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Mechanical Properties and Comprehensive Assessment of RAP-ECC Materials
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摘要: 为提高工程水泥基复合材料（ECC）的力学性能及环保可持续性，将沥青混合料回收料（RAP）碾碎成粉粒状和细砂，完全替代硅砂，掺入ECC制备了RAP-ECC材料。为获得RAP-ECC材料的力学性能、应变硬化和断裂特性、微观结构及可持续性，首先开展了不同RAP掺量（0%、25%、50%、60%、100%）下RAP-ECC单轴拉伸、压缩及四点弯曲试验，其次开展了最优配合比下RAP-ECC的三点弯曲和单裂缝拉伸试验，利用扫描电子显微镜对RAP-ECC拉伸破坏试件的断口进行纤维破坏情况，骨料/基体界面过渡区（ITZ）的微观结构分析，最后综合材料力学性能、隐含碳排放及经济性建立了RAP-ECC的综合评价指标。结果表明：RAP-ECC单轴拉伸后具有显著的应变硬化和多微裂缝特征，RAP的掺入提高了ECC的抗拉/压/弯强度，RAP-50%的初裂应变是ECC的1.3倍，抗拉强度为其1.32倍，极限应变达4.68%，且RAP-50%薄板的抗弯强度约为ECC薄板的1.38倍，RAP-60%的平均抗压强度约为ECC抗压强度的1.25倍，但RAP的掺入降低了其极限拉应变，RAP-50%的极限拉应变最大且与RAP-0%相近；计算得到ECC与RAP-50%的伪应变硬化指数分别为12.00和14.02，均大于2.7；RAP-50%的综合评价指标值最大，相较ECC提高了74.3%，说明其综合性能最优。Abstract: To enhance the mechanical properties and environmental sustainability of ECC， the reclaimed asphalt pavement （RAP） was crushed into powder and fine sand to fully replace silica sand in engineered cementitious composites （ECC）， developing RAP-ECC materials. To investigate the mechanical properties， strain hardening and fracture characteristics， microstructure， and sustainability of RAP-ECC， this study first measured the asphalt content in RAP using centrifugal separation. Uniaxial tensile， compressive， and four-point bending tests were conducted on RAP-ECC with different RAP incorporation ratios （0%， 25%， 50%， 60%， 100%）. Subsequently， three-point bending and single-crack tensile tests were performed on the optimal RAP-ECC mix. Furthermore， scanning electron microscopy was used to analyze the fiber failure conditions and the microstructure of the interfacial transition zone （ITZ） between the aggregate and matrix in the fractured tensile specimens of RAP-ECC. Finally， a comprehensive evaluation index for RAP-ECC was established by integrating mechanical properties， embodied carbon emissions， and economic efficiency. The results indicate that after uniaxial tension， RAP-ECC exhibited significant strain hardening and multiple microcrack characteristics. The incorporation of RAP improved the tensile， compressive， and flexural strengths of ECC. The first crack strain of RAP-50% was 1.3 times that of ECC， its tensile strength was 1.32 times higher， and its ultimate strain reached 4.68%. Additionally， the flexural strength of RAP-50% thin plates was 1.38 times that of ECC thin plates. The average compressive strength of RAP-60% was approximately 1.25 times that of ECC. However， the incorporation of RAP reduced the ultimate tensile strain， with RAP-50% exhibiting the maximum ultimate tensile strain， which was similar to that of ECC. The calculated PSH values for ECC and RAP-50% were 12.00 and 14.02， respectively， which are greater than 2.7. RAP-50% had the highest value of comprehensive evaluation indicators， which was 74.3% higher than that of ECC， indicating its optimal comprehensive performance.
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