WSU researchers use coal waste to create sustainable concrete
New coal concrete reduces energy demand, greenhouse emissions
PULLMAN, Wash. – Washington State University researchers have created a sustainable alternative to traditional concrete using coal fly ash, a waste product of coal-based electricity generation.
The advance tackles two major environmental problems at once by making use of coal production waste and by significantly reducing the environmental impact of concrete production.
Xianming Shi, associate professor in WSU’s Department of Civil and Environmental Engineering, and graduate student Gang Xu, have developed a strong, durable concrete that uses fly ash as a binder and eliminates the use of environmentally intensive cement. They report on their work in the August issue of the journal, Fuel.
Reduces energy demand, greenhouse emissions
Production of traditional concrete, which is made by combining cement with sand and gravel, contributes between five and eight percent of greenhouse gas emissions worldwide. That’s because cement, the key ingredient in concrete, requires high temperatures and a tremendous amount of energy to produce.
Fly ash, the material that remains after coal dust is burned, meanwhile has become a significant waste management issue in the United States. More than 50 percent of fly ash ends up in landfills, where it can easily leach into the nearby environment.
While some researchers have used fly ash in concrete, they haven’t been able to eliminate the intense heating methods that are traditionally needed to make a strong material.
“Our production method does not require heating or the use of any cement,” said Xu.
Molecular engineering
This work is also significant because the researchers are using nano-sized materials to engineer concrete at the molecular level.
“To sustainably advance the construction industry, we need to utilize the ‘bottom-up’ capability of nanomaterials,” said Shi.
The team used graphene oxide, a recently discovered nanomaterial, to manipulate the reaction of fly ash with water and turn the activated fly ash into a strong cement-like material. The graphene oxide rearranges atoms and molecules in a solution of fly ash and chemical activators like sodium silicate and calcium oxide. The process creates a calcium-aluminate-silicate-hydrate molecule chain with strongly bonded atoms that form an inorganic polymer network more durable than (hydrated) cement.
Aids groundwater, mitigates flooding
The team designed the fly ash concrete to be pervious, which means water can pass through it to replenish groundwater and to mitigate flooding potential.
Researchers have demonstrated the strength and behavior of the material in test plots on the WSU campus under a variety of load and temperature conditions. They are still conducting infiltration tests and gathering data using sensors buried under the concrete. They eventually hope to commercialize the patented technology.
“After further testing, we would like to build some structures with this concrete to serve as a proof of concept,” said Xu.
###
The research was funded by the U.S. Department of Transportation’s University Transportation Centers and the WSU Office of Commercialization.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Another age old tech up for a Nobel or something. They have been using fly ash in concrete for over 1/2 a century. It has pozzolanic properties which means it sets up like cement when wetted and with addition of lime. Ditto for volcanic ash (glass), and a number of waste products. When you produce Lithium chemicals (Li- ion batteries, etc.) from the mineral spodumene -a lithium aluminosilicate, you roast the ore and extract lithium sulphate solution. The hydrous aluminu silicate residue sets up like concrete when water content is reduced to ~50%.
Coal ash concrete designed to be previous so water can flow thru, that should be great on the foundation of your house. Good thing it wasn”t used on Hoover Dam. Apparently it won’t be good for all aplications.
This sounds like “We have this fancy thing graphene oxide, let’s try to mix it up with other stuff and see what happens.”
It’s an exploratory kind of research that can produce useful results.
But it is kinda disheartening to read the litany of distrustful grumbling from grumpy men about anything new.
Well I’ve read all the comments up until this time. This comment is for Crispin in Waterloo.
Crispin- you tried mightily, to tell people that this was NOT cement with a fly ash filler, but a completely different product called a geopolymer. They should have all done what I did after reading your first comment- google “geopolymer”. A great learning experience.
To me your most telling comment as it applies to this post, is that the stuff is already commercially available. So what is new or novel about their research? The article doesn’t say,
Anyway thanks for your comments.
Yeah, Crispin; ditto what the Old Engineer said. Thanks for trying.
Thanks, Old engineer.
