| Insufficient anti-sliding performance of asphalt pavement is one of the main distresses affecting traffic safety.This paper proposed a new preventive maintenance: Thin Friction Course(TFC).The TFC is mixed with single particle size basalt aggregate ranging from 3 to 5mm,asphalt emulsion and Portland cement.Then the well mixed mixture is paved on the original pavement at atmospheric temperature.In this paper,the raveling resistance of TFC was studied.Firstly,the effects of curing conditions,emulsion types,and cement amounts on the development of the TFC strength were analyzed.On this basis,the suitable curing scheme was determined.Then,the effects of design parameters,including emulsion,SBR latex,cement dosages,on the raveling resistance of TFC,especially moisture-induced and freeze-thawing raveling resistance,were studied by using the wet track abrasion test(WTAT).It is confirmed that the bonding strength between asphalt and aggregate consists of the adhesion of asphalt-aggregate and the cohesion inside asphalt bulk.Therefore,the binder bond strength(BBS)test was selected to evaluate the adhesion strength of asphalt-aggregate specimens under different test conditions,such as immersion and freeze-thawing conditions.Furthermore,the effects of SBR and cement dosages on the adhesion strength were studied.Meanwhile,the strain sweep test was used to evaluate the effects of SBR and cement dosages on the cohesion strength of emulsion residue.Finally,the interlayer pull-off test and direct shear test were used to analyze the influences of TFC design parameters,tack coat dosages and environmental conditions on the bonding strength between the TFC and the original pavements.According to the results,the curing conditions have significant influence on the TFC strength development and the suitable curing scheme is determined as curing at 60? for 24 hours.The emulsion dosage is confirmed as the most significant factor affecting the raveling resistance of the TFC specimens,including the early,moisture-induced and freeze-thaw raveling resistance.Specimens with high emulsion dosages demonstrate low aggregate loss and stable raveling performance.When the emulsion dosage increases to 14%,the raveling performance tends to be stable.Similarly,the increase of cement amount has a continuous improvement of TFC moisture-induced raveling resistance.However,the increase of cement amount can lower the TFC aggregate loss at the initial freeze-thawing cycles and increase the sensitivity of the raveling performance.When the freeze-thawing cycles are more than 5 cycles,the effect of cement amount on the freeze-thawing raveling resistance is diminished.In addition,the increase of SBR dosage can slightly improve the raveling resistance of TFC.With the increase of SBR dosage,the sensitivity of TFC raveling resistance under immersion and freeze-thawing conditions decreases.However,when the SBR dosage is 9%,the pull-off strength measured in BBS test is inferior to other specimens with low SBR dosage.On the other hand,the increase of cement amount will enhance the pull-off strength.Therefore,the BBS test may be inappropriate to evaluate the effect of cement on the adhesion strength of emulsion residue-cement mastic and aggregate.Furthermore,the addition of SBR and cement can enhance the stiffness of emulsion residue-cement mastic.What's more,the addition of SBR can improve the deformability of emulsion residue,while the addition of cement will worsen the deformation ability of emulsion residue-cement mastic.According to the correlation analysis,the correlation between the moisture-induced raveling resistance of TFC and the maximum shear stress of asphalt cohesive property is the best,with a correlation coefficient of 0.88.However,the correlations between TFC freeze-thawing raveling resistance and adhesive and cohesive parameters are poor,with the correlation coefficients less than 0.6.It indicates that the moisture-induced raveling of TFC is mainly attributed to the cohesive failure under water immersion conditions.In addition,the increase of the tack coat dosage can significantly improve the interlayer bonding strength and shear strength of the TFC and the underlayer.When the amount of tack coat emulsion is 0.6-0.8kg per square meter,the interlayer bonding performance reaches is the best.The effects of TFC emulsion,cement,and SBR latex dosages on the interlayer bonding performance is not significant.In this paper,the raveling resistance of TFC mixture was firstly studied.Then the adhesion and cohesion strength were further evaluated.On this basis,the correlation between adhesion and cohesion strength with the raveling resistance of TFC was analyzed. |
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