Re-use of Pulverised Glass

I'm just postulating through my hat here, however has anybody in your organisation done a "real world" cost analysis comparing the two products?

I would suggest that transport would be a significant cost as part of that equation.

That said it doesn't matter what the load is, there are transport cost involved. But the differential is nominally 60 odd Kilometres, that does equate to a fair bit of money if we're talking a number of loads, not to mention the return trip time.

If your receiving "free" or nominally low cost fill as against the Screened Pulverised Glass then what is the incentive to use the SPG? Aside from helping a mate with a backyard full of broken beer bottles?

Your query is valid, and I too would want all the boxes ticked before I signed off on it.

You know what the parameters and behaviour is of the sand and fill. If it is in a "critical" area of your project it would be better to go with the proven product.

My tuppence worth.

Thanks for the prompt reply.

The "real world" cost is more dollars out of our pocket to use the stuff when averaged across all locations.

But we are being challenged to be good environmental stewards by utilising this material in preference to mined sand. (They are pulling out the "environment" card.)

Personally, the costs involved to pulverise, screen/grade, wash and transport all seem to be greater than the alternative, but we have been requested to provide an engineering justification for the non-use of this material.

Note that we are also being asked to authorise the material as replacement to a proportion of sand in concrete where we have raised other concerns relating to slip surfaces and so on.

Transport is a significant portion of the cost, and so is the "availability" factor. Our response crews need access to stockpile material 24/7 while the "creator" of this stuff is only open 12/5. We are also extremely reluctant to use it in residential areas until there is significant longer term history, so we still have to maintain segregation of this stuff from the sand and gravels normally used. (Again, none of these is an engineering reason, but rather seen as logistics that could be managed.)

It will be interestign to see where this ends up.

But who's responsible for waste glass re-use? That would be the people on the other end of the supply chain, and they need convincing, apparently. You point out a valid systemic problem, but don't criticize someone trying to alleviate a problem for failing to solve aspects of the problem beyond their control. (They may be worthy of criticism on other grounds.)

Ever since someone here pointed out that glass should be re-used, not recycled, I feel a twinge of regret every time I throw out a glass container.

If we're going to account for the energy costs of transportation, 40% reduction in energy [probably man hours too] for compacting is not insignificant

JAE[just an engineer] was asked for potential technical reasons this material should not be used, so far none have been indicated

If anything there seem to be some benefits

the usefulness coming down to strictly economic factors

the usefulness coming down to strictly economic factors

However, the vendor of the product is promoting the material on an environmental basis, and on that basis it may not be better than the locally available alternative, and could be worse, because of increased emissions in transportation and increased petroleum usage.

I would question the 40% energy saving in compaction. 1. It seems unlikely: crushed glass is too much like sand. 2. There are many applications in which the sand fills interstices between gravel or rock, and in those I doubt that the would be any measurable energy savings.

If I were JAE, I'd ask for real data from a third party that show that, in JAE's application, there is an energy benefit large enough to counter the higher energy usage and CO2 emissions in transportation.

I'm wondering who the 'we' is that is pressuring you to use the crushed glass. It may not matter, but they seem to have some authority or otherwise you would just tell them to 'go away' [insert stronger term if you want ].

I'd pull out my own environment card and point out: 1. that the extra hauling mileage would be burn more hydrocarbon fuels and thus be detrimental to the environment, and 2. that the crushed glass is potentially recyclable for human use, whereas the sand cannot be without a significant amount of processing; so overall, it's bad environmental engineering to use high-grade unproven material when the low grade material has a proven environmental record.

How is burning extra fuel to transport the crap being a "good environmental steward"? Glass is about as recyclable as it comes, you make beer bottles out of it! That there is a vital natural resource you are throwing in the ditch! I say tell them to fold their environmentalist card until it is all sharp corners and shove it up their bunghole.

All that said, if the economics were different, unless it is leaded glass or something, I really can't see any environmental issue with the proposal.It is nothing but artificial obsidian after all.

From the USGS Minerals Information Statistical Compendium

Transportation is a major factor in the delivered price of construction sand and gravel. The cost of moving construction sand and gravel from the plant to the market often exceeds the sales price of the product at the plant. Because of the high cost of transportation, construction sand and gravel continues to be marketed locally. Economies of scale, which might be realized if fewer, larger operations served larger marketing areas, would probably not offset the increased transportation costs. Truck haulage is the main form of transportation used in the construction sand and gravel industry. Rail and water transportation combined account for about 10% to 20% of total construction sand and gravel shipments.

The large distance (75km) would seem to make this a bad deal, environmentally.

Note that we are also being asked to authorise the material as replacement to a proportion of sand in concrete where we have raised other concerns relating to slip surfaces and so on.

I'd have some concerns about "adulterating" concrete for anything but cosmetic use, but that's just me. This is not my area of expertese. Although I have had peripheral exposure to the building trade.

