The Influence of Water Glass on the Technological Parameters of Shotcreteby Walter Lukas, Innsbruck Univ, Innsbruck, Austria,
Wolfgang Kusterle, Innsbruck Univ, Innsbruck, Austria,
Abstract: Shotcrete used in tunneling must follow a clearly defined early strength development in order to comply with stresses from rock deformations and drilling and blasting. Accelerators are used to achieve the required early strength results. However accelerators affect many concrete properties negatively at a later stage. This negative affect of accelerated concrete compared to unaccelerated concrete should be as low as possible if shotcrete is used as a temporary or permanent structural element. The shotcrete testing facility of the Institute for Building Materials and Materials Testing was used to investigate the influence of accelerators based on Aluminates and Sodium Silicate (Water glass) or dry and wet shotcrete. Compressive strength, E-modul as well as shrinkage and creep were monitored for up to a year. Samples were subjected to water and air curing. Bond strength was tested after 28 days. Results showed the negative effect of more than 10% sodium silicate dosage on many concrete properties. Compressive strength and E-modul are lower compared to unaccelerated concrete. Shrinkage and creep results are higher. Air curing showed a very negative effect. Shotcrete subjected to these conditions is not suitable for temporary or permanent support.
Subject Headings: Shotcrete | Material tests | Glass | Compressive strength | Construction materials | Tunneling
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