Untersuchungen zu Herstellungs‐ und Instandhaltungs kosten von unterschiedlichen Konzepten zur Sicherstellung der Dauerhaftigkeit von Parkbauten

Research of production and maintenance costs for alternative concepts to ensure the durability of parking buildings There is currently an intense discussion about how to ensure the durability of parking buildings. Without having carried out a comprehensive cost analysis for the alternatives for durability concepts costs are nevertheless used as an argument for or against a certain execution. In this publication the costs of various execution concepts are compared on the basis of a virtual two‐storey underground garage with standard dimensions for the two major components of ”suspended ceiling“ and ”baseplate“. For instance the cost analysis includes the production costs for the minimum reinforcement in dependence of the examined surface protection or of the waterproofing system respectively. Furthermore the costs for maintenance, inspection and repair among other aspects are compared in dependence of the surface protecting system for a service life of 50 years. This cost approach takes into account consists of market fluctuations as well as scheduled maintenance cycles by considering medium, minimum and maximum costs. For the suspended ceiling the following coating or waterproofing systems respectively are examined: surface protection system ”OS 11“; ”mastic asphalt (single/double layer) with asphalt sheeting ”; ”mastic asphalt (single/double layer) with surface protection systems OS 10“ and ”PMMA“ protecting surface system. For the base plate two load cases are investigated: ”water exchange zone“ (WW) and ”water pressure“ (WD) in combination with the following surface protection systems: ”OS 11“, ”mastic asphalt (single/double layer) with asphalt sheeting“ and ”OS 8 with accompanying crack treatment“. For the ongoing maintenance costs, engineering values are chosen in accordance to the current state of knowledge. It is expected that current research projects are going to provide scientific results in the near future allowing an update of this cost analysis.     

在役钢筋混凝土变电构架耐久性的研究和分析

对处于不同环境下的变电站在役钢筋混凝土构架进行了氯离子含量检测,分析了侵蚀深度与氯离子含量的关系及环境因素对氯离子侵蚀的影响,根据检测结果对在役钢筋混凝土变电构架进行了耐久性寿命评估,评估结果与现场调查结果较为一致。     

Fenton degradation of 4-chlorophenol contaminated water promoted by solar irradiation

The degradation of 4-chlorophenol (4-CP) contaminated water by Fenton process with or without solar irradiation assistance were investigated. It was found that the COD degradation and mineralization efficiency of 4-CP were more than 90% when a 30 min treatment of solar photo-Fenton oxidation process was applied and under an optimum [H₂O₂]₀/[Fe²⁺]₀ ratio of 40, the COD degradation and mineralization efficiency increased 65% as compared to Fenton oxidation. Meanwhile, the AOS values increased from −0.33 to 2.13 in solar photo-Fenton process while no significant improvement for AOS values was found in Fenton process, implying a higher degree of oxidation for 4-CP in solar photo-Fenton process. In addition, increasing the intensity of solar irradiation seemed to be beneficial for treatment of 4-CP contaminated water. Formation of chloride ion as a result of mineralization of organically bounded chlorine was identified during the treatment of 4-CP solution. Near-stoichiometric accumulation of chlorine was observed during the degradation of 4-CP in both Fenton and solar photo-Fenton processes. However, accumulation rate of chloride ions were much faster in solar photo-Fenton process. The degradation of 4-CP was found to obey a pseudo-first-order reaction kinetics. As compared to Fenton process, the presence of solar light in photo-Fenton process increases the reaction rate by a factor of 6.5 and 15.8 for COD and TOC degradation, respectively. In other words, during the treatment of 4-CP contaminated water, solar photo-Fenton process possesses notably higher mineralization efficiency in a relatively short radiation time as compared to Fenton process, and could enhance the degradation treatment of refractory organic wastewater such as 4-CP in a cost-effective approach.     

The importance of SO2 and SO3 for sulphation of gaseous KCl - An experimental investigation in a biomass fired CFB boiler

This paper is based on results obtained during co-combustion of wood pellets and straw in a 12 MW circulating fluidised bed (CFB) boiler. Elemental sulphur (S) and ammonium sulphate ((NH₄)₂SO₄) were used as additives to convert the alkali chlorides (mainly KCl) to less corrosive alkali sulphates. Their performance was then evaluated using several measurement tools including, IACM (on-line measurements of gaseous alkali chlorides), a low-pressure impactor (particle size distribution and chemical composition of extracted fly ash particles), and deposit probes (chemical composition in deposits collected). The importance of the presence of either SO₂ or SO₃ for gas phase sulphation of KCl is also discussed. Ammonium sulphate performed significantly better than elemental sulphur. A more efficient sulphation of gaseous KCl was achieved with (NH₄)₂SO₄ even when the S/Cl molar ratio was less than half compared to sulphur. Thus the presence of gaseous SO₃ is of greater importance than that of SO₂ for the sulphation of gaseous KCl.     

