Accelerated Laboratory Tests Research Articles

해양환경 폭로에 의한 슬래그 치환 콘크리트 및 슬래그 콘크리트의 염화물 이온 침투 저항성

In this research, it was examined chloride ion penetration resistance of slag-replaced concrete and cementless slag concrete considering marine environmental exposure conditions of splash zone, tidal zone and immersion zone. In the design strength of grade 24 MPa, the specimens were tested to determine their compressive strength, scanning electron microscopy images and chloride migration coefficient. Further, chloride ion penetration depth and carbonation depth of specimens exposed to marine environment were measured. Experimental results confirm that chloride migration coefficient of specimens tended to decrease with increasing the replacement ratio of ground granulated blast-furnace slag in accelerated laboratory test. In addition, the specimens exposed to the tidal zone were found to be the greatest chloride ion penetration depth compared to splash zone and immersion zone. On the other hand, the chloride ion penetration depth of the specimens exposed to splash zone tended to increase with increasing the replacement ratio of ground granulated blast-furnace slag in contrast with the results for the tidal zone and immersion zone.

Improvement in Durability of Oil Heat Treated 16-Year-Old Acacia mangium in Laboratory Tests

Improvement in the durability of oil heat treated Acacia mangium through accelerated laboratory tests was studied. A. mangium logs of 16-year-old harvested and segregated into the bottom, middle, and top portions. These were oil-heat treated in a stainless steel tank with oil palm oil as a heating medium at temperatures 180, 200 and 220 °C for the duration of 30, 60 and 90 minutes respectively. The wood samples dried and grounded into sawdust, air-dried again before undergoing durability tests. Accelerated 12 weeks laboratory durability studies conducted on the treated A. mangium. Fungi of Pycnoporus sanguineus, Gloeophyllum trabeum and Coriolus versicolors inoculated on the woods. Untreated samples used as controls. The results showed that durability of the wood improved with an increase in temperature and duration of the treatment. The oil heat treatment process reduced the attack of G. trabeum from 5.02%, 4.41% and 4.38% in the control samples to 0.54-4.55%, 0.91-4.41% and 1.08-4.38% at the bottom, middle and top portions, respectively. The attack of C. versicolors reduced from 11.48%, 14.27% and 15.68% in the control samples to 1.87-10.19%, 3.10-12.69 and 4.78-15.10% at the bottom, middle and top portions. However, the attacked of P. sanguineus were less effective with 31.42%, 18.24% and 10.53% in control samples to 3.71-10.18%, 5.74-14.59% and 4.37-17.08% at the bottom, middle and top portions. Heavy colonization of mycelia occurs in vessels of the untreated A. mangium wood in comparison to the oil heat treated wood observed through scanning electron microscope.

On the mechanisms of the corrosion of weathering steel by SO2 in laboratory studies: influence of the environmental parameters

We report here on the mechanisms underlying the corrosion of weathering steel in accelerated laboratory tests using artificially polluted SO2-atmospheres. The role of corrosion parameters such as the SO2 concentration, the exposure time, the relative humidity and temperature of the environment are discussed in detail. Through the extensive use of Mossbauer spectroscopy in both its transmission and electron detection modes, as well as with the help of other analysis techniques, the characterization of the different corrosion products at the various stages of the corrosion process has been carried out. The results complement the data obtained in field studies and help to understand the mechanisms involved in this complex phenomenon.

Wet/dry accelerated laboratory test to simulate the formation of multilayered rust on carbon steel in marine atmospheres

ABSTRACTThe prolonged exposure of carbon steel in marine atmospheres with high chloride deposition rates and long times of wetness of the metallic surface leads to the formation of thick multilayered rust. The present work proposes an accelerated cyclic laboratory test based on immersion (4.2 min) in a 3.5% NaCl solution followed by drying (12 min) under infra-red lamps in the laboratory atmosphere. The carbon steel corrosion process is thus accelerated, giving rise to the generation of thick rust layers in relatively short times. The rust phases and the structure of the rust layers formed offer a good approximation to the multilayered rust formed in marine atmospheres. The study includes a gravimetric evaluation of the magnitude of corrosive attack and a characterisation of the rust phases and corrosion layers formed using XRD, optical microscopy and SEM.

