The Mechanical and Self-Sensing Properties of Carbon Fiber- and Polypropylene Fiber-Reinforced Engineered Cementitious Composites Utilizing Environmentally Friendly Glass Aggregate

In order to facilitate waste glass recycling and enable the monitoring of concrete structures, this study prepares a new type of self-sensing engineered cementitious composite (ECC) via the use of glass sand instead of silica sand. The health monitoring of a concrete structure is achieved through the addition of polypropylene (PP) fibers to enhance the flexural toughness of concrete, and adding carbon fibers (CFs) to make the concrete self aware, enabling it to sense the load changes and structural damage. The fiber dosage of ECC is optimized to analyze the effects of different fiber types and dosages on the mechanical and self-sensing properties of concrete. The results show that the hybrid fibers produce a good synergistic effect on mechanical properties, and the presence of excess fibers causes the mechanical properties of concrete to deteriorate. The critical fiber volume fraction required for the strain hardening of PP ranges from 0.75% vol to 1% vol. At different PP dosages, the CF dosage shows a positive correlation with the initial crack strength. By analyzing the effect of varied curing times and CF doping on the initial resistivity, it is found that the threshold value of CF conductivity is 0.7% vol. The role of CFs in the flexural sensitivity and pressure sensitivity tests is explained from the perspective of fiber distribution, and the fiber distribution theory is verified with scanning electron microscopy (SEM). The optimal level of CF doping for flexural sensitivity and pressure sensitivity is determined to be 1.1% vol and 0.7% vol via the use of self-sensing performance tests, respectively. An increase in PP fiber doping leads to a decrease in the initial resistivity and self-sensing properties of the material. The results of this research provide guidance regarding how to determine the optimal fiber dosage flexibly for different engineering works.

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