The Effect of Sodium Silicate on the Behaviour of Shotcretes for Tunnel Lining
Luigi Coppola
DISA, University of Bergamo, Dalmine (BG), Italy.
Alessandra Buoso
DISA, University of Bergamo, Dalmine (BG), Italy.
Denny Coffetti
DISA, University of Bergamo, Dalmine (BG), Italy.
Patricia Kara *
EMIB, Faculty of Applied Engineering, University of Antwerp, Belgium.
Sergio Lorenzi
DISA, University of Bergamo, Dalmine (BG), Italy.
Franco D’Alessandro
BASF C.C. Underground Construction, Treviso (TV), Italy.
*Author to whom correspondence should be addressed.
Abstract
Present case study investigates the rheological, mechanical and in-placing performances of fiber-reinforced shotcrete manufactured with different fibers (steel, glass and polypropylene) and with sodium silicate based set-accelerating admixture for tunnel linings. The study compares the performances of concretes manufactured and fully compacted with those shotcretes which are manufactured directly on the job-site. The influence of sodium silicate accelerator on mechanical and rheological properties of fiber-reinforced shotcretes with respect to reference concrete were evaluated. It was observed that: The addition of fibers does not influence slump and workability retention with respect to reference concrete, independent of type and dosage of fibers; Spraying and set accelerator dosage determined a decrease about of 10-30% in compressive strength compared to that of concrete placed and vibrated without sodium silicate accelerator; The set-accelerating admixture has negative effect on compressive strength of fiber-reinforced shotcrete (15%).
Keywords: Sodium silicate based set-accelerating admixture, mechanical and rheological properties.