What are the primary causes and indicators of spalling in concrete bridges?

Kareem Hesham Mahmoud Awad

“The primary causes of spalling in concrete bridges are corrosion of reinforcing steel and freeze-thaw cycles. Corrosion of rebar causes it to expand, creating internal pressure that fractures the surrounding concrete. Freeze-thaw cycles occur when water penetrates the concrete, freezes, and expands, also creating internal pressure. Other causes include impact damage, alkali-aggregate reaction (AAR), and poor concrete quality. The indicators of spalling include visible cracks in the concrete surface, rust stains emanating from the cracks, and loose or detached pieces of concrete. The presence of delamination (separation of layers) can also be an early indicator of impending spalling. Spalling exposes the reinforcing steel to further corrosion and weakens the structural integrity of the bridge, requiring timely repair.”

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Abhay Kumar

“Primary causes are due to corrosion of embedded reinforced steel and envirnmental weathering such as when moisture and chlorides penerate the concrete as a result steel rebar corrode and converted into rust and expands. As a result, this exapnsion create internal tensile stress and puch the concrete outward induces crack in the concrete. Moreover, repeated freeze thaw cycles also contributing to the spalling as water trapped inside the concrete's pores. Main indicators are Rust straning on the concrete surface. Surface cracking follow grid pattern of the underlying reinforced steel. Concrete is flaking, chipping or completely breaking away from the main structure.”

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