The base course is used in rigid pavements 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 subgrade volume change; and (6) increase the structural capacity of the pavement (6).
Base courses are available in various materials, including asphalt, concrete, and cobblestone. Asphalt and concrete bases must be resealed periodically to maintain their effectiveness over time.
Cobblestones are large rock fragments that can only be found in certain areas of the world such as Europe and North America. They were originally harvested from beaches and riverbanks and then either laid flat or set on end into mortar to form a road surface. Today, most cobblestones are produced by quarrying larger rocks and then grinding them down into smaller pieces for use in roads.
The base course should be thick enough to provide adequate support but not so thick as to be difficult to remove if needed. Thicker base courses may require mechanical excavation before any other pavement material is placed on top of it.
In general, the lower the traffic density, the thicker the base course should be. High-traffic areas may only need to be 1 inch or less in thickness.
Roads with heavy truck traffic usually require a thicker base course than ones designed for passenger cars.
Foundations offer the structure's ground stability: they disperse the structure's weight across a vast area to avoid overwhelming the underlying soil (possibly causing unequal settlement). They also protect the soil beneath buildings from erosion caused by water runoff. Finally, foundations provide a stable base for plumbing and wiring, which cannot be done above ground level.
The function of a foundation is to support the building until it is strong enough to bear its own weight. The type of foundation used depends on such factors as the load it will have to carry and the climate where it will be located. In addition, the location of the foundation relative to other structures on the site may affect what kind of foundation is needed.
For example, if a building is going to be located on highly erodible soil, then an underground foundation should be used so that the soil will not be destroyed by the time the building is completed. If a building is expected to face heavy snow loads, then a deep foundation should be used to prevent damage to the roof due to snow loading.
The function of a foundation is to provide support for a building. The method by which this support is provided varies depending on such factors as the type of structure and its location relative to other structures on the site.
Base courses are often made of crushed aggregate or HMA. The subbase is often made of lower-quality materials than the base course but higher-quality materials than the subgrade soils. A subbase course isn't always necessary or useful. Subbase courses are often made of crushed aggregate or designed fill. They provide traction and stability for the overlying base course and may also help control erosion. Their thickness varies by application but is usually about 6 inches (152 mm) or more.
A base course without a subbase can cause problems with water infiltration and drainage, as well as erosion. The use of a subbase under the base course reduces these issues while still providing stable ground for building foundations.
Subbases can be made of various materials including: sand, gravel, crushed rock, asphalt, concrete, etc. The type of material used depends on the needs of the project. For example, if the area is going to be used for parking or other non-permanent structures, then crushed rock or asphalt would be appropriate choices for the subbase. If the area is going to include buildings that will be occupied year-round, then using a softer material such as sand or gravel for the subbase could lead to future maintenance issues due to soil loss caused by water penetration into the voids between the rocks in the subbase.
The thickness of the subbase should be based on how much traffic will be passing over it.
The base and sub-base courses might be composed of either bound or unbound granular layers. According to Indian requirements (MORT & H 2001), examples of base or sub-base layers include: granular sub-base (GSB), water bound macadam (WBM), wet mix macadam (WMM), and so on. Bituminous substance is used to make the binder course. Examples include: asphalt pavement, concrete, etc.
Base courses are designed to provide traction for vehicles driving over them. They usually consist of two components: a rough surface called the base course and a smooth surface called the top layer. The base course can be made of various materials such as sand, gravel, crushed rock, slag, and recycled tire rubber. It should be at least 6 inches (152 mm) thick to give drivers enough grip from all weather conditions. The base course helps vehicles stop in case of emergency and also reduces noise pollution.
The top layer is made of a flexible material that can be worn away by vehicles traveling over it. It should be at least 1 inch (25 mm) thick and should be maintained regularly to ensure clear visibility for drivers.
There are three types of base courses: binders, breaker, and anti-erosion. In binders, the base course is made of bitumen or other petroleum products. In breakers, the base course is made of stone or brick. Anti-erosion base courses are used where there is a risk of groundwater contamination.
What are the applications of bases?
|Ammonium hydroxide||As a reagent in the laboratory In making fertilizers, rayon, plastics and dyes|
|Calcium hydroxide||In making cement and mortar In making bleaching powder In whitewashing In removing acidity of soils|
Prior to construction, the natural elevation of the ground surface near to the intended walls of a structure is referred to as the adjacent grade. The adjacent grade should be uniform with respect to height and material across a site. Unconsolidated or loose soil will tend to settle during periods of rain or melting snow, which can cause the adjacent grade to become non-uniform.
The adjacent grade should be sufficiently high so that water does not flow into it from outside the building site. This prevents water from accumulating next to the building and also prevents water under the influence of gravity from flowing into low-lying areas where it may cause problems such as erosion or flooding. The required height depends on several factors such as the type of soil, its moisture content, etc. But generally, the minimum required height is 1.5 times the maximum annual rainfall in inches over the entire site.
For example, if the site is expected to receive 36 inches of rain per year, the adjacent grade should be at least 18 inches higher than the lowest point on the site. If the site is expected to receive 24 inches of rain per year, the adjacent grade should be at least 12 inches higher than the lowest point on the site.