In the scenario of a new slab connected to an existing slab with bleed, which surface condition is anticipated?

• A. The surface will become glassy and hard
• B. The surface will develop cracks
• C. The surface will set too quickly
• D. The surface will show no surface distress

Answer: (B)

When a new slab is poured and tied to an existing slab, the two act as a single mass and can’t move independently. As concrete cures, it loses moisture and shrinks. The restraint provided by the existing slab at the joint means the shrinkage of the new concrete creates tensile stresses in the surface layer. If those tensile stresses exceed the concrete’s strength, cracks develop, typically near the joint where restraint is greatest. Bleed means water rises to the surface during curing and can leave a laitance layer, but it doesn’t prevent cracking; it can also make the surface more vulnerable to distress. So the anticipated surface condition is cracking along the joint.