What is subbase course?

Subbase Course. The layer between the base course and subgrade. It functions primarily as structural support but it can also minimize the intrusion of fines from the subgrade into the pavement structure and improve drainage.

What is the difference between subbase and base courses?

Base may consist of unbound materials, such as gravel or crushed stone, or stabilized materials, such as asphalt-, cement- or lime-treated materials. The subbase course is typically a granular borrow that is placed between the base and subgrade. It can be constructed as either a treated or untreated layer.

What is the purpose of sub-base?

The subbase layer is typically used to protect the pavement from the effects of frost heave and/or used to improve the constructability of the pavement layers above the subbase.

What is the subbase layer?

A.

The subbase is the layer of aggregate material that lies immediately below the pavement and usually consists of crushed aggregate or gravel or recycled materials (see Section 6C-1 - Pavement Systems for more information).

What is subbase material?

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.

Preparation of base course and sub base

What is base course material?

The base course or basecourse in pavements is a layer of material in an asphalt roadway, race track, riding arena, or sporting field. It is located under the surface layer consisting of the wearing course and sometimes an extra binder course.

What are the two types of base course?

Two types of base courses will be con- sidered in this paper, the fine a^regate type and the coarse aggregate type. The fine aggregate type material contains less than 35 percent of coarse aggregate (material re- tained on a No. 10 sieve) and the coarse aggregate type contains from 35 to 70 percent coarse aggregate.

What is a subgrade layer?

The sub-grade layer of a pavement is, essentially, the underlying ground. It is also known as the "Formation Level", which can be defined as the level at which excavation ceases and construction starts.

Is Sub-base necessary?

Do I really need a Sub-base? The short answer is: if the pavement will be trafficked by vehicles, then yes, but if it will be foot-traffic only, then not necessarily. The type of paving or surfacing that will be used is one of the key factors in determining whether a sub-base will be required.

What is subgrade in construction?

Subgrade is that portion of the earth roadbed which after having been constructed to reasonably close conformance with the lines, grades, and cross-sections indicated on the plans, receives the base or surface material. In a fill section, the subgrade is the top of the embankment or the fill.

What is the minimum thickness of subgrade?

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 is base subbase and subgrade?

American Concrete Institute's defines, Subgrade as the native soil (or improved soil), usually compacted and Sub base is a layer of gravel on top of the subgrade. A solid subbase is a key to a successful building project.

Is sub base and road base the same?

A road base is defined as a layer or layers of bound material intended to give structural integrity to a pavement. The base consists of well-graded material, usually crushed stone. Sub-base consists of a lower quality material, sometimes crusher-run product, or the finer fraction of crushed stone production.

What are the layers of road construction?

What is aggregate base course?

Aggregate Base is used as the base course under asphalt pavement roadways, under concrete slabs and structural foundations, and as backfill material for underground pipelines and other underground utilities within a roadway.

Which soil is best for subgrade?

A clayey soil generally has a low CBR value (less than 8). Sands are more granular and drain better and will generally have CBR values between 15 and 35. Gravel will have the best CBR values, generally 25 and up. That is why it is suggested to save the best material to cap the subgrade.

How do you prepare subgrade?

The subgrade shall be prepared in lengths of not less than 100 metres at any one time, unless otherwise approved by the Engineer. Subgrade material shall be scarified to a depth of 150 mm until the soil is fully loosened. Any lumps or clods shall be removed or broken to pass a 50 mm sieve.

What is base course in civil engineering?

The lowest course or first course of a wall. The first layer of material laid down in construction of a pavement.

What is bituminous base course?

1. Bituminous Base Course. Base course layer in a bituminous pavement consists of mineral aggregates such as gravel, stones and sands bonded together with bituminous materials. This layer is used as the foundation on which surface course or binder is placed.

What is top course used for?

Our Top Course is 20mm all passing, and ideal for finishing civil construction projects like roads, car parks, driveways and paths before sealing with asphalt or overlaying with decorative products. It is finer than base course and when compacted produces a hard and smooth surface.

Can I use sand as a sub-base?

Simply put, sand isn't sturdy enough to work well as a subbase for something like a driveway. With areas like patios, which don't require a ton of load-bearing, sand as a subbase works fine, though it's not as reliable as gravel.

Do you need a subbase for concrete?

Subbase for Concrete Slab

The subbase placement is optional and it serves as a work platform for construction of the slab and provide more uniform support for the slab. As the thickness of subbase increases, the ultimate load carrying capacity of slab increases.

How much subbase 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.