I have driven Tippers and the like.

But we are being challenged to be good environmental stewards by utilising this material in preference to mined sand. (They are pulling out the "environment" card.)

My immediate thought is "follow the money/influence". Also who benefits from this and as you have rightly said what is/are the long term issues.

Starting to sound like a dud deal (maybe for you?).

(We have an arrangement where property developers have dump sites for clean sand that we can use. They avoid the landfill fees and we have a ready and cheap supply.)

Gee, if your getting a good porportion of the material this way, how can management justify the cost of the "environmental" material?

Unless its really political. In which case bump the responsibility for its use back up the food chain. That'll sort out the brave from the foolhardy..

It might make sense in some situations, but not this one. You have a ready supply of cheaper raw materials. Let someone else save the world this time.

I can't quite grasp the idea that the old glass doesn't have value as recycled glass. Around here the trucks go door to door once a week picking up glass, metal cans and paper. I don't think they break even on the money, but going door to door is very expensive. When the glass is available by the truck load I would think it would be valuable.

I'd be very worried about some worker in the future trying to repair the pipeline.....say down in the excavated trench using a gas-operated pipe saw and as a result getting a couple of glass frags right into his/her eye. I can see a lawsuit happening with use of this glass stuff. Leave the ground-up glass for recycling and use in concrete flowable fill or asphalt concrete fillers.

If it has NOT been approved by your state Dept. of Transportation for use on their projects then stay away from it....unproven technology, and most likely UNTESTED too!

Use the mined gravel or a good quality concrete flowable fill product that's already been approved statewide!

Good luck!

You are all re-inforcing my original opinion (not to use the material), but where is the "engineering reason" to not use this material?

to answer a few of the background questions that are being asked or implied.

This glass material is the "fines" from the kerbside pick up and recycling. They crush that stuff and anything smaller than "x" is not acceptable as return feedstock to the glass manufacturers. These fragments are then graded and crushed to this smaller size requirement.

Regarding the OH&S for "glass in eye" and abrasion, the independant (Government endorsed) reports indicate this is material to be no worse than normal sand/gravel for many parameters and in fact better for some. There have been limited trials conducted using real workers in a major city laying pipes in a variety of blends using sand/glass mixtures up to 100% glass. The workers gave positive reports, but others not involved in that trial created a veto on the approval.

Significant quantities are being used in roadmaking activities (blended into the mix) but there is still an excess.

I'm beginning to bend to the idea that we treat this material as a "suitable alternative" and use from that stockpile when convenient. (As opposed to substitution of this material completely.)

There may be a totally differnt outcome. This stuff, being "non-reactive" to moisture levels may prolong the life expectancy of our pipeline assets and actually reduce the amount of work that needs to be done on pipes in the future. Are we actually inhibiting a good change?

Again, thanks to all for the ideas and different perspectives on this matter. The local "CR" (Coffee room) discussion is limited in scope for this sort of issue.

"anything smaller than "x" is not acceptable as return feedstock to the glass manufacturers"

I know this isn't answering your question but why won't they take small bits of glass?

My information is "second hand" via the study done in the major city, but it seems to relate to two different characteristics.

Firstly, the feedstock to the crusher could include normal window glass, bottles and in some cases "pyrex" material. The larger fragments of pyrex are able to be segregated in the glass re-processing, while these "fines" cannot. ?Different melt temperature?

The second is that fines tend to float on the melt and are difficult to incorporate. (Same thing happened with recycling aluminium cans until they modified some furnaces.)

I know it would be possible to overcome the second concern with an engineering solution, but the first seems to be their focus, citing "a melt of up to 200 tonnes could be contaminated by a tiny proportion of impurity." I suspect that they have a submerged screen that is able to segregate the higher melting point materials provided the pieces are large enough.

Could you aks for an assay certificate verifying that the sand is free of heavy metal contaminants. If ok, use a blend of sand and pulverised glass, then you cover both bases - proven versus environmentally friendly. If the suppliers of the glass make any claims you are not 100% happy with, let them put it in writing.

Could the glass be contamnied with lead or mecrury? Say, old CRT tubes. Sound like and easy way to dump waste. Just a thought.

Here's an Aussie approval (Dept of Environment, NSW) of the exact usage you're considering:

http://www.livingsustainably.net.au/enews/07aug/GlassNewSand.htm

:)

Mark Bingham
Relativity PL
http://relati.com

i cant see it being good to breath in the dust.I know it is washed but it will still have dust. it maybe not any more harmful than other backfill material,but i would not like to be the grade man. the government says it is ok,didn't they say that about asbestos at 1 time. in flow fill it sounds like a great idea. the use of glass in bituminous concrete didn't last very long,that is around here anyway. if used i would think you should get a recycling credit and be eligible for GREEN funding. also if stock piled that stuff i would think would blow all over the place,like it does when put down on traffic stripes. does the owner of the pipe line (water , sewer dept) want to take the chance ?? i do not know but will it give off static electricity ? lots of stuff to think about. good luck.

