KDOT explores use of Kansas volcanic ash in concrete

Pop Quiz: When you are walking on a sidewalk are you walking on cement or concrete?

If you answered concrete, you are correct.

Concrete is the result of cement mixed with aggregate, sand and water.  Cement is the binder that hold everything together.

In an effort to explore using alternative materials in concrete, KDOT’s Bureau of Research explored the possibility of using Kansas volcanic ash as a supplementary cementitious material, or SCMs. SCMs are materials other than cement that are used to bind the mixture to create concrete.  A popular SCM is fly ash which is a waste product of coal. Because industries are switching to natural gas, coal isn’t being used as often and subsequently, a reduction in fly ash is the result.

KDOT primarily uses fly ash in KDOT concrete projects and bridge decks to improve strength and permeability characteristics.

At one time, the Rocky Mountains were volcanic and erupted sending ash into parts of Kansas. Because the ash is still present, KDOT decided to test the ash to see if this was a local resource that could be used.

Unfortunately, the report found that Kansas volcanic ash is not a viable substitute,

“Testing indicated that Kansas volcanic ash has few cementitious properties and as a result, when added to concrete, it has several possible negative effects, including increased bleed, increased set time, negative effect on strength, permeability, and finishing,” the report said.

Rick Kreider, Bureau Chief of the Bureau of Research, said that although Kansas volcanic ash is not an option for a SCM, the in-house research project was still a success because KDOT found that using this substance would not be a suitable solution. 

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