I have come to the conclusion that I'm currently living in the wrong part of the world (actually, I knew this before moving here but that's another story). The whole county I'm living in sits on top of gravel deposits. If you dig down 1-2 meters you'll find more clean gravel than you can excavate (the water table is pretty high and a long reach excavator can only go so deep). But despite this vast abundance of gravel, it still sells for 50 euros per cubic meter- trucking costs extra. This has brought me to look for alternatives for making concrete. Crushed concrete sells for 10 euros a cubic meter. There are only 2 grades that I have found nearby. Course and fine. The course stuff is about the consistancy of rip-rap mixed with item 4. The fine stuff is crusher run with 3/4" aggregate with a lot of fines. If it gets wet before compaction, it turns to mud. I'm wondering if the fine material will be suitable as a gravel replacement. My concern is the % of fines maybe being too high. I'm thinking adding extra cement into the mix would improve it. I'm considering this for residential slabs on compacted sub-base. This is not for footings, walls or bridges. If it's suitable substitute, the savings are huge. I'm interested in hearing your ideas on this.
Crushed concrete has wide spread use here in Michigan. The large size, here it is known as 1x3s, is used quite a bit. Its big use is as mud tracking mats for construction sites. Lay down a layer to geotextile fabric, and then a layer of 1x3s, and traffic leaving the site has quite a bit of mud knocked off of the tires. 1x3s are also used in bridging situations and undercuts. Undercut and fill your poor area with 1x3s, then choke it off with a finer gravel, or filter fabric and then stone. The fines are used as typical road gravel. It is either used as a 21A or 22A road gravel, depending on the screen the fines pass through. It makes a decent substitute imo. It all depends on your source for material though. Concrete crushers around here using demolition concrete have been a sore spot for the industry, sending out cheap product, but it contains a lot of wood, brick, and I have even seen carpet. The cleaner the material the better. It is also preferred to get a concrete that was used as highway, or good county roads, as it meets certain specs that other concrete doesn't. Heres a Link to a Federal Highway Admin summary of Michigans use of crushed concrete http://www.fhwa.dot.gov/pavement/recycling/rcami.cfm
Thanks for the link Turbo! I haven't seen any wood or carpet in the mix yet. I think that's mainly because nobody seems to want to pay to haul away demolition debris that can be burned on site. :beatsme I think I'm going to use the RCA as a gravel substitute. Now I just need to find a big enough mixer that I can mount on the back of a tractor.
May be a little large for your purpose, maybe not, but how about a small batch plant and make your own concrete, then use Georgia buggys to transport mix to slab your pouring. Just a thought. http://www.cementech.com/dev/index.php?option=com_k2&view=item&layout=item&id=9&Itemid=15
The main problem I see in the recycled concrete is too many fines. That is why concrete gets washed sand, because with too many fines, you will have a hard time getting the cement powder to coat the particles and "glue" the whole thing together. You would end up with a product more like a cement treated base than a flowable concrete mix, IMO It may be a good enough idea to rent a small portable mixer and get dome of the recycled material to do some test batches with . You might come up with a market for it somewhere.
I know nothing about this aforementioned stuff, just curious. Would it be possible to make a screen to remove the excessive fines to make an acceptable concrete aggregate? Depending on the market in his area, it might be practical to develope a method for Joispoi to make use of this stuff and produce a profitable product with it. Just a thought. Good grief, that last sentence has a ring like peter piper picked a peck of pickled peppers. Geeez. :lmao
Screening is easy enough to do, it's getting rid of all the fines that would be the problem. Without the coarse aggregate, it doesn't have much structure. I can't think of a good use for it. Maybe there's an untapped market for silt or sludge substitute that I don't know about. JD, that's good advice. I've already got a small mixer for the test batches. I'm thinking that if I make the mix richer than standard, enough cement will get in there with the fines to make an acceptable light-load concrete. The batching plant is a good idea, but I'm not looking to get into the concrete business. (I actually found a used 7 yard mixer for 1,500 euros. I'd have to put a motor on it and build a base or find a truck to put it on). I just want to find a way to save/make some extra money on some upcoming work. Maybe a batching plant would create a niche in the market for lower priced concrete.:beatsme Quality of the concrete would be tough to control, though. It would only be as good as the RCA that's used to make it.