In joining a new slab to an older slab, if the new work bleeds during pouring, what surface outcome should be anticipated?

• A. The surface will become indistinguishable from the original slab
• B. The surface will show a polished finish
• C. The surface will remain crack-free
• D. The surface will develop cracks

Answer: (D)

Bleeding in fresh concrete creates a weak, laitance-rich surface layer as water rises and carries fine cement to the top. When you pour against an older slab, the joint is restrained by the existing concrete, so as the new concrete cures and undergoes shrinkage, tensile stresses develop at the surface. The presence of the laitance further weakens bonding at the surface, making it more susceptible to cracking under those restrained conditions. Therefore, cracking is the expected surface outcome around the joint.