Making Cement from Recycled Materials

This is what we do using mostly mineral based cements which can accommodate much higher levels of post consumer waste than can Portland cement. They are also stronger and sequester CO2

If you would like file transfers and copies of testing email me tesla-was-right@hotmail.com

Dear Sir,

Thanks for your information. I will send the copy of my report as soon as it is ready.

Dr.ram

Hello mrswamy,

I thank you for the reply.

No need for the full report. The site probably cannot handle that. An outline of your decisions would be nice.

Take care.

One waste material there is a lot of is fly ash from coal plants. You should be able to get all you want free. It exhibits cementitious or pozzolanic properties which reportedly make it useful in cement.

Hello ron,[p]

The type of 'concrete' you mention is very old and was made by and probably prior to the Romans.

It is generally known as 'Slag Cement' and the Romans used volcanic ash in their concrete for lightness. However, care should be taken as this type of cement, or more correctly (if mixed with stones) 'concrete', cannot take the same weight as concrete made from Portland Cement. It is also liable to attack by various chemicals.

Mortar used in masonry was made using a different formulation in this case instead of using pumice they substituted a finely ground material made from broken bricks or ceramics. This was used to bind the stones or other building material together. Good examples of this are some of the Roman Aqueducts that are still standing today.

Check out this site:

http://www.iflyash.com/specflyash.htm

It gives the ASTM references for standards World wide. Very useful site.

This allows you to know the 'standard' you are working with and the properties of the fly-ash cement or concrete you are using.

Take care

Another is blast furnace slag. But after they found it could be used for road base it wasnt free anymore.

It seems to me that posters here are confusing cement with concrete. Certainly waste building products like brick and concrete can be crushed and processed for use as some or all of the aggregate in a new concrete mix. Portland Cement is produced by burning limestone in a kiln and then crushing and grinding the 'clinker' that results from the firing. Once the cement is hydrated during the cure in a concrete mix, which is a one-way reaction, it no longer has the ability to hydrate again.

Recycling of hard materials that are the result of demolition work has been in use for several decades and continues to grow and be refined. The major problem is in managing the various undesirable elements in the demolition materials, i.e., wood, metal, soft brick, gypsum board, paper, etc. My observations have been that it is virtually impossible to segregate all of the deleterious materials during the crushing and screening of demolition products. If the only source of the recyling infeed is waste concrete from batch plant waste piles, then this concern is likely not an issue.

There could be some special situations where the inclusion of some deleterious material is acceptable, but none that come to mind, as there is typically a rigorous process involved to design a mix for the intended use and then monitor the product for compliance.

Hello Doogleass,

GA to you Sir, for your detail. =

Take care.

Where I live the home of Lehigh Portland Cement, the four major cement manufactures; LaFarge, Buzzi, Essroc, and Keystone are all switching their fuels to mixture of Hazardous waste, recycled plastic, rubber tires, and either coal, gas or fuel oil. Is this a common practice at most cement mills? Even though all three companies are jumping through all sorts of environmental hoops it seems to be worth it. Up to now our township has been giving all of our recycled plastic to them. They are charging fees to recieve hazardous materials. I'm sure they have deals for the old tires. So in a way they are using recyclable products in the cement just not construction materials.

I do know one waste product that one of the quarry I work at produces the cement companies love. It's a waste slurry that is high in silica and alumina clay. The buy between 10,000 and 30,000 tons a year.

There are many co-products used in the construction industry. PA uses fly-ash from coal plant ash an additive to help increase strength. Bag-house fines from quarries and asphalt plants can be used for road construction, agri-lime, and/or reused through the plants for asphalt mixes. Millings from road way are used for sub-base in roads and used back into the asphalt plant. Below is a list from PA Department of Environmental Protection of a wide variety of co-products.

http://www.depweb.state.pa.us/landrecwaste/cwp/view.asp?A=1239&Q=522140

Try these for size: low carbon cement (yes, not concrete--cement), made from mixed recycled materials, or (get this!) from saltwater and sequestered CO2 from power plants:

http://www.celticcement.com/globalcementmag06.html

http://www.calera.biz/pdf/scientifc_american%20copy.pdf

Thanks. Your information is useful for my literature review.

Regards.

Rams

Fly ash from coal fired power stations is close to cement but is deficient in lime.

If power stations could be convinced to add pulverized limestone to their pulverized coal they would have saleable cement as by product. Some experimentation would be needed as there may be clinker problems, but this should be able to be overcome with minor design mods.

When I suggested this to a very senior engineer in a power producer I was told "we are in the power generation business, not cement", so it was not tried.

Returns would be comparable to income from power generation, instead of the cost of fly ash disposal. Extra cost would be limestone, handling and pulverizing.

Similarly, if coal fired power stations (where they have plenty of real estate available) would absorb their CO2 in water they could grow algae which could be made into pellets and sold as stock food. Net returns here would probably exceed income from power production.

The downside is that a lot of water is needed, but this could be done using the sea. The required real estate would not then be a problem.