【作者】 李斌；

【导师】 刘全涛；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2018， 硕士

【摘要】 沥青是一种粘弹性材料,在荷载间歇期可自动修复其内部的微裂纹,这种自修复性能与温度密切相关,通过提升愈合温度可增强沥青混凝土的裂纹修复能力。利用电磁感应加热提高导电沥青混凝土的愈合温度是一种先进的沥青路面养护方法,但目前缺少关于沥青混凝土电磁感应加热的温度分布及其梯度愈合特性的研究,且沥青混凝土的感应加热速率偏低。针对上述问题,本文研究了钢纤维沥青混凝土电磁感应加热作用下的温度梯度分布特性与梯度愈合规律,并通过钢棉纤维与钢渣复掺显著提升了沥青混凝土的感应加热速率。首先,制备了可被感应加热的钢棉纤维沥青混凝土,通过力学性能确定了钢棉纤维最佳掺量为6%,同时对钢棉纤维沥青混凝土电磁感应加热作用下的温度分布特性进行了研究。结果表明:感应加热下沥青混凝土在纵向上存在明显的温度梯度,加热时间越长、加热距离越近,温度梯度越大;将沥青的软化点温度作为沥青混凝土产生有效愈合的起始温度,并据此测定了感应加热对沥青混凝土产生的有效愈合深度,愈合深度与加热距离和加热时间有关,加热距离越小、加热时间越长,有效愈合深度越大,在加热距离为10mm和20mm时沥青混凝土的有效深度分别为4.7cm和3.8cm(表面温度约100℃)。其次,采用三层小梁试件断裂-感应加热-断裂试验对钢棉纤维沥青混凝土的电磁感应加热愈合特性进行了研究。结果表明:与微波加热相比,在相同的表面温度下电磁感应的温度梯度特性导致其愈合效率偏低;感应加热作用下沥青混凝土在纵向上表现出明显梯度愈合的特性,愈合效率沿纵向递减,感应加热时间越长,试件纵向愈合效率相差越大;缩短加热距离和增加愈合次数(延长愈合时间)均可提高试件的愈合效率。最后,通过钢渣与钢棉纤维复掺制备了快速感应加热沥青混凝土,并对其性能进行了研究。结果表明:复掺钢渣可将钢棉纤维沥青混凝土的感应加热速率提高34%,同时可提高其愈合效率;钢渣降低了混凝土整体的热传导能力,钢棉纤维能增加混凝土的热传导能力;钢棉纤维能够提高水稳定性、高温稳定性、低温抗裂性能,而钢渣降低了水稳定性、增强高温稳定性、对低温抗裂性能影响不大。其他力学性能表明:钢渣和钢棉纤维均能提高沥青混凝土强度,但钢棉纤维增强了混凝土的韧性而钢渣降低了韧性表现为脆性破坏。更多还原

【Abstract】 Asphalt binder is a viscoelastic material and it has a potential to heal the microcracks inside during the rest period.The self healing property of asphalt binder is highly temperature-dependent and increasing the temperature can enhance its self healing ratio.Increasing the temperature through induction heating to enhance the crack healing properties of asphalt concrete is an advanced maintanence method for asphalt pavement.However,the temperature distribution and the gradient healing behavior in vertical direction of asphalt concrete with induction heating have not been fully investigated.The induction heating speed of asphalt concrete needs further improvement.To solve the above problems,this paper investigated the induction heating and gradient healing characteristics of steel fiber asphalt concrete and steel fiber-steel slag composite asphalt concrete was prepared to enhance the induction heating speed.Firstly,basalt asphalt mixture AC-13 was designed,and the optimal steel fiber content 6% was determined according to the mechanical properties of the mixture.After gradation design,the induction heating characteristics of steel fiber asphalt concrete were tested.The Infrared image of the sample after induction heating shows great gradient temperature distribution.Shorter distance and longer heating time results in more remarkable gradient temperature distribution.The softening point of the binder was defined as the effective healing temperature for asphalt cocnrete;the effective healing depth of the sample was deterimined as the depth at which the temperature reached the softening point of the binder.Results showed that shorter heating distance and longer heating time resulted in deeper effective healing.In this paper,the effective depth of the sample at 10 mm and 20 mm heating distance was 4.7cm and 3.8cm respectively when the surface temperature reached 100℃.Secondly,the induction healing characteristics of steel fiber asphalt concrete were studied by three-point bending fracture-healing test on three layered beam samples.Compared with microwave heating,induction heating resulted in lower healing ratio of the sample at the same surface temperature due to the temperature gradient.Asphalt concrete showed gradient healing behavior and the healing efficiency decreased gradually in the longitudinal direction.The healing gradient increased with the increase of the heating time.Shortening the heating distance and increasing the heating times can enhance the healing ratios of the all three layers of the sample.Thirdly,steel slag/steel fiber composite asphalt mixture was designed for high induction heating purpose and its properties were investigated.The results show that steel fiber/steel slag composite can increase the heating speed of the mixtrue by 34% compared with using steel fiber alone.The induction healing efficiency of asphalt concrete is also increased by steel fiber/steel slag composite.Thermal constant tests show that steel fiber can improve the heat conduction properties of asphalt concrete,while steel slag has a negative effect on this property due to small holes inside.Road performance results show that steel fiber can improve the moisture stability,high-temperature anti-rutting performance and low-temperature anti-cracking property of the mixture.While steel slag decreases the moisture stability,improves the high-temperature anti-rutting,but has little influence on low-temperature anti-cracking properties.Both steel fiber and steel slag can improve the strength of the mixture.Steel fiber modified asphalt concrete shows obvious ductility properties,while adding steel slag decreases the ductility of the mixture.更多还原