Nondestructive Testing and Evaluation of Concrete Parking Garages

Public works departments need test procedures for assessing the current condition of concrete in public facilities such as parking garages. Nondestructive testing can provide ultrasonic pulse velocities that can be used as an indicator of concrete quality. A procedure is presented that can be used to collect and analyze ultrasonic measurements. The procedure was applied for all of the public garages in Montgomery County, Md., to identify garages that needed immediate maintenance. Based on the measured data, the effect of the age of the concrete on the pulse velocity was investigated and a model was developed. The model can be used to determine where a garage is in its life cycle. The effect of elastomeric membranes, used to protect the concrete slabs on pulse velocities, was evaluated with the results indicating that the use of membranes extended the life of the concrete by about 10%, or an equivalent of 3 years of design life. A method of evaluating the effect of steel reinforcement on the pulse velocity was developed and applied. The method can be used to identify the optimum spacing between the transmitter and receiver in nondestructive testing.