Instandsetzung einer Betonbrücke mit Walzträgern nach dem Prinzip des Kathodischen Korrosionsschutzes

Für die Instandsetzung chloridbelasteter Stahlbetonbauwerke muss bei den so genannten konventionellen Verfahren oftmals Beton in großer Tiefe abgetragen werden. Dies verursacht hohe Kosten, stellt einen erheblichen Eingriff in das Bauwerk dar und führt nicht zuletzt zu Nutzungseinschränkungen während der Instandsetzung. Aus diesem Grund gewinnt der Kathodische Korrosionsschutz (KKS) von Stahl in Beton, eine zum Großteil zerstörungsfreie Instandsetzungsmethode, als wirtschaftliches Instandsetzungsverfahren korrosionsgefährdeter bzw.‐geschädigter Bauteile zunehmend an Bedeutung. Nachfolgend wird die Instandsetzung der Brücke über den Auer Mühlbach in München mit KKS beschrieben. Das Tragsystem der Auer Mühlbachbrücke besteht aus einbetonierten Walzträgern, die mit diskreten Einzelanoden geschützt wurden. Auf Grund der sehr hohen Überschüttung und der verkehrlichen Bedeutung dieser Brücke war der KKS besonders vorteilhaft anwendbar, da es während der gesamten Instandsetzung keinerlei Einschränkungen des Verkehrs gab. Repair of a Concrete‐Bridge with Rolled Section Beams applying the Principle of Cathodic Protection When repairing reinforced concrete structures containing chlorides by conventional methods, it is often necessary to remove the concrete to great depths. This causes high costs and leads to a significant intervention of the structure, combined with a limitation of use whilst repair measures. This is the reason why Cathodic Protection (CP) of reinforcement in concrete is gaining importance as predominantly non‐destructive, costeffective repair measure of structures susceptible to or damaged by corrosion. Consecutively the repair measure of the bridge over the Auer Mühlbach in Munich using CP is described. The load bearing system of the bridge of Auer Mühlbach consists of rolled section steel beams, which are protected using discrete anodes. Due to the high ground cover and the high importance to the intra‐urban traffic, the application of CP was in particular advantageously as the traffic has not been limited whilst the repair measure.     

Climate-change impacts on hydrology and nutrients in a Danish lowland river basin

The Mike 11-TRANS modelling system was applied to the lowland Gjern river basin in Denmark to assess climate-change impacts on hydrology and nitrogen retention processes in watercourses, lakes and riparian wetlands. Nutrient losses from land to surface waters were assessed using statistical models incorporating the effect of changed hydrology. Climate-change was predicted by the ECHAM4/OPYC General Circulation Model (IPCC A2 scenario) dynamically downscaled by the Danish HIRHAM regional climate model (25 km grid) for two time slices: 1961-1990 (control) and 2071-2100 (scenario). HIRHAM predicts an increase in mean annual precipitation of 47 mm (5%) and an increase in mean annual air temperature of 3.2 degrees C (43%). The HIRHAM predictions were used as external forcings to the rainfall-runoff model NAM, which was set up and run for 6 subcatchments within and for the entire, Gjern river basin. Mean annual runoff from the river basin increases 27 mm (7.5%, p<0.05) when comparing the scenario to the control. Larger changes, however, were found regarding the extremes; runoff during the wettest year in the 30-year period increased by 58 mm (12.3%). The seasonal pattern is expected to change with significantly higher runoff during winter. Summer runoff is expected to increase in predominantly groundwater fed streams and decrease in streams with a low base-flow index. The modelled change in the seasonal hydrological pattern is most pronounced in first- or second-order streams draining loamy catchments, which currently have a low base-flow during the summer period. Reductions of 40-70% in summer runoff are predicted for this stream type. A statistical nutrient loss model was developed for simulating the impact of changed hydrology on diffuse nutrient losses (i.e. losses from land to surface waters) and applied to the river basin. The simulated mean annual changes in TN loads in a loamy and a sandy subcatchment were, respectively, +2.3 kg N ha(-1) (8.5%) and +1.6 kg N ha(-1) (6.9%). The rainfall-runoff model and the nutrient loss model were chained with Mike 11-TRANS to simulate the combined effects of climate-change on hydrology, nutrient losses and nitrogen retention processes at the scale of the river basin. The mean annual TN export from the river basin increased from the control to the scenario period by 7.7%. Even though an increase in nitrogen retention in the river system of 4.2% was simulated in the scenario period, an increased in-stream TN export resulted because of the simulated increase in the diffuse TN transfer from the land to the surface-waters.     

