Influence of Confinement Pressure on the Development of Three Stage Curve for Bituminous Mixtures

摘要

As part of the mechanistic-empirical pavementrndesign procedure, the flow number test is used to rank thernbituminous mixtures for rutting. In the flow number test, arnsample is subjected to 0.1 s of loading followed by 0.9 srnrest period and a haversine load waveform is used. This testrnprotocol has serious limitation and these are due to thernloading conditions applied and the post-processing procedurernfollowed for flow number determination. In thisrninvestigation, three changes were made in the existing flowrnnumber protocol. The first one was in the load waveform.rnA trapezoidal waveform was used instead of the haversinernload waveform. The second change was related to loadingrnconditions. Different combinations of confinement andrndeviatoric loading were applied and the final choice wasrnmade based on the resulting three stage creep curve. Thernthird change was related to post-processing method and arnFrancken model to capture the complete three stages ofrndeformation was used. A BC mix with mid-gradation followingrnMoRTH (Specifications for roads and bridge works.rnIndian Roads Congress, New Delhi 2013) guidelines wasrnused with VG30 and CRMB60 binder. PReSBOX shearrncompactor was used for making cylindrical samples ofrn94 mm diameter and 150 mm height. The samples wererncast with a target air voids of 6 %. All the testing wasrncarried out at 50 and 60 u0003C. Different confinement conditionsrnranging from 50 to 200 kPa were used with therndeviatoric loading ranging from 200 to 600 kPa. Therninfluence of modified binder was clearly seen in therndevelopment of three stage curve. The collected data wasrnpost-processed using Francken model and the flow numberrnwas determined. This flow number was bench marked withrnthe existing flow number protocol and it was seen that therernwere gross discrepancies.