What happens if you have too much water in your concrete?

UK Home Improvement

What Happens If You Have Too Much Water In Your Concrete?

Mixing concrete takes knowledge, practice and skill; the correct ratio of cement to water needs to be used to ensure the final strength of your cured concrete. 

Why is water used in concrete?

Water is an essential ingredient of any type of concrete. The water in a concrete mix hydrates the cement to form a paste, the paste is then mixed with aggregates and a chemical reaction, known as ‘curing’ takes place between the cement and the water. 

The strength of cured concrete is dependent on the ratio of cement to water in the mix, this ratio can be adjusted by an expert to allow for different weather conditions, climates and workability requirements. For more information, check out our article about pouring concrete in different weather conditions.

What happens when concrete is too wet? 

There are several potential consequences of having too much water in your concrete mix, all of which change the ratio of cement to water and can impact your project. 

Having too much water in your concrete will reduce the strength of the cured slab, increasing the risk of shrinkage and cracking. Cracked concrete is particularly problematic in a climate where you can expect freezing and thawing conditions, as the slab will not be as durable. If your concrete mix is too wet it will also be more porous once cured, making it difficult to achieve the desired finish and potentially making it not fit for purpose.

In short, a concrete mix that is too wet could seriously impact the durability, longevity and strength of your project. It’s a potentially costly and completely avoidable issue. 

How to tell if concrete is too wet

Expertly mixed concrete is tested for workability and defects before it is poured, this also ensures concrete is consistent across a larger delivery in multiple batches. A ‘slump test’ involves filling a cone of freshly mixed concrete on a hard, non-absorbent surface and testing how it subsides or slumps. An expert can check if the mix is too wet by measuring the slump and identifying the shape the concrete settles into once the cone is removed. 

True slump, when the concrete retains the cone shape and sinks evenly across the top, indicates that the mix is workable and the materials are adequately combined. A measurement of how much the concrete sinks in ‘true slump’ is a reliable way to check that batches of concrete are mixed correctly and will be consistent once cured.

Shear slump is when one side of the cone shears off or sinks and falls away from the top, if this happens the mix is likely to be too wet as the materials are not bonding (sticking together) enough. Collapse slump occurs when the ratio of water to cement is completely incorrect, causing the pile to collapse. With both shear slump and collapse slump the test should be repeated once the mixture has been amended. 


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