Fabrication and Mechanism of the Action of Polyurea Formaldehy de-Bio-oil Microcapsules
To investigate the healing effect of microcapsules on microcracks in asphalt pavements,microcapsules were first prepared by in-situ polymerization from polyurea formaldehyde(as microcapsule wall)and bio-oil(as microcapsule heart).The appearance morphology and thermal stability of the microcapsules were investigated by scanning/transmission electron microscopy and thermo gravi-metric analysis.Subsequently,these microcapsules were incorporated into styrene-butadiene-styrene(SBS)modified asphalt to create microcapsule/SBS-modified asphalt,and the effect of microcapsules on the performance of the composite modified asphalt pavement was investigated by dynamic shear rheometry and segregation tests.Finally,the healing effect of microcapsules was verified by ductility healing rate test and the healing mechanism was analyzed by a combination of macro and micro tests.The results show that the micro-capsules exhibit a quasi-spherical shape with a relatively rough surface,increasing the contact area with asphalt.In addition,the mi-crocapsules have better thermal stability and their microcapsules wall can withstand the high temperature environment during the asphalt mixture production.With the addition of microcapsules,the low temperature plasticity and heat resistance of the composite modified as-phalt are both improved.In addition,the storage modulus and loss modulus of the composite modified asphalt are also improved,i.e.,the incorporation of microcapsules enhance the viscoelastic properties of SBS modified asphalt,which can be attributed to the good com-patibility of the added microcapsules with SBS and base asphalt.The microcapsules are uniformly dispersed within the asphalt and em-bedded in the network structure presented by SBS,which is confirmed in the segregation tests and fluorescence microscopy test.The highest healing rate of the composite modified asphalt is achieved when the content of microcapsules is 0.4％.
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