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- Structural slab design is straightforward in temperate climates where the soil is strong, and with some adjustments challenging conditions are met as well. In cold climates footings and foundation walls are more common than structural slabs. Footing and foundation wall structures minimize the risk of freeze-thaw action in the soil that can lead to structural failure; footings can be dug deep, transferring the load to soil below the frost line. Structural slabs meet the conditions with sub-grade preparation and concrete design.
- The ground bears the load of the structure. The sub-grade has to be uniform and it should allow water to drain through to prevent soil movement from freeze-thaw action. Compaction is essential to maintaining the uniformity. The slab can settle or bend a little without causing damage; a stable sub-grade will support it even as it flexes. If the sub-grade is weak, the concrete has to be thicker to resist bending.
- Structural slabs are usually at least 4 inches thick, and thickened at the edges to form an integral footing to strengthen the structure. The concrete is reinforced with steel to increase the concrete's tensile strength -- the ability to withstand stretching, or pulling, forces. Steel bars are used for the thickened edges and mesh is installed for the body of the slab. Control joints are carefully placed to control cracking; the crack will stop at the planned break.
- The concrete mix and curing affects its performance and lifespan. Most concrete for slabs is designed for 3,000 to 4,000 pounds per square inch (psi) of compressive strength -- pressure weighing on it from loads. Concrete mix for slabs includes large aggregate and as little water as possible; more water makes weaker concrete. Once poured the concrete is cured as long as possible, with temperature and moisture levels controlled to let concrete set to optimum strength,
Structural Slab Foundations
Site Preparation
Structural Slab Design
Concrete for Structural Slabs
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