Mobilisation of heavy metals by deicing salts in a roadside environment

The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.     

Quantitative study of the kinetics of hydrogen evolution reaction on aluminum surface and the influence of chloride ion

The behaviors and kinetics of hydrogen evolution reaction (HER) on pure aluminum with passive film in the presence and absence of chloride ion are quantitatively investigated by using the tip generation/substrate collection mode of scanning electrochemical microscopy (SECM) with dual Al/Pt ultramicroelectrode (UME) as tip electrode and Pt UME as substrate electrode. The standard rate constants k⁰ and transfer coefficients α_H of HER in ClO₄⁻- and Cl⁻-containing solution are 6.9 × 10⁻⁷ cm/s and 0.22, 7.1 × 10⁻⁶ cm/s and 0.19, respectively. Results show that the kinetic of HER is slow and the destruction of Cl⁻ on passive film can significantly promote the HER on Al surface. Moreover, these α_H far less than commonly used 0.5 in corrosion research, can explain the great difference between theoretical Tafel slopes and experimental results. Besides, the existence of current plateau in Al electrode explains the large difference in corrosion potential during parallel testing.     

聚硫氯化铝和硫酸铝混凝剂使用效果的对比性研究

本文对新型净水剂——聚硫氯化铝和传统的硫酸铝混凝剂的净水效果进行对比研究。聚硫氯化铝在冬季低水温,高氨氮的原水情况下,不仅提高了出厂水水质,而且节省制水成本.并且简化了生产工艺的操作控制,值得推广。     

Effects of chloride and sulfate on the rate of oxidation of ferrous ion by H2O2

The rates of oxidation of Fe(II) by H(2)O(2) in the presence of sodium perchlorate, sodium nitrate, sodium chloride and sodium sulfate salts (0-1M) have been compared in the study. Experiments were carried out in a batch reactor, in the dark, at pH <3, 25+/-0.5 degrees C and at controlled ionic strength (< or =1M). The experimental results showed that the rates of oxidation of Fe(II) in the presence of chloride, nitrate and perchlorate were identical. In the presence of sulfate, the rate of oxidation of Fe(II) was faster and depended on the pH and the concentration of sulfate. The pseudo second-order rate constants for the reaction of H(2)O(2) with Fe(2+), FeCl(+) and FeSO(4) were determined as 55+/-1, 55+/-1 and 78+/-3 M(-1) s(-1), respectively.     

Heavy metal mobility in intertidal sediments of the Scheldt estuary: Field monitoring

The current paper aims to check whether the factors affecting metal mobility in intertidal sediments and floodplain soils of the river Scheldt, as identified under controlled greenhouse conditions in previous studies, also play a similar role under variable field conditions. Moreover, we aimed to assess the importance of these factors as a function of sampling time and depth, with respect to the natural variations in water table levels. This field monitoring revealed that the mobility of metals in intertidal sediments of the Scheldt estuary indeed are affected by factors which were identified to affect the metal fate in the upper sediment layer in previous greenhouse experiments. However, the effects were often less pronounced under field conditions. This can be attributed to the lower sampling resolution, the occurrence of interactions between factors, the disturbance of microbial communities during setup of greenhouse experiments and the more moderate environmental conditions in the field, affecting microbial and enzymatic activities. At most of the sampled wetlands, the level of the water table fluctuated only slightly during fall, winter and spring, whereas it decreased substantially during summer, especially at the sites with more sandy sediments. The highest sulphide concentrations were found at the sites where the water table level never decreased considerably. These sulphides primarily suppress the availability of Cd, Cu, Ni and Zn. Organic complexation resulted in the mobilisation of Cu, Ni and Cr. The concentrations of Cd, Ni and Zn in the pore water were affected by Fe/Mn oxide reduction, whereas Cd and Zn concentrations appeared to be also affected by the salinity.     

Effect of fine crack width and water cement ratio of SHCC on chloride ingress and rebar corrosion

SHCC (Strain Hardening Cement-based Composite) is a material known for its strain-hardening behavior under tensile and bending stress and its characteristic numerous small cracks. SHCC is expected to show superior durability because of the fineness of the cracks. In this study, chloride ingress through cracks into SHCC and progress of rebar corrosion in three mixtures of SHCC with various water-cement ratios were investigated. Through a chloride solution immersion test, it was confirmed that chloride could penetrate through even very fine cracks. The resistivity of cracked SHCC against chloride ingress is mainly governed by the accumulated crack width and the water cement ratio. Chloride pre-mixed SHCC specimens were left in a high-temperature, high-humidity chamber for 11 months to promote rebar corrosion. While the accumulated crack width and the water cement ratio were both influential to an increase in corrosion area, only the water cement ratio had bearing on corrosion loss.