Q.: A customer complains that the corner of his driveway next to the street cracked when a heavy truck made a delivery. This was a 5-inch slab. Should the driveway have been doweled to the street pavement, or what is the best construction method to prevent this from happening?
A.: It has been recommended that the driveway slab be thickened 25 percent at the junction--that is, at the curb line if there is one, or at the pavement edge.
The thickened end should be tapered back for a distance of 5 feet. If there is a sidewalk parallel to the street that intercepts the driveway, the driveway should be thickened on both sides of the sidewalk.
Try this answer.
Use one or two pieces of 1/2-inch reinforcing bar, 2 to 3 feet long in the corners as shown in the drawing. With steel used in this way the concrete won't crack from loading even if the driveway is only 4 inches thick.
By the method recommended in the August issue the concrete could be 10 inches thick and still crack. Note also that the sidewalk should be 5 inches thick if, as Problem Clinic seemed to say, it is to intersect a 5-inch-thick section of driveway.
-Theodore Hemleben Hemleben Construction Company Wapakoneta, Ohio
A third alternative, which we have used for 15 years in Middletown, Ohio is to allow the crack but to control it by merely striking a joint as shown in the drawing.
The joint should form an isosceles triangle whose two equal sides are each 2 feet long.
ACI Committee 302 says that tooled joints to control cracking must be cut 1/4 the thickness of the slab.
-William F. Klosterman City Engineer Middletown, Ohio