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

• Published in: Construction & building materials 2021-02, Vol.270, p.121453, Article 121453
• Main Authors: Ortiz, Camila, Lillo, Patricio, Lopez, Mauricio
• Format: Article
• Language: English
• Subjects: Adherence; Bonding; Lightweight concrete (LWC); Nano silica; Polypropylene fiber (PF); Residual load; Safety; Shotcrete
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2020.121453

•A lightweight fiber-based structural shotcrete was made using expanded glass aggregate (EGA).•70% of EGA reduced density by 30% and yielded compressive strength above 22.5 MPa.•6 kg/m3 of polypropylene fibers increased in the residual load up to 2.9 MPa; the effect was linear.•The proposed safety index was greatly increased with 6 kg/m3 of fibers and 70% of expanded glass LWA. 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/m3 of PF increase residual loads up to 2.93 MPa, 70% of LWA reduced density below 1,600 kg/m3 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.