Energy absorption capacity for fibre reinforced sprayed concrete : effect of panel production technique, fibre content and friction in round panel tests with continuous steel support (Series 8 and 9)

摘要

The test program is part of the on-going revision of The Norwegian Associations publication no. 7 (Sprayed concrete forrock support), which among others is to be harmonized with the new European regulations for determination of energyabsorption capacity of fiber reinforced sprayed concrete.After realising the very significant and varying effect of friction in panel tests with continuous support of wood it wasdecided to concentrate the further investigations on support of steel.The present results show that the average coefficient of variation for the energy absorption capacity (EAC) at 25 mm displacementamong all 6 individual sets in Series 8 was 7.1 % and among the six sets in Series 9 it was 8.7 %.For the parallel sets in Series 8 performed with and without friction-reducing bedding material, the results show that frictionbetween the panel and the supporting ring of steel constitutes 25.7% and 25.0% of what is taken to be energyabsorbed by the panel at final displacement of 25 mm. This is in line with earlier results.The cast panels had on average 90% energy absorption capacity compared to the sprayed panels. Possible influencingparameters are different air content, fibre orientation, compaction and w/c-ratio for cast and sprayed panels. The amountsof data are yet too scarce to draw general conclusions.Series 9 was dominated by the panel fibre contents being strongly overdosed compared to the intended nominal dosagesand, correspondingly, the energy absorption values became high, especially for the steel fibre mixes. The fiber measurementsin fresh concrete differed strongly from the fibre measurements that was done on samples from the panels aftertesting.