Expanding foam made me nervous. It is used for surface pot/sink hole
filling in other countries (they make a giant cone shaped plug of it).
However, If you can pump down expanding foam, why can you not pump
down a concrete slurry under (very) high pressure?

On 22 Sep, 12:08, "js.b1" wrote:
Expanding foam made me nervous. It is used for surface pot/sink hole
filling in other countries (they make a giant cone shaped plug of it).
However, If you can pump down expanding foam, why can you not pump
down a concrete slurry under (very) high pressure?

that would make the whole structure even heavier wouldn't it? and what
sort of pressure we talking to force slurry up/out/into surrounding
ground? and hold it whilst it sets....

At a guess I'd say the huge expansive rate of the urethane plus the
narrow (22mm?) insertion hole means it forces *itself* out/under/into
everywhere it can get - in effect making a wider/deeper/stabler
foundation than what existed before?

Jim K

On Sep 22, 2:57*pm, Jim K wrote:
that would make the whole structure even heavier wouldn't it? and what
sort of pressure we talking to force slurry up/out/into surrounding
ground? and *hold it whilst it sets....

Injecting a concrete slurry would be heavier than expanding foam, but
probably lighter than traditional 1m^3 concrete blocks every few feet.
No idea what pressure would be required, I wondered if it were
possible perhaps combined with aeration (aluminium?).

Underpinning can get more involved than just concrete blocks - it can
require pile-inside, pile-outside, join by poured beam.

So underpinning by expanding foam could be particularly attractive if
it works for 20yrs - at least you can start saving and if it fails it
is not exactly difficult to cut through expanding foam.


At a guess I'd say the huge expansive rate of the urethane plus the
narrow (22mm?) insertion hole means it forces *itself* out/under/into
everywhere it can get - in effect making a wider/deeper/stabler
foundation than what existed before?

Wider foundations do spread the load better, although I think the aim
is as much to link the building to the stable ground beneath by
eliminating the low friction mush inbetween.

I recall such foams are not truly waterproof, but are more moisture
stable I think than say clay - so underpinning one side of a building
might have implications for the other side if that is say on clay with
trees.

A lot better & cheaper than the concrete pile solutions... perhaps
Barratt would like to adopt it for their new build foundations :-)

On Wed, 22 Sep 2010 06:57:15 -0700 (PDT), Jim K wrote:

... and what sort of pressure we talking to force slurry up/out/into
surrounding ground? and hold it whilst it sets....

Nothing that the oil industry would have any problem with. Recent
pressure test on the final bottom plug on MC252 was to 15,000 psi
IIRC.

--
Cheers
Dave.