Aggregate Freeze-Thaw Testing and D-Cracking Field Performance 30 Years Later

摘要

Premature deterioration of concrete pavement due to D-cracking has been a problem in Kansas since the 1930s. Kansas geology includes mineable limestone coarse aggregates with variable durability in the eastern portion of the state. Due to this variability and historically poor D-cracking field performance, the Kansas DOT initiated intensive identification and tracking of individual mined beds, as well as frequent durability testing during production in the 1980s. D-cracking field performance of concrete pavements containing limestone coarse aggregates was investigated in 2010-2012. Results of this investigation indicate that the rate of D-cracking decreased, but the minimum rate of D-cracking presence in concrete pavements is more than 30%. In reaction to these results, KDOT implemented changes aimed at mitigating the risk of D-cracking. Implementation actions included increasing the number of freeze-thaw cycles for aggregate in concrete prisms from 300 to 660 cycles, freeze-thaw testing of all aggregate types (not just limestone) in concrete, focusing aggregate sampling at the point of concrete production, and including an "acceptable field-performance history" criterion for concrete aggregates. Ongoing research is being conducted to develop new methods to identify durable aggregates and faster testing techniques.