Meaning
Geological and structural processes involve the washing away of fine soil particles from beneath a concrete slab due to water movement or slab deflection. This subgrade erosion creates air voids under the concrete, leaving the slab unsupported and highly prone to cracking under normal operating loads. This issue is common near joints and cracks where water can easily penetrate the floor.
Erosion Mechanism
When a heavy vehicle drives over a joint with high deflection, it creates a pumping action that forces water and loose soil up through the crack. This continuous movement slowly carries away the fine aggregate from the subgrade, creating a void beneath the concrete. The size of this void increases with every loaded pass.
Soil type and drainage conditions heavily influence the rate of aggregate loss.
Structural Impact
Without the uniform support of the subgrade, the concrete slab must carry the entire load through its own bending strength. This increases the internal tensile stresses in the slab, eventually leading to structural cracking. These cracks further accelerate the erosion process by allowing more water to enter.
Stabilization Technique
Repairing the damage requires injecting polyurethane resin or microfine cement grout into the voids to restore uniform support. This intervention fills the empty space and compacts the remaining soil. It prevents the recurrence of erosion.
