ABSTRACT
Toughness is one of the most critical parameters for the use of fibre-reinforced shotcrete in underground support applications since it represents the ability of the shotcrete to sustain loads after cracking. In this study, the age-dependent toughness of macro-synthetic and steel fibre-reinforced shotcrete was characterized according toASTM C1550-02. ASTM C1550-02 round determinate panels were prepared using alkalifree accelerated sprayed concrete and tested at early and late ages ranging from 1 to 180 days. The age-dependent strength of the panels was determined from in-situ core compressive strength tests from 1 to 91 days. Strength development profiles from 15 MPa to 65 MPa were studied. Energy absorption as a function of panel deflection and time of testing, which is representative of the strength development, is presented for the different fibre types and fibre properties. In the case of steel fibres, an age-dependent peak in the energy absorption capacity is observed for high panel deflections. This behaviour is not observed for the synthetic fibres. Characteristics of the mix design relating to these observations are briefly discussed.