Effect of sol–gel layers obtained from GLYMO/MTES mixtures on the delamination of a cataphoretic paint on AA1050

In this study, the performance of different sol–gel layers produced from different mixtures of silicon alkoxides precursors (γ-glycidoxypropyltrimethoxysilane, GLYMO, and methyltriethoxysilane, MTES) applied on AA1050 aluminum alloy as a pretreatment prior to depositing an electrophoretic paint (polyether–polyamine polymeric blend) is investigated. The structure of the sol–gel coatings was characterized by means of ATR FTIR, while the corrosion protection properties were assessed by polarization curves. Accelerated laboratory tests, such as exposure in both neutral and acetic salt spray chambers and filiform corrosion tests, were employed to investigate the corrosion protection properties of the cataphoretic paint-coated samples. The failure mechanisms of the different coatings were investigated. The experiments revealed that the presence of GLYMO in the sol–gel coating seems not to be suitable for acting as a coupling agent between the paint and the aluminum substrate. On a positive note, this work shows that the filiform corrosion test seems to be the most appropriate test to evaluate the efficiency of sol–gel layers employed as pretreatment to enhance the corrosion protection provided by a paint on an aluminum substrate.

Concrete performance subject to coupled deterioration in cold environments

The design of concrete durability is normally based on the assessment of its performance when subject to a single deterioration mechanism. In reality, concrete structures are subject to varying environmental exposure conditions which often results in multi-deterioration mechanisms occurring. The Nordic climate, with cold harsh winters, poses a severe challenge to the long-term durability of concrete. The most common deterioration mechanisms are freeze-thaw damage, carbonation and chloride induced corrosion. Research is now more focused on the assessment of coupled deterioration mechanisms. For instance, evaluating how cracks resulting from freeze-thaw influence chloride ingress, or how carbonation changes the surface properties and thereby influencing freeze-thaw scaling and chloride penetration.This paper presents the results of research projects at VTT focusing on coupling deterioration mechanisms. These research projects have built on several decades of concrete durability research at VTT, including 15years of field station studies. The durability of the concretes has been assessed using both accelerated laboratory testing and also from in situ exposure results from field stations. This research has contributed to the development of concrete performance models and service life tools, supporting a holistic approach for deterioration assessment.

Alkali–aggregate reaction: performance testing, exposure sites and regulations

Several laboratory performance tests for alkali–aggregate reaction (AAR) have been used worldwide for about 20 years. However, a review performed one of the present authors in 2006 concluded that none of the test methods meets all the criteria for an ideal performance test. In the last decade, research has been performed in several countries with the aim to improve current AAR performance test methods and develop alternative tests. The Rilem (The International Union of Laboratories and Experts in Construction Materials, Systems and Structures) Technical Committee (TC) 258-AAA (2014–2019) is also focusing on this topic. The main purpose of this technical committee is to develop and promote a reliable performance-based testing concept for the prevention of deleterious AAR. Strong emphasis will be placed on the implementation of the Rilem methods and recommendations as national and international standards. It is crucial to link the results from the accelerated laboratory testing to field behaviour, primarily against field exposure sites. Some results from such exposure sites are included in this paper.

Accelerated laboratory testing of aggregate friction properties

Abstract This paper presents a thorough analysis of an experimental method for measuring aggregate friction properties. The second-generation Aggregate Image Measurement System (AIMS) is used to measure coarse aggregate surface texture before and after polishing in a modified Micro-Deval (MD) test procedure, in addition to Variable Speed Friction Test (VST) samples. Investigating the relationships between AIMS-MD angularity and texture, a weak relationship was found between VST friction values and AIMS angularity after MD polishing for 105 min (AMD-105). Furthermore, the strong correlation between AIMS AMD-105 texture and the surface texture of VST friction samples indicated that MD is a viable option for replacing VST as a polishing mechanism. Finally, cluster analysis was conducted to obtain threshold for classifying aggregate angularity and texture into acceptable and non-acceptable zones (i.e., defining the criteria for qualifying aggregates for friction purposes).

