Expansive Soil Issues

We just wet it down, run the hose for a bit, then put down a layer of compacting dirt, run the compactor over that and it's good to go....

http://www.concreteconstruction.net/how-to/site-prep/site-preparation-making-a-proper-bed-for-concrete_o

The work has been completed, and i was very satisfied with the compaction , my concern is , if the evaporation in this dry climate will shrink the soil when the volumn of water starts disappearing . What happens to the expanded soil when the water is removed ? Does it stay expanded and leave micro voids , or shrink ? Unfortunately the project ( building and concrete ) will be delayed for months

Well you got yer moles and worms and ants and spiders and other burrowing animals that live in the soil, not to mention any dirt left exposed accumulates seeds blowing around and with a little moisture and sun, all of the sudden you have weeds growing in your base....

Go to a lake, with a sandy shore, draw a bucket full of lake water, and pour it gently on a dry spot, and watch it swell up a little bit, in the middle. As the water over-saturates the interstitial voids, in the middle, that portion of the water will push the overlying sand upwards, slightly. Wait a while and the voids will drain out, and the swelling will then subside. If the spot is of an expansive clay, the the swelling may remain for muuuuuch longer...

So, the (water-retention-behavior) will vary with the sand-clay-combination, the amount of water imparted to it due to intervening rainfall, the acting over-burden, the externally-induced transient vibration, heat-cool cycles, time-lapse, etc.

In other words, how can it not change over ''6 to 8 months''?...

So, do re-grade, re-compact, re-excavate, and re-test to applicable standards, like ASTM DD-1557, etc., among others, and hope an underground aquifer has not worked it's way into your project area, in the mean time...

And lastly, don't trust nuclear gauge tests because they don't ''read'' moisture levels, in the top foot of compacted earth, all that consistently, in my experience...

Powdered lime is good for soil consolidation

http://civil.utm.my/mjce/files/2013/10/Consolidation-Characteristics-of-Lime-Stabilised-Soil.pdf

Thanks TonyS

Ever seen the water holes in Ozz, Africa, America? When they dry up, what happens? Cracks right! Evaporation of soil = Cracking = Shrinkage.

I suspect you're on the right track. The whole idea with digging out and wetting & compacting it to the correct % is to have it at an approximately "neutral" moisture content. Check with the engineers doing the recommendations, but my instincts (that remarkable engineering tool!) tells me that you probably need to do the concrete layering within days, not weeks & months. If no moisture is added (rain or hosepipe or flood), the water will evaporate from the soil after a while, the speed of which depends on the air humidity, wind, temperature and soil characteristics. (This way you reduce the amount of movement due to shrinkage/expansion of the soil, reducing the possibility of cracks in the concrete after the next dry or rainy season.)

Why would you waste the effort and do it so long in advance of the concrete works anyway?

This sounds like a disagreement or for whatever a work stoppage and work resumption question.

A. Preparation was completed, but slab was not poured.

B. Funds available for preparation, but not available for the pour.

C. Weather conditions permitted preparation, but impeded pour.

D. _________

Like any type of construction preparatory work, the main build needs to be followed by the finish within a timely manner.

This progression of steps can be applied towards many different building application's​.

1. On wood, old paint is removed, surface is sanded and filled, primer is applied asap followed by top coat.

2. Metal to be repainted is sanded, rust remover is applied then rinsed, as soon as drying is completed, a primer is applied, as soon as primer is dried, a topcoat is applied.

Same goes with concrete.

Hesitation during any of the steps generally requires the builder to re do any or all of the preparatory steps.

With respect to concrete, water or lack of, drying or Frost cycle, infill, inorganic or organic, compaction or settling may affect application and or long term durability of pour.

Resultant lifting, cracking, uneven settling or other unwanted conditions may occur.

If you do decide to continue, it is at your own risk.

The best approach would be to regrade, reset forms, compact, then do your pour and finish.

I had to fire building contractor , hence the delay and my concern . Im going to place some EDPM rubber roofing from recycle over the site ( 12,000 sq ft ) to protect and to trap ground moisture