slab on grade, over thick gravel base

[JLSE]

A contractor wants to use a slab on grade, atop three or four feet of gravel fill. I have heard recommendations to use anywhere from 3/8" to 3/4" consolidated crushed rock.. I have heard recommendations to use well graded and compacted base 3/8" minus.... and even ASTM C-33 sand.

Can't seem to find any documentation on it...

Can't seem to find any recommendations on how to prepare the site either.... whether benching is required, etc.

Any recommendations here?

 

[dik]

Any well compacted 'A Base' or equivalent will provide the capacity and stabilty. How is the slab loaded? and is there a problem with the sides 'washing' away? 1:2 vertical:horizontal slope or better.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JLSE]

Dik
Whats an 'A' base?
Nothing special on the loading. Just concerned about settlement of the slab, including creep. It is by a hillside, Id count on some migrating water.
Thanks

 

[dik]

'A' base is common used term for granular material with certain durability features and a reasonably well defined gradation that allows for compaction. It's a common term in many areas of North America. From my project notes:

GRANULAR 'A' (GRAVEL)
CRUSHED ROCK COMPOSED OF HARD DURABLE UNCOATED FRACTURED FRAGMENTS PRODUCED FROM ROCK FORMATIONS OR BOULDERS OF UNIFORM QUALITY, OR A MIXTURE OF CRUSHED GRAVEL, SAND AND FINES COMPOSED FROM NATURALLY FORMED DEPOSITS ONFORMING TO THE PROVINCE OF MANITOBA SPECIFICATIONS FOR AGGREGATE FOR GRANULAR BASE COURSE FOR CLASS A

FILL SHALL CONFORM TO:
SIEVE SIZE (ASTM) PERCENT PASSING
3/4 INCH 100
5/8 INCH 80-100
NO 4 40-70
NO 10 25-55
NO 40 15-30
NO 200 8-15

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Good Granular A packs almost like 'rock' and is capable of supporting significant loading. Water will pond on the compacted surface.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik