Concrete Foundation Walls - Structural Deterioration And Damage
Problem: Cracks and spalling from under-strength concrete.
Cause: Insufficient design strength.
While minimum standards for concrete strength are mandated by building codes, construction practices and site conditions commonly result in reduced strength - either because water is added to the concrete on site or because weather conditions affect the concrete.
Solutions: Specify concrete with minimum compressive strength in excess of minimum building code requirements, see Figure 1. Always check with your local building department for your code requirements.
Figure 1 - Concrete Strengths
- To provide increased strength and improved water-tightness, use 2,900-psi (20-MPa) concrete for foundation walls and basement slabs.
- Many builders recommend using concrete with a minimum strength of 4,350-psi (30-MPa) for garage slabs and other concrete exposed to freeze / thaw cycles.
- Air entrainment improves concrete durability and resistance to freeze / thaw cycles. A common building code requires 5% to 8% air entrainment for garage and carport floors and exterior steps.
- Another common code requires that concrete mixes not exceed a slump of 4 inches; (100 mm) for slabs and 6inches (150 mm) for walls.