The assessment of freezing-thawing index of aggregates in various environments of Northwest Direh catchment, Kermenshah Province

Considering the effects of geological environments of natural aggregates accumulation on the weight loss rate of aggregates resulted from freezing-thawing, the relationship between geological environments and the weight loss rate of aggregates has been investigated in this study. The lithology of upstream catchment was the same (thick Asmari limestone) for all aggregates samples. Samples were gathered from 2 taluses, 12 fans and 3 river beds. Samples were transferred to laboratory and then the weight loss rate (in accordance with tex-432- A standard) and the jointing intensity were measured. Based on the results, colluvial environments (taluses) have the highest weight loss rate (14% for size of 16-19 mm) and river environments have the lowest weight loss rate (less than 1% for size of 2.36-4.75 mm). The aggregates of alluvial fans have the intermediate amount compared to two previous environments. In alluvial fan aggregates, the weight loss rate decreases when the area and length of main stream of catchments increases. Also, aggregates size affects the weight loss rate so that increase in the size of aggregate causes the rise in weight loss. Relationship between aggregate size and weight loss rate is affected by geological environments. The difference of weight loss between fine and coarse aggregates is high in talus environments as well as alluvial fans with small catchments, while it is less in river beds and fans with large catchments. In fact, the size effect of aggregate on weight loss decreases or eliminated in river beds and fans.