Spritzbeton-Technologie ´06

Accelerated cast-in-place concrete as an alternative to sprayed concrete?

Jürg Schlumpf, Sika AG, Tunnelling & Mining, Switzerland

Sprayed concrete differs from cast-in-place concrete by the possibility of accelerating it just on time, either by use of set accelerators or by addition of the water just before application. For cast-in-place concrete either high uncertainty regarding workability life, requiring to allow for longer waiting times before striking, or limited applicability have to be put up with. Thanks to the development of a new system, a combination of equipment and concrete admixture technology, such limits can now be distinctly shifted. Now it is possible to accelerate concrete, presenting highly extended workability life, just before placing it and thus to plan hardening and formwork striking times. This new technology is above all suitable in tunnel construction with long transportation distances or difficult logistics conditions. Thanks to this innovation, the limits between sprayed and casted concrete are considerably shifted!