Probabilistic Fracture Mechanics Simulation of Stress Corrosion Cracking Using Accelerated Laboratory Testing and Multi-Scale Modeling

A propagation approach to manage stress corrosion cracking (SCC) is justified for modern high-strength alloys that exhibit low-subcritical crack growth rates, and is enabled by maturing probabilistic fracture mechanics and mechanism-based hydrogen damage modeling. A computer program, SCCrack, is developed based on stress intensity (K) similitude and fast Monte Carlo analysis to predict SCC life distributions from input distributions of variable material crack growth rate (da/dt vs. K), starting crack size, environment, and stress. Growth rates are obtained using an accelerated experiment that exploits precision electrical potential measurement of crack propagation, small crack size, and slow-rising K loading. Data are leveraged by fundamental models of SCC threshold (KTH) and H-diffusion limited Stage II da/dt, built on the hydrogen environment assisted cracking mechanism. With these inputs, SCCrack enables multi-scale “What if?” simulations of the effects of alloy-environment-precorrosion-stress variable...

A Degradation Model for Solid Oxide Fuel Cell Anodes Due to Impurities in Coal Syngas: Part II Estimation of Tolerance Limits

AbstractAn engineering analysis based on calibrated numerical predictions was performed to estimate the minimum allowable impurity concentrations in coal syngas intended to be used in Solid Oxide Fuel Cells (SOFCs) operating for over 10,000 h. Arsine and phosphine, impurities that are known to have the most deleterious effects on the cell performance due to their affinity to have strong relations with the anode catalyst by formation of secondary phases, were investigated. Time to failure was taken as the operation time when 60% performance loss is incurred, estimated by the previously developed one‐dimensional degradation model. Limiting concentrations were determined for arsine and phosphine fuel contaminants for electrolyte and anode supported SOFCs. Predicted lifetimes for single cells can provide a basis for estimation of SOFC stack lifetimes operating on coal syngas. Extrapolation of results from the numerical simulations based on accelerated laboratory tests at relatively higher concentrations can provide guidance into predicting the cell failure at low impurity concentrations.

The erosion of the beaches on the coast of Alicante: Study of the mechanisms of weathering by accelerated laboratory tests

One of the main problems that coasts around the world present, is the regression and erosion of beaches. However, the factors involved in these processes are unclear. In this study, the influence of sediment erosion on beach regression has been analysed. In order to do that, a three-step investigation has been carried out. Firstly, coastline variations of four Spanish beaches have been analysed. Secondly, a study on sediment position along the beach profile has been developed. Finally, the process that beach sediments undergo along the surf zone when they are hit by the incident waves has been simulated by an accelerated particle weathering test. Samples of sand and shells were subjected to this accelerated particle weathering test. Results were supplemented with those from carbonate content test, XRD, SEM and granulometric analysis. Results shows a cross-shore classification of sediments along the beach profile in which finer particles move beyond offshore limit. Besides, it was observed that sediment erosion process is divided into three sages: i) particles wear due to crashes ii) dissolution of the carbonate fraction, and iii) breakage and separation of mineral and carbonate parts of particles. All these processes lead to a reduction of particle size. The mechanism responsible of beach erosion would consist of multiples and continuous particle location exchanges along the beach profile as a consequence of grain-size decrease due to erosion.

Long-term stability of PEG-based antifouling surfaces in seawater

Poly(ethylene glycol) (PEG) is a hydrophilic polymer that has been extensively used in the biomedical and marine environment due to its antifouling properties. In the biomedical field, PEG has been successfully used to functionalize surfaces due to its resistance to cell and nonspecific protein adsorption. However, the long-term stability of PEG has limited its use in some areas. In the shipping industry, there is a great need for long-term solutions to keep the hulls of the ships fouling-free. The long-term stability of PEG in polydimethylsiloxane (PDMS) fouling-release coatings is studied here, in both accelerated laboratory tests and real seawater conditions. This article shows how PEG-based copolymers, which have been exposed in fouling-release coatings to real-life seawater conditions, are isolated and compared to those exposed to accelerated laboratory testing with successful results. The influence of the chemistry of the PEG compounds, the chosen laboratory degrading agents, and the possible degradation pathways and products are discussed.

Glassy state of wood polymers in native and thermally modified wood: effects on long-term material performance in service

This research analyses the effect of a glassy state of wood polymers, as found in some dense naturally durable wood species and in thermally modified wood (TMW), on their equilibrium moisture content, mechanical and fungal resistance (durability) performance. In the EN350-class I durability range, moisture and fungal durability are argued to become controlled by the physical state of wood polymers rather than their chemical composition. Glassy polymers may assist the dimensional stability and fungal resistance of wood, as characterised by standardised accelerated laboratory tests. However, for long-term mechanical performance and fungal resistance in service, strong cross-links must prevent the natural (aging) relaxation of the glassy state. Physical aging is expected to occur in TMW, as opposed to naturally durable wood species. The current test methodology for dimensional and fungal stability does not take physical aging effects in wood polymers into account.

