Recycling of FRP wind blade waste material in concrete

英国在风能领域的投资增加将导致风力涡轮机制造的激增。由于疲劳限制，纤维增强聚合物（FRP）风力涡轮机的设计寿命约为20年，预计到2050年海上风力发电场将产生大量建筑垃圾。FRP的再利用策略，如热解，侧重于纤维的保留，由于材料[2]的高价值，对碳特别感兴趣。然而，这些方法能耗更大，而且往往会导致纤维的损坏和降解。机械回收和使用FRP材料替代骨料或混凝土中的纤维增强是另一种方法（下循环）[3]。再生FRP （FRPcrete）混凝土的机械性能取决于FRP针的长径比，低长径比导致压缩和拉伸性能[3]的显著下降，而高长径比导致优异的拉伸性能[4]。然而，当在混凝土结构构件中使用密集钢筋笼时，高长宽比的FRP针会导致结块和混凝土多孔。纤维在FRP针中的排列对FRP混凝土的拉伸性能起着重要的作用，而拉伸的再生FRP棒通过裂缝桥接效应产生更高的韧性。然而，在FRP叶片中，纤维取向在同一层压板内（通过厚度变化）和叶片上发生变化。尽管大多数玻璃钢叶片由玻璃纤维增强聚合物（gfrp）制成，但在回收过程中也可以发现碳纤维增强聚合物（CFRP）层压板阻碍了标准化。为了使FRP混凝土具有可靠的力学性能，需要解决的其他关键方面是GFRP在混凝土碱性环境中的耐久性以及影响混凝土破坏过程的FRP针和水泥基体之间界面过渡区（ITZ）的结构完整性。该项目的目的是评估考虑不同变量（例如FRP针的优化几何形状和骨料替代率）的结构应用中FRP混凝土的短期和长期机械性能。实验和数值工作将使用验证和集成设计方法进行。最终目标是开发出能够有效利用FRP风叶片废料的混凝土。1)考虑到制造限制（钢筋、混凝土离析和FRP针团聚），找到FRP针的最佳几何形状（长宽比）和骨料替代率。2)寻找FRP针的最佳表面变形（如喷砂和沟槽），以增加FRP/混凝土界面处的粘结。3)建立一个分析模型来预测FRP混凝土的力学性能，考虑FRP针几何形状、纤维取向、纤维类型（碳和玻璃）和骨料替代率的变化。4)通过进行渗透性和力学试验来评估frp混凝土的长期性能。5)研究大型梁的尺寸效应和受力性能

The increased UK investments in the wind energy sector will result in an upsurge in the fabrication of wind turbines. Fibre Reinforced Polymer (FRP) wind turbines have a design life of approximately 20 years due to fatigue limitations [1] and a high volume of construction waste is expected from the offshore wind farms by 2050. FRP reuse strategies, such as the pyrolysis, focus on fibre retention with a particular interest in carbon due to the high value of the material [2]. Yet, these methods are more energy intensive and can often lead to damage and degradation of the fibres [2]. Mechanical recycling and use of FRP material as aggregate replacement or fibre reinforcement in concrete is an alternative method (downcycling) [3]. The mechanical properties of concrete with recycled FRP (FRPcrete) depends on the aspect ratio of the FRP needles with low aspect ratios leading to considerable decrease in both compressive and tensile properties [3] and high aspect ratios resulting in superior tensile performance [4]. However, high aspect ratios of FRP needles can lead to agglomeration and porous concrete when a dense steel reinforcement cage is used on site in concrete structural elements. Fibre alignment in FRP needles plays a significant role in the tensile performance of FRPcrete and pultruded recycled FRP rods result in higher toughness via the crack bridging effect [4]. However, in FRP blades the fibre orientation changes within the same laminate (through thickness variation) and across the blade. Despite the majority of FRP blades being made of Glass Fibre Reinforced Polymers (GFRPs), Carbon Fibre Reinforced Polymer (CFRP) laminates can also be found inhibiting standardisation in the recycling process. To provide FRPcrete with reliable mechanical performance, other key aspects that need to be addressed are the durability of GFRP within the concrete alkaline environment and the structural integrity of the interfacial transition zone (ITZ) between the FRP needle and cement matrix that affects the concrete failure process. The aim of the project is to assess both the short-term and long-term mechanical performance of FRPcrete for structural applications considering different variables (e.g. optimised geometry of FRP needles and aggregate replacement ratio). Both experimental and numerical work will be conducted using a validation and integration design approach. The end goal is to develop concrete that can effectively take advantage of the FRP wind blade waste.Objectives1) Find the optimum geometry (aspect ratio) of FRP needles and aggregate replacement ratio considering manufacturing limitations (steel reinforcement, concrete segregation and FRP needles agglomeration).2) Find the optimum surface deformation of FRP needles (e.g. sand blasting and grooves) to increase the bond at the FRP/concrete interface.3) Build an analytical model to predict the mechanical performance of FRPcrete considering variations in FRP needle geometry, fibre orientation, type of fibre (carbon and glass) and aggregate replacement ratio.4) Assess the long-term performance of FRPcrete by conducting both permeability and mechanical tests.5) Address size effects and the mechanical performance of large-scale beams