What are the basic reasons providing base course under cement concrete slab.1 pointControl of pumpingControl of frost actionImprovement of drainageControl of shrinkage and swellAll

The base course under a cement concrete slab serves several important functions:

1. Control of Pumping: Pumping is the ejection of soil or fine materials from beneath the slab due to the pressure exerted by the load. A well-graded base course can help prevent this by distributing the load evenly and reducing the pressure on the underlying soil.

2. Control of Frost Action: In cold climates, the freeze-thaw cycle can cause the ground to heave, which can damage the slab. A base course can help insulate the slab from the ground, reducing the risk of frost heave.

3. Improvement of Drainage: A base course can help improve drainage by providing a path for water to flow away from the slab. This can help prevent water from pooling under the slab, which can cause damage over time.

4. Control of Shrinkage and Swell: Changes in moisture content can cause the soil to shrink or swell, which can lead to uneven support for the slab. A base course can help mitigate this by providing a stable, well-drained layer for the slab to rest on.

So, all the options mentioned are basic reasons for providing a base course under a cement concrete slab.