Self-healing Capabilities of Ultra-High Performance Fiber Reinforced Concrete with Recycled Aggregates

This study examines the effect of recycled aggregates on the stimulated autogenous self-healing of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) when exposed to wet and dry conditions. Recycled aggregates have been produced by crushing four months old UHPFRC specimens with an average compressive strength of 150 MPa. Two different percentages (50% & 100% by weight) of recycled aggregate (0–2 mm) have been used as a substitute for the natural aggregate in a reference UHPFRC mix to produce recycled UHPFRC. After an assessment of the overall mechanical properties of the recycled UHPFRC mixes, one year old notched beam specimens were pre-cracked to the width of 150 µm through a three-point flexural test. The self-healing capacity of recycled UHPFRCs has been investigated in terms of water absorption tests, regain in flexural strength and microscopic crack healing, at scheduled times after pre-cracking (0 days, 1 month, 3 months and 6 months). Constant wet/dry healing conditions were maintained throughout the experiment. The specimens with recycled UHPC aggregate showed better and longer self-healing than the specimens with natural aggregate, which provides additional value to the overall environmental sustainability of the investigated category of materials.