Flächendatenbank für die hydrogeologische Karte im bayerischen Bodeninformationssystem

The hydrogeological survey of Bavaria has recently been intensified in order to produce a countrywide hydrogeological map at the scale of 1:50,000 by 2015. The spatial data will be seamfree, reflect the 3D-character of hydrogeological maps and comprehensive search functions will be available for the whole dataset. A spatial database was designed which incorporates the complex relations of rock and groundwater bodies. The underlying relational data model integrates the following main object types: propagation of the upper aquifers and surface layers, rock bodies, structural surfaces together with point data and fault lines, groundwater bodies as well as groundwater surfaces together with point data and the distribution of different types of groundwater potential. The database was developed as an ArcGISextension using the Geodatabase as a relational database. The application of this system supports the mapping process and guarantees a consistent data structure. After integration into the Bavarian Soil Information System, the hydrogeological spatial data will be available for the users in a searchable format.     

Towards a rapid, non-contact shaping method for fibre metal laminates using a laser source

Since their initial development, fibre metal laminates (FMLs) have slowly started to be used by industry, particularly the aerospace sector. One of the reasons for the relatively slow adoption of FMLs is due to the difficulties faced in shaping them to the desired geometry. Whilst traditional processes such as roll forming are effective in shaping monolithic materials, these processes could potentially destroy the mechanical properties of the composite layer. The approached investigated here uses thermal or laser forming (LF) to shape flat panels of thermosetting glass fibre based FMLs into 2D geometries. This initial empirical investigation covers the effectiveness of the various LF processes and the effects of various parameters have on the forming process. These include laser parameters such as power and velocity and material parameters such as FML lay-up strategy, fibre orientation and comparison with monolithic materials.     

Surface nano-aggregation and photocatalytic activity of TiO2 on H-type activated carbons

The main objective of this work is to detect any associative or synergistic effects between TiO₂ and activated carbon in 4-chlorophenol photodegradation. Different activated carbons (AC) were prepared from Tabebuia pentaphyla wood by means of physical activation with CO₂ or by extensive carbonization under N₂ flow at temperatures from 450 °C up to 1000 °C during 1 h. Results indicate a clear correlation between photocatalytic activities of titania with texture and surface chemistry of AC. Kinetic results of 4-chlorophenol photodegradation indicate that for most of mixed TiO₂ and AC solids a synergistic effect between both solids is observed. Surface nano-aggregation of TiO₂ on AC was observed by scanning electronic microscopy and dispersion of TiO₂ nanoparticles was improved as a function of more basic surface pH of AC. In conclusion, an increase of electronic density in carbon support clearly introduces an enhancement in titania's photoactivity for 4CP photodegradation. This beneficial effect indicates that it is possible to obtain clean water in a much shorter period of time by employing some selected AC in conjunction with TiO₂.     

