what is the difference between subbase and base course

Subbase Course - One or more layers of specified material of design thickness, placed on a subgrade to support a base or surface course. A subbase is not often used. Base Course - One or more layers of specified material of designed thickness, placed on a subbase course or a subgrade to support a surface course.

Full Answer

What is a sub-base?

This is the layer (or layers) under the base layer. The properties and function of this layer are similar to those under flexible roads/pavements. A sub-base is not always needed and therefore may often be omitted.

What is the difference between the ABC and sub-base?

It is placed by means of attentive spreading and compacting to a minimum of 95% relative compaction, providing the stable foundation needed to support a pathway, foundation, driveway or roadway. The Sub-Base is a layer of small chipped aggregate and dust, typically Crushed Fines, which is laid above the ABC on driveways or heavy traffic areas.

What are the different types of base course?

Types of Base Course 1 Granul ar Base Course 2 Macadam Base 3 In-water bound Macadam 4 Treated Bases More ...

What is the difference between PCC and sub-base?

The properties and function of this layer are similar to those under flexible roads/pavements. A sub-base is not always needed and therefore may often be omitted. This is the layer directly below the PCC layer and generally consists of aggregate or stabilized sub-grade.

What is base course used for?

Under rigid pavements, the base course is used to: (1) provide uniform and stable support, (2) minimize damaging effects of frost action, (3) provide drainage, (4) prevent pumping of fine-grained soils at joints, (5) prevent volume change of the subgrade, (5) increase structural capacity of the pavement, and (6) ...

Is sub base and subgrade same?

The subgrade is the soil that is usually compacted when preparing for slab installation. Thus, you find this soil at the bottom of the slab system. The subgrade may refer to the native soil or the improved soil delivered from a different source. The subbase refers to the layer placed on top of the subgrade.

What is the difference between a subbase and a base of a road?

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 is base subbase and subgrade?

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.

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 does sub base include?

Sub-base material is produced by crushing either limestone or granite rock. The sub-base is designed to evenly spread the load on traffic bearing areas such as pavements and roads. Made up of a load-bearing layer of aggregate, the sub-base is laid on the sub-grade layer below.

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 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.

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.

Sub Base Course of Rigid Pavement

This is the layer (or layers) under the base layer. The properties and function of this layer are similar to those under flexible roads/pavements. A sub-base is not always needed and therefore may often be omitted.

Base Course of Rigid Pavement

This is the layer directly below the PCC layer and generally consists of aggregate or stabilized sub-grade.

What happens if you water a base course?

Excess watering is wasteful, but more importantly, it may result in serious damage to the subgrade. Most of the water that falls on granular material penetrates to the subgrade almost immediately and this could create serious problems. This "sponginess" and resultant movement under wheel loads is usually first noticed as excessive looseness of base materials. The Inspector should be on guard for any soft spots that may develop in the roadway following rains or excessive watering. If this condition should occur, a thorough investigation shall be made and corrective measures taken before paving.

Why is lime admixture used in subgrades?

The subgrade may be treated to improve its ability to support traffic loads. The improved load carry capability occurs because the lime admixture reduces the volume change characteristics and plasticity of the soil.

Is the riding surface of a completed pavement dependent on the base surface upon which it is laid?

To a great extent the riding surface of the completed pavement is dependent on the base surface upon which it is laid. Since smoothness of the pavement is one of the qualities most desired by the road users, the Resident Engineer should be satisfied that every means possible has been expended to obtain a finished base course having a cross section true to line and grade within the specified tolerance.

What is sub base?

Sub Base: It is layer of granular material provided above subgrade generally natural gravel. It is usually not provided on subgrade of good quality. It is also called granular subbase. a. Function of Sub base in Road Cross Section.

What should subgrade material be?

The subgrade material should be clean and free from organic matter and should be able to be compacted by roller, to form stable sub-base. The material should have following characteristic.

What is the layer under the wearing surface?

2. Base course. It is the layer immediately under the wearing surface (Applies whether the wearing surface is bituminous or cement concrete and or more inch thick or is but a thin bituminous layer). As base course lies close under the pavement surface it is subjected to severe loading.

What is a base course?

Base course. 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 . If there is a sub-base course, the base course is constructed directly above this layer.

How thick is a base course?

Otherwise, it is built directly on top of the subgrade. Typical base course thickness ranges from 100 to 150 millimetres (4 to 6 in) and is governed by underlying layer properties.

What is a sub base?

The Sub-Base is a layer of small chipped aggregate and dust, typically Crushed Fines, which is laid above the ABC on driveways or heavy traffic areas . The thickness of sub-base can range from 1″ to 2″ inches on light weight traffic areas like pathways and paver patios above the sub-grade when a ABC is not required,

What is aggregate base course?

Aggregate Base Course often referred simply as ABC, has certain desirable properties. Base Course in pavements refers to the sub-layer material of an asphalt roadway and is placed directly on top of the undisturbed soil (Sub-Grade) so as to provide a foundation to support the top layers of the pavement. It is typically made of a recipe of different ...