The joint saw is a self-propelled or hand-guided device for cutting control joints (dummy joints) in fresh concrete or for opening up asphalt and concrete pavements for repair work. The cutting tools are diamond-tipped or corundum-bonded saw blades with diameters ranging from 300 mm to 1,200 mm.
In concrete construction, control joints must be cut within a few hours after pouring (early-cut) to prevent uncontrolled crack formation caused by shrinkage stress. The cutting depth is typically one quarter of the slab thickness. In asphalt construction, joint cuts serve to prepare repairs: clean, vertical cut edges enable the precise installation of new asphalt wearing course layers.
Self-propelled large joint saws from manufacturers such as Lissmac, Tyrolit, and Norton cut to depths of up to 500 mm and are used in highway and runway rehabilitation. Hand-held joint saws with gasoline or electric drives are common in building construction and smaller road work. Wet cutting (with water cooling) is standard, as it minimizes dust generation and extends the service life of the saw blade.