How To Slump-Test Your Concrete Mixture To Get A Strong And Durable Cured Surface

5 May 2016
 Categories: , Articles


Anytime you are completing your own do-it-yourself concrete work, you need to make sure you have mixed the dry concrete with the right amount of water. Without mixing your concrete properly, you run the risk of your concrete mix being either too wet or too dry. This will result in concrete that cracks and flakes apart from its low strength and durability. And you don't need to wait until your concrete cures and begins to show damage to know you mixed the concrete incorrectly: you can use the slump test to verify the mixture. Here are instructions to help you mix and complete a slump test on your concrete to verify its consistency for your concrete to have the most strength and durability.

Combine and Assess Your Concrete Mixture

In a wheelbarrow or a concrete mixer, combine your concrete dry mix with the amount of water indicated on the concrete package instructions. If the concrete mixture is too sloppy and you can see water escaping from the mixture, you have combined the mixture using too much water. If the concrete is too thick and dry, you have not added enough water to the concrete mixture. In both of these situations, you will not be able to do a slump test because the concrete is not workable for the test. Add a bit more dry mixture or water to make your concrete a more even consistency to do the slump test. 

Complete the Slump Test

To do the slump test, you can use a testing cone found at most home improvement stores. For example, you can find a standard-sized 12-in tall testing cone with a base diameter of eight inches and a top diameter of four inches. If you don't have access to a testing cone, you can make your own with a plastic or foam cup with its bottom cut off. Although this home-made version may not be as tall as a standard-sized testing cup, you can get similar results.

Place the cone with its top side down on a flat surface, such as a piece of plywood or sturdy paper plate. Fill up the cone with concrete in three to four sections to make sure no air bubbles get compacted into the cone with the concrete. Turn the cone upside-down so the base is now sitting on the flat surface, and lift the cone from the concrete. 

Analyze the Test Results

The cone of concrete should slump down from its original cone-shape if the test was done right. If one side of or your entire cone of concrete collapses, you need to collect a new sample of concrete from your mix to retest it. Set the testing cone next to the pile of concrete. Using a ruler, measure the difference in height between the testing cone and the concrete pile. If your concrete pile is one-half to three-fourths the height of the testing cone, your concrete is ready to be poured. 

If your concrete has remained the same size as the testing cone, your mix is too dry and needs more water mixed in. Add in small incremental amounts of water, slump-testing a new sample of concrete after you add each additional amount of water, until the concrete passes the slump test.

If your concrete pile is less than half the testing cone's height, the concrete is too wet and needs more dry concrete mix added to it. Add in small incremental amounts of dry mixture, slump-testing a new sample of concrete after you add each additional amount of dry mixture until the consistency is correct to pass the slump test.

Use this information to mix and test your concrete to ensure it cures strong and durable. For more tips or help with your project, you can also contact experienced concrete contractors from a company like Claggett & Sons Inc.