May 9, 2012


The construction of the Pearl continues as interns and visitors pitch in to make new forms and pour concrete. Previously we were using wire ties to hold the concrete forms in place. This worked well enough but made moving the forms up the wall for the next pour somewhat challenging and time-consuming.

A section of wall built using the old forms

The technique we're using this year involves commercial snap-ties made to create a six-inch retaining wall, that makes moving the forms up the wall a "snap".

A section of wall continues to rise using the new forms.

It takes 8 snap-ties and 16 "shoes" to hold the form in place while we pour 3 to 4 mixes between the forms to create the next section of the rising wall.

A Snap-Tie and a Shoe

After a pour had cured for at least 24 hours, we can undo the shoes, remove the forms, and reposition them. This goes quickly because we just lift the form so that what was the upper row of ties now fits into the lower row of holes. Add more snap-ties for the new upper row, button up the form and it's ready for the next pour.

Half of a form showing the snap-tie ends with shoes wedging them in place.

Each time we reposition the forms we coat the inside with a mixture of half diesel fuel and half used motor oil. This acts as a release agent and keeps the concrete from sticking to the plywood forms.

One snap tie with the shoe wedging it in place.

There is another shoe on the other end of the snap-tie holding the forms together. After we finish filling the forms with enough mixes of concrete to cover the upper row of snap-ties and use the concrete vibrator to get excess air out of the concrete, we push irregular shaped rocks into the top of the pour. The protruding rocks will help the next layer of concrete bond with the previous layer.

A look between the forms as we finish the day's pour.