Waste Plastic Recycling and Properties of Cement

Hello coffeebean

You will not get a proper bond, between the plastic pieces and the cement/sand/aggregate mix.

All "cement included" mixes = Concrete, Cement plaster and the like, set by crystallisation, not by drying, as is commonly supposed.

The extra water used in the mixing quantity, is carefully measured, so that crystallisation can commence by growing needle like barbed crystals throughout the mixture.

These crystals extend, becoming interlocked, more and more until approximately 28 days has expired. (Refer Concrete 28 day strength).

Once crystallisation is completed, the slab dries out slowly, the excess water not required evaporates from the concrete surface, taking about one month per inch of thickness plus one month to do do.

Thus a 6 inch thick slab will take around 7 months to "dry out".

Because of your proposed use of non-bonding plastic into the concrete mix, the crystallisation products which cannot bond onto them will not properly propagate throughout the mix, and you will end up with weak concrete.

Likewise, you cannot guarantee exactly where those plastic pieces will end up, in the finished product, they may all end up in the same place, or close together.

So, it would not be wise to use that "plastic filler" anywhere in a structural unit.

It may be OK to use it in a non-load-bearing floor slab situation.

There have been many failures of concrete over the years, some caused by improper "fillers".

Personally, I would refuse to use such a "filler" material.

Sure it's cheap, or free, but at the expense of long-term strength of what you make from it.

Kind Regards....

http://rudimentsofwisdom.com/pages/cement.htm

Cool page. Wow, a cement coil spring?

for the original poster, I would stay far far away from adding plastics to a cementitious concrete mix, as there will be no bond between the concrete and the plastic. That is, unless there was no structural need for the concrete, such as a weight or thrust block application. Even then I'd be wary.

I really cannot see an upside to this idea.

Thank you all for taking time to respond. Sparksation, much obligued for your in depth comments.

Cement/sand/fine pebbles may be combined with plastic fiber usually polyester and is used for some type of fiber-concrete boats and shot on as fiber-reinforced concrete or "shot-crete" (gunite). Stainless

Concrete has also been used in combination with bamboo in china and depending on how much cover (cm of cement/concrete over fibers/rods) can last many years.

As an extender generally means a significant amount of materials (say 40%), then you are talking similar to light weight concrete which usually uses cinder, oyster shell and the like with very higher surface area and surface texture.

For casting, make 50-100 cubes with various % amounts and test for compressive strength...etc.

Tom

Thanks for bringing up the idea to make test samples. So far responders agree that it may be OK to use the proposed cement/plastic mix in non-load bearing situations. You have further defined that an extender means @40%. My question to you is, % w/w or v/v? Either way with the proper mixer reasonably accurate and repeatable results can be achieved as far as mix % and dispersion, so on this particualr point I disagree with Sparkstation. Thank you all again for your valuable input.

Hello again coffeebean

Pf course you are entitled to disagree with me.

Sincerity of belief is never a substitute for truth.

<"How much of the recycled materials can be incorporated without compromising the basic casting properties of cement?">

The answer to that question, is Zero, as I explained earlier.

Of course you can mix 95% of rubbish into a cement/sand/aggregate mix, but it's strength will be very low.

The High-alumina cement structure failures over many years, prove that.

In the end, you get what you pay for: RI=RO - Rubbish In = Rubbish Out.

Kind Regards....

Great remarks there Sparkstation. Would you like to comment on additives like superplastisizers, iron filings (tiny nail like things in place of real reo) and finally fly ash? I'm all ears up here as there's a number of 'enthuasts' spruking these additives. Also, since they are breaking up like Weetbix here this past 12 months, concrete used for seawalls. Thanks Mark

cement can tolerate fibers because the cross sectional area is small ccompared to the length and fibers have one thing concrete lacks...tensile strength. That means the boats or other strytures made with fibrated concrete over an inert wire mesh frame can be quite long lasting and resilient.

On the other hand if you add wide areas of plastic film, very thin, but wide in area, these will represent an easy shear plane as there will be almost zero bond between the plastic and the cement.

Bulk pieces of plastic, say 1/2" balls will reduce the ccompressive strength by whatever proportion they make up.

That said,, if you make a wall with embedded plastic foam bits, you do lose strength, but you gain insulation values, and if you design to accomodate this, it works very well.

http://srmi.biz/Tips.Insulation___Air_Sealing.Foam_insulation.htm

...if you add wide areas of plastic film, very thin, but wide in area, these will represent an easy shear plane as there will be almost zero bond between the plastic and the cement...

Hi, Aurizon.

Based on what I´ve learned in this thread my proposal will include detailed protocols for running trial mixes and making cast samples for mechanical testing. Also that it´s important defining the best L to W ratio for the waste film chaff and careful selection of knives for the mill is critical.

