A lightweight fiber-based approach to reduce the risk of concrete detachment in shotcrete fortified tunnels

摘要

Concrete detachments in shotcrete-fortified tunnels are a hazard to workers and users that can be reduced by changing density, residual load and bond strength. A factorial experimental design was carried out in the laboratory to assess the influence of lightweight aggregates (LWAs), polypropylene fibers (PF) and nano silica (NS) in the mixture performance. Results indicate that 6 kg/m(3) of PF increase residual loads up to 2.93 MPa, 70% of LWA reduced density below 1,600 kg/m(3) with structural compressive strength above 22.5 MPa. The safest mixtures had fibers to withhold the unbonded shotcrete piece and LWA to reduce the detachment and impact energy involved. (C) 2020 Elsevier Ltd. All rights reserved.