This material, or class of materials, is the most interesting thing to appear in ages for my type of work: design of domestic heating appliances. It permits single artisans to make products at least as good as huge companies because it eliminates kilns and clay-based parts.
The only tech comment to add is a reply to aTheoK about ‘glass’. The term ‘glass’ does not mean soda glass like windows and jars. Amorphous metals without a crystal structure are also glassy. Bulk glassy alloys, they are called. So the ‘glass’ referred to above is melted ash that has a ‘clinker’ or ‘glassy’ appearance. Geopolymers can be based on bonding such glasses using high pH activators at room temperature. They set quickly and can be extremely strong – like re-melted rock. The age of limestone cement is closing its doors.
Pervious might not be too good a trait.
It has it’s places.
For a time, maybe a decade ago, Xcel sold fly ash to a companion operation at its Ft. Morgan, colorado power plant, to make cement. Unfortunately, a new environmental mandate to capture yet more sulfur made the fly ash unusable for this purpose. It is possible to make perfect the enemy of good.
Ok it’s not for building but the Chinese don’t have form in anything of quality-
“Are NEW Chinese buildings really FALLING DOWN?”
There’s an awful lot of blah blah going on in this discussion. I’ll start by saying that I have been deeply involved with cement systems for the past ~40 years so can claim to have some expertise on the subject (I think). I have worked with all kinds of cements, binders & aggregates including most that have been mentioned in this thread – Portland, GGBS, metakaolin, wollastonite, a multitude of pozzolans and fly-ashes, aggregates of a hundred flavours, compositions & densities and all manner of exotic admixtures to modify strength, rheology (flow properties), permeability, density, etc. As such, I welcome all research on improvements to existing materials used in construction, civil and industrial engineering.
Having said that, the use of the words “graphene” (albeit as oxide) and “nano-“ immediately fire up my BS detectors. “Geopolymer” is another woed that sounds pretty cool. Let’s face it, these words are used to make otherwise mundane topics “sexy” so their inclusion, merited or otherwise, is suspicious to me.
If truth be told, most “cementing” technology involves nano-materials and always has done…..we just didn’t call them “nano-“ until recently and most of this was for marketing purposes. Particle size ranges for cement and many binders/admixtures including fly-ash are in the nano- to micro- range – from say 100nm to 100 microns. The former represents the fines, he latter the coarser particles. So nano- isn’t new here although it’s true that appropriate deployment of carefully selected particle sizes can improve certain properties of the finished material. Geopolymers sound cool but clays may justifiably be given this descriptor since they are complex aluminosilcates.
Flyash comes in many flavours and there are different classes defined by BS, ASTM, etc. Some of these are relatively inert and require the use of an alkali (usually provided by excess line from cement) to activate them and bind them. Others are intrinsically hydraulic and will set into a hard stone when combined with water alone, even in the absence of Portland cement.
So, bottom line, this “novel” system needs to be looked at closely to see whether it really represents something new or whether it’s just a re-labelling of existing technology with judicious selection of the component materials. I’ll be interested to read more about it.
The place to start is the non-cement materials. While water may be involved, it is usually an activated surface of a glassy material or a phosphate bonded alumina over 40%. Aluminum dihydrogen phosphate (MW 318) releases three water molecules for each reacted ADP molecule. As it sets, it gets wetter! After drying it will take 1300 C the next day.
How are they going to get the toxic metals out?
This is nothing new. Coke slacks have been used to make cement for donkeys years in Europe.
As an retired engineer at a coal plant, coal ash has been used in concrete for decades. A particular form of ash called spheroids that certain coals and/or boiler units produced was sold and used as a strengthening agent in concrete. The tiny spherical ash particles present would resist crack propagation in the cured concrete.
Of course, nowadays the availability of this concrete additive has been reduced considerably.
Australian company Wagners has been developing and commercializing geopolymer concrete based on flyash, blast furnace slag and activators entirely replacing portland cement, for over a decade. They have used it in their airport pavement and currently in their wharf project plus it has been used in other smaller projects. They note a number of potential benefits over Portland cement based concrete including higher tensile strength and chemical resistance in marine environments, acidic soil condition and sewer applications. They also indicate a saving of CO2 emissions and push the green credentials. Local design standards have yet to include non-portland cement based concrete so accepance has been limited.
