Relative Durability Research Articles

Effect of nitridation on the properties of Na–Zn–P–O glasses

Phosphate glasses generally have a low melting temperature, a low glass transition temperature (Tg) and a high thermal expansion coefficient (α) [1–6]. These characteristics make them potential candidates for low temperature applications, such as the molding of optical elements [7] and sealing to high expansion metals [8]. However, the applications of phosphate glasses are greatly limited in practice by their poor chemical durability [6, 9]. It has been shown that the chemical durability of phosphate glasses could be significantly improved by nitridation and/or addition of appropriate additives, due to the increase of crosslink density and bonding strength in the glass network [9–18]. The effect of nitridation on the glass properties results in the two-coordinated oxygen atom being replaced by the three-coordinated nitrogen atom [19–22]. Either doping the melt with metal nitrides or remelting the glass in an ammonia atmosphere can lead to the incorporation of nitrogen atoms into the glass network [23–25]. Higher nitrogen contents can be obtained by the remelting method than by doping with metal nitrides [10, 24]. It has been shown that the nitrogen content of nitrided glasses would increase with increased remelting temperature and remelting time, but this may make melt volatilization more likely [10–12]. The purpose of this work is to improve the chemical durability of sodium-zinc phosphate (Na Zn P O) glasses by remelting the base glasses at a lower temperature and a shorter holding time under an ammonia (NH3) atmosphere. A base glass with composition 50P2O5–20Na2O– 30ZnO (mol%) was investigated in this study. The base glasses were prepared from mixtures of reagent grade sodium dihydrogen phosphate (NaH2PO4), zinc oxide (ZnO), and ammonium dihydrogen phosphate (NH4H2PO4). Well-mixed powders were melted in an alumina crucible in air at 850 ◦C for 1 h. The melts were quenched and crushed to frits. Then the crushed base glasses were nitrided in alumina boat crucibles under a flowing anhydrous ammonia atmosphere at 600 ◦C for different durations, from 0.5–5 h. The ammonia flow rate was kept at 300 cm3/min. After selected periods of time, the glass samples were removed and annealed in a preheated furnace under an air atmosphere. Then the oxynitride glass samples were cooled overnight to room temperature. Density measurements were carried out at room temperature, using the Archimedes method with deionized water as the immersion fluid. A micro-Vickers tester was used to measure the hardness with a 300 g load on polished glass samples. Glass powders were used for the differential thermal analysis (DTA) at a heating rate of 10 ◦C/min to determine the glass transition temperature (Tg). The relative chemical durability was estimated by measuring the dissolution rate of the polished glasses, which were immersed in deionized water for 24 h at 30 ◦C. The nitrogen content in the glasses was analyzed by an inert-gas fusion method, using an oxygen-nitrogen analyzer. X-ray photoelectron spectroscopy (XPS) spectra of N 1s core levels were recorded by a V. G. Scientific EscaLab 210 XPS spectrometer. The X-ray source was Mg Kα (hν = 1253.6 eV). The nitrogen contents of the nitrided glasses with various remelting times are shown in Fig. 1. The nitrogen content of the glasses increases with increasing remelting time, reaching a maximum value of 1.81wt% (2.9 at.%) for a remelting time of 5 h. The dissolution rate and concentration of nitrogen in the glass network are affected by glass composition and the remelting conditions. It was suggested that higher temperatures significantly accelerate nitrogen dissolution [11, 12, 26]. Alkali phosphorus oxynitride (Na P O N and Li P O N) and sodium alkalineearth metaphosphorus oxynitride glasses have been studied [10, 25, 26]. Lithium phosphorus oxynitride glasses that were prepared at 700 ◦C for 48 h had a maximum nitrogen content of 9.2 wt%, whereas those glasses that were prepared at 800 ◦C had a value of 12.6 wt% [12]. The nitrogen solubility in sodium alkaline-earth metaphosphorus oxynitride glasses decreased with increasing concentration of alkaline-earth oxides [26]. It was suggested that the divalent cations

Chemical alteration of tephra in the depositional environment: theoretical stability modelling

AbstractThe study of the chemical stability of vitreous material in aqueous media is well‐established. There has to date been little consideration of the implications of variations in the chemical durability of tephra in Quaternary tephrochronology. Chemical alteration can take the form of cationic leaching from the matrix, or complete destruction of the silica network, either of which could constrain the ability to chemically identify distal tephra. Here we apply established models of vitreous durability to the published chemical analyses of a large number of Icelandic tephras in order to predict their relative durabilities under equivalent conditions. This suggests that some important tephras have relatively poor chemical stability, and that rhyolitic tephras are, in general, more stable than basaltic. We conclude that tephras should be expected to show predictable differential chemical stability in the post‐depositional environment. Copyright © 2003 John Wiley & Sons, Ltd.

Relative efficacy of heartwood extracts and proprietory wood preservatives as wood protectants

The relative potentials of either heartwood extracts (air dry extracts in 60 percent methanol) of very durable woods (Afzelia africana J.E. Smith;Erythrophleum suaveolens (Guill & Perr.) Brenam. Syn.E guinensis G.Don. orMilicia excelsa (Welw) C.C. Berg. Syn.Chlorophora excelsa (Welw) Benth.) or any of two proprietary wood preservatives (AWPA type “C”-Chromated Copper Arsenate (CCA) or 5 percent solution of AWPA Standard Designation P “9” type “C”—Pentanchlorophenol (Penta) in light oil solvent) to suppress attack on pressure treatedAntiaris toxicaria Lesch Sapwood by either any of three species of decaying fungi (Coridopsis Polyzona Klotzch;Lenzites trabea; orTrametes cingulata Fr.) under soil block exposure conditions were investigated and threshold values determined. Extract/preservative dosages were either 8.009; 24.778; 48.056; 96.111 or 144.167 kg m−3 (0.5; 1.5; 3.0; 6.0 or 9.0 1b/ft3). Exposure was for either 14 or 28 weeks and in accordance with ASTM D1413-72 Provisions. Conclusions reached were that at threshold values the ability of either any of the heartwood extracts or proprietary wood preservatives to suppress attack under conditions in this study was significant at 0.01. Relative efficacy of those biocides was dependent on fungal species. Neither any of the heartwood extracts nor any of the proprietary wood preservatives (except in the case ofTrametes cingulata attack on CCA treated wood at highest retention level) was able to confer “very durable” rating on treated wood. Possible reasons for the reduced relative durability of extracts visa vis native heartwood were advanced. At the highest retention level (144.167 kg m−3) there was no significant difference (at 0.05 level) between efficacy of each of the heartwood extracts and any of the proprietary wood preservatives (CCA or Penta).

Systolic and diastolic function of the univentricular heart

Current surgical palliation for the patient with functional single ventricle provides long-term survival for the majority of patients. Nevertheless, because of the increased hemodynamic load, cardiac reserve is intrinsically reduced by these interventions. Preservation of ventricular systolic and diastolic function is therefore particularly important for this patient population. This article reviews the published data concerning ventricular systolic and diastolic function in patients after early palliation with