The Constructor

Common Concrete Construction Mistakes at Site and How to avoid it?

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Poor concrete construction methods and workmanship are responsible for the failure of buildings and structure. The poor construction methods and workmanship are caused due to negligence and inadequate quality control at the construction site. The main reason for poor construction methods is due to:
  1. Poor Workmanship
  2. Inadequate Supervision
  3. Inadequate Quality Control

Common Concrete Construction Mistakes at Site

Below states are some of the poor concrete construction methods that are identified and recommended to be avoided as per BS 8110. The effect of these incorrect practices is explained below.

1. Incorrect placement of steel

The placement of steel must be performed under proper guidance and drawing. Incorrect placement of steel reinforcement can result in inadequate cover for the structure. Having an insufficient cover for the structure will invite corrosion activities that affect the reinforcement. This attack is very severe for structures located near to water bodies. If the steel is placed out of position other than what is needed, a mass load acting over the area can result in sudden failure or collapse of the structure.

2. Inadequate cover to reinforcement

As mentioned above, wrong steel placement that affects the concrete cover can result in the following adverse effects:

3. Grout leakage

This issue is observed during the concrete placement and compaction. A good formwork must be air tight and free from leakage. If the joints of the formwork are not tightly fit, there are chances of leakage of water from the grout. Leakage of water will leave a hardened concrete with a lesser amount of cement, fine aggregates and a concrete with a huge number of air voids and pores.

4. Incorrect Construction Joints

The construction joints must be made with proper preparation and compaction. Before making a joint with old concrete, the surface has to be washed, cleaned and placed with a few fresh concrete. After which the concrete is placed continuously. If the joint is not in good condition, it results in moisture penetration thus results in concrete staining.

5. Poor compaction

If the concrete mix is of higher quality and the compaction work is poor, then the concrete structure made is of low grade. Proper ramming or vibration to make the fresh concrete compact will avoid the chances of having a honeycombed porous concrete. A good compaction will give dense and an impermeable concrete.

Fig.1: Honey Combed Hardened Concrete

6. Segregation of Concrete

The separation of aggregates from the mortar mix of the concrete is called as segregation of concrete. Segregation can be caused due to the following reasons:

Fig.2.Concrete Segregation

Over-compaction by vibration or ramming will result in the aggregate sinking. Use of plasticizers in extra too result in segregation. A concrete placed with segregation will give the structure an uneven and porous surface.

7. Poor curing

Complete hydration of concrete is facilitated by good curing. Poor curing cannot compensate for the water lost from the concrete due to evaporation. This will adversely affect the strength of the concrete. Loss of moisture content can result in the shrinkage cracking of the concrete.

8. Use of High Water Content

Use of a high amount of water to meet the need for workability will bring down the strength of the concrete. This will increase the porosity and permeability of the hardened concrete. This, in turn, will result in corrosion of the reinforcement. It is strictly recommended to have a correct water-cement ratio for the concrete mix.  
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