Well,

There you go!

I'd sign off on it, technically, in ALL respects. Environmentally, not a problem.

You have to do the math for yourself and make your own 'ends meet', and justify the mileages.

Cheers,

Stu.

Glass is formulated using all most all periodic table based on end need. I was involved in window glass which is safe for this project and also worked on leaded glass for x-ray protection and low temperature Cerdip package development for high reliability computer microprocessor as well as glass to extend life of highly radio active waste.

If not carefully quality controlled done may run the risk to do more harm than good. It is my strong advice to get the element tested randomly batch to batch before use. Then you have to work out it cost and benefit and make a decision

Are the pipes water pipes? what if you get a crack or hole in a pipe will the glass

get into the water? drinking crushed glass is probably worse for you than drinking

sand, just a thought.

Just picked up on this discussion and it's not at all my field but one thing caught my eye and that was the early mention of wanting to use it in concrete. I have a very distant memory from way back in the late sixties/early seventies that when they tried to re-enforce concrete with glass, as per resins or plastics, it failed because the cement attacked the glass. maybe this has been solved but I'd want a lot of reassurance before I committed to it's use. As for this problem it sounds like it will come down to the whole cost of the glass against the fact that you are in effect already "recycling" the sand locally.

I'm not sure about Straight glass, but FRP [fibergalss reinforced plastic] rebar in not uncommon & is superior in many ways

Glass fiber reinforced concrete and cement products have been around for decades as well.

It reacts still. Concrete is based on calcium aluminate and common glass (window and bottled similar) is based on sodium aluminum, borosilicate. This will reacts with concrete as long as we have water in air and water in concrete.

How much will be degradation I have not worked on this

You might find some useful info here.

"since it is glass rather than silica sand is actually lower risk for silicosis/dust diseases."

If this has been part of the information you have been given it is false. Silicosis is a hazard that those that work with any glass product have to deal with.

If both the sand or the ground glass are washed to the same specs there maybe no difference between the two.

The glass has been freshly broken so the fragments still have sharp edges. So I would believe it would have the potential to be more of a hazard to cause silicosis the the sand dust. As the sand has had an undetermined amount of years to grind against itself to dull those edges in it's formation.

In transporting either product sand or the glass over a distance it will create its own dust. The added distance of the glass it would create more. With the sharp edges I would factor even more dust created. As these sharp edges break off.

These questions you need to address for the safety of your workers that will be using the ground glass product. The problem in it's use may not be an engineering one but an occupational safety issue. The effects of which may not be learned 10 to 20 years after use.

I had used crushed bottles to insulate walls in pig's farm. I found it to be very good material. It also prevented bugs, mice and rats from entering into walls and proved to insulate very well. I also used that in concrete basement, as sand was not available in that farm. I think it would be very good material for your use. I do not think the people who offered it to you exaggerate its property as replacement for sand. My advice it to go ahead full speed and save money. We use glass in glassware and glass jars to store food. It is not toxic and mixes pulverized glass dust with soil pretty well. I do not think it could create any problems in the future, unlike Asbestos, which is very toxic. Indeed masks should be used to prevent inhaling of glass dust, but you can always have some stupid that oppose that. Compacting glass particles is very efficient too. I also used a torch to have nice shiny surface, but you do not need that probably.

Thanks all for comments so far.

Back to the original dilemma. What technical reasons preclude the use of this crushed glass material?

So far, I only see sharp pieces (which crusher fines that are already satisfactorily used tested to be worse.) and dust issues including silicosis, (where the crushed and graded glass tests as 1% of the exposure level of local sands already being used).

The additional emotional issues relating to us being used as the dump site for material that could be better directed into a re-use program, cleanliness (where this material is washed and graded while raw sand is not when used as backfill.) Concern over potential ingress into water pipes (which can also happen with sand and where the highest risk is biological contamination as the relative density of the crushed glass will enable it to settle.)

I'm more and more convincing myself that this material be described as a "suitable alternative" rather than substitute and be approved for use where readily available.

The pipe materials themselves probably represent greater risk in cutting and handling, with various plastic materials, along with heritage Asbestos cement, cast iron with lead joint seals, and the manual handling issues they pose.

Again thanks all for your input. I'll keep an eye on this thread for a little while to come but will probably not respond further unless something spectacular comes to light. If anyone thinks that I've missed some crucial item, them please send me a personal message for clarification.

Have a wonderful Christmas time.

is crushed glass approved for the type of work intended? sand has known properties where-as other materials may not. i would'nt take the chance. it may come back to bite you on the ass farther down the road.