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Self-compacting concrete structures in Switzerland
Tunnelling and Underground Space Technology Tunnelling and Underground Space Technology 19 (2004) 480
incorporating Trenchless Technology Research
www.elsevier.com/locate/tust
WTC 2004
Self-compacting concrete structures in Switzerland Ju¨rg Schlumpf
*
Marketing & Technical Department, Tunneling & Mining Division, Sika Schweiz AG, Widen, Switzerland
Self-compacting concrete (SCC) was introduced in Switzerland in 1998, and there are now two main fields of application firmly established where today, in Switzerland, the use of SCC is technically and economically advantageous. One field covers all kinds of rehabilitation work in civil engineering and the other all concreting work where the geometric situation creates difficult conditions for pouring of concrete. In both cases, the increased or high expenditure of work for pouring the concrete into the forms makes the SCC solution economically viable which after all in practice is decisive. The industry moreover offers since sometime ready mixed SCC cements having the potential of extending the economic viability considerations to normal concrete structures. From the point of view of concrete technology, it may be added that the quality of placing clearly outdoes all other influence parameters in importance where concrete durability is concerned and that SCC, if the mix is properly designed is by far superior. Further spreading of SCC applications exclusively depends on its economic positioning as a high price product or a volume application product. The paper presents four examples of applications, satisfying different durability requirements. Concreting of the tunnel under the river Emme (impervious, frost-resistant SCC for the concreting of side walls in a tunnel advanced by cover-and-cut method). Rehabilitation of the Schneich tunnel (freeze–thaw–deicing salt resistant, reduced-shrinkage SCC as facing concrete on tunnel walls). SCC meeting the durability specifications of AlpTransit Gotthard (prequalification tests for sulphate-resistant, impervious SCC meeting the severe requirement of having to remain workable for 6 h at high temperatures). Extension Hotel Crowne-Plaza (economically placed SCC for normal concrete structures). Since self-compacting concrete (SCC) was introduced in Switzerland different projects, in the sectors durable concrete and economically placable concrete, have been executed in the described fields of application rehabilitation of civil engineering structures and concreting work under difficult or labour-intensive placing conditions. It has shown that quality requirements with regard to mechanical properties, impermeability, frost resistance and, with higher expenditure, freeze-thaw- deicing salt resistance, can be met. Concrete mixes for SCC require a higher content of fines, leading to max. 20% increase of shrinkage, if due care is taken when designing the mix. This increases the risk of crack formation. As a result of the higher fines content the elastic modulus is about 20% lower so that, in comparison with conventional concrete, ductility is better, which again has a positive influence on cracking behaviour. The applications presented here prove the suitability of SCC also for durable concrete structures. Wider spreading of this technology primarily depends on development of materials prices, on innovative solutions such as compounded SCC cements, on marketing efforts and on the trust placed on SCC technology. Keywords: SCC; Self compacting concrete; Gotthard base tunnel; Durability of SCC; Prequalification Alp transit Gotthard; Slump flow
*
Tel.: +41-56-649-3440; fax: +41-56-649-3400. E-mail address: [email protected] (J. Schlumpf).
doi:10.1016/j.tust.2004.02.080
incorporating Trenchless Technology Research
www.elsevier.com/locate/tust
WTC 2004
Self-compacting concrete structures in Switzerland Ju¨rg Schlumpf
*
Marketing & Technical Department, Tunneling & Mining Division, Sika Schweiz AG, Widen, Switzerland
Self-compacting concrete (SCC) was introduced in Switzerland in 1998, and there are now two main fields of application firmly established where today, in Switzerland, the use of SCC is technically and economically advantageous. One field covers all kinds of rehabilitation work in civil engineering and the other all concreting work where the geometric situation creates difficult conditions for pouring of concrete. In both cases, the increased or high expenditure of work for pouring the concrete into the forms makes the SCC solution economically viable which after all in practice is decisive. The industry moreover offers since sometime ready mixed SCC cements having the potential of extending the economic viability considerations to normal concrete structures. From the point of view of concrete technology, it may be added that the quality of placing clearly outdoes all other influence parameters in importance where concrete durability is concerned and that SCC, if the mix is properly designed is by far superior. Further spreading of SCC applications exclusively depends on its economic positioning as a high price product or a volume application product. The paper presents four examples of applications, satisfying different durability requirements. Concreting of the tunnel under the river Emme (impervious, frost-resistant SCC for the concreting of side walls in a tunnel advanced by cover-and-cut method). Rehabilitation of the Schneich tunnel (freeze–thaw–deicing salt resistant, reduced-shrinkage SCC as facing concrete on tunnel walls). SCC meeting the durability specifications of AlpTransit Gotthard (prequalification tests for sulphate-resistant, impervious SCC meeting the severe requirement of having to remain workable for 6 h at high temperatures). Extension Hotel Crowne-Plaza (economically placed SCC for normal concrete structures). Since self-compacting concrete (SCC) was introduced in Switzerland different projects, in the sectors durable concrete and economically placable concrete, have been executed in the described fields of application rehabilitation of civil engineering structures and concreting work under difficult or labour-intensive placing conditions. It has shown that quality requirements with regard to mechanical properties, impermeability, frost resistance and, with higher expenditure, freeze-thaw- deicing salt resistance, can be met. Concrete mixes for SCC require a higher content of fines, leading to max. 20% increase of shrinkage, if due care is taken when designing the mix. This increases the risk of crack formation. As a result of the higher fines content the elastic modulus is about 20% lower so that, in comparison with conventional concrete, ductility is better, which again has a positive influence on cracking behaviour. The applications presented here prove the suitability of SCC also for durable concrete structures. Wider spreading of this technology primarily depends on development of materials prices, on innovative solutions such as compounded SCC cements, on marketing efforts and on the trust placed on SCC technology. Keywords: SCC; Self compacting concrete; Gotthard base tunnel; Durability of SCC; Prequalification Alp transit Gotthard; Slump flow
*
Tel.: +41-56-649-3440; fax: +41-56-649-3400. E-mail address: [email protected] (J. Schlumpf).
doi:10.1016/j.tust.2004.02.080