A project of mine that is under construction uses wedge inserts and bolts in the edge of the concrete slab to attach the shelf angles for the brick masonry. Several of these inserts were mistakenly left out of the slab. Is there any reason why expansion anchors can't be used where the inserts were left out?
In general, if the expansion anchors are properly sized there should be no problem. But be sure to consider two things. First, if the concrete slab is prestressed, find the location of the tendons before starting. If these tendons are cut or even nicked in drilling holes for the expansion anchors, they may snap, causing injury or partial collapse of the structure. Second, be sure to locate the expansion anchors accurately. Unlike wedge inserts, expansion anchors do not permit vertical adjustment. If only a few wedge inserts were left out, use them to bolt the shelf angle finger-tight to the slab. Lay the brick to the underside of the angle. Then accurately position the shelf angle and drill through the horizontal slots in the angle to install the bolts. If an entire row or inserts was left out, support the shelf angle on the masonry below with shims until the anchors are installed. Be sure to remove the shims afterward, so you'll have a true expansion joint below the angle.