Defects in Concrete

Some defects are obvious only to a trained eye, others, such as cracking, are obvious to anyone. There are many different types of defects in concrete. Some common defects, their causes and how to prevent and repair them are explained below.   

 

Type of defect : Rain Damage

It is mean that the surface has bits washed away or many small dents.

What cause the rain damage? It is heavy rain, it is because raining will happen anytime anywhere, people can’t control the weather, and it will damage the concrete once the concrete has been setting. Rainwater also being allowed to run across the concrete surface.

How to prevent rain damage? Does not setting the concrete if it looks like raining will happen soon. The worker can cover the concrete when it is raining, if there is looks like might raining, worker also can cover the concrete to prevent damage.

How to repair the concrete if it is damage by rain? It can finishing concrete, it is screeding, floating or trowelling the concrete surface to density and further compact the surface of concrete, as well as giving it the look you want. If the concrete has not hardened and damage is minimal the surface can be refloated and re-trowelled taking care not to overwork excess water into the surface.

Type of defect : Colour Variation

Colour Variation is means by different in colour across the surface of concrete and it may appear as patches of light and dark.

Why this defect will happen? It is because of uneven curing conditions, curing is means to cover the concrete so it stays moist. By keeping concrete moist the bond between the paste and the aggregates gets stronger. Concrete doesn’t harden properly if it is left to dry out.

How to prevent colour variation? It can use an even concrete mix when placing, compacting and finishing and keep concrete evenly moist, and do not use driers.

Many colour variations from workmanship will be permanent. How can repairing this defect? There are some ways to remove specific stains such as oil and grease stain, rush, timber and algal and fungal growth. Rectification of colour variation from stains is a very difficult operation and may need repeated gentle treatments with a weak acid.  

Type of defect : Spalling

It is mean that when the slab edges and joints chip or break leaving an elongated cavity.

What cause spalling happen? Edges of joints break because of heavy loads or impact with hard objects. As concrete expands and contracts the weak edges may crack and break. Beside, when entry of hard object such as stone into joints may cause spalling when the concrete expand.

How to prevent spalling? It can design the joints carefully, it also need to keep the joints free from rubbish. It also needs to keep heavy loads away from the joints and edges until they have properly hardened.

Ways to repair spalling. For small spalled ares, scrape, chip or grimd aways the weak areas until you reach sound concrete, make sure you brush the old concrete clean of any loose material. Then refill the area with new concrete or repair mortar. Compact, finish and cure the new patch carefully.