Saturday, May 28, 2011

Architectural Concrete cont. 2

 The Quisnel Drive home is moving along nicely: the main floor walls are being framed up while the architectural concrete formwork also goes another floor higher. Below is a picture of the formwork for the architectural section that will be a main feature of this house from street level. Of note is the extra bracing at the corners, as this is the most likely spot for concrete forms to develop gaps.

On Thursday this week, we poured the section above with the help of Excellence Concrete Pumping and their impressive concrete pump truck.

When placing concrete, a concrete vibrator is used to remove trapped air. Architectural concrete requires very tidy formwork with little to no gaps or holes because during vibrating, the concrete liquefies and the cement and water (or cream as we call it) will find any hole or gap and spill out readily, leaving behind the sand and gravel of the concrete mix. When the forms are removed, the concrete will be rough and sandy where there were holes and smooth where there were no holes. To avoid this, we use new sheets of paper-faced plywood, butting factory edges together for a tight fit, and, as you can see below, we spray an expanding foam into the tie holes or where there are any gaps to completely seal the forms.

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