A 17-year-old parking facility in metropolitan Detroit is experiencing floor slab deterioration. An investigation was performed to determine the nature and extent of deterioration and identify probable restoration alternatives. The i nvestigation involved visual observation, materials testing, a chain drag de lamination survey, and determination of concrete cover to slab reinforcement. The structural frame con-ei~ ts cf a 12-in.-C. hick flat plate floor slab system spanning in two directions sup-ported by columns approximately 30 ft on centers. Floor slab reinforcement in the top and bottom slab sections are galvanized reinforcing steel bars. The floor slab and ceiling deteriorated from corrosion-induced spalling. Chain drag and coring surveys indicate that approximately 26 percent of exposed floor surfaces and S percent of ceiling surfaces are delaminated or spalled to a depth of about 2 in. Clear concrete cover is generally good, with a low cover of about l. 25 in. and an average cover of about 2.25 in. The chloride content of the concrete, determined within the top 3 in. of the slab, ranged from 25.2 to 8.5 lb/yd'of concrete. The average concrete compressive strength of the floor slab is about 5,670 psi. The average air content of the concrete was determined to be 2. 3 percent. Slab concrete pH ranges from 9.93 at the deck surface to 10. 82 at tbe 3-in. depth. Reinforcement section loss of upwards to 20 percent was noted at isolated areas.

The objective of this paper is to provide a report on the field performance of a 17-year-old parking structure with galvanized flonr slab~ einforccmcnt. The case study is for the Kennedy Square Parking Garage in Detroit. The parking facil! t~•, built in 1965, consists of a slab on grade and two supported levels of parking. The parking lev ls are located directly beneath a pedestrian plaza, complete with plantings and a wading pool. The structural system for the supported level consists of a conventionally reinforced flat slab with drop panels and circular columns. The slab has galvanized steel reinforcing bars in the top and bottom mat of slab reinforcement. Typical slab reinforcement is shown in Figure 1.