Refinement and Validation of the Washington Hydraulic Fracture Test

Principal Investigator:

Mark Snyder, Former University Researcher, Civil, Environmental and Geo-Engineering

Co-Investigator

Project Summary:

D-cracking and other forms of aggregate-related freeze-thaw damage have often been associated with concrete pavements in Minnesota. The best approach for preventing these types of distress is to avoid the use of aggregate sources that exhibit poor freeze-thaw performance in concrete pavements. Currently, the most widely-accepted methods of evaluating aggregate freeze-thaw durability involve the preparation and freeze-thaw testing of concrete beams that contain the aggregate in question. These tests are generally time-consuming ( requiring months to complete) and require the use of expensive equipment and highly-skilled operators. A more rapidtest of aggregate freeze-thaw durability was developed under the Strategic Highway Research Program. This test, called the Washington Hydraulic Fracture Test (WHFT) was developed by Dr. Donald J. Janssen (University of Washingtion) and Dr. Mark B. Snyder (University of Minnesota). The WHFT equipment is relatively inexpensive and allows a single laboratory technician to assess the freeze-thaw durability of several samples of aggregate in as few as seven working days. The WHFT was further developed under a research contract sponsored by the Michigan Department of Transportation and recently completed by Drs. Janssen and Snyder. The primary goal of the Michigan project was to determine the correlation between the results of the WHFT and the freeze-thaw test currently used by MnDOT. This project did demonstrate the value of the WHFT as a rapid screening test for many concrete aggregates. However, this research also resulted in the development of recommendations for test procedure changes and equipment modifications that will further reduce required testing efforts and may improve the reliability and interpretation of the WHFT results. These equipment and procedural modifications should be implemented and evaluated to provide MnDOT and other highway agencies with the best possible tool for evaluating aggregate freeze-thaw durability. The objective of the proposed research is to improve MnDOT's ability to rapidly evaluate the potential freeze-thaw durability of aggregate sources intended for use in PCC pavement applications. This will be accomplished by refining and validating the Washington Hydraulic Fracture Test using Minnesota aggregate sources. MnDOT will also be provided with a working test apparatus for use in implementation.

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