Pouring Parking Pad During Rainy Season on Clay

[THBuilder]

I want to pour a 15 cm thick reinforced concrete parking pad on wet clay during rainy season. The parking pad is completely covered by the second floor, but it is not possible to dry the clay completely. Lime or other treatment materials are not available. This is for a 2 car home. I am thinking of compacting it wet, laying some plastic across the entire surface, making a mesh using some leftover 12, 19 and 25 steel, drilling holes into 2 surrounding walls (perpendicular) and 2 columns (opposite the side wall) and inserting the mesh ends into the holes to prevent the slab from sinking. Then pour the concrete.

I expect it to rain daily for the next 60 days and I cannot postpone. Dry season (near zero rainfall) will last 180 days and I expect the soil to dry completely.

Should this work without me having to worry about it collapsing under a load of 2 family cars?

 

[Ron]

Let it float...don't tie to surrounding concrete.

 

[dik]

What type of clay... high or low PI

Water reduces the shear strength... therefore the bearing capacity a tad...

Dik

 

[BAretired]

We don't know the soil conditions at your site. It would be prudent to ask for a geotechnical evaluation of the soil before proceeding.

Slabs on highly plastic clays will heave due to swelling when soil moisture content rises. In that case, drying the clay is not advisable. It is sometimes better to saturate the soil to prevent heaving.

If the soil is not capable of carrying the load on its own, it is unlikely that reinforcement inserted into holes in the walls will prevent the slab from sinking. You would need to reinforce it as a structural slab.

BA

 

[THBuilder]

Thank you for the replies thus far. They are much appreciated and helpful. The site is in a rural area (not USA) and there are no technical resources available to provide more detailed info. The clay is firm underfoot as I allowed it to saturate for 3 weeks, adding ~10 cm each week and tamping it down manually. Being about 81 kg myself, if I jump up about 30 cm with hard soled boots on and land on the end of one heel, I leave a heel print about 3 cm deep. Primitive method, but perhaps it may help.

Please keep the advice coming.

 

[BAretired]

Will the slab be subjected to frost?

BA

 

[THBuilder]

No frost at all. Tropical climate (Thailand).

 

[BAretired]

Based on the "heel test", I'm guessing your slab should be okay.

BA

 

[THBuilder]

Thank you all for the input. I am incorporating it all including an idea that came to me to use some leftover gypsum board as an expansion joint between the slab and the surrounding concrete.

 

[THBuilder]

Edit: Should read simply "joint" not "expansion joint".

 

[cvg]

there are probably better leftover materials to use than drywall. styrofoam, pressure treated lumber, redwood, all would be better for joint filler.

 

[BAretired]

I would not use drywall as a joint filler as it will wick up moisture and be subject to mould, a health hazard to the occupants.

In my opinion, you don't need a joint filler at all and are probably better off without one. The concrete slab will shrink away from the walls naturally, giving you a satisfactory joint with no special effort from you. If you want a sealant, put it on after the concrete has cured.

If you inist on using a joint filler, use a waterproof material such as AIFB (Asphalt Impregnated Fiber Board) with a bead of sealant over it.

BA