Select Testing to Screen Materials for Specification Compliance

In 1998 the South Dakota Department of Transportation (SDDOT) initiated a policy of allowing only vinsol resin air entraining admixtures (AEA's) for use in concrete mixtures due to a recurring problem with low compressive strength in both structural and paving concrete which had occurred the year before. A research project, SD1998-03 Investigation of Low Compressive Strengths of Concrete in Paving, Precast and Structural Concrete had shown that the use of other, gum rosin-based and synthetic AEA's could result in flocculating clusters of air bubbles on aggregate surfaces compromising the bond between the aggregate and paste. The return to vinsol resin-based admixtures alleviated the problem but one manufacturer's product, alleged to be a vinsol resin AEA, has been associated with numerous instances of low compressive strength on projects over the ensuing years. A check of the patent literature for this company reveals an intriguing reference-paraphrased as- "For example, an AEA based on a vinsol resin by-product, which is believed to be suitable for use in the present invention is available from the manufacturer, under its trade name." Interestingly, only one company, Hercules Incorporated, manufactures vinsol resin and any "byproduct" cannot be considered the same as a true vinsol resin material. In a similar scenario, a "polysulfide epoxy" used by the department as a bridge deck sealing epoxy overlay system for the last decade has radically changed in appearance and physical properties since the first experimental applications. The manufacturer provides assurance that the system is essentially the same and still promotes the material as a 100% solids polysulfide epoxy in their literature. Since the original development, the epoxy material has changed color (green to yellow as neat epoxy), setting time (8 hour cure to less than four hours) and smell (somewhat objectionable sulfide odor to slight amine odor). Numerous projects have also had problems with bond failure and epoxy curing issues. Research is needed to develop screening protocols for insuring the product types listed above, as well as any other suitable materials, are in compliance with specification requirements or not allowed for use. The objectives of this research project is to: (1) define laboratory and field procedures suitable for analyzing, discriminating whether given materials (i.e. vinsol resin AEA's, polysulfide epoxies) meet specification requirements and allowing acceptance screening and (2) develop approved product lists for certain materials based on the results of these protocols. Research tasks for this project are as follows: (1) Review current literature with respect to suitable chemical analysis procedures for materials selected for specification verification. (2) Meet with the technical panel to review project scope and work plan. (3) Acquire samples of materials from both manufacturers and construction projects for both test development and compliance screening. (4) Develop and refine appropriate testing protocols for each material class identified capable of clearly discriminating whether, based on composition and performance testing, a material meets the specification requirements. This approach should be based on component manufacturer's samples, where obtainable, or, if necessary, marked departure of certain products from other, compliant materials. (5) Screen all products currently on the Approved Products List for a given class of materials (i.e. AEA's). (6) Formulate recommendations for each materials class with regard to whether a given product should be retained on the Approved Products List or removed due to noncompliance. (7) Provide a clear rationale for each testing protocol developed, its ability to discriminate between suitable and unsuitable materials and the scientific basis for rejecting noncompliant materials. (8) Provide a plan for screening any new materials in the categories being examined with the requirement that samples submitted for acceptance will be considered based on a manufacturer's obtaining independent laboratory test results using the appropriate protocol. (9) Prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations. (10) Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.