Corrosion of reinforcing steel in concrete structures causes concrete cracking, steel diameter reduction and eventually loss of safety. In infrastructure this is mainly due to penetration of chloride ions from de-icing or marine salts. Conventional repair means heavy, labour intensive and costly work and economic pressures (time and money) work against the required quality level. Consequently, conventional repair is short lived in many cases in practice. Corrosion reappears quickly and the structure needs to be repaired again after a relatively short time, further increasing life-cycle cost. A completely different situation applies to cathodic protection (CP) of steel in concrete as a repair method. Cathodic protection of reinforcing steel has been applied successfully to concrete structures with corrosion damage for more than 25 years. This paper reports on past experience and presents a model for predicting life cycle costs for maintaining CP systems. Results will be presented from an inventory of CP systems in The Netherlands installed between 1987 and 2009 on about 150 structures, for which performance and maintenance data are reported. The large majority provides corrosion protection for a long time. Degradation of components and overall systems seems to occur in limited numbers. Failure of components and total systems as a function of age is quantified. On the average, the time until minor repairs of parts is necessary is about 15 years. Global failure of the anode, which necessitates near complete replacement of the system, is rare. Based on the statistical analysis of field data, the cost of maintaining a CP system is predicted using a life cycle cost model.

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In order to be able to improve concrete modelling based on its constituent, more knowledge is needed about the material behaviour of these constituents. In this research the focus is on the behaviour of hardening concrete, therefore the properties of hardening cement are of most relevance. Information about cement paste behaviour can be used as input for computer models that are able to represent concrete as a heterogeneous material. During the development of these models the output has to be verified with data from actual concrete. In order to be able to perform measurements on autogenous deformation of cement paste a new test setup was developed. The design is based on the Temperature Stress Testing Machine (TSTM), a setup used for experiments on autogenous deformation in concrete. A device available at the Microlab, called the mini tensile testing machine served as a basis to create the mini-TSTM. The device can either measure the free deformations of cement paste or it can measure the build up of stress in the paste if these deformations are restrained. This part of the research is described in [2]. For the modelling of the heterogeneous material the Delft Lattice Model is used. This is based on a lattice of beams to which different material properties can be assigned. The measured paste deformations from the mini-TSTM are imposed on this lattice as a load. The development of the stiffness (Young's modulus) of the cement paste is taken from Hymostruc, a computer model that determines properties of hardening cement. The material properties of the other concrete constituents, in this case the aggregates, are based on assumptions. The properties and the displacements of the cement develop over time, therefore this model runs a calculation for every time step. With the model simulations of free shrinkage and restrained shrinkage tests on concrete are simulated and the results are compared with the experimental outcome. Qualitatively the results look promising. More tests and simulations are needed to exactly define all the relevant parameters in the model.