In-Situ and Laboratory Investigation on Leaching and Effects of Early Curing of Shotcrete

  • 1 KTH Royal Institute of Technology Division of Concrete Structures, , 100 44, Stockholm
  • 2 KTH Royal Institute of Technology Division of Concrete Structures, , 100 44, Stockholm

Abstract

During the construction of a rock tunnel in Stockholm, several sections with leaching shotcrete (sprayed concrete) were found one year after the spraying was completed. An investigation was therefore conducted, and its results are presented in this paper. The amount of leaching after such a short time indicated that a one-sided water pressure existed in combination with a permeable shotcrete. The reason for the water pressure was likely a partly unsuccessful grouting that created sections with leaking water. The permeable shotcrete could be a combined result of insufficient curing and the use of accelerators, and the effect of in-situ curing was therefore investigated. A total of six slabs were sprayed and cured under different conditions in the tunnel. Test results according to standards indicated that curing has no significant effect on the development of mechanical strength or water penetration through the shotcrete. However, this is believed to be a result of the test method rather than the non-existing effect of curing. Lastly, some modifications to the test standard were proposed for future studies of in-situ curing.

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  • 1. Malmgren L, Nordlund E & Rolund S: “Adhesion strength and shrinkage of shotcrete”. Tunnelling and Underground Space Technology, Vol. 20, 2005, pp. 33-48.

  • 2. Ansell A: “Investigation of shrinkage cracking in shotcrete on tunnel drains”. Tunnelling and Underground Space Technology, Vol. 25, 2010, pp. 607-613.

  • 3. Sjölander A & Ansell A: “Numerical simulations of restrained shrinkage cracking in glass fibre reinforced shotcrete slabs”. Advances in Civil Engineering, No. 8987626, 2017.

  • 4. Carlswärd J: “Shrinkage cracking of steel fibre reinforced self-compacting concrete overlays: Test methods and theoretical modelling”. PhD Thesis, Luleå University of Technology, Luleå, Sweden, 2006.

  • 5. Ekström T: “Leaching of concrete: experiments and modelling”. Report, Division of Building Materials, Lund University, Lund, Sweden, 2001.

  • 6. Galan I, Baldermann A, Kusterle W, Dietzel M & Mittermayr F: “Durability of shotcrete for underground support-Review and update”. Construction and Building Material, 202, 2019, pp. 465-493.

  • 7. Neville A M: “Properties of Concrete”. Fifth Edition. Pearson Education Limited. Harlow, England, 2012.

  • 8. Neville A M & Brooks J J: “Concrete Technology”. 2nd edition. Pearson Education Limited, Harlow, England, 2010.

  • 9. Powers T: “A discussion of cement hydration in relation to the curing of concrete”. Proceedings, Highway Research Board, Vol. 27, 1947, pp. 178-188.

  • 10. CEN: “EN 13670: Execution of concrete structures”. Technical report, Brussels, Belgium, 2009.

  • 11. Zhang J, Wang J & Gao Y: “Moisture movement in early-age concrete under cement hydration and environmental drying”. Magazine of Concrete Research, Vol. 68, 2016, pp. 391-408.

  • 12. Eriksson,D: “Numerical models for degradation of concrete in hydraulic structures due to long-term contact with water”. Licentiate Thesis, Div. of Concrete Structures, Dept. of Civil & Architectural Engineering, KTH Royal Institute of Technology, Stockholm, Sweden, 2017.

  • 13. Van Tittelboom K & de Belie N: “Self-healing in cementitious material – A review”. Materials, Vol. 6, 2013, pp. 2182-2217.

  • 14. Nijland T G, Larbi J A, van Hees R P J, Lubelli B & de Rooij M: “Self healing phenomena in concretes and masonory mortars: A microscopic study”. Proceedings, First International Conference on Self-Healing Materials, Noordwijk and Zee, The Netherlands, 2007.

  • 15. Lagerblad B, Fjällberg L & Vogt C: “Shrinkage and durability of shotcrete”. Proceedings, Shotcrete Elements of a System, Queenstown 2010.

  • 16. Trafikverket: “Rules for Tunnel Construction”, TDOK 2016:0231, Trafikverket, Borlänge, Sweden, 2016. (In Swedish).

  • 17. CEN: “EN-1992-1-1: Design of concrete structures - Part 1-1: General rules and rules for buildings”. Technical report, Brussels, Belgium, 2008.

  • 18. Boverket: “BFS 2013:10 EKS 9 – Swedish appendix to Eurocode”, Boverket, Karlskrona, Sweden, 2013. (In Swedish).

  • 19. CEN: “EN-12390-3: Testing hardening concrete - Part 3: Compressive strength of test specimens”. Technical report, Brussels, Belgium, 2009.

  • 20. CEN: “EN 14488-3: Testing sprayed concrete - Part 3: Flexural strengths”. Technical report, Brussels, Belgium, 2006.

  • 21. CEN: EN-12390-8: “Testing hardening concrete - Part 8: Depth of penetration of water under pressure”. Technical report, Brussels, Belgium, 2019.

  • 22. CEN: “EN-14488-4: 2005+A1:2008 Testing sprayed concrete - Part 4: Bond strength of cores by direct tension”. Technical report, Brussels, Belgium, 2008.

  • 23. ASTM: “C1550-2: Standard test method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panels)”. Technical report, American Society for Testing and Materials, USA, 2012.

  • 24. Bryne L E, Ansell A & Holmgren J: “Laboratory testing of early age bond strength of shotcrete on hard rock”. Tunnelling and Underground Space Technology, Vol. 41, 2014, pp. 113-119.

  • 25. Bjureland W, Johansson F, Sjölander A, Spross J & Larsson S: “Probability distribution of shotcrete parameters for reliability-based analyses of rock tunnel support”. Tunneling and Underground Space Technology, Vol. 87, 2019, pp. 15-26.

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