Dear reader we were discussing about steel fiber reinforced shotcrete (SFRS) especially its rebound performance. We know coarse particles rebound more and in case of SFRS steel fibers rebounds more than any other aggregates of shotcrete materials.
So in a hardened concrete surface we will have richer concrete than that is batched. ‘Rich concrete’ term is used in respect of cement content but the dose of fiber becomes less in hardened surface than expected in batching.
That is the purposes of introduction of fibers are not served. Again we will be billed for total amount of concrete materials and fibers too. Thus our exception will be lowest possible rebound.
Rebound, as expressed as percentage, depends on many parameters. The factors those are important-
- Parameters of concrete pump
- Distance of nozzle
- Spraying angle
- And most important is skill of nozzzlemen
- Method of shotcreting
Again fiber size and shape have influence on rebound and direction of shotcreting has also influence. Say
- More rebound in shotcreting to overhead than shotcreting in horizontal direction
- Regarding shape, flat ended fibers have less rebound than other shape
- Regarding size, very light and very fine fibers have more rebound than heavier fibers.
An overall reduction in rebound can be achieved by using micro-silica in concrete mix both of fibers and aggregates. This also reduces dust during shotcreting.