Under contract with the research and development branch of the alberta transportation department, the university of calgary began work to assess the first-crack strength and toughness parameters of concrete and shotcrete to which steel and polypropylene fibers had been added. Laboratory tests employed concrete typical of that normally specified for bridge deck overlays and shotcrete typical of that used for repairing deteriorated portions of supporting bridge structures. To these mixtures were added various types and sizes of steel and polypropylene fibers; silica fume was also included in a few fiber-matrix combinations. Laboratory results showed first-crack strengths from 5.0 To 6.4 MPa for matrixes without silica fume and from 7.9 To 8.6 MPa for those with silica fume. Longer high-aspect-ratio fibers suitable for conventionally mixed overlays produced material with elastic-plastic performance and toughness index (i sub 10) about 10, residual strength factor (R sub 5, 10) about 100. Combinations with other high-aspect-ratio fibers yielded lower levels of performance, as did those with the shorter low-aspect-ratio fibers needed for shotcrete. Based on these laboratory findings, 26 bridge decks were restored with steel fiber reinforced concrete overlays and structural repairs were made to the beams, piers, or abutments of 19 bridges using steel fiber reinforced, dry-process shotcrete.
Samenvatting