Automated Steel Placement (Tube-Feeding)
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.
When tube feeding steel, the longitudinal bars are distributed on the base, approximately spaced, lapped, and tied manually. During placement, the longitudinal bars are raised up on rollers and threaded through bell-ended tubes within the concrete spreader where they are held at the specified vertical and horizontal positions as the concrete is placed between the tubes.
Few, if any, contractors use the tube feeding method for steel placement. A number of problems have been reported with tube feeding, primarily related to ensuring the steel is at the proper depth in the pavement. Steel too high in the pavement has resulted in corrosion of the reinforcement and spalling of surrounding concrete, and even exposed steel in some instances. Steel too low in the pavement can result in undesirably wide crack widths. While tube feeding does eliminate the labor required for placing the steel on chairs, and permits access to the base in front of the paving operation (although not for concrete placement), the potential problems associated with this technique may far outweigh the benefits.