Strength, ductility and stiffness of fibre-reinforced shotcrete

Abstract

In mining flexible linings are preferred because large displacements of underground openings are often allowed. This often results in extensive cracking of the shotcrete. Therefore, ductility of shotcrete is very important. In an investigation comprising 45 beam tests and 33 panel tests, Young's modulus, residual flexural strength and absorbed energy were determined for shotcrete reinforced by polypropylene fibres, steel fibres and steel mesh. The residual flexural strength was determined as the average strength over the displacement range 0–4 mm. Beams reinforced with steel fibres had higher residual flexural strength than beams reinforced with polypropylene fibres or steel mesh. The shotcrete reinforced with steel fibres and the best polypropylene fibres had almost the same energy absorption in the panel tests (0–25 mm displacement range) as well as in the beam tests (0–20 mm displacement range). Young's modulus of reinforced shotcrete determined by beam tests was lower than that derived from compression tests of cast concrete