Concrete Slump and Affecting Factors

Concrete Slump Definition and Affecting Factors

People who work in concrete construction field know that concrete slump is the main technical index of fresh concrete in our country.

Concrete slump is mainly refers to the plasticizing properties of concrete and its pumpability. Main influencing factors of concrete slump are: graded change, water content, weighing deviation and dosage of admixtures, the temperature of the concrete is very easy to be ignored.  Concrete slump is refers to the concrete workability, specifically is to ensure the normal conduct of construction, including the water retention of concrete, liquidity and adhesiveness.

Slump is a characteristic of fluidity of fresh concrete. Generally speaking, the greater the slump, the better the fluidity of fresh concrete. However, slump is not a comprehensive representation of the quality of fresh concrete, or at least it does not reflect the stability of fresh concrete.

How do we test the concrete slump?

Concrete slump test method: with an upper mouth 100mm, lower mouth 200mm, high 300mm horn-shaped slump bucket, fill concrete into it by three times, each time after filling with tamping hammer hit 25 times along the wall of the bucket evenly from the outside to inside, after tamping, wipe flat.

Then pull up the bucket, concrete will have collapse phenomenon due to self-weight, with the bucket height (300mm) minus the collapse of the highest point of concrete, known as the concrete slump.

If the difference is 100mm, the slump is 100.

As a liquidity indicator, the greater the slump, the better the liquidity.

When the slump is greater than 220 mm, the slump cannot accurately reflect the fluidity of concrete. The average diameter after concrete expansion, namely the slump spread, is used as the fluidity index.

During the slump test, the cohesiveness and water retention of the concrete mixture should be observed to evaluate the workability of the concrete mixture comprehensively.

By adding concrete polycarboxylate superplasticizer can greatly improve concrete slump and workability.