We probably need some context about what type of construction joint you're talking about. Slab on grade? In a column of a high-seismic region structure? Answers will differ on the application and what reinforcement is present.
I am assuming you are asking the question regarding joints in a framed one-way or two-way slab. Why are you asking for a minimum dimension? Contractors generally want to maximize the areas of their pours. We establish the rules for locating construction joints but we let contractors locate the joints wherever they wish, subject to our rules. We don’t specify a max or min dimension between CJ’s. One exception: we do specify the pour strip width in pt slabs (usually 3’-10” in order to install a 4' wide sheet of plywood in the pour strip and allow lap spliced bottom bars (up to #6) to be installed, but besides that, the issue has never come up. We always ask for submittal of a drawing showing the locations of proposed construction joints, so if the contractor is proposing anything unusual, we’ll be able to spot it ahead of time, and call them to discuss.