Accelerated Laboratory Test Suggests the Importance of Film Integrity of Sealers on the Protection of Concrete from Deicer Scaling

AbstractThis work reports the laboratory performance of five film-forming sealers that protect concrete from deicer scaling (15 freeze-thaw and wet-dry cycles in diluted NaCl or MgCl2 solution). Regardless of the presence or type of sealer, no apparent scaling occurred on the concretes exposed to 2.54% by weight MgCl2 solution, but there was significant reduction in their splitting tensile strength (up to 55% for the nontreated concrete). The best-performing sealer in mitigating this risk of strength reduction was the methyl methacrylate (MMA) polymer. For the concrete exposed to 3% by weight NaCl solution, the scaling resistance and ability of strength preservation were significantly improved by the presence of a sealer. Regardless of the sealer type, the initial rate of water absorption of surface-treated concretes was greatly reduced by the sealer by at least 68%. The water absorption behavior of the sealer-treated concrete showed a strong correlation with mass loss caused by salt scaling. The concrete...

Effect of hydrophobic surface treatment on freeze-thaw durability of concrete

The effect of surface treatment using silanes on the frost durability is investigated on both laboratory and field specimens in an accelerated laboratory test. Measurements include moisture uptake during the pre-saturation and F-T stages, cumulative mass loss and internal bulk cracking under frost salt/water exposure. It is found silane treatment substantially reduces surface scaling, but cannot prevent bulk moisture uptake or the occurrence of the internal frost damage when concrete is insufficiently air entrained. Salt scaling is dominated by the capillary suction process in the thin surface region under freezing which can be curtailed by the pore lining effect from silanes creating a hydrophobic barrier to the ingress of external liquid. This in turn suppresses ice growth in the surface region, evidenced by the complete elimination of sub-freezing dilation in a length-change measurement of small-scale concrete specimens with surface treatment. However, internal frost damage is controlled by the universal degree of pore saturation which in turn is dependent on the bulk moisture uptake.

Accelerated Vibration Test of coolant channel components under simulated flow induced excitation

The present study outlines the accelerated testing procedure of a Grayloc joint assembly for possible loosening of its nut due to flow induced vibration. The concern of the Grayloc nut getting loosened in the absence of a lock nut due to flow induced vibration and the resulting fretting in the feeder pipes in contact due to differential creep in the neighbouring channels has been addressed here. The severity of the test was decided based on actual site measurement under different operating flow conditions and comparison of power spectral density (PSD). The laboratory test results were extrapolated for estimation of life of the component under operating condition using inverse power law approach. The uniqueness of the accelerated test is that the component under test has not been led to failure for assessing its operating life unlike conventional accelerated testing. From the tests and analysis, it was deduced that 80h of accelerated laboratory testing was equivalent to 5.26 full power years (46,080h) of the reactor operating life. The test duration was enough to obtain approval from the regulatory body to operate the reactor.

Study on the corrosion protection performance of new ferrite/kaolin core-shell pigments in epoxy-based paints

Purpose – The purpose of this study is to prepare core-shell ferrites/kaolin pigments and compare their efficiency in protecting metal substrates to original ferrites. The new pigments are based on precipitating a shell of different ferrites that comprise only 10-20 per cent of the whole pigment on kaolin (core), which is a cheap and abundant ore comprising 80-90 per cent of the prepared pigment. These new pigments combine the properties of both its core and shell counter-parts, exhibiting improved corrosion protection properties. Furthermore, the pigments are represented as efficient, economically feasible and eco-friendly with comparable efficiency to that of original ferrites in protecting steel substrates. Design/methodology/approach – The new pigments were characterized using different analytical and spectrophotometric techniques, e.g. transmission electron microscopy, energy-dispersive X-ray analysis and X-ray fluorescence. The pigments were then incorporated in epoxy-based paint formulations. The physico-mechanical properties of dry films and their corrosion properties were tested using accelerated laboratory tests in 3.5 per cent NaCl for 28 days. Findings – The results of this study revealed that ferrite/kaolin core-shell pigments performance was almost close to that of the ferrite pigments in the protection of steel, and, at the same time, they confirmed good physico-mechanical properties. Practical implications – These pigments can be applied in other polymer composites, e.g. rubber and plastics, as fillers and reinforcing agents. Originality/value – Ferrite and ferrite/kaolin are environmentally friendly pigments, and they can impart high anticorrosive behavior to paint films with concomitant cost savings.

