Michigan Residential Builders License Practice Test

What is the time limit for placing concrete control joints after installation?

1. Within 1 hour

2. Within 6 hours

3. Within 4 to 12 hours

4. Within 24 hours

The correct answer is: Within 4 to 12 hours

The correct choice is based on industry standards for the placement of concrete control joints. Control joints are essential for controlling cracking in concrete slabs by allowing for movement as the concrete dries and hardens. Placing control joints within 4 to 12 hours after the concrete has been poured is ideal because, during this time frame, the concrete is still sufficiently green and can be cut without causing excessive damage or crack propagation. Waiting too long can lead to the formation of uncontrolled cracks as the concrete continues to cure and settle. The time frame helps to ensure that the joints can effectively do their job of managing stress in the slab. If joints are placed too early, before the concrete has reached the right level of stiffness, it can lead to uneven cuts and ineffective control. Conversely, if the joints are not cut within the recommended time, they may no longer help in managing the cracks, undermining their intended purpose.