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就地冷再生发展中遇到的技术难题
来源:https://www.sddhfjx.com/ 日期:2022-07-25
就地冷再生技术可以利用绝大部分或全部旧沥青层,有效降低环境污染,提升路面施工的经济性,但在诸如施工设备工作参数匹配、骨料粒径的级配控制、旧沥青混合料的沥青性能恢复等关键技术方面,国内还没有专业的科研机构进行深入研究,也没有形成成熟的解决方案,技术应用上还存在着相当大的困难。现阶段,就地冷再生技术存在以下几个方面的问题亟待解决。
In situ cold recycling technology can use most or all of the old asphalt layer to effectively reduce environmental pollution and improve the economy of pavement construction. However, in terms of key technologies such as the matching of working parameters of construction equipment, the grading control of aggregate particle size, and the asphalt performance recovery of old asphalt mixture, there is no professional scientific research institution in China to conduct in-depth research, and no mature solution has been formed, There are still considerable difficulties in the application of technology. At this stage, the following problems need to be solved in the field of cold regeneration technology.
(1)没有充分考虑施工设备机械结构和工作参数对再生效果的影响。目前,国内外大多数就地冷再生设备的再生鼓为联组三角带定速比皮带传动方式,其铣刨刀具的切削线速度为定值。个别小功率再生设备虽然采用变量液压系统驱动,具有再生鼓转速连续可调功能,但与大中型就地冷再生设备一样,都没有真正实现再生鼓工作转速(对应铣刨刀具线速度)与设备行走速度、再生深度的自动匹配。这使得在不同再生深度工况下,设备的行走速度不同,再生鼓对旧沥青路面的切削量也会随之发生变化,从而使再生混合料的粒径和级配处于一种连续的波动变化状态。如果施工过程中没有对各相关参数及时进行控制和调整,在某一工况的某一时段就可能由于工作参数的不匹配,使得再生料粒径规格超出级配设计范围,形成不合格混合料,终影响养护或维修工程的再生质量。
(1) The influence of mechanical structure and working parameters of construction equipment on regeneration effect is not fully considered. At present, the regeneration drum of most in-situ cold regeneration equipment at home and abroad is a combined V-belt constant speed ratio belt transmission mode, and the cutting linear speed of its milling tool is a fixed value. Although some small power regeneration equipment is driven by variable hydraulic system and has the function of continuous adjustable speed of regeneration drum, like large and medium-sized local cold regeneration equipment, it does not really realize the automatic matching between the working speed of regeneration drum (corresponding to the linear speed of milling cutter) and the walking speed and regeneration depth of the equipment. This makes the walking speed of the equipment different under the working conditions of different regeneration depths, and the cutting amount of the regeneration drum on the old asphalt pavement will also change accordingly, so that the particle size and gradation of the recycled mixture are in a continuous fluctuating state. If the relevant parameters are not controlled and adjusted in time during the construction process, the particle size specification of recycled materials may exceed the range of grading design due to the mismatch of working parameters in a certain period of time under a certain working condition, forming unqualified mixtures, which will eventually affect the regeneration quality of maintenance or repair projects.
(2)没有充分考虑工作装置机械结构特性对再生料的拌和均匀性和级配影响。作为铣拌类养护设备中的两款核心机型,沥青路面就地冷再生机和冷铣刨机在技术发展和设备应用方面同根同源,有着相同的技术基础,但却有着不同的发展方向。就地冷再生机的再生工作装置是再生鼓,冷铣刨机的铣刨工作装置是铣刨鼓,二者都是通过转子转动,带动其上面分布的切削刀具对路面进行铣削。但是,就地冷再生考虑更多的是,再生鼓上刀具排布对再生沥青混合料粒径的控制,并保证再生料的充分拌和,还要考虑二次破碎时滚筒外缘与刀具之间所形成空间的合理性,以保证再生料的均匀性和终级配。
(2) The influence of the mechanical structure characteristics of the working device on the mixing uniformity and gradation of recycled materials was not fully considered. As the two core models of milling and mixing maintenance equipment, asphalt pavement in situ cold recycling machine and cold milling machine share the same root and the same technical foundation in terms of technical development and equipment application, but they have different development directions. The regeneration device of the local cold regeneration machine is the regeneration drum, and the milling device of the cold milling machine is the milling drum. Both of them drive the cutting tools distributed on it to mill the road surface through the rotation of the rotor. However, in-situ cold regeneration considers more about the control of the particle size of recycled asphalt mixture by the arrangement of cutters on the regeneration drum and the full mixing of recycled materials. It also considers the rationality of the space formed between the outer edge of the drum and the cutters during secondary crushing, so as to ensure the uniformity and final grading of recycled materials.
