You can't get the same result using the recycled concrete because there's too much friction between the sand and angular crushed stones in the recycled mix. The recycled concrete does compact very well using rollers or plate compactors, but as you said, that's very tough to do in your case.

Use clean stone, and compact it in 6-8" lifts with a vibratory compactor. We recently did a huge subterranean parking garage where some of the areas have 10' of stone under the slab, and the area between the exterior walls and the sheetpiling got backfilled with almost 40' of stone.

The usual range employed is between 9.5mm and 37.5mm in diameter. - Fine aggregates are usually sand or crushed stone that are less than 9.55mm in diameter. Typically the most common size of aggregate used in construction is 20mm. A larger size, 40mm, is more common in mass concrete.

The best sub-base for a concrete slab is gravel. The soil has to be prepped first before the gravel can be laid down; pouring concrete directly onto rock is not considered a best practice.

My great-uncle has one of those homes that is a single story built on a 8" poured slab with fiber impregnated concrete. He has a water leak near where the water line comes in under the slab. We have dug up the water line to the slab and not found the leak, but we can see where water is coming from somewhere under the house slab.

No, you do not need rebar for a 4-inch slab of concrete on grade. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Rebar is recommended on concrete measuring 5 – 6 inches thick.

Form boards can be 2-by-4-inch wood boards or flexible hardboard secured to wooden stakes; form boards are necessary to hold wet concrete in …

Concrete may seem strong, but after many years, elements, and pressure, it will eventually crack. So in order to make your concrete last as long as your money that went into it, adding a layer of crushed stone under a slab of concrete will increase the life of your investment. Here are 3 reasons why a layer of crushed stone is important to the life of your concrete:

Can I mix my own concrete for a slab? To mix your own concrete for footings and piers, use 1 part Portland cement, 2 parts clean river sand, and 3 parts gravel (maximum of 1 inch diameter and specially washed for concrete mixing). Add clean water, a little at a time, as you mix. The concrete should be plastic, not runny.

The most common size is 1/8″ thick (4 mm) and 6″ long by 6″ wide (150 mm x 150 mm). Neither rebar nor mesh rust inside the concrete like one might suspect. The curing of concrete seals it off from oxygen, which is what causes the rusting of steel. That's why thicker slabs of …

If you drive on this concrete and apply pressure to it, the concrete tries to bend or stretch to conform to the hollow spot. The result is almost …

We can use crushed stone as a capillary break if there are no fines in the crushed stones—but the stones don't act as a vapor barrier. So it is common to use crushed stones with no fines as a capillary break—and then add a plastic sheet over the top of the stones in contact with the concrete as a vapor barrier.

Re: Self-Compacting 3/4" stone. Many times a set of plans will call for rock to be compacted. This can not happen. Even with sand generally all you do if a vibratory compactor is run on it is to cause it to flow out from under the compactor. Things that have alot of fines like 304, 411 or soil can be compacted.

Malcolm, I had assumed 4" was sufficient. If it needs 6", I will comply, but at $675 per 22ton load, it hurts. :) Also, when you say - [top dress the 6" below the slab with a drainable fill] - you are talking about the 3/4" gravel between the ground and the concrete, or in my case between the ground and Fomular 250 25 psi and then concrete.

What do you put under paving slabs? 3: Mortar preparation. Lay the paving slabs on a full mortar bed, which should support the whole slab, not just the corners. Use a mortar mix of 6 parts sharp sand to 1 part cement. Mix together with just enough water to …

It is also difficult to maintain a level sand surface when pouring concrete, and therefore difficult to maintain a uniform thickness of the concrete slab. Using sand as a base also requires more concrete; the softer base beneath the slab means you have …

Crusher-run gravel compacts well but does not drain very fast -- at least not as fast as 3/4-inch crushed stone (no fines). Talk to a soils engineer if you are worried -- but in my experience, either crusher-run gravel (compacted) or 3/4-inch crushed stone can be used under footings. So can rigid . An engineer may disagree.

Answer (1 of 3): Anything is possible, but not always recommended. Two things to consider are bearing pressure and early thermal cracking. 1) Assuming its a pad foundation, you will have a significant increase in bearing pressure, which could cause issues that result in a size increase to lower ...

Yes, you should put a vapor barrier under concrete slabs to prevent moisture from wicking up into the slab and onto the surface of your concrete slab, patio, or driveway.Ensure the vapor barrier is above both the gravel and rigid and immediately below the slab. Moisture wicking up into a slab can cause unsightly wet spots on top of your slab, and the efflorescence can be hard to remove.

