why do we compact base course

The base course material, according to ACI 302, "Concrete Floor and Slab Construction," should be "compactible, easy to trim, granular fill that will remain stable and support construction traffic." ACI 302 recommends material with 10 to 30% fines (passing the No. 100 sieve) with no clay, silt, or organic materials.

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What is the recommended base course compaction for construction?

2. Normally, in my experience, base courses are compacted to 98 to 100% of the maximum dry density (MDD) Modified Proctor. 3. GeoPaveTraffic indentifed several aspects that are important.

Is compaction necessary in subbase or subgrade soil?

Further, if subbase or subgrade soils require bridging in any fashion, a higher stability and compaction in the base will be necessary. My point is not to summarily dismiss the compaction requirement.

What is the advantage of compaction to 100%?

Compacting to 100% takes out most of the additional compaction that will be done by traffic. Not such a big deal with rigid pavement, but can be significant with flexible pavement. Further, if subbase or subgrade soils require bridging in any fashion, a higher stability and compaction in the base will be necessary.

Does compaction level affect stability?

If the compaction level isn't there, then neither is the stability. Some materials have sharply peaked compaction and stability curves. Compacting to 100% takes out most of the additional compaction that will be done by traffic. Not such a big deal with rigid pavement, but can be significant with flexible pavement.

What is compacted base course?

Subgrade—this is the native soil (or improved soil), usually compacted. Subbase—this is a layer of gravel on top of the subgrade. Base (or base course)—this is the layer of material on top of the subbase and directly under the slab.

What is base compaction?

By Brian Fortner Compaction. The concept of a base paver is fairly basic; the plate vibrates below the machine causing smaller particles in the soil to settle in the voids of the material underneath, forming a sturdy compact base.

What is the purpose of base course?

Function of base course To act as the foundation of the road pavement and to transfer the traffic load safely to the sub base and sub grade. To withstand high shearing stresses due to the impact of traffic.

What is the purpose of aggregate base course?

Their purpose is to help transition surface loads from the pavement to the subgrade, evenly support the pavement surface profile, and protect the overall pavement system from water intrusion and deformation.

How do I compact aggregate base course?

1:122:47Base Compaction - YouTubeYouTubeStart of suggested clipEnd of suggested clipIf the tires make a permanent indentation. The base has not been compacted enough if you can drive aMoreIf the tires make a permanent indentation. The base has not been compacted enough if you can drive a 3/8 inch or ten millimeter spike into it with less than a three pound hammer.

What is a base course in construction?

Lower surfacing layer formed by bituminous mixtures. When the surfacing has a thickness of more than 8 cm it is usually made in two layers, wearing course (upper) and base course (lower).

Why do you need to ensure the compaction of subbase courses in road construction?

Increasing Subgrade Support Subgrade should be compacted to adequate density before pavement placement. If it is not, the subgrade will continue to compress, deform or erode after construction, causing pavement cracks and deformation.

Why is there a need for a base course in road construction?

The base course serves as a foundation for the paving. Depending on the stresses to be expected, the road comprises various layers of different thickness in order to withstand the most diverse weather conditions and remain serviceable for many decades.

What is the function of base course in rigid pavement?

Base Course It provides (1) additional load distribution, (2) contributes to drainage and frost resistance, (3) uniform support to the pavement and (4) a stable platform for construction equipment (ACPA, 2001). Bases also help prevent subgrade soil movement due to slab pumping.

What is a compacted aggregate base?

An aggregate base is a dense-graded compacted aggregate that is normally placed on a prepared subgrade in accordance with Section 105.03. Materials used for aggregate bases are required to be size No.

What is the difference between sub base and base course?

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 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 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.

Why do you need 100% compaction?

There are many reasons to specify 100% compaction. For one, you are practicing in a geographical area outside the one in which you normally practice. There could be a quirk of the local materials that requires that degree of compaction to achieve appropriate stability (such as a CBR).

Is it difficult to achieve optimum moisture?

It is not difficult to achieve as long as optimum moisture is also achieved for a long enough period of time to complete the compaction. This is much easier to achieve if the percent passing the #200 sieve is on the high side of the specified range.

Why is subgrade compaction important?

help ensure that freeze/thaw movement is uniform. Subgrade compaction is an act that is sometimes overlooked in private, non-inspected, construction projects but (depending on the soil type and condition) can be critical in future performance of pavements.

Why is compaction important for pavement?

Compaction achieves the following: increases load bearing capacity. helps reduce future rutting/settling.

What type of rollers are used for subgrade compaction?

On a medium scale, subgrade compaction can be done with a plate tamp attachment for a backhoe or excavator. On a large scale, drum rollers are utilized. The different types of rollers include: smooth drum, vibratory, pneumatic, and sheepsfoot.

What is compacting subgrade?

Compacting Subgrade. Subgrade compaction is the act of grading, shaping, and compacting the natural subgrade materials prior to placing an aggregate base or pavement. It mechanically increases the unit volume (density) of the soil or base.

Why isn't subgrade testing done?

The primary reason testing isn’t done on a subgrade is that the material typically isn’t uniform either in gradation or composition, so to come up with an accurate proctor sample is difficult and requires time consuming lab testing from various locations of the subgrade.

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 ...

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 made of?

Aggregate is made from quarried rock, recycled asphalt, or concrete. 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.