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South Dakota Department of Transportation
Project Synopsis
SD1996-10


Title: Evaluation of PCC/AC Joint Sealant
Project Researcher: Hal Rumpca, SDDOT
Project Manager: Jon Becker
Research Period: 1/1/1996 - 12/31/1998
Status:
Cost: $10,000.00

Problem Statement: The South Dakota Department of Transportation (SDDOT) has built portland cement concrete pavement structures using asphalt concrete shoulders. For years 3405 Modified Joint Sealant has been used to seal the longitudinal joints between these two types of pavement. Sealing these joints is important, because the intrusion of moisture can remove fine aggregates, causing faulting or settlement of the asphalt at the joints. Because the 3405M sealant has failed in many installations throughout the state, several test sections have been installed using two self-leveling silicone joint sealants developed by Dow Corning. Dow 888SL was evaluated in 1988, and Dow 890SL was evaluated beginning in 1990-1994. Dow 888SL was developed for use on PCC pavements only, where the newer Dow 890SL was developed especially for the purpose of sealing joints between PCC and AC pavements. The report documenting the evaluation of the 890SL is SD90-13, PCC/AC Shoulder Joint Seal Evaluation.

The Dow 890SL performed very well for five years. Unfortunately, because of a long curing time, Dow Corning decided to reformulate the product. Therefore, the product was not available for the remainder of the project, which resulted in two of the objectives not being met. The optimum shape factor and the actual water infiltration were not determined. Also, the sealant was not subjected to high moisture levels resulting in shear forces between the two pavements conditions present in much of the state. Other problems with test sections in the study included poor pavement with many cracks, which resulted in an unfair evaluation. The study recommended that the Office of Research should initiate a project to evaluate the performance and cost-effectiveness of the reformulated sealant in 0.5 and 0.75 channels on new or recently constructed asphalt shoulders in a wet climate. A sample of the reformulated Dow 890SL was obtained after the study. It did not meet the manufacturer's specifications, and required seven days to cure. Work must be done to determine whether the 890SL can be improved to meet the specification.

SDDOT has specifications for joint sealant on transverse joints. These same specifications are used for longitudinal joints. This may not be appropriate because the two types of joints may behave differently, requiring the use of different materials. Work must be done to determine whether specifications for joint sealants on PCC/AC joints are appropriate.



Findings: The SDDOT Materials Lab conducted in-house tests on both the Crafco Incorporated Roadsaver 903 SL Silicone and Dow Corning 890 SL Silicone sealants. The results of the tests were compared to the SDDOT 1998 Standard Specifications for Roads and Bridges, Section 870 Concrete Joint Sealer Specifications as well as to each manufacturer's silicone sealant specifications. Military Specification S-8802E and ASTM Designation 5893-96 Standard Specification for Cold Applied, Single Component, Chemically Curing Silicone Joint Sealant for Portland Cement Concrete Pavements were reviewed to determine appropriate curing and tack free times for the silicone samples. Neighboring states were contacted to determine if they used silicone sealants to seal longitudinal joints between PCCP and AC pavements. The results of the survey, as well as recommendations from Crafco Incorporated are contained in the report. Based on this information, the researcher recommended that the SDDOT only allow the use of approved hot-pour sealants for PCCP/AC longitudinal joints.

Research Objectives:
1  To determine whether reformulated 890SL or other products work in PCC/AC applications
2  To varify or recommend specifications for PCC/AC shoulder joint sealants.
3  To determine the optimum shape factor for material using a minimum of material.

Research Tasks:
1  Perform a literature search including manufacturers, interviews with other DOT’s regarding products, specifications, evaluation methods, and application equipment.
2  Prepare a work plan detailing test sections, material to evaluate, method of evaluation, and preparation of joint. Also consider whether to include test sections experimenting with sandblasting the joint, and the use of backer rod.
3  Meet with the technical panel to evaluate and revise the work plan.
4  Varify or recommend PCC/AC longitudinal joint seal specifications, and determine whether product(s) meet them.
5  Lab test the product(s) for adhesion, cohesion, elongation, and optimum shape factor in a range (3/8” - 1”) of vessel widths.
6  Install test sections and field test the product in the range of vessel widths in a rehabilitation project, new construction project, and a project using edge drains, to determine actual water infiltration at a treated joint.
7  Perform evaluation and cost analysis, and outline procedure to evaluate new sealant products.
8  Submit a final report including findings, conclusions, test and evaluation methods, and recommendations.
9  Present findings and recommendations to the Research Review Board.

Documents Available:
SD1996_10_final_report.pdf

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