Cold weather slows the cement/water reaction (cement hydration process) which in turn increases the set time of freshly placed concrete. The National Ready Mixed Concrete Association (NRMCA) discusses a good rule of thumb that a 20 degree drop in concrete temperature will approximately double the concrete setting time.
In 1995, 22 years ago, my favorite article, mainly because of the quote below, appeared in Builder Magazine. The question was asked, “…what’s the best way to prevent cracks in garage slabs?” The answer… “Move to another planet. Here on Earth cracks in garage slabs are like Cal Ripken at shortstop - always there.”
A crazed concrete surface contains a network pattern of very shallow, fine/hairline cracks. They do not penetrate much below the surface of the concrete. They rarely are more than 1/8” deep and are more noticeable on steel troweled surfaces. They are most visible when the concrete is drying after the surface has been wet.
Drying shrinkage cracks are cracks that form in concrete after the concrete has hardened. In general, these cracks are those brought on by shrinkage of the concrete. As the concrete dries or goes through thermal changes we anticipate volume changes. Cracks will appear at any time and any place where the stress within the concrete to pull it apart (tensile stress) exceeds the strength of the concrete to hold itself together.
Plastic shrinkage cracks are cracks in the surface of concrete, usually flatwork, that appear before the concrete actually achieves “final set”. Perhaps more appropriately stated: they form while the concrete is still “plastic”. They are relatively short in length, often parallel, and do not extend throughout the depth of the slab nor do they extend from edge to edge.