Stone And Concrete Tub Made With Forms

In the last post I showed some ideas for reusing materials

 from old mobile homes at El Dorado Hot Springs in Arizona.

In the last photo I showed forms made from the walls and floor.

Now let's look at that tub.

The project was to build a new soaking tub from stone,

 that would not leak.

 They have had lots of problems with leaking in their existing stone tubs.

Above is the tub after half the wall has been done,

ready for the forms to be reassembled for the next pour.

Going back to the beginning,
 the above slab had already been poured as the bottom of the tub.

Since the stone were rather rounded

 and I would not be here for the whole project,

 I elected to build forms for the walls of the tub.

My helpers had never done this kind of work,

so I wanted a procedure that we all could work with easily.

Plus we had lots of wood for the forms.

Since the tub needed to be 28" deep we built the forms 16" high 

so we could do the walls in two sections.

The shallower form depth made it easier to work

 with the stone inside the form.

It was easy to brace the form on the inside as you can see above.

All the forms and bracing are done with self tapping screws
 to make disassembly easier,
and if the forms are not to be used again they are easier to take apart.

The corners had extra cross braces at the top,

as well as recycled metal straps.

The plywood at this end is screwed into the strut of the adjoining wall.

We did not use any oil on the forms for quick release
 as we didn't want the oil residue on the concrete.

To stabilize the outside bottom of the form we drove metal stakes

 into the ground as well as stone piled around the bottom in critical areas.

I did not want to use tie wire at the bottom of the form to hold it together 

as I was concerned about it rusting from water in the future hot pool.

The forms are 11" wide.

All the mixing was done in a wheelbarrow.

Our materials were spread around the area

 and could easily be accessed by the wheelbarrow.

And once mixed, the wheelbarrow could be positioned

 on site wherever we were working.

We used  a very stiff (dry) mix for setting the stone

of 3:1 sand to masonry cement.

After a load of that we would mix a couple loads of

 1 portland - 2 sand - 3 crushed 3/4' gravel concrete to fill behind the stone.

The latex bonder seen above was painted on the slab

 inside the forms for a better bond between the slab and the walls.

The admix was added to both the masonry mortar and the concrete 

at roughly 3 water to 1 admix to increase the workability 

and bonding of both the mortar and the concrete.

It also makes it all more water impermeable.

First the stones were set in the mortar and we immediately came back

 and backfilled with concrete.

It is best to have as few cold joints as possible 

so we tried to get as much done as possible each time we started mixing.

Next time we will take the forms off and show the next step in the post:
More On The Stone And Concrete Tub Made With Forms.

To see the finished tub go to the post:
Concrete And Stone Hot Spring Pools.

 And a couple of notes:

-Given the choice I would build a more narrow formed wall of concrete

 and tile it inside and out to make it easier to build and more waterproof.

-Pouring the wall with the floor ( or base ) in one pour 

would avoid any cold joints leaking.

And finally, I debated long and hard about using rebar,

 as I was afraid it would rust from moisture migrating through the concrete

and swell, cracking the wall.

Any ideas out there on that?

To see another look at formed stone work see my post from last year:

Formed Stone And Concrete Walls.