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How does a slump test check strength?


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November 03, 2010 11:06PM

Slump check does not measure strength. It measures workability. Workability is the ease with which concrete can be placed in position.

Correct as far as it goes! Slump refers to workability however it is also, all telling as to the water content of the mix. The more water, the easier it will work! Problem becomes, too much water will increase the porosity making the concrete weak and susceptible to early degradation because contaminates are able to enter and commence corrosion of embedded steel.

A concrete that is easy to work that has a high water content [ more than .40 ] is known for shrinkage cracking due to rapid evaporation of the high water content. These cracks caused by rapid loss of water decrease compressive strength and invite early corrosion. This type of concrete also experiences, curling and ASR as well as efflorescence in a very short time period.

Strength is a function of correct hydration, slow internal curing and careful design of a mix for the intended service criteria and not a whole lot to do with slump!