Environment

Furnace waste may find use in longer-lasting concrete

Furnace waste may find use in ...
Salt is hard on ice ... and on concrete
Salt is hard on ice ... and on concrete
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Salt is hard on ice ... and on concrete
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Salt is hard on ice ... and on concrete

Salt may indeed keep winter roads free of ice, but it also actively degrades them. There may be a way out of the conundrum, however. Drexel University's Dr. Yaghoob Farnam has been experimenting with making "salt-proof" concrete that incorporates waste products generated by coal furnaces and the smelting process.

Ordinarily, regular Portland-style cement contains calcium hydroxide, which reacts with road salt (calcium chloride) to form calcium oxychloride. Unfortunately, calcium oxychloride expands as it forms, creating cracks in the concrete.

Fortunately, though, Farnam believes that fly ash, slag and silica fume could be used to replace the calcium hydroxide. The mixture serves much the same purpose, yet produces very little calcium oxychloride when combined with salt. Additionally, given that the fly ash, etc are currently unwanted and plentiful waste products, concrete made with the mixture should also be cheaper than traditional concrete.

In lab tests, when samples of regular concrete were exposed to road salt, they began degrading in just eight days. By contrast, samples of the fly ash concrete remained undamaged over the same period.

Farnam and his team are also looking at using a protective surface layer of bacteria to prevent calcium oxychloride formation on concrete.

Source: Drexel University

7 comments
VincentWolf
Now if we can just find substitutes for Lithium battery solvents that protect against dendrite formation.
MerlinGuy
Using Fly Ash in concrete is old news. The main reason that it isn't used in concrete is that different types and sources of coal and different furnaces produce fly ash with different chemical versions. These different versions make it impossible to calculate the resulting concrete strength. Another researcher attempting to get his grant extended by claiming an obscure quality of something they are studying is going to save the world.
Fairly Reasoner
Fly ash concrete. Not a new idea.
zr2s10
I think getting rid of salt on the roads all together would be a better project. Getting sick of my cars rotting out from underneath me. Even with constant washing, the salt just eats them away.
Douglas Bennett Rogers
Silica free concrete is desired for salt water applications. When glass reinforcement is put into cement it needs protection. The CaOH must be in reacted ingredient. Cement is essentially CaCO3, or lime stone.
PeterOsborne
Yes indeed, cinder in cement s a very old formula. I think coal cinder and ash cement blocks are still made.
Gregg Eshelman
2000+ year old Roman concrete was made with coal ash. That's why it's still around after more than two millennia.