(3)没有充分考虑铣刨切削作业及公路自身特性对再生料的拌和均匀性与级配的影响。就地冷再生机在进行沥青层就地再生或稳定层就地再生的施工过程中,由于刀具对原有旧混合料的铣刨破碎作业,部分混合料的骨料粒径破碎变小,同时又有部分再生混合料(包括沥青混凝土混合料)经破碎后粒径满足要求,充当了再生料骨料的角色,再生铣刨物料的级配发生了较大变化;另外,路面前期维修养护时,不同施工期、不同工艺要求修筑的路基或路面(包括沥青路面)性能存在较大的差异,尤其是使用时间较长、病害类型较多或发生多次损坏的公路,在再生过程中,不同的养护作业和施工工艺使得后期路面的各种参数相比原设计参数生产了不同程度的偏离。这些影响再生效果的因素都不可能在就地冷再生施工方案设计中予以充分考虑,并且不会在后期施工过程中全部排除,因而会使再生料的均匀性和级配的性能恢复效果大打折扣。
(3) The influence of milling and cutting operations and highway characteristics on the mixing uniformity and gradation of recycled materials was not fully considered. During the construction process of in-situ regeneration of asphalt layer or in-situ regeneration of stable layer, due to the milling and crushing of the original old mixture by the cutter, the aggregate particle size of some mixtures becomes smaller. At the same time, the particle size of some recycled mixtures (including asphalt concrete mixtures) meets the requirements after crushing, playing the role of recycled aggregate, and the gradation of recycled milled materials has changed greatly; In addition, during the early maintenance of pavement, there are great differences in the performance of subgrade or pavement (including asphalt pavement) built in different construction periods and process requirements, especially for roads that have been used for a long time, have more disease types or have been damaged for many times. During the regeneration process, different maintenance operations and construction processes make various parameters of the later pavement deviate from the original design parameters to varying degrees. These factors that affect the regeneration effect cannot be fully considered in the design of in-situ cold regeneration construction scheme, and will not be completely eliminated in the later construction process, which will greatly reduce the uniformity of recycled materials and the performance recovery effect of grading.
(4)现有就地冷再生技术没有充分考虑恢复和利用旧沥青材料中沥青的性能,影响就地冷再生技术在高速公路及高等级沥青公路养护领域的推广应用。目前的就地冷再生通过将沥青层(全部或部分)材料、基层材料再生料混合作为满足所需承载力的基层材料使用,降低了再生料的使用等级。这些材料虽然具有一定的强度、刚度和水稳性,但由于是将再生料中的旧沥青与旧混合料一起作为骨料使用,没有充分考虑再生混合料中旧沥青的性能恢复,只能在县、乡村道路翻修或国、省道的基层修筑中使用,不能在高等级公路的沥青面层全面推广应用。通过数据对比发现,老化沥青混合料相对性能优良的新沥青结合料,其粘性过高、柔韧性不足等常规路用性能上的不足,严重影响了再生料的全面使用。因此再生沥青混合料的质量与厂拌热再生料和热拌沥青混合料的质量存在一定的差距,不能满足沥青混合料的面层质量标准,基于以上原因,在没有新的技术出现前,冷再生料只能用于柔性基层或半刚性基层的基层和底基层。所以,通过改善再生料中已老化沥青在粘稠性、薄膜粘结力等方面的性能参数,加快对恢复和利用再生沥青混合料中沥青成分方面的研究,恢复其路用性能,是今后就地冷再生技术研究的一个重点。
(4) The existing in-situ cold recycling technology does not fully consider the recovery and utilization of the performance of asphalt in old asphalt materials, which affects the promotion and application of in-situ cold recycling technology in the field of Expressway and high-grade asphalt highway maintenance. The current in-situ cold recycling reduces the use level of recycled materials by mixing asphalt layer (all or part) materials and recycled base materials as base materials to meet the required bearing capacity. Although these materials have certain strength, stiffness and water stability, because the old asphalt in the recycled material is used together with the old mixture as aggregate, the performance recovery of the old asphalt in the recycled mixture is not fully considered, so they can only be used in the renovation of county and rural roads or the base construction of national and provincial roads, and cannot be fully promoted and applied in the asphalt surface course of high-grade highways. Through data comparison, it is found that the new asphalt binder with good relative performance of aging asphalt mixture has deficiencies in conventional road performance such as high viscosity and insufficient flexibility, which seriously affects the comprehensive use of recycled materials. Therefore, there is a certain gap between the quality of recycled asphalt mixture and that of plant mixed hot recycled asphalt mixture and hot mixed asphalt mixture, which cannot meet the surface quality standard of asphalt mixture. Based on the above reasons, before the emergence of new technology, cold recycled asphalt can only be used for the base and subbase of flexible base or semi-rigid base. Therefore, by improving the performance parameters of the aged asphalt in the recycled material in terms of viscosity, film adhesion and so on, accelerating the research on the recovery and utilization of the asphalt components in the recycled asphalt mixture and restoring its road performance is a key point of the research on the in-situ cold recycling technology in the future.
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