Type 1 Crushed Concrete - 50mm down to dust. Best used as a sub-base for roads, underneath blocks, as well as layering in between concrete or tarmac and as a hard core for projects such as car parks. 6F2. Type 3 Crushed Concrete - 0-63mm reduced fines.

Pour the Concrete. Buy bags of concrete designed for building retaining walls by stacking the bags and pouring water over them. You can also use quick-drying concrete mix. Be sure to wear gloves and a mask. Break open the bags and pour the dry concrete directly into the trench and fill the trench to the top. It should be at least two inches deep.

Hairline cracks in a concrete slab are rarely a cause for concern. They can be controlled, but not eliminated. A crack in a slab of 1/8 inch or less is typically a normal shrinkage crack and not a cause for concern. If the crack is larger or growing larger (an "active" crack), or one side of the crack is higher than the other, then you may ...

Dig 150mm into your patio area. Lay a compacted sub-base of 100mm. Cover the area with 40mm of concrete mix. Lay paving slabs 15mm into the concrete with a 10-15mm gap. Leave to set for at least 24 hours. Fill the gaps between the paving slabs with concrete mix.

Soil Settles. If un-compacted, or poorly compacted, soil or fill sinks under a slab you end up with a hollow spot. If you drive on this concrete and apply pressure to it, the concrete tries to bend or stretch to conform to the hollow spot. The result is almost always a crack and the concrete slab drops down.

HASTINGS on Aug 29, 2015. Just to let all know. Yes you can put concrete over river rock. Marilyn the big trick is going to make sure that it is level to start with and frame it out. You may want to bring some sand in to help level. Then once you have it all prepared and ready to pour.

The problem will be putting any kind of finish on it. You need to get a little "milk" to the surface to trowel it smooth. You may be able to smear a cement water slurry over the surface after the concrete has set a little but a couple of people with hoes and a wheelbarrow can easily mix up enough concrete to do a small slab.

My understand and the big reason for the sand between the plastic and concrete is so concrete company can get by with a 5 or 6 inch slump instead of 3 inch slump. That is so they don't need to hire 2 or 3 or 5 extra people to move the concrete when it just sits in one spot after it is placed and won't self level.

When it comes to building, hardscaping and landscaping materials, there are a lot of varieties from which to choose. Exploring the differences between similar materials such as crushed stone and gravel, rock vs stone will help you select the best materials for your project.. Crushed stone is made from rocks that have been broken down by machines called crushers, giving the stones more angular ...

Or 1/2 inch to 3/4 gravel with the fines from gravel pits. We would use the asphalt millings for roads to access jobsites. ... both slab on grade and multi story with tilt up concrete walls. Without exception, the common base for the concrete has been reclaimed asphalt. ... Funny thing is the reason why more people do not use millings under ...

This home is very rural, an hour away from the nearest concrete plant. Concrete placing and finishing in the area runs about $7 per square foot for a four inch slab. The cost figures the same amount of sub-slab insulation if either concrete or Advantech are used, so the cost difference is materials and labor to install subfloor.

The question I have is whether I can use the lava rock as a base for the concrete rather than using something I'd have to buy. ... the freezing ground under the slab will heave and destroy your concrete, which will be a huge waste of money. So if you need to dig down more, which you'll find out quickly (if you're in N CA go 16-24", if you're in ...

There aren't many reasons to have only a 1-inch thick concrete surface. It is too thin to use as a flooring just by itself; however if you need to resurface damaged concrete, a 1-inch layer is a good amount. The old surface is prepared so that the new concrete will adhere, then the new cement is added.

2. Compact or roll the gravel in 12" lifts to prevent the slab from sinking. 3. Use a laser level to get the final dirt grade flat. This makes for a uniform slab placement and setting the forms is much easier. Most of the concrete slabs we pour are 6" thick.

pouring a slab foundation. The base course material, according to ACI 302, "Concrete Floor and Slab Construction," should be "compactible, easy to trim, granular fill that will remain stable and support construction traffic.". ACI 302 recommends material with 10 to 30% fines (passing the No. 100 sieve) with no clay, silt, or organic ...

For a perimeter footing of only 5cy, it is very doable if you can haul the equipment and materials into the site. If you can get a tractor in there, consider a tractor-mounted PTO mixer. I have done numerous pours of a yard or 2 without any help at all. My Mixer80 is rated at a …