Study on low-temperature performance of basalt fiber asphalt mixture under the condition of extremely cold and large temperature difference
[Objective]As a typical temperature-sensitive material,asphalt mixture frequently exhibits severe low-temperature cracking when serving in extremely cold regions with large temperature differences in northern China.The introduction of SBS modifier and fiber additives to the asphalt mixture can enhance its various road performances.Current studies on the low-temperature performance of fiber asphalt mixture(FAM)in extremely cold regions with large temperature differences are lacking.To address this research gap,this paper replicates the working state of FAM under extreme-temperature conditions and investigates the influence mechanism of asphalt types and basalt fiber characteristic parameters on the low-temperature performance of FAM.[Methods]By simulating the low-temperature tolerance of FAM in extremely cold regions of northern China,based on the Thermal Stress Restrained Sample Tests(TSRST),the low-temperature beam bending test,and the freeze-thaw splitting test,the influence mechanism of asphalt type,basalt fiber length,and basalt fiber diameter on the low-temperature performance of FAM is examined.The temperature stress evaluation of constrained specimens adopts the standard EN 12697-46,the initial temperature is 5℃,and the cooling rate is-10℃/h.[Results]The results of TSRST reveal that the four freezing parameters are consistently influenced by the asphalt type and the fiber diameter.The low-temperature performance of SBS asphalt is greater than that of#70 matrix asphalt.Given the same fiber dosage and fiber length,the low-temperature performance of FAM decreases with the increase in diameter.Fiber with a diameter of 7 μm improves the low-temperature performance of AC-13 FAM the most.Fracture temperature and fracture strength decrease stepwise with the increase in diameter.The variance analysis of the TSRST results reveals that asphalt type has the greatest effect on freezing parameters.The results of the low-temperature bending test present that the maximum bending strain of the test group with a fiber length of 6 mm and diameter of 7 μm is the largest.Given the same dosage and diameter,fiber with a length of 6 mm has better low-temperature improvement ability than fiber with lengths of 3 and 12 mm.The results of the freeze-thaw splitting test reveal that the freeze-thaw splitting strength and freeze-thaw splitting strength ratio of the four#70 matrix asphalt mixtures are remarkably lower than those of the SBS asphalt mixture mixed with the same fibers.The performance of#70 asphalt in the freeze-thaw splitting test is not outstanding.The variation rules of fiber parameters and freeze-thaw splitting test results reveal the same rules as the first two low-temperature performance tests.[Conclusions]Two kinds of asphalt and nine kinds of basalt fibers with varied lengths and diameters are chosen to examine the effect of asphalt types and characteristic parameters of basalt fibers on the low-temperature performance of FAM.Three low-temperature performance tests can mirror the low-temperature crack resistance performance of FAM.Compared with the low-temperature beam bending test and the freeze-thaw splitting test,the TSRST test and the four frozen parameters can more precisely display the low-temperature crack resistance performance of FAM under severe conditions.The use of SBS can immensely enhance the low-temperature tolerance of FAM under extreme temperatures.The low-temperature performance of basalt FAM is greatly related to asphalt types,fiber diameters,and fiber lengths.The enhancement of the low-temperature performance of FAM with three lengths of 3,6,and 9 mm fibers reveals a trend of first rising and then falling.The low-temperature performance of FAM with basalt fiber diameters of 7,16,and 25 μm decreases slowly.Among the 14 groups of FAM evaluated,basalt fiber with a length of 6 mm and diameter of 7 μm achieves the best effect in improving the low-temperature performance of FAM.The results can serve as an experimental reference for the application of basalt fibers in extremely cold areas and can be used as a teaching case in the field of civil engineering graduate courses,concentrating on the distinctive design requirements of road engineering in highly cold areas.
pavement engineeringextremely cold regionasphalt mixturebasalt fiberthermal stress restrained sample test
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