Inspection of Reinforcement Placement
See FHWA’s CRCP Design and Construction Guidelines for the references included in this page. A new, more comprehensive FHWA CRCP Design, Construction, Maintenance and Rehabilitation manual is currently under development and this page will be updated upon its release in the spring of 2016.
Steel reinforcement should be properly inspected to ensure that spacing, splice lengths, and patterns are consistent with design requirements.(98) At a minimum, the following checks should be performed and documented prior to concrete placement:
- Ensure all longitudinal lap and ties of all splices to assure that the minimum lap of the reinforcing steel is maintained. (see Figure 46)
- While it is important to check the distance between longitudinal reinforcement bars (see Figure 47), it is even more important to ensure the correct number of bars is in place.
- Periodically check that the reinforcing steel is placed within the specified vertical tolerance. When chairs or transverse bar assemblies are used, this is accomplished prior to concrete placement by pulling a string line transversely across the roadway at the grade of the new pavement and measuring down to the reinforcing steel and checking the steel for movement as the paver passes (see Figure 48).
- Although the supports are designed to hold the steel at the correct depth, the midpoint between the chairs should be checked for possible sags. When tube feeders are used, a probe, or ruler, is inserted to determine the depth to steel from the surface of the slab at several locations across the paving width.
- Ensure there are no broken steel chair welds or plastic chair joints, bars are properly aligned, there are a sufficient number of wire ties on lap splices, and bars are lapped properly. Special precautions should be taken to prevent bar bending and displacement at construction joints.
- Remove foreign materials prior to placing concrete.
At a minimum, the following inspection techniques should be employed as the concrete is being placed:
- Monitor the reinforcing steel at either the spreader or paver to ensure that reinforcement is not displaced by the fresh concrete.
- Regularly check the depth of the reinforcing steel behind the paver, which can be accomplished when the concrete is plastic or hardened (see Figure 49).
- The depth of reinforcing steel in plastic concrete may be determined as previously mentioned or by excavating to the steel and directly measuring the depth from the slab surface. Should the location not be correct, paving operations should stop until the problem is corrected. Generally movement of the reinforcement occurs more often with tube placement than when presetting steel on chairs.
For hardened concrete, either a Ground Penetrating Radar (GPR) or magnetometer can be used to locate the position and depth of steel (after calibration with coring results). However, at this point remedial measures are limited, unlike a check during construction.