Concrete slump test

Concrete slump test

In construction and civil engineering, the Concrete Slump Test (or simply the Slump Test) is an in situ test or a laboratory test used to determine and measure how hard and consistent a given sample of concrete is before curing.
The Concrete Slump Test is, in essence, a method of quality control. For a particular mix, the slump should be consistent. A change in slump height would demonstrate an undesired change in the ratio of the concrete ingredients; the proportions of the ingredients are then adjusted to keep a concrete batch consistent. This homogeneity improves the quality and structural integrity of the cured concrete

Purpose
The goal of the Concrete Slump Test is to measure the consistency of concrete. Many factors are taken into account when satisfying requirements of concrete strength, and to make sure that a consistent mixture of cement is being used during the process of construction. The test also further determines the “workability” of concrete, which provides a scale on how easy is it to handle, compact, and cure concrete[3]. Engineers use the results to then alter the concrete mix by adjusting the cement/water ratios or adding plasticizers to increase the strength of the outcome concrete mix.M

Procedure
The Concrete Slump Test has witnessed many technological advances, and some countries even perform the test using automated machinery. The simplified, generally accepted method to perform the test is as follows:

Apparatus
Large pan
Trowel to mix concrete mixture
Steel tamping rod
Slump cone
Ruler
Concrete (Cement, water, sand & aggregates).

Steps
Place the mixing pan on the floor and moisten it with some water. Make sure it is damp but no free water is left.
Place the sand in the pan. Add the cement and mix it with the sand.
Add the coarse/fine aggregate and thoroughly mix.
Mix the water and dry cement ingredients thoroughly using the trowel.
Firmly hold the slump cone in place using the 2 foot holds.
Fill one-third of the cone with the concrete mixture. Then tamp the layer 25 times using the steel rod in a circular motion, making sure not to stir.
Add more concrete mixture to the two-thirds mark. Repeat tamping for 25 times again. Tamp just barely into the previous layer(1")
Fill up the whole cone up to the top with some excess concrete coming out of top, then repeat tamping 25 times. (if there is not enough concrete from tamping compression, stop tamping, add more, then continue tamping at previous number)
Remove excess concrete from the opening of the slump cone by using tamping rod in a rolling motion until flat.
Slowly and carefully remove the cone by lifting it vertically (5 seconds +/- 2 seconds), making sure that the concrete sample does not move.
Wait for the concrete mixture as it slowly slumps.
After the concrete stabilizes, measure the slump-height by turning the slump cone upside down next to the sample, placing the tamping rod on the slump cone and measuring the distance from the rod to the ORIGINAL DISPLACED CENTER.