@mikemorgan5015

5 days ago

This appears to be a monolithic(single pour) wall and slab pour. Monolithic pours are stronger and structurally superior to multi-stage pours that inherently include "cold joints" where the two pours meet. This was a major error in form construction. The hydraulic pressure at the bottom of a pour can be tremendous. If there is insufficient shoring and bracing, this happens. It is most common on pours where the two sides of a wall form cannot be tied together like a retaining wall where one side is formed and the other is earth. The amount of bracing required on these types of pours is exponentially more than a standard wall pour where the forms are held together with wall ties. I don't see any wall ties in these forms. The hydraulic load is transferred from the fluid concrete to the skin of the forms to the vertical lumber to the horizontal walers. The bottom plate MUST be sufficiently secured to at the bottom. without wall ties, the entire load where the pressure is highest is born by the bottom plate of the forms. The hardware securing the plate to at the bottom appears to be insufficient and therefore sheared off, allowing the bottom of the forms to blow out. Decades ago, as an apprentice form carpenter, I was warned that when doing a one sided wall form to figure on using twice as much bracing as you think it needs, then double it. This was not even close to sufficient bracing from what I can see in the video. Another huge factor is the concrete mix design. The more fluid(high slump) the mix is, the higher the hydraulic pressure on the forms. Wall like this should be poured in lifts and only vibrated slightly into the previous lift to allow the lower initial lifts to begin to set and stiffen, reducing the hydraulic pressure horizontally on the forms. But you must pour the lifts fast enough to avoid cold joints between lifts.

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