Development of Laboratory Test Methods to Replace the Simulated High-Temperature Grout Fluidity Test

摘要

This report contains a summary of the research performed to develop a replacement for the high-temperature grout fluidity (HTGF) test. The HTGF test was employed in the past by FDOT to qualify post-tensioning (PT) grouts for use in post-tensioned bridge construction. The HTGF test, however, is expensive and cumbersome to conduct in a typical construction materials testing laboratory. The objective of this research project was to develop a replacement for the HTGF test using a dynamic shear rheometer (DSR). Initially, exploratory studies were conducted using a number of DSR test methods and geometries to develop or adopt a method that provides more consistent and rational rheological results than the currently used flow cone test method. These studies led to the adoption of the viscosity test with a cup and ribbon geometry. The shear rate used in the viscosity test (50 s-1) was based on data from the literature and from the estimated shear rate at the nozzle of a flow cone. In addition to the DSR test development, HTGF tests were conducted twice on four different commercially available PT grouts. PT grout temperatures increased an average of 7 degrees F (4 degrees C) over the course of the circulation during HTGF testing. Line pressures measured at the pump during circulation ranged from 100 to 350 psi (4 kPa to 17 kPa). Viscosity results measured during the HTGF test were correlated to performance of the PT grouts. The viscosity results compared well with flow cone results with an R2 value of 0.85. From these data, performance classifications were developed based on the results of the testing. Finally, DSR testing was conducted at University of Minnesota-Duluth (UMD) and National Institute of Standards and Technology (NIST) to provide a comparison of the viscosity results from these laboratories to those produced by the University of Florida. Trends in viscosity test results compared well with results from both UMD and NIST. Absolute magnitudes, however, varied somewhat. This is thought to be due to the sensitive nature of the mixing and conditioning process. Additional performance classifications were developed based on the findings of these studies.