Assessing Frost Resistance of Concrete Aggregates in Minnesota

Abstract

This study was undertaken to identify test procedures capable of reliably assessing concrete aggregate freeze-thaw durability and establish appropriate acceptance criteria for the same. Highway condition surveys were performed to document the field freeze-thaw performance of selected aggregate sources representing a range of frost resistance. Cores were obtained for laboratory testing and evaluation, and samples of the original aggregate sources were obtained for use in performing environmental simulation tests [i.e., variations of ASTM C 666 and the Virginia Polytechnic Institute (VPI) single-cycle slow-freeze test] and correlative tests (e.g., absorption capacity, Iowa pore index test, X-ray diffraction and fluorescence analysis, and hydraulic fracture test). Petrographic examination was used to correlate aggregate geological and engineering properties with the results of environmental and correlative tests. A suite of tests was developed for more accurately assessing the probable field performance of any given aggregate as a function of its original geological origin and probable environmental exposure. Petrographic examination is used first to identify aggregate composition and provide a basis for selecting subsequent durability tests, which may include the hydraulic fracture test, VPI single-cycle slow-freeze test, and ASTM C 666 Procedure B (modified to use salt-treated aggregates).