Can I Use Gravel As A Sub Base?


In this publication, a subbase is defined as the layer of material that lies immediately below the concrete pavement. Some engineers call this a base course since that term is used to designate the first layer beneath an asphalt surface.

Is Sub Base the same as Type 1?

Type 1 material is graded from 40mm down to dust and is used for a regulating course under highways, sometimes referred to as sub-base.

What does sub base include?

In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles.

Can I use concrete as a sub-base?

Any potential ‘soft-spots’ in the subgrade can allow the concrete to sink from the center or turn up from the edges. Owing to its inflexibility, the concrete slabs can crack. As concrete is highly compressed and heavy, it may crack under its own weight if not provided a suitable sub-base.

How does sub-base work?

A sub-base works by distributing a point load over a larger area. The interlock between adjacent particles of the sub-base material ensures that a relatively thin layer of the right sort of crushed aggregate can dramatically improve the ability of the ground to carry comparatively heavy loads.

What is a Type 1 Sub Base?

MOT Type 1 is a crushed material, 0-40mm in size and usually made from granite or limestone. This makes it an extremely strong and hardwearing material once it has been compacted. Due to its strength, MOT Type 1 is usually used as a sub-base creating a stable surface for roads and pathways.

What is Type 2 aggregate?

Our Type 2 is a crushed aggregate with extra dusts and fines, which makes the perfect sub base for a range of domestic and commercial construction projects. Graded to 50mm down to dust and fines no specified grading, it is finer than our MOT Type 1 sub base, as it is composed of fewer larger angular scalpings.

What is Type 3 sub base?

Type 3 sub-base is a pure crushed granite, limestone or clean crushed concrete. Usually a 40mm product that has been screened to create a reduced fines aggregate. This product is fully certified according to the Specification for Highway Works. This is the most widely used sub-base where less fines are required.

What is the difference between subgrade and subbase?

A subgrade is made up of native soil that has been compacted to withstand the loads above it. … There is no consistency in regards to the terms of subbase and subgrade, but normally the subgrade is the native soil while the subbase is the layer of soil or aggregate on top of the subgrade.

What is the minimum thickness of subgrade?

5. What is the minimum thickness of compacted sub grade? Explanation: The minimum thickness of sub grade required is 300mm and in highways it is 500 mm as they are provided with the maximum best facilities.

What material is used in base course?

The base course is generally com- posed of granular material such as crushed aggregate, gravel, selected soil, or a mix- ture of selected soil and aggregate.

What can I use instead of sub-base?

Other materials supplied for use as a sub-base include ballast and crusher run, however these offer little control over the balance of solids and fines. Although unsuitable for use under areas of heavy traffic or commercial projects, these materials should be perfectly suitable for patios and standard driveways.


Can pea gravel be used under concrete?

If the soil is disturbed and packed or unstable such as some clays, a base will provide a solid underpinning for the slab. If you use crushed rock and dust, it will need to be packed. It will pack substantially. Pea gravel, on the other hand won’t pack.

What do I put under slabs?

Step 1. Paving slabs are bedded in a mortar mix with four parts sharp sand to one part cement. Measure your quantities using a shovel or a bucket – for example, four buckets of sand for every one bucket of cement.

What are the 4 main types of aggregates?

Aggregate is a landscaping term that’s used to describe coarse to medium grain material. The most common types of aggregate that are used in landscaping include: crushed stone, gravel, sand, and fill. Varying in material and stone size, each type can have its own purpose when it comes to landscaping projects.

How are aggregate classified?

Classification of aggregates based on: Grain Size

The size of fine aggregates is defined as 4.75mm or smaller. That is, aggregates which can be passed through a number 4 sieve, with a mesh size of 4.75mm. Fine aggregates include things such as sand, silt and clay. … Coarse aggregates measure above the 4.75mm limit.

What is Type 1 aggregate used for?

Ballast, gravel and hardcore

MOT Type 1 (hardcore) is crushed carboniferous limestone, used to create a hardcore base under patios, paving, driveways and artificial grass. It can also be used as a filling product.

How much sub-base do I need?

Measure the length and width in metres of the area you wish to fill with a sub base aggregate e.g. 20m x 10m. Multiply the length and width to find the area in square metres. Multiply by the depth e.g. 150mm. Multiply by 2 to get the tonnage required.

What is the difference between type1 and type 3 stone?

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. … Type 3 Crushed Concrete – 0-63mm reduced fines. Oversized Clean Crushed Concrete – 75mm-100mm (no fines)

Is Type 1 good for drainage?

MOT Type 1 is permeable so assists with drainage and as it includes the larger stones it won’t easily wash away.

What is the best sub-base for concrete?

What is the Best Base for a Concrete Slab? Most people build a driveway or a patio so in that case, a good choice would be a mix of coarse and fine aggregate which will create a compactable base. Overall, a mix of crushed stone and stone dust is the best base material for any concrete flatwork.

How deep should a sub-base be for a driveway?

The depth of the sub-base will depend on the size of vehicles using the drive with a typical domestic construction requiring a minimum depth of 100mm but preferably 150mm to be able to take cars. The most common sub-base material is DT Type 1 (MOT) which consists of crushed rock graded from 40mm down to dust.