МЕТОД УСКОРЕННЫХ ЛАБОРАТОРНЫХ ИСПЫТАНИЙ АЛЮМИНИЕВЫХ СПЛАВОВ С ЦЕЛЬЮ ПРОГНОЗИРОВАНИЯ ИХ КОРРОЗИОННОЙ СТОЙКОСТИ В УСЛОВИЯХ МОРСКОЙ АТМОСФЕРЫ

МЕТОД УСКОРЕННЫХ ЛАБОРАТОРНЫХ ИСПЫТАНИЙ АЛЮМИНИЕВЫХ СПЛАВОВ С ЦЕЛЬЮ ПРОГНОЗИРОВАНИЯ ИХ КОРРОЗИОННОЙ СТОЙКОСТИ В УСЛОВИЯХ МОРСКОЙ АТМОСФЕРЫ

New eco-friendly anticorrosive core-shell pigments

Purpose– The purpose of this paper is to present the preparation of core-shell ferrites/kaolin pigments and comparing their efficiency in protecting metal substrates to original ferrites which were also prepared. Core-shell structured particles are recently gaining lots of importance due to their exciting applications in different fields; these particles are constructed from cores and shells of different chemical compositions which show ultimately distinctive properties of varied materials different from their counterparts. The new core-shell pigment is based on shell of different ferrites that comprises only 10-20 per cent of the whole pigment on kaolin (cores) which is a cheap and abundant ore that comprises 80-90 per cent of the prepared pigment. The new pigments do not only comprise two different components, but they also contain pigment and extender in the same compound; their loadings in the paint formulations ranges from 50 and 75 per cent of the whole pigment. The work showed that these eco-friendly and cheap core-shell pigments are comparable in their efficiency to that of ferrites in protecting steel substrates.Design/methodology/approach– The different ferrites and ferrites/kaolin pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray (SEM/EDAX) and transmission electron microscopy (TEM). Evaluation of these pigments was done using international standard testing methods (ASTM). After evaluation, the pigments were incorporated in solvent-based paint formulations based on medium oil-modified soya-bean dehydrated castor oil alkyd resin. The physico-mechanical properties of dry films and their corrosion properties using accelerated laboratory test in 3.5 per cent NaCl for 28 days were determined.Findings– The results of this work revealed that ferrite/kaolin core-shell pigments were close in their performance to that of the ferrite pigments in protection of steel, and at the same time, they verified good physico-mechanical properties.Practical implications– Treated kaolin can be applied in many industries beside pigment manufacture and paint formulations; it can be applied as reinforcing filler in rubber, plastics and ceramic composites. Also, it is applied in paper filling, paper coatings and electrical insulation.Originality/value– Ferrite and ferrite/kaolin are environmentally friendly and can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints, for example paper, rubber and plastics composites.

Effect of metakaolin on the chloride ingress properties of concrete

Research and practical experience have shown that partial replacement of cement by metakaolin improves concrete durability as a result of the refinement of the pore structure. While much research has been presented on concrete performance with metakaolin, it is scarce concerning the transport properties of chlorides in concrete with metakaolin, in natural conditions (i.e., un-accelerated). This study determines the chloride diffusion coefficients for several concretes with vary levels of cement replacement with metakaolin, and compares these results with chloride migration coefficients obtained from accelerated laboratory testing. In this study, two cement types (CEM I 42,5R and CEM IV/A 42,5) and two cement contents levels where used with metakaolin replacement levels varying from 10-20%. Concretes where tested for fresh properties, compressive strength, electrical resistivity, chloride ingress characteristics (natural diffusion and migration), and mercury intrusion porosimetry. The results show improved strength, durability properties and chloride penetration resistance of concretes with metakaolin. Furthermore, the use of metakaolin in fly ash concrete improves the early age performance of the concrete (<90 days), counteracting the delay in strength and durability gain typically associated with fly ash concrete. The results obtained from this study fulfil the lack of critical input for service life design models of reinforced concrete structures in chloride environments, with emphasis on concretes with metakaolin replacement.