Bleeding during the concreting of a new slab joined to an existing slab leads to which surface condition?

• A. The surface will develop cracks
• B. The surface will cure with a flawless finish
• C. The surface will show excessive setting time
• D. The surface will peel away from the substrate

Answer: (A)

Bleeding raises water to the surface during placement, which creates a weaker, paste-rich top layer (laitance) and reduces the surface’s ability to resist tensile stresses. As curing proceeds and moisture is lost, plastic shrinkage stresses develop in the surface. When the new slab is joined to an existing one, movement is restrained at the joint, so those stresses cannot relieve themselves easily. The combination of a weak surface layer and restrained shrinkage concentrates tensile stress right at the surface, leading to cracks.