrete construction, we generally use w/c= o.45. If the w/c is greater than 0.45 the excess water (which isn’t participate in hydration process) will remain as pore in concrete. When concrete dries out it is filled with air and reduce the concrete density. As a result, it reduces the strength and durability of concrete.

Type and amount of cement:
The primary factors affecting concrete compressive strength is the amount of cement. The higher the cement content, the greater the tendency for shrinkage cracks to form while the concrete is curing and hardening. Types of cement also has a great impact on the properties of hardened concrete.

Type and amount of aggregate:
The strength of concrete mostly depends upon the strength of aggregate. The coarse aggregates act like bone in concrete. If we use low quality aggregate in concrete mix, the strength of concrete will be low. The amount of aggregate greatly affects the properties of hardened concrete. Increasing the amount of aggregate at a constant cement content reduce the concrete strength. Strength of concrete can also be affected by the type of aggregate. Such as, angular and rough surface concrete increase the concrete strength. Because, rough surface of aggregates make strong bond between cement paste and aggregates than smooth surface aggregates. In other side, round and smooth surface aggregate decrease the concrete strength. Larger size aggregate with lower water requirement can produce strong concrete. But, using larger size aggregate without decreasing water content decreases the strength of concrete. Aggregates add strength to concrete and reduce its potential for shrinkage.

Weather condition:
Increase of water temperature, either at mixing stage or during curing, augment the rate of strength gain of concrete. In cold climates, exterior concrete is exposed to repeated freeze-thaw cycles which can potentially be very damaging. Freeze-thaw deterioration is one of the most serious threats to concrete durability. Concrete durability also depends on the volume stability. All materials expand and contract with changes in temperature. Concrete also expand and contract with changes in moisture content. For reversible thermal expansion and contraction, concrete experience initial shrinkage as the cement hydrates and excess construction water evaporates. This initial shrinkage is permanent. Reversible expansion and contraction caused by later temperature or moisture changes. Excessive shrinkage can cause concrete to crack. The cracks allow moisture to penetrate and vicious cycle of deterioration may begin.

What factor, do you think, affect the hardened concrete properties most? Please share in comments

3 comments :

  1. weather conditions since its a bit difficult for us to control weather conditions

    ReplyDelete
  2. How size and shape of specimen affects the compressive strength of concrete?

    ReplyDelete
  3. How size and shape of specimen affects the compressive strength of concrete?

    ReplyDelete

 

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