Trail-Following Pheromones in Basal Termites, with Special Reference to Mastotermes darwiniensis

In the framework of an evolutionary study, trail pheromones have been studied in the most basal extant termite, Mastotermes darwiniensis (Mastotermitidae), and two other basal termites, the Termopsidae Porotermes adamsoni (Porotermitinae) and Stolotermes victoriensis (Stolotermitinae). Although workers of M. darwiniensis do not walk in single file while exploring a new environment under experimental conditions and are unable to follow artificial trails in ‘open field’ experiments, they do secrete a trail-following pheromone from their sternal glands. This unique behavior might reflect a primitive function of communication of the sternal gland. The major component of the pheromone appears to be the same in the three basal species: the norsesquiterpene alcohol (E)-2,6,10-trimethyl-5,9-undecadien-1-ol. This represents a new chemical category of trail-following pheromones for termites. The quantity of pheromone was estimated as 20 pg/individual in M. darwiniensis, 700 pg/individual in P. adamsoni, and 4 pg/individual in S. victoriensis. The activity threshold was 1 ng/cm in M. darwiniensis and 10 pg/cm in P. adamsoni. In M. darwiniensis, the trail pheromone was secreted by sternal gland 4 and to a lesser degree by sternal gland 3, sternal gland 5 being almost inactive. This study highlighted phylogenetic relationships between the Mastotermitidae and two subfamilies of the Termopsidae, the Porotermitinae and the Stolotermitinae. Furthermore, it indicated a heterogeneity within the Termopsidae, with Porotermitinae and Stolotermitinae on one hand, and Termopsinae on the other. Finally, Mastotermitidae and Termopsidae, with C14 trail pheromones, are clearly separated from the Kalotermitidae, Rhinotermitidae, and Termitidae that secrete C12 or C20 trail pheromones.     

The stability of refractory oxides in sodium-rich environments

The infiltration of molten electrolyte and sodium is known to deteriorate the refractory in aluminum electrolysis. The mineralogical changes due to reactions with molten fluorides have previously been described throughly, while the effect of sodium has not been considered in detail. This paper presents an experimental study of the chemical stability of some refractory materials in sodium-rich environments. The materials were exposed to sodium vapor at 800°C for 4 hours. The mineralogical transformations and deterioration of the materials due to reactions with sodium were analyzed by x-ray diffraction and optical and electron microscopy.     

Soft-Chemistry Synthesis, Characterization, and Stabilization of CGO/Al2O3/Pt Nanostructured Composite Powders

Soft-chemistry routes were used to synthesize Ce_0.9Gd_0.1O_1.95-based powders with attractive and stable structural, morphological, and textural properties. In the intermediate temperature range between 500° and 700°C, the average Gd-doped CeO₂ (CGO) crystallite size is in the range 9–22 nm and the specific surface area varies from 43.4 to 8 m²/g. Above 700°C, a phase separation occurs between ceria and gadolinium oxide. Addition of alumina was found to be useful in stabilizing the CGO nanocrystallites at a high temperature and to avoid phase separation. A homogeneous dispersion of Pt nanoparticles (<10 nm at 1000°C) in the CGO materials was found to be possible by post-impregnation, although direct insertion of the Pt precursors during the synthesis led to aggregated particles, with less potential for catalytic applications.     

Dynamic mechanical properties and morphology of high‐density polyethylene/CaCO3 blends with and without an impact modifier

Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the relaxations and crystallization of high‐density polyethylene (HDPE) reinforced with calcium carbonate (CaCO₃) particles and an elastomer. Five series of blends were designed and manufactured, including one series of binary blends composed of HDPE and amino acid treated CaCO₃ and four series of ternary blends composed of HDPE, treated or untreated CaCO₃, and a polyolefin elastomer [poly(ethylene‐co‐octene) (POE)] grafted with maleic anhydride. The analysis of the tan δ diagrams indicated that the ternary blends exhibited phase separation. The modulus increased significantly with the CaCO₃ content, and the glass‐transition temperature of POE was the leading parameter that controlled the mechanical properties of the ternary blends. The dynamic mechanical properties and crystallization of the blends were controlled by the synergistic effect of CaCO₃ and maleic anhydride grafted POE, which was favored by the core–shell structure of the inclusions. The treatment of the CaCO₃ filler had little influence on the mechanical properties and morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3907–3914, 2007