基于环形加载试验的稳定型橡胶沥青热再生混合料抗裂性能研究

Study on Crack Resistance of Stable Asphalt Rubber Hot-recycled Mixture Based on Annulus Loading Test

为改善厂拌热再生沥青路面材料的抗裂性能,将新型稳定型橡胶沥青应用于厂拌热再生技术当中,设计并制备了热再生沥青混合料EME-20。同时,为优化混合料抗裂性能评价方法,设计开发了环形加载试验,基于70#道路石油沥青制备的AC-20混合料确定了最佳试验参数,并提出了极限荷载Fmax、破坏变形δFmax、劲度指数IRT及断裂能W等评价指标。结合环形加载与小梁弯曲试验,对不同旧料掺量的橡胶沥青再生混合料开展了抗裂性能对比研究。结果表明:依托UTM-25试验平台,在10℃、5 mm/min加载条件下能够稳定、完整地检测环形加载试验过程中的荷载-变形曲线,从而准确反映混合料的抗裂性能;随着橡胶沥青混合料中旧料掺量的提高,环形加载试验极限荷载Fmax及劲度指数IRT逐渐增大,破坏变形δFmax及断裂能W逐步降低,说明旧料的掺加使得橡胶沥青混合料的强度和模量提高,但抗变形能力和综合抗裂性能有所下降;稳定型橡胶沥青再生混合料的低温抗裂性能良好,当旧料掺量低于20%时极限弯曲应变达3000με以上,即使在50%的旧料高掺量下极限弯曲应变仍大于2500με;基于环形加载试验获得的检测结果与小梁弯曲试验结果相关性良好(R2>0.9),对再生沥青混合料抗裂性能的评价有较好的可靠性。

In order to improve the crack resistance of hot in-plant recycled asphalt pavement materials,the newly developed stable asphalt rubber is applied to hot in-plant recycling technology,and hot-recycled asphalt mixture EME-20 is designed and prepared.The annulus loading test is designed and developed to optimize the evaluation method of crack resistance of mixture,the best test parameters are determined based on the AC-20 mixture prepared from road petroleum asphalt No.70,and the evaluation indicators,including ultimate load Fmax,failure deformationδFmax,stiffness index IRT and fracture energy W,are proposed.Combining with annulus loading test and beam bending test,the crack resistances of hot in-plant mixture with different RAP contents regenerated by stable asphalt rubber are compared and analyzed.The result shows that(1)Relying on the UTM-25 test platform,the force-displacement curves can be stably and completely detected under 10℃and 5 mm/min loading conditions during the annulus loading test,thus the crack resistance of the mixture can be accurately reflected.(2)with the increase of RAP contents in the asphalt rubber mixture,the ultimate load Fmax and tensile stiffness index IRT increase gradually,and the fracture displacementδFmax and the fracture energy W gradually decrease in the test,which indicates that the addition of RAP improves the strength and the modulus of rubber asphalt mixture,but reduces the deformation resistance and the comprehensive crack resistance.(3)The low temperature crack resistance of recycled mixture modified by stable asphalt rubber is good.When RAP content remains below 20%,the ultimate flexural strain reaches 3000με,and the ultimate flexural strain still remains above 2500μεeven at 50%of the RAP content.(4)The test result of annulus loading test shows good correlation with the beam bending test(R2>0.9),it has good reliability for evaluating the crack resistance of recycled asphalt mixture.