The influence of reusing ‘Formtex’ controlled permeability formwork on strength and durability of concrete

The effects of the reuse of ‘Formtex’ Controlled Permeability Formwork (CPF) liner on strength and durability properties of concrete were investigated at two different water-cement ratios and the results are reported in this paper. Test blocks were cast using the CPF on one side and impermeable formwork (IF) on the opposite side of the mould so that direct comparisons could be made between the two. The strength was assessed using the Limpet pull-off tester and both the air permeability and the water absorption (sorptivity) were measured using the Autoclam Permeability System. Both these instruments measured the ‘covercrete’ properties. In addition, cores cut from the test specimens were subjected to an accelerated carbonation test and a chloride exposure test. The results showed that the ‘Formtex’ CPF increases the surface strength and the durability of concrete compared to the IF. There was an almost complete elimination of blowholes. The permeability of concrete decreased and its resistance to the ingress of both carbon dioxide and chlorides increased when CPF was used. The beneficial effects of the Formtex CPF were most evident in concrete of higher water-cement ratio. With the reuse of the Formtex liner twice, that is a total of three uses, the performance of the CPF to improve the properties of concrete remained almost the same. In this research the CPF liner was cleaned thoroughly between each use, which must be adhered to for site applications for reproducing the beneficial effects observed in the laboratory.     

水杨酸五溴苯酚酯的合成

本文首次报道一种新的酯类化合物水杨酸五溴苯酚酯的合成方法。此酯可望作为一种阻燃剂新品种而被使用。     

Inhibition effects of LAB and LABS on iron corrosion in chlorine solutions at different temperatures

In this study, the corrosion of iron is studied using gravimetric and potentiodynamic polarization method at different temperatures and at pH 9 level in 0.1 M NaCl solutions containing different concentrations of linear alkyl benzene (LAB) and linear alkyl benzene sulphonate (LABS). Potentiodynamic polarization experiments show that corrosion rate in presence and absence of LAB and LABS increases with increasing temperature from 303 to 338 K. The corresponding activation energies are determined. Moreover, the protective film formation on metal surface is investigated by means of FTIR. It has been concluded from the results that LABS is more effective in preventing iron corrosion than LAB.     

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.     

Impact of chloride on the mineralogy of hydrated Portland cement systems

Chloride ion is in part bound into ordinary Portland cement paste and modifies its mineralogy. To understand this a literature review of its impacts has been made and new experimental data were obtained. Phase pure preparations of Friedel's salt, Ca₄Al₂(Cl)_1.95(OH)_12.05·4H₂O, and Kuzel's salt, Ca₄Al₂(Cl)(SO₄)_0.5(OH)₁₂·6H₂O, were synthesized and their solubilities were measured at 5, 25, 55 and 85 °C. After equilibration, solid phases were analysed by X-ray diffraction while the aqueous solutions were analysed by atomic absorption spectroscopy and ion chromatography. The solid solutions and interactions of Friedel's salt with other AFm phases were determined at 25 °C experimentally and by calculations. In hydrated cements, anion sites in AFm are potentially occupied by OH, SO₄ and CO₃ ions whereas Cl may be introduced under service conditions. Chloride readily displaces hydroxide, sulfate and carbonate in the AFm structures. A comprehensive picture of phase relations of AFm phases and their binding capacity for chloride is provided for pH ∼ 12 and 25 °C. The role of chloride in AFt formation and its relevance to corrosion of embedded steel are discussed in terms of calculated aqueous [Cl⁻]/[OH⁻] molar ratios.     

Chemical model for cement-based materials: Thermodynamic data assessment for phases other than C-S-H

In the context of waste confinement, concrete may be used both as a confinement and as a building material. Concerning radwaste, the heat released during radioactive decay will modify the equilibrium constants of the minerals forming the concrete. The present work aims to elucidate the temperature dependency of the thermodynamic functions related to minerals from the concrete or associated with some of its degradation products. A large set of experimental data has been collected, for the chemical systems SO₃-Al₂O₃-CaO-CO₂-Cl-H₂O and SiO₂-Al₂O₃-CaO-H₂O, including iron and magnesium bearing phases. Most of the data collected concern experiments in aqueous media but results from calorimetric studies were also included, when available. Based on selected thermodynamic properties for each phase, predominance diagrams were drawn for the chemical elements listed above. Phase relations reported into predominance diagram appear rather consistent with most of the literature results. The case of katoite has been especially discussed, because it shows inconsistencies with respect to a hydrogarnet-grossular solid solution and with respect to phase relations reported into already published works. Finally, we underline the chemical compatibility of Portland cement pastes with carbonate aggregates, compared to silicates, for long-term storage applications.     

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。     

Microstructure and performance of AZ80D magnesium alloy by purification of chloride flux containing Er

The purification effects of Er addition in chloride flux during smelting on microstructure, tensile properties, and corrosion resistance of as-cast AZ80 D magnesium alloy were carried out. The results show that Er addition in the flux can eliminate the MgO inclusions and improve the tensile properties and corrosion resistance of the alloy. Using chloride flux mixed with 8.0 wt% Er, σb and δ of the as-cast AZ80 D magnesium alloy can be improved from 150 MPa and 2.1 % to the maximum value of 230 MPa and 4.8 %, respectively. Meanwhile, the corrosion rate decreases from 1.10 to 0.12 mg·（cm^2·d）^-1 in 5 wt% NaCl solution. However, with increasing Er content in chloride flux further, φ-（Al7ErMn5） and τ-（Al66.7Mg23.3Er10） phase are formed, and the morphology of γ-（Mg17Al12） phase is modified. The coarse φ-（Al7ErMn5）phase along dendrite boundaries decreases cohesion force between dendrites, which results in the worse of tensile properties.     

SOLVENT EXTRACTION WITH ORGANOPHOSPHONIC MONO-ACIDIC ESTERS

Mono-acidic liquid ion exchangers (extractants) containing the phosphonyl functional group arc reviewed.     

Binding of externally supplied chlorides in micro silica concrete under field exposure conditions

Chloride binding has remarkable influence on the chloride penetration and hence, on the time to corrosion initiation in reinforced concrete structures. Previous studies have mainly looked at the chloride binding from internal sources in laboratory, which is not representative of practical situations. The current work focuses on the chloride binding characteristics of concrete samples exposed to an external source of chlorides from the sea water at Persian Gulf region. Some of the important parameters including w/c ratio, silica fume replacement and effect of chloride concentration on chloride binding were investigated in order to provide insight into the distribution of free and bound chloride ions after a long-term exposure.The results of the current study suggest that the chloride binding capacity increases with increasing the w/c ratio and chloride concentration but decreases by using silica fume. A general equation was also developed correlating the total and bound chloride in order to obtain more accurate service life prediction.