Q.: Which is better, a joint made by hand when concrete is still plastic or a joint cut by a saw after a day or two? Why?
A.: As far as the function of the joints in preventing shrinkage cracking is concerned, one serves as well as the other provided both are cut to the required depth. Hand-tooled joints offer a disadvantage in some circumstances, however, because the radius at the edge of the joint may be objectionable particularly where joints are subject to wheeled traffic. Such joints are harder to seal against impact and may deteriorate mechanically in use. The sharp shoulders of sawed joints are easier to seal and maintain against breakage from the impact of wheels.