The effect of fines content on the frost susceptibility of subbase and subgrade material

The freezing and thawing process has detrimental effects on the structural integrity of roads in regions experiencing seasonal frost conditions. The determination of the frost susceptibility of subbase and subgrade soils is an important part of material selection and can significantly impact construction costs. However, it is effected by many parameters and can be determined on three levels of complexity. Advanced methods, although more accurate, can require specialized equipment, training, and a greater amount of time to process test data. Such advanced testing is currently not included in the KGM design manuals and procedures. In this study, the results of freeze thaw tests conducted using a specially designed frost susceptibility cabin located in the laboratory of Soil Stabilization and Research Development Group of the TC General Directorate of Highways, Research Department (KGM, ARGE) are presented. The device conforms to ASTM D5918 requirements and is capable of conducting a fully-automated 5-day freeze-thaw program which includes two freeze-thaw cycles. Four samples can be tested simultaneously with automatic recording of temperatures, water intake and heave. The new testing device has been used to test a quarry-based gravel with varying percentages of fines content. This study evaluates the influence of fines content and type on the frost susceptibility of mixtures of gravel and sand. The coarse grained material consisted of crushed rock aggregates derived from a limestone quarry with size fractions: 12-19 mm, 5-12 mm, 0-5 mm and fines or "Filler". Other fine grained material were added to the mixtures included commercially available Kaolinite and Bentonite minerals and a natural clay, denoted "YK". Fine grained materials were added in percentages varying from 5.24% to 18%. The samples were compacted at maximum dry density and optimum moisture content and CBR values were determined for the as-compacted, soaked and post-freeze thaw states. The frost heave rates and the segregation potential were calculated. The analysis shows that the freeze-thaw testing cabin gives reliable test results. The results also show that the frost susceptability increases with an increase in the fines content and that mineralogy and grading of the soils impact the frost susceptibility.