集料复配情况下沥青混合料小梁弯曲试验研究

Study on the beam bending test of asphalt mixture composed by mixed aggregates with different densities

为考察不同来源集料进行配合比设计时,由于密度差异导致的矿料级配组成与设计级配组成不一致对混合料性能的影响,首先提出了完整的密度修正办法,用于不同密度集料混掺使用时采用修正质量称量以确保设计体积百分比符合要求.然后,以UTM小梁低温弯曲试验对密度修正过程进行了验证,考察了集料密度修正、粉胶比、不同集料来源、轮碾次数和加载速率对小梁弯拉应变的影响.结果表明:混合料集料复配时若不进行密度影响修正,则会改变混合料中矿料的体积百分率,尤其是填料的百分比,继而影响粉胶比和混合料低温性能.进行密度修正后,质量称量在保证达到设计体积百分率的情况下,集料岩性不影响混合料低温性能.粗级配相较中值级配和细级配,具有良好的低温性能.压实次数能较大程度影响混合料的抗弯拉变形能力.加载速率能极大影响测试弯拉应变值,试验时须谨慎设定.

The actual volume gradation was deviate from the target volume gradation due to density difference between the aggregates composing the asphalt mixture.In order to investigate its influence on the performance of asphalt mixture,the revised method for the gradation design was proposed firstly to assure the target volume gradation by the revised mass weighing method.Then,the universal testing machine（UTM）was adopted to verify the revising process by the beam bending test（BBT）.The aggregates density difference,ratio of filler/bitumen（F/B）,different aggregate lithology,compaction number and loading rate of BBT were all evaluated to give the following results.The density difference should not be neglected for it will affect the ratio of filler in the mixture,especially the ratio of F/B and followed by low temperature performance of mixture.The aggregate lithology will not affect the low temperature performance of mixture if the density difference is taken into consideration to assure the target volume gradation.Compared to the medium and fine gradation,coarse gradation possesses better low temperature performance.Compaction number could affect the mixture bending ability to a large extent.Loading rate of BBT could greatly influence the bending strain,which should be set up carefully.