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South Dakota Department of Transportation
Project Synopsis
SD1996-19


Title: Delamination Surveys on Bridge Decks Overlaid with RACS
Project Researcher: Dan Johnston, SDDOT
Project Manager: Hal Rumpca
Research Period: 5/1/1997 - 2/28/2000
Status:
Cost: $10,000.00

Problem Statement: The Department has over 470 bridge decks with Rubberized Asphalt Chip Seal (RACS) overlays. Because of the masking effect of the RACS it is difficult to get an accurate assessment of the deck condition, especially the amount of delamination. Chain drag surveys in the past have indicated significant areas of delamination but we have gotten mixed results when confirming it with cores. There are currently several other non-destructive testing methods available including Infrared Thermography (IRT), Ground Penetrating Radar (GPR), and Impact Echo (IE) testing. These need to be evaluated to determine if they are effective while the RACS is in place. The condition of the deck is a large part of the rating system used for bridges. Bridge ratings are a part of the formula in determining the amount of bridge replacement funding each state is eligible for. Accurate data for making decisions regarding scope of work and extent of deck repair is needed for preparing repair plans.

Even though the use of RACS as a bridge treatment has fallen off substantially, those bridges already overlaid with RACS represent a substantial long term evaluation problem which will not be eliminated for several decades. The removal of a RACS to perform deck repairs or concrete overlays also represents a major problem due to the need to scarify the surface of the deck to eliminate the RACS. After scarification a bridge deck overlay is normally required to correct grade because the removal process destroys the original deck surface. In some cases the actual condition of the deck is much better than the delamination survey indicates and an overlay may not have been really necessary. We need to explore and develop feasible technologies or procedures for removing RACS without damaging the underlying decks.



Findings:
Title: Delamination Surveys on Bridge Decks Overlaid with RACS
Project Researcher: Dan Johnston, DOT
Project Manager: Hal Rumpca
Research Period: 5/1/1997 - 2/28/2000
Status:
Cost: $10,000.00

Problem Statement: The Department has over 470 bridge decks with Rubberized Asphalt Chip Seal (RACS) overlays. Because of the masking effect of the RACS it is difficult to get an accurate assessment of the deck condition, especially the amount of delamination. Chain drag surveys in the past have indicated significant areas of delamination but we have gotten mixed results when confirming it with cores. There are currently several other non-destructive testing methods available including Infrared Thermography (IRT), Ground Penetrating Radar (GPR), and Impact Echo (IE) testing. These need to be evaluated to determine if they are effective while the RACS is in place. The condition of the deck is a large part of the rating system used for bridges. Bridge ratings are a part of the formula in determining the amount of bridge replacement funding each state is eligible for. Accurate data for making decisions regarding scope of work and extent of deck repair is needed for preparing repair plans.

Even though the use of RACS as a bridge treatment has fallen off substantially, those bridges already overlaid with RACS represent a substantial long term evaluation problem which will not be eliminated for several decades. The removal of a RACS to perform deck repairs or concrete overlays also represents a major problem due to the need to scarify the surface of the deck to eliminate the RACS. After scarification a bridge deck overlay is normally required to correct grade because the removal process destroys the original deck surface. In some cases the actual condition of the deck is much better than the delamination survey indicates and an overlay may not have been really necessary. We need to explore and develop feasible technologies or procedures for removing RACS without damaging the underlying decks.



Findings:

Research Objectives:
1  To determine the accuracy and cost effectiveness of IRT, GPR, and IE for delamination detection on bridge decks with RACS.
2  To evaluate the accuracy and cost effectiveness of these techniques on conventional and overlaid bridge decks without RACS.
3  To develop a technology or procedure capable of removing RACS without damaging the deck beneath.

Research Tasks:
1  Review available literature on IE, IRT and GPR for delamination detection and RACS removal.
2  Explore the feasibility of using FHWA's IRT and GPR demonstration equipment.
3  Identify suitable candidate bridges for testing, with and without RACS.
4  Develop a work plan for testing and evaluation including logistics and necessary contracts.
5  In cooperation with the FHWA and the cooperative researchers, conduct IE, IRT and GPR testing on candidate bridges followed by RACS removal, retesting and conventional chain drag surveys.
6  Evaluate the use of new technologies or procedures for RACS removal.
7  Analyze and compare the effectiveness of the various testing and removal methods including their cost-effectiveness.
8  Recommend changes in bridge deck condition survey procedures and methods for RACS removal.
9  Submit a final report summarizing relevant literature, research methodology, findings and conclusions.
10  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Documents Available:
SD1996_19_final_report.pdf

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