There is an optimum time to saw contraction joints in new concrete pavement. Why?

There is an optimum time to saw contraction joints in new concrete pavement. Sawing cannot be carried out too early because the saw blade would break out particles from pavement and this results in the formation of jagged and rough edges. Such raveling is undesirable as it would impair the appearance and the ability to seal the joint properly.

Sawing cannot be implemented too late. When the volume of concrete is reduced significantly owing to drying shrinkage or thermal contraction, it induces tensile stress owing to the restraint of such reduction. When the tensile stresses exceed the tensile strength of concrete, cracking would result and form in other locations instead of the planned location of contraction joints.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.