Q.: What is the best way to repair joints in pavement in which the slab on one side of the joint may be from 1/8 to 3/8 inch lower than the adjacent slab?

A.: First the condition of the concrete and subbase in the vicinity of the joint must be determined. The slab must be stabilized as needed in this area by pressure grouting and installing edge drains. Spalls must be repaired and joints resawed and sealed.

The two slabs can then be brought to the same level by a diamond grinding machine that cuts the surface of the high slab down to the level of the low slab. The American Concrete Pavement Association says that a fault 1/3 inch high may be tapered to zero in a distance of 3 feet from the joint, while a 1/2-inch fault may require a distance of 5 feet. Grinding is done with a multiple-blade saw that produces skid-resistant corduroy grooves in the longitudinal direction of the pavement. The work can begin at either the high or low end of the portion to be cut. Residue from the grinding operation should be removed so that it does not flow into gutters and drains or become airborne through the action of traffic or wind. Four-lane pavements may require grinding of only the slow-moving lanes, since faulting may be negligible in the lanes that have carried little truck traffic, though some feather-edge grinding may be needed where the two kinds of lanes abut.