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Certain types of buildings are more suited to a giant mat slab or single deep mass foundation due to the surrounding soils or the mass of the structure above.

Those characteristics lead to a placement like this — one giant mass of reinforced concrete. It has no seams or joints leading to a place where the segments would have to transfer forces, instead it is all one giant mass performing as a unit. The reinforcing makes it work as a single unit — think of a hammer head — an item cast that takes forces and transmits them as a whole.

That outlines the benefits. The drawbacks are that such a placement takes a very long time to reach its design strength. A footing, wall, beam or slab is typically designed for its cured strength at 28 days. It does continue to chemically cure and develop crystalline structure past that point, but most of the curing has occurred by that point. A giant mass placement (or pour if you will) stays slowing curing in the center for an extremely long time, months to take full load and years for the ultimate curve to be reached.

Dangers are batch plant failures, design mix mistakes or equipment failures in delivery or in the pumps that distribute it. Usually a number of plants are involved in the supply for just that reason. A fire on the only highway leading to a job sight can cause entire loads to be delayed and wasted and the placement to begin to set without supply to keep the placement underway as a single mass.

Can you imagine a placement where the batch plant calls in the middle and says, “we have found some of our trucks used to supply aggregate to the batch plant were used to haul soy beans and we have contaminated some of the loads of mixed concrete with soy beans — STOP the pour!!!” Such things have happened — that comes from a project where I knew the superintendent — he destroyed his cell phone he took the call on by throwing it at a wall.