During diurnal temperature variation, it may be necessary to saw every 3rd or 4th joint before sawing the intermediate joints.

During diurnal temperature variation, it may be necessary to saw every 3rd or 4th joint before sawing the intermediate joints.

• A. 1st/2nd
• B. 2nd/3rd
• C. 3rd/4th
• D. 4th/5th

Answer: (C)

Diurnal temperature variation creates forces in concrete as it expands and contracts with the daily heating and cooling cycle. Controlling where those movements crack the concrete is done by sawing joints in a staged pattern so relief is provided gradually rather than all at once. Sawing every 3rd or 4th joint first creates primary relief planes at wider intervals, which helps distribute the restrained shrinkage over the slab more evenly and reduces the risk of excessive restraint that could cause curling or random cracking. After those larger-relief joints have been cut and the pavement continues to dry and stabilize, the remaining intermediate joints can be cut, finalizing the joint pattern so cracks are intercepted along planned lines. Cutting the closer joints first or cutting all joints at once can over-stress the concrete or fail to control movement as effectively, so the 3rd/4th sequence provides the best balance for managing diurnal movement.

Diurnal temperature variation creates forces in concrete as it expands and contracts with the daily heating and cooling cycle. Controlling where those movements crack the concrete is done by sawing joints in a staged pattern so relief is provided gradually rather than all at once. Sawing every 3rd or 4th joint first creates primary relief planes at wider intervals, which helps distribute the restrained shrinkage over the slab more evenly and reduces the risk of excessive restraint that could cause curling or random cracking. After those larger-relief joints have been cut and the pavement continues to dry and stabilize, the remaining intermediate joints can be cut, finalizing the joint pattern so cracks are intercepted along planned lines. Cutting the closer joints first or cutting all joints at once can over-stress the concrete or fail to control movement as effectively, so the 3rd/4th sequence provides the best balance for managing diurnal movement.