n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - The effect of material composition on the properties of dry shotcrete : technical paper

Volume 46, Issue 2
  • ISSN : 1021-2019



The rebound of dry shotcrete mixes can be a large 'add-on' cost in construction projects and it is in the interest of the contractor and the owner to keep these costs to a minimum. The type and nature of materials used are important factors affecting the rebound. Two types of aggregate (natural river sand and crushed aggregate) as well as partial replacement of Portland cement with silica fume and fly ash have been investigated. The same amount of steel fibres was added to all mixtures so that the ductility properties of shotcrete could be evaluated. Laboratory trails were undertaken to determine the influence of materials on the rebound and the mechanical properties of shotcrete. This study was expanded to assess the cost implication of using the above materials. Shotcrete manufactured using natural river sand and plain cement was used as reference. Results indicate that substantial reductions in the rebound and cost can be obtained when using crushed aggregate, with greater reductions being experienced when a combination of 8 % silica fume and 15 % fly ash is used as cement replacement. This seems to be a solution to the problem of obtaining sand for shotcrete in regions where natural sand are either not available in sufficient quantities or are of unsuitable quality.

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