Performance of fly ash pellets in cold climates

The construction season is very short due to difficulties of water handling in cold regions. The harsh climate of cold areas causes soil to be frozen from September to May. The main scope of this study is to investigate whether the engineering properties of lightweight pellets produced from fly ash by cold bonding process are durable enough for use in geotechnical engineering applications in cold regions. Potential use of pellets without compaction with water is investigated. Therefore, the pellets were covered with snow to represent frozen soil and subjected to the freeze-thawing cycles. A cycle in this experiment is intended to correspond to one year duration in the cold regions. Cold bonding pelletization technique was used to produce fly ash pellets of sand and gravel size. Pellets have been exposed to ten freeze-thaw cycles. The pellets were observed with the thermal imager during freeze-thaw. Then, freeze-thaw procedure was evaluated by thermal imaging during freeze-thaw cycles. California Bearing Ratio (CBR), direct shear, cyclic simple shear and crushing value tests were conducted. An optical microscope was used for the observation of the surface of pellets. Thin section analysis was performed on pellets to observe the microfabric of the inner section of the pellets. Then, ESEM analysis was performed to examine the microfabric of pellets. Based on test results, although pellets lose strength after freeze-thaw, they still preserve their form. Usage of proper paving may lead to successful applications of fly ash pellets in cold climates. Limited construction season of cold regions may be extended with the use of fly ash pellets. Better understanding of the cold weather performance of fly ash pellets will lead to enhanced utilization in cold climates.