Polypropylene fibers can be added to concrete to serve as a secondary reinforcement. Generally they are added in the proportion of up to 4 or 5% by volume, however, 1 to 2% is most practical in terms of ease of thorough mixing. Too high a percentage can cause the fibers to form clumps ( "meatballs" ). Size ranges of fibers are usually 0.25 to 3 inches in length and 0.0002 to 0.030 inches in diameter. It is unsure how larger pieces or differing types of plastic admixture would behave in a concrete mix, but they might add lightweight or insulating properties to a mix. Trial mixes should be made to measure the performance of the proposed mix using the size, types and proportions of plastic that are proposed.

Sounds like Coffeebean has a mind of his own and is going to do as he pleases.

I gather, from his remark about the selection of knives by the mill, he is talking about scrap sheet material from a mill that makes sheet plastic for various uses; lots of scrap.

Because he is talking about selection of tools for the mill I also conclude he has an interest in lots of this waste product for lots of concrete projects.

Sounds like another disaster fixing to take place in some developing country, where many such disasters have and do take place. Reminds me of the history of this country, U.S., where when we were first developing industry many similar disasters took place and where, for somebody's penny-pinching, still occasionally do take place.

Because he is insistent on focusing on that mill product it is obvious Coffeebean does not understand the difference between incorporation of high tensile plastic fibers and shredded sheet product which has virtually no tensile strength but will have enough face area to constitute a shear face.

Neither does he appear to have enough experience to proceed with extreme caution.

Wonder where he is located?

Sparky...I knew about water of crystallization and such, thanks to Brooklyn Technical H.S., but I never heard about 28 days to extend and complete its crystalline structure, curing, nor the long period of drying.

Thanks.

j.

Bravo

Actually might be easier to melt and extrude and then blister as rough as possible FIBERs rather than SHEETs. Use a very dull knife/blade

But as a minor reinforcement element we are talking big differences for "Extenders" as in light weight concrete - still same problem - boil and blister pellets.

Let him do the cube tests - and if it works OKAY

TOM

You´re very perceptive Jack J but dead wrong on several counts. The project is primarily a waste disposal solution, not a mortar mix business based on passing bad product. There´s such thing as laws, standards and liability, you know. The difference between incorporation of high tensile plastic fibers and shredded sheet product has been made sufficiently clear by Sparkstation, aurizon, et.al. Thank you.

Now you sound like somebody here in the states who could and would submit test samples to certified labs.

Your further comment says you may try to get concrete companies to incorporate the plastic materials into concrete they deliver to construction sites as part of a scheme to deal with plastic waste.

You get a mark for trying to solve a problem. Another for the fact that the final determinant of the safety of the scheme will be the concrete companies who will look askance at any ideas about inclusion of materials they have not dealt with previously.

No need to guess at what their response will be, but nice try for trying to find a way to include waste in a usable product.

j.

To :CoffeeBeans.

May I suggest that you contact the New-Zealand Contributors. These may, I am reasonably certain , be able to locate traces of the inventor of a mix which contained precisely what you are after at present.

This inventor went to the extent of widely showing the result of his work(s) , which, to alll intent and purposes were highly and, technically : successfull. He was trying to find interested overseas buyers of the technique. So that , about ten years ago, (when I was very active in China) sought my assistance. (The Chinese had their own invention which consisted in outer suburbs of Beijing (in particular) to almost instant transformation of certain types of plastics into : direct production of :commercial grade distillate fuel. This was by a patented, coal- fired , primitive but effective re-cycling system.

I lost track of this person but believe that he would have obtained, if not : international patents most probably , local NZ protection.

In case of your further interest in waste re-use an Australian special crusher designer has succeeded in the re-use of glass bottles . He is able to economically transform , with his crusher designs :waste glass and or crushed bottles into various sizes of sands .These can then either be re-used as an additive (for the glass making factories, and who themselves use : silica sand for glass making) by reliable production of various sized :

" glass sand(s) "

or the alternative is to use the crushed glass (after screening for size) into cement

Good luck and good hunting

"Labor Omnia Vincit "

Friends,

Certainly an enthusiastic thread. Considering the wide range of opinions expressed, I think that experimentation by Coffeebean is worth-while. Conventional wisdom says that as wet concrete mixes spread out they tend to segregate with the finer materials spreading further than the coarser, resulting in very poor strengths. Yet, after years of research into additives, LaFarge came up with certain ones which allow an extremely pourable and self-leveling mix with very good compressive strength values. It was so fluid with no extra water having been added, that the standard slump cone measurement was meaningless.

I suggest to anyone so inclined, the Portland Cement Association's "bible" on the design of concrete mixtures is a very useful source of information.

Regarding the curing of concrete, the hydration/crystallization process never really ends. Compressive strength continues to rise as time passes. The 28 day time is chosen because usual designs of mixes will have reached over 80% of their ultimate strength by this time.

Regards to all--JMM