Project: New High Tech Shotcrete (High strength, deformability and waterproof)_x000D_

Tunnels constitute an essential link in modern communication networks; but the construction of increasingly long and deeply located tunnels requires overcoming the problems resulting from low-quality ground sections, and structural repair works of existing tunnels keeping gage. It is in many sections that support elements have to face very large strains that may lie somewhere between 5% and 10%._x000D__x000D_Shotcrete, the most commonly used support element in conventional tunnel construction methods, is noted for its unconfined compressive strength of 35 MPa and for a failure strain of 1%._x000D__x000D_Since the maximum strain that shotcrete can tolerate is much below that of low-quality grounds, its use in sections with major strains raises serious problems, essentially bearing on delays in the construction and the corresponding extra costs._x000D__x000D_Concerning the above mentioned problems, the concept being raised in this research is that of finding a shotcrete with greater strength, larger strain ability and higher impermeability than those currently available. This process will provide a new tool to achieve the current durability requirements of 100 years. _x000D__x000D_In order to achieve this, the following objectives should be met:_x000D__x000D_- Development and formulation of a new prototype of concrete admixture (nanotechnology based) for a new polymeric shotcrete, which makes possible to obtain high compressive strength (50/60 MPa), failure strain (10%) and high impermeability (9 bar)._x000D_- Formulation and dosification of new shotcrete in order to reach uniaxial compressive strength of at least 50/60 MPa, failure strain of 10% and water resistance at 9 bar._x000D_- Establishment of a new industrial process that, in addition to the usual shotcrete dosage, will allow the industrial development of a high-strength, large-strain (i.e. more ductile) ability and ultra high impermeability type of shotcrete._x000D_- Formulation and implementation of a constitutive model that may adequately predict the mechanical performance of the new shotcrete in order to perform the dimensioning calculations with the right precision._x000D_- Development of the innovative real scale test protocols for validation of the new shotcrete process._x000D_- Development of a new tool as independent instrument (Software prototype) for the determination of the quality of the final shotcrete (user-friendly computer program)._x000D_- Implementation of a new tool for special tunnel repair works keeping gage._x000D__x000D_The shotcrete market in Europe is near to 950.000 cubic meters/year, 410.000 cubic meters/year corresponding to underground infrastructures, and 80.000 cubic meters/year corresponding to repair works of existing tunnel infrastructures._x000D__x000D_The consortium formed for this research project has three Ps:_x000D__x000D_- Geocontrol (Spain): a leading Spanish engineering company,_x000D_- Sika (Spain): probably the best admixtures manufacturer._x000D_- GIG (Poland): one of the best research institutes of underground works._x000D__x000D_Geocontrol will be assisted by one subcontractor,Santa Barbara Foundation, with probably the most important experimental tunnels in Europe._x000D__x000D_The consortium intends to introduce this new high tech shotcrete in a maximum of two years time since the end of the project (July 2016).

Acronym NANOSHOTCRETE (Reference Number: 6317)
Duration 01/07/2011 - 30/06/2014
Project Topic Tunnels are an essential link in modern communications networks; but the construction has problems with the ground support and specially in tunnel repair work._x000D_The goal is to find a shotcrete with greater strengths, larger strain ability and high impermeability than those currently available.
Project Results
(after finalisation)
The nanoshotcrete (NS) project has achieved two comercial products, but has CO results of the project we can talk about: the product, the calculation system and the validation._x000D__x000D_Product._x000D__x000D_The new admixture “SikaPlast® NS-2” and “SikaTell NS-1” are an evolution of “SikaPlas®t NS-1”, improving its performance in E-modulus, adherence and waterproofing properties, to obtain a high tech shotcrete with better properties and execution COly in these aspects. There are necessary two products to obtain these improved performance in E-modulus._x000D__x000D_The new “SikaPlast® NS-2” is based on an ultimate Sika polymer, less sensitive to different SikaPlast different cements, COly blended cements, and more compatible with silica and nanosilica. Sika is continuously developing new polymers. Since the year 2000, when first Viscocrete superplasticizer was developed, more than 50 different polymers have been created with very diverse applications._x000D__x000D_Polymer of “SikaPlast® NS-2” is a high range water reducer for applications which require excellent workability in combination with high water reduction in concrete. “SikaPlast® NS-2” is a superplasticizer with high robustness and high compatibility with other admixtures and accelerators._x000D_Combined high water reduction with excellent workability or slump life are indispensable for a concrete with the requirements of this high technology shotcrete. _x000D__x000D_All new SikaPlast® products are designed to have an excellent workability and pumpability. The improvement in pumpability reduces the pump pressure and decreases energy consumption. “SikaPlast® NS-2” is a new technology of high range water reducing admixture for this application. The aim of this product line, SikaPlast® Powered by Viscocrete, is a competitive application with a robust fresh concrete behaviour._x000D__x000D_Calculation system_x000D__x000D_In order to calculate the adequate primary support lining for a tunnel, it is important to take into consideration the requirements that this structure will need for its proper operability. It is important to now the natural conditions of the terrain in order to adapt the tunnel’s requirements, therefore we expose the following methodology related to this process._x000D__x000D_Shotcrete designs. It must be stated that a very important aspect in the design of the lining, is the durability of a concrete structure must be able to withstand, over its lifetime, for which it has been designed, the physical and chemical conditions to which it is exposed, and that could eventually lead to its degradation as a result of the different loads effects and stresses considered in the structural analysis. A durable structure must be achieved with a strategy to consider all possible degradation factors and act accordingly on each of the design phases, implementation and use of the structure_x000D__x000D_Validation_x000D__x000D_The first step in a validation criterion approach is the identification of general performance requirements from the industrial point of view. It is clear that all the new high tech shotcrete materials (lining solution in general) must be accepted by the customers._x000D_But also the following validations hace been perfomed:_x000D__x000D_Validation for the new high tech shotcrete Constituents. _x000D_Validation for the new high tech shotcrete Mix (projected)._x000D_Validation for the new high tech chemical Admixture._x000D_Standards applied for the Demonstration._x000D_Validation, conformity and control of Dry process Shotcrete results._x000D_Validation, conformity and control of Wet process Shotcrete results._x000D_
Network Eurostars
Call Eurostars Cut-Off 6

Project partner

Number Name Role Country
3 Geocontrol S.A. Coordinator Spain
3 Glówny Instytut Górnictwa (Central Mining Institute) Partner Poland
3 Sika S.A.U. Spain Partner Spain