The main focus of the Action is centred in the production of innovative recommendations/guidelines that pave the way for the next generation of construction codes for service life of CBM and structures. This will take advantage of recent research developments, with the clear goal of placing Europe in the leading position on standards for CBM construction, which is a fundamental factor to improve Europe's competitiveness.
The strategy to achieve the goals of the Action is considered to be a comprehensive one, by creating the necessary conditions for integrative research work involving both experimental and numerical simulation (analytical) approaches. Furthermore, it will focus on the synthesis and systematization of knowledge so as to create sets of rules and recommendations that are both advanced, yet feasible to implement in standards. This comprehensive approach is bound to create synergies and opportunities that would not be brought about otherwise. Even though all the institutions involved are adequately equipped with the tools for the experiments and simulations planned, there are currently no integrative efforts being made in the EU, a gap that will be filled with the present COST Action. In fact, the necessary blending of specialists from both similar fields and complementary fields within CBM science can be assured with the strong and effective networking allowed by Action meetings and workshops, and more importantly by interpenetration on a day-to-day basis through STSM’s.
In regard to the experimental approach, which is dealt with in WG1, a better understanding of the existing experimental methods to characterize CBM properties and their complementary relationships are pursued. The Action will focus on a wide set of properties, encompassing several sets of interest, including fresh properties, chemical properties, thermophysical properties, electrochemical properties, transport properties, mechanical properties (short term and delayed), volume stability and cracking. Special focus will be given to techniques that are non-destructive and allow quasi-continuous property assessment from early ages and throughout service life. This objective will be pursued by all the experimental laboratories involved in the Action because they have equipment and facilities to deal with most or even all of these properties and measurements. It should be noted that apart from equipment that currently match existing standards, the laboratories involved in this COST Action possess self-developed methods for determining several properties, but such methods still require Europe-wide acceptance in order to fully transfer to existing regulations and explore their full market potentials. Therefore, one of the fundamental tools for WG1 will be a round-robin testing program involving distinct centres, which will allow direct intercomparison of experimental methodologies on the same test materials. The round-robin testing will have more than one series throughout the Action, according to the progressive findings that are obtained, and the necessity of deepening insights into unresolved issues. Apart from the mutual validation of experimental techniques and highlighting the validity and added value of newly developed techniques, the workgroup outcomes will also include better understanding of the materials themselves (database of properties). This will offer new opportunities to simulation/predictive models both in terms of validation of modelling assumption/strategies, and opportunities for the validation of simulation results (interaction with WG2 to be presented next). The outcomes of WG1 in terms of newly available techniques and their corresponding practices will also provide direct information for the last workgroup of the Action (WG3), which focuses on drafting recommendations and assist product development towards the market.
In parallel with the experimental works of WG1, synergetic efforts will be made in relation to numerical/analytical simulation approaches to deal with the service life of CBM and structures as part of the scope of WG2. It is reminded that the present Action has a special focus on adequate behavioural prediction from early ages that has been recognized to have significant impact on service life, thus demanding approaches that allow adequate simulations in such initial time span. Therefore, in combination with the development and evaluation of simplified prediction methods feasible for everyday design calculations, sophisticated models for multi-scale and multi-physics simulation of CBM and structures will be deployed, taking advantage of in-house developments of several research institutions involved in the Action. The work of WG2 will be deployed at two different scales: (i) the material scale; (ii) the structural scale. For the material scale, specialized models for micromechanics modelling (multi-scale approaches) will be deployed, targeted to allow the prediction of material properties from information about the mixture components. At the structural scale, macro-scale approaches will be deployed aimed at thermo-hygro-chemo-mechanical modelling of structural behaviour throughout the service life. The necessity of a multi-physics approach to the macro-scale problem is dictated by the necessity of explicitly considering non-uniform distribution of temperature and moisture in CBM structures so as to adequately consider thermal and hygral (shrinkage) stresses that strongly affect service life performance. Apart from the integrative research efforts that the Action will bring about through networking amongst the various members (with distinct models and approaches), the strongest tools of WG2 will be the benchmarking studies. A set of specific simulation case-studies both for material behaviour prediction (micro-scale models) and for structural behaviour prediction (macro-scale models) will be selected for simulation benchmarking. The selection of benchmarking examples will benefit from the material-scale testing made in the scope of WG1, whereas the structural scale case studies will likely be obtained from previous works by team members (involving material characterization and in-situ monitoring), but will preferably profit from specifically devised real scale examples, such as the one studied in the scope of the CEOS project, where restraint to deformation has an important role on the cracking and deformational behaviour. Another truly important target of WG2 is to achieve homogenized understandings on modelling assumptions that can be recommended and adequate selection of modelling parameters (e.g. material properties and boundary condition modelling). The agreement on best-practices for modelling assumptions and parameters will strongly benefit from the benchmarking efforts, and will have strong interaction with the last workgroup of the Action (WG3) that is described below.
The third Workgroup of this Action (WG3) is targeted to “develop recommendations and products”. Based on clarifications of the scientific issues underlying the control of thermal cracking, restrained shrinkage effects, early desiccation, and rebar and fibre influence on these processes (clarifications achieved in the scope of WGs 1 and 2), the aim of this WG is to draw guidelines and establish proposals for improving existing standards with respect to a better combined accounting of imposed/restrained deformations and effects of service loads on the control of effective serviceability and durability of concrete structures. Recommendations and guidelines will be issued, in adequate formats to be proposed for inclusion of adapted provisions especially at the design stage (eventually in Eurocode 2) and in the guidance documents for material specification (eventually EN 206 standard). These recommendations will favour a better anticipation of several critical issues which have too often been addressed only during execution. It is therefore expected to establish strong links with regulating agencies, particularly the European Committee for Normalization (namely through TC250), and the International Federation for Structural Concrete - fib - (namely through TG4.1) which issues the well-known Model Codes for structural design of reinforced concrete.
The workplan of WG3 will also encompass support to the development of new products emanating from the knowledge created in WGs 1 and 2. Together with the accumulated knowledge, and the norm-like recommendations that will be issued, which include both experimental techniques (WG1) and numerical/analytical simulation approaches (WG2), there will be a strong support to the development of new products together with the industry partners (both at the level of experimental equipment and software). The connection of researchers with the reality of product development is therefore another important outcome of WG3, facilitating the penetration of newly developed methods in the market. It is also important to remark the involvement of owners, contractors and other stakeholders of the construction process in WG3, both for assisting product development and drafting and checking of regulations/standards.