Why do you need hardcore under concrete?

What is Hardcore Used for? A hardcore bed provides an essential part of a strong foundation for building work; when well-compacted it gives a base in which the builder can have confidence when infilling the upper layers. This is an invaluable commodity when it is necessary to raise the level of a floor.

Do you need hardcore before concrete?

You can't lay a concrete base directly onto soft ground, so a hardcore sub-base is essential.

Why use hardcore when building a concrete slab?

This type of material offers a well-compacted base that provides reassurance for the builder when infilling upper layers. Hardcore is an indispensable solution that is necessary to raise the level of a floor, forming the lower layers of road construction that protect any surface from stresses over time.

Do you need base under concrete?

Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Gravel is especially important in clay soil because it doesn't drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains.

What is the point of hardcore?

'Hardcore' is the construction term used to denote 'engineered' infill material that is placed within the confines of a building foundation (after removal of any unsuitable ground layers) in order to support a ground-bearing floor slab (Figure 1).

Do I need gravel under concrete slab?

Can I use old bricks as hardcore?

No as you would get uneven settlement.

Can I pour concrete directly on dirt?

Long story short, yes you can pour concrete over dirt.

What happens if you don't put gravel under concrete?

Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.

Can you pour concrete without gravel base?

Yes, you can pour concrete over dirt. If you have a very compact soil-type, such as solid clay, then you may have ground that is solid enough to support a slab over a period of time. One of the big risks for pouring directly onto the earth is water pooling beneath the slab and traveling up into the slab.

Can I use ballast instead of hardcore?

Ballast is available in different types for different needs. 0-20mm ballast is perfect for sub-base and concrete foundations. 20mm screened ballast is versatile and can be used on driveways, footpaths, oversite fill as well as sub-bases. Raised ballast is reserved for backfill, driveways and binding hardcore.

What do you put down before laying concrete?

To shore up the subsurface, sprinkle a thin layer of cement sand onto the gravel and dampen it with water. Do not leave any standing water and allow the dampened sand to dry for about an hour before pouring the concrete. Ground preparation is key to pouring sidewalk, driveway or any other concrete slab.

How deep should a concrete base be?

The concrete base should be at least 75mm thick, with a similar layer of sub base, so you will need to excavate to the required depth and ensure that all plants, stones and debris are removed before compacting the ground with a roller or tamper.

Is sand a good base for concrete?

As a general rule, stay away from using sand as a subbase. You're better off using gravel; your concrete will last longer and have less of a chance of cracking over time.

What is a good base for concrete?

The base in concrete construction is usually a form of crushed stone. Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage.

Can you pour concrete over rocks?

Big rocks are not a problem as long as there is uniform concrete coverage and adequate rebar for temperature fluctuations. If the big rocks protrude up above grade and if you have a few in a row, it will weaken the slab. We like things uniform, including the grade, thickness of the concrete, etc.

Can you pour concrete over grass?

Cheap and versatile and easy to pour, concrete will last you years down the road. You can pour it just about everywhere—including on the grass. Although it takes a little work, pour concrete over grass to create that walkway you always wanted or that mowing preventative you could previously only dream about.

Is 3 inches of concrete enough?

A concrete patio slab should be at least 4 inches thick and have a compressive strength of 3,000 PSI. You're free to make it thicker or stronger, but unless specifically required for your patio build, it's likely overkill to surpass 4 inches in thickness.

Do you need a rebar for a 4 inch slab?

For 4” concrete slabs used for driveways and patios, #3 rebar is common. Driveways that will support daily traffic by heavy trucks frequently use 1/2″ or #4 steel bar.

What happens to soil under concrete?

Before the concrete is laid, any topsoil will be stripped off and removed, so this will automatically remove most of the soil microbe population, the seed bank, important nutrients such as nitrogen and sulphur, plus a good proportion of other mineral nutrients and trace elements.

How long does it take for 4 inches of concrete to cure?

The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic.

Can I use paving slabs as hardcore?

They'll be absolutely fine as long as you break them up well - hard work though!! Put dolomite hardcore on top as this compacts better with the wacker.

Can you use broken concrete as sub-base?

It will be fine.

How thick does concrete need to be for a shed base?

Concrete Shed Base Depth

For ordinary garden sheds, a thickness of 3" (75mm) is sufficient in most situations. On soft clay, or on larger buildings, increase the thickness to 4" (100mm) laid on 2" (50mm) of finely broken and compacted hard-core if required.