Preparation And Properties Of High Performance Asphalt Crack Filling Material

Crack is one of major disasters of asphalt pavement. Crack has effect on suitability and safty of driving and water on the surface may infiltrate into roadbase through the cracks, which greatly weakens the strength and stability of the road, and will cause the asphalt pavement suffer more severe damage. At present, polymer modified asphalt and polymer modified asphalt emulsion are widely used as the crack filling materials (CFM). However, most of the CFMs show low adhesive strength, poor low temperature flexibility and durability. The stripping of the CFM from cracks often occurs, when the pavements shrinkage under low temperature conditions, which leads to the formation of new cracks. In order to overcome shortcomings of currently existing CFMs, the SBS modified crack filling materials with good performance were prepared by means of grafting modification of SBS and organo-montmorillonite (OMMT) in this paper. The results of this paper are as follows:1. Methyl methacrylate grafted SBS (MMA-g-SBS)> acrylic acid grafted SBS () and maleic anhydride grafted SBS (MAH-g-SBS) with different grafting degree (GD) were prepared by solution graft polymerization. The GD of grafted SBS modifiers were investigated by means of chemical analysis and the structure of the grafted SBS modifiers were characterized by Fourier transform infrared spectroscopy (FTIR). CFMs were prepared by asphalt and MMA-g-SBS, AA-g-SBS and MAH-g-SBS, respectively. The effects of GD on physical properties, microstructure, mechanical properties and ageing resistance properties of CFM with grafted SBS modifiers were studied. The results showed that, with the increase of GD of grafted SBS, the ductility and elastic recovery of all CFM with grafted SBS modifiers obviously enhanced. The softening point, viscosity and penetration of MAH-g-SBS modified asphalt CFM also increased, but the softening point and viscosity of MMA-g-SBS and AA-g-SBS modified asphalt CFMs decreased slightly. Mechanical properties testing showed that the adhesive strength of all CFM with grafted SBS modifiers was greatly enhanced due to the grafting of MMA, AA and MAH to SBS. Meanwhile, the tensile strength, elongation at break and flexibility at low temperatures of the CFM were also improved to some extent.2. The ageing resistance properties of the grafted SBS modified asphalt CFM were evaluated by the long-term heat ageing, thin film oven test (TFOT), the pressure ageing vessel (PAV) and long-term ultraviolet(LTUV) ageing. The results showed that the thermo-oxidative ageing of SBS modified asphalt CFM was delayed remarkably after MMA, AA and MAH grafted to SBS, which means that the ageing resistance properties of grafted SBS modified asphalt CFMs were improved obviously. The improvement of grafted SBS modified asphalt CFM in ageing resistance can be attributed to the grafted structure of SBS. During the grafted process, the MMA, AA and MAH monomers are easily reacted with C=C double bonds functional group in SBS, accompanied by the formation of graft copolymer, that leads to the decrease of C=C double bonds, and finally reducing the heat degradation of SBS molecular chains. However, compared with the MMA-g-SBS and AA-g-SBS CFM, the MAH-g-SBS modified asphalt CFM exhibits better aging resistance properties. This is because MAH was grafted to SBS by single molecule grafted way during the grafted process. Under the conditions of same grafting degree, the numbers of C=C double bonds of MAH-g-SBS are less than that of the MMA-g-SBS and AA-g-SBS. So it exhibits the best aging resistance properties.3. The effects of antioxidant, UV absorber and organo-montmorillonite (OMMT) on the thermal-oxidative ageing of MAH-g-SBS modified asphalt CFM were investigated. The results showed that the aging resistance properties of MAH-g-SBS modified asphalt CFM were enhanced to some degree by introduction of a small amount of antioxidant and UV absorber. Compared with the antioxidant and UV absorber, the OMMT displays better improving effectiveness for aging resistance of MAH-g-SBS modified asphalt CFM. It can be attributed to form of exfoliated structures in OMMT/MAH-g-SBS modified asphalt CFM, and the silicate layer of OMMT which uniformly dispersed among asphalt at nanometer-scale can efficiently prevent permeation or pervasion of oxygen in the CFM Therefore, the attacking of the oxygen to SBS and asphalt molecular chains is restricted evidently, and the aging resistance properties of OMMT/MAH-g-SBS modified asphalt CFM are improved significantly.4. XRD analysis indicated that the interlayer spacing of OMMT in SBS modified asphalt crack filling materials was widened and an exfoliated structure was formed, which can obstruct oxygen penetrating into material. The improvement of aging resistance of OMMT/SBS modified asphalt crack filling materials can be abscribed to the barrier of peeled OMMT layer to penetration of oxygen.5. On the basis of reviewing foreign test regulations and domestic test methods, the performance of OMMT/MAH-g-SBS modified asphalt CFM was tested. All the results suggested that the OMMT/MAH-g-SBS modified asphalt CFM exhibited good low temperature flexibility and aging resistance properties.