It is also fundamentally fireproof.
Wouldn’t the permeability to water be an issue w/ the re-bar used to reinforce the structure(s)?
I’m thinking that the re-bar would rust/decompose MUCH faster w/ this product.
Kudos to the researchers’ efforts: Keep on thinking clearly!
That’s going to be a bit radioactive, as there is significant Thorium, U-238 and U-235 refined from coal in the ash by burning, enough U-235 to fuel a equivalent sized nuclear power plant in fact (Gabbard et el, ORNL 1987). Also by far the largest man made radiocative emissions to the environment, far more than nuclear p[ower, but its coal so that’s OK.
BUT, if that is only elevating the background I’d build my house from it, as enhanced low background radiation up to around 500mSv pa tones up the immune system to resist cancer better. Normal background is 2mSv pa. evacuation level is 20mSv pa, but natural levels globally are up to 500mSv pa with no epidemiological effects, except some studies show positive immune responses, and such exposure is an adjunctive treatment to chemo and radiotherapy to enhance the immune response when they are not advisable.
This was not understood when the regulations were made, and most evacuations following nuclear accidents have been unnecessary in fact, the bureaucrats in unnecessary haz mat suits wavig meters have killed thousands of people at Chernobyl and Fukushima as a consequence of wholly unnecessary evacuations. But why isn’t it mentioned?
At the other end of the spectrum, high natural levels of radon, about 1700 pC/l, are sought out for therapeutic purposes, especially pain relief.
https://www.theatlantic.com/health/archive/2013/11/inside-a-radioactive-health-mine/281265/
IIRC, this was tried many, many years ago. May even have been tried commercially.
As other have posted “nothing NEW under the sun”..usually these reports NEVER refer to all others’ work gone before their “discovery”. The Portland Cement Assoc. and The National Lime Association, as well as the US Army Corp Eng. have massive amounts of reports on Pozzolanic materials/additives such as ash, lime, including RICE HUSK ASH “RHA” another waste product from burning of rice hulls- Many ‘natural home builders’ use the RHA, when available, to make their own “Roman cement” walls and floors. Of course breathing in this stuff kills your lungs, so the average dolt shouldn’t have access. But rice hulls themselves are used as light weight filler with clay and lime for walls and blocks. Fun to play with these materials for home-made projects.
This from a 2004 report, based on much earlier studies: “Coal fly ash has been successfully used in Portland cement concrete (PCC) as a mineral admixture, and more recently as a component of blended cement, for nearly 60 YEARS. As an admixture, fly ash functions as either a partial replacement for, or an addition to, Portland cement and is added directly into ready-mix concrete at the batch plant. Fly ash can also be interground with cement clinker or blended with…” SEE: http://www.ce.memphis.edu/1101/notes/concrete/PCA_manual/Chap03.pdf
PrivateC
While what you write is all true, this is not a cementitious material. It is a way to set materials chemically to produce a form of artificial rock. It can in some cases be argued it is a metal or a glass like borosilicate glass.
My great great grandfathers business was doing this in 1857. They actually also produced moulded concrete fire places. The core business was Spence & Dixon based in Pendleton, Manchester and produced high value borax from gas producers waste ammonia and shale. They also produced prussian blue from waste leather soles. Those victorians could teach us a lot. I found the diary of Peter Spence in a Runcorn museum, hidden in a laboratory book and it is a treasure trove of information. You can source the information in the Manchester Evening News. Check out the first great pollution trial which involved the early pioneers of climate science, particularly Robert Angus Smith (who coined the term acid rain)-he appeared for the defence. Evidence included the first photographs of acid damaged trees.
Sorry-I meant high value Alum-not borax
Your heading should read “Making Cement from Fly Ash” Concrete is the product, Cement is the binder
In the Tampa Florida area there is a shortage of flyash that is used to reduce the cement required to make concrete. It is being imported by ship. Silica fume is used as a substitute when fly ash is unavailable.
To my knowledge flyash has been used in concrete for over 30 years and this is not a new practice.