Evaluation of Frost Resistance Tests for Carbonate Aggregates

Abstract

D-cracking is a progressive distress associated primarily with the use of coarse aggregates that deteriorate when they are critically saturated and subjected to repeated cycles of freezing and thawing. The present study was undertaken to consider better acceptance criteria for concrete aggregates and to allow for the use of more local Minnesota aggregates through selected aggregate beneficiation techniques. Condition surveys of concrete highway pavements were performed to document the field freeze-thaw performance of selected aggregate sources representing a range of frost resistance. Cores were obtained from these sections for laboratory testing and evaluation, and coarse aggregates were obtained from the original sources for use in performing environmental simulation tests [i.e., variations of ASTM C666 and the Virginia Polytechnic Institute (VPI) single-cycle slow-freeze test] and correlative tests (i.e., absorption and bulk specific gravity, Portland Cement Association absorption and adsorption tests, Iowa pore index test, acid insoluble residue test, X-ray diffraction analysis, X-ray fluorescence analysis, thermogravimetric analysis, and the Washington hydraulic fracture test). The tests that provided the best correlation with field performance included a modification of ASTM C666 Procedure B (specimens prepared with salt-treated aggregates), the VPI single-cycle slow-freeze test, and the Washington hydraulic fracture test. Other test procedures were correlated with field performance to lesser extents. It was noted that petrographic examination of pavement cores can help to distinguish between D-cracking and other conditions that can produce distresses with similar appearances (e.g., distresses caused by secondary mineralization, embedded shale, poor mix design, and alkali-aggregate reaction).