Test of concrete durability - Zeebrugge port, Dornoch Bridge

Test of concrete durability - Zeebrugge port, Dornoch Bridge

           Due to limited space, human conditions, concrete durability test are completed in the laboratory and laboratory tests are ideal conditions of test, although with a test strip

            It is easy to control and has the advantages of fast test speed, but it is usually very different from the actual service environment of the engineering structure, and it is generally short term test or accelerated test. For chloride ion erosion, the   Only focusing on the capillary adsorption, diffusion, infiltration in a certain way, can not fully reflect the natural environment in the life cycle of the concrete structure of the durability of changes in recent years, more and more people  more emphasis on long-term field trials.Schueremans for a long time in the observation experiment in northwestern Belgium near Beihai port of zeebrugge. In order to improve the durability of the quay wall, local authorities decided in 1993 after its completion. With a permeable coating surface treatment, the general situation of the quay wall as shown in Figure 4.28

           Engineering uses does not contain solvent isobutyl triethoxy silane, according to the laboratory test, first determine the infiltration type paint spraying amount for 300g/m it. To avoid a possible sea water erosion, quay wall after stripping in concrete surface is dry before should be should be first surface treatment; in concrete form removal after 7 days after the second surface treatment, in order to increase the depth of penetration of the silane. Researchers respectively in the spot and in 2005 to the wharf of drill core sampling analysis, taken from the quay walls in the five core samples were: 1 tidal zone not by surface treatment of core samples; 2 tidal zone in the upper not by surface treatment of core samples; 3 tidal zone after surface treatment of core samples; 4 tidal zone in the upper after surface treatment of core sample; 5 quay wall surface cores treated.

           According to the Belgian standard NBN B15-250 (1990) and chloride ion distribution in core sections in the field of core sample. Only chloride ions in water soluble chloride ion. Therefore, the chloride ion is measured in two parts, free chloride ion and chloride ion in Friedcl salt. The measured results are shown in figure 4.29~4.33, the average value obtained by chemical titration analysis.

          The tidal zone in the smaller discreteness in chlorine ion content, and tidal zone in the upper chlorine ion content of discrete greatly, which is mainly due to tidal zone in the upper algae, splashing water, salt crystallization, carbonation environment exposure conditions of the difference of the concrete subjected to chloride ion erosion of the uncertainty becomes large, as can be seen from the figure. It is obvious that the chloride ion content of the untreated concrete is higher in the tidal zone due to the barrier of the barrier. At the outer surface of 2.2%, at the depth of 95mm is 0.9% (as a percentage of cement quality), and after surface treatment with silane content of chloride ion in concrete is much lower at the outer surface to the depth of 1.2%.95mm 0.03%. on the surface of the quay wall is only affected by chloride ion erosion of sea fog, less content of chlorine ion, while the detection in 1998 and 2005, at tidal zone by surface treatment of concrete in chloride concentration from the surface location of 15mm is still high, and without surface treatment of chloride ion concentration in concrete values, results from the 2005 test, in a deeper position (25mm) to detect the concentration of chloride ion and the 1996 results are basically the same. Shows that the chloride concentration and initial concentration of chloride ions is still.

      Schueremans calculated the mean and variance of chloride diffusion coefficients (table 4.1) according to the relevant data in the field test, and the reliability method was used to predict the service life of the terminal. The failure probability is 0.5, 0.15 and 1.5 (the corresponding target reliability index is 0, 1 and 0.07 respectively). The failure probability is 0.5, and the 0.15 is the failure probability of the ISO2394 to the normal use limit state. The critical concentration of chloride ions is 0.7% of the quality of cement. The thickness of the reinforcement of the protection layer is 120mm, the concentration of chloride ion in the reinforced surface exceeds the critical concentration of chloride ion, and the calculated service life is shown in table 4.1. It can be seen that, in the case of the main factors of structural damage, the surface treatment of permeable coating can greatly improve the service life of the concrete structure. Of course, to achieve the prediction of service life, not completely collapsed structure failure, but the concrete in the steel surface chloride concentration of more than 0.7%, steel corrosion as the end of the life of the structure.

             Nanukuttan located in the north-east of Scotland Dornoch bridge in the vicinity of the 7 years exposure test, test of the pier as shown in Figure 4.34, which part of the pier use permeable coating surface treatment, some not. It is found that the chloride content of concrete is similar to that of the untreated concrete bridge piers (see Figure 4.35 and 4.36). Analysis of the reasons, first of all, the ebb and flow of water level change is 2m, concrete surface pressure head greater penetration of type surface treatment of capillary absorption effect is large, but of chloride ions by diffusion, osmosis effect is not large; secondly the experiment coagulation of water to binder ratio is 0.4, concrete density, resistance to chloride ion erosion is strong (by determination of the chloride ion diffusion coefficient is less than 4x10- negative 32m L / s) and penetration type coating is difficult to glue to relatively small penetration of concrete, so the resistance to chloride ion erosion of increase inconspicuously.