Plastic shrinkage cracks occur when the slab surface is drying faster than the bleedwater is rising to the surface.

Plastic shrinkage cracks occur when the slab surface is drying faster than the bleedwater is rising to the surface.

• A. True
• B. False
• C. Only in cold weather
• D. Not related to bleedwater

Answer: (A)

Plastic shrinkage cracking happens while concrete is still in its plastic state, when the surface loses moisture to evaporation faster than bleed water can reach and rise to the surface. As the surface dries, the top layer loses water and contracts, while the underlying concrete may still have moisture available via bleeding. If evaporation outpaces this bleeding, tensile stresses develop in the surface layer and cracks form. That makes the statement true: the cracking is driven by rapid surface drying relative to bleedwater rise. It can occur in hot, windy, low-humidity conditions and is indeed related to the bleedwater process—not limited to cold weather and not unrelated to bleedwater.

Plastic shrinkage cracking happens while concrete is still in its plastic state, when the surface loses moisture to evaporation faster than bleed water can reach and rise to the surface. As the surface dries, the top layer loses water and contracts, while the underlying concrete may still have moisture available via bleeding. If evaporation outpaces this bleeding, tensile stresses develop in the surface layer and cracks form. That makes the statement true: the cracking is driven by rapid surface drying relative to bleedwater rise. It can occur in hot, windy, low-humidity conditions and is indeed related to the bleedwater process—not limited to cold weather and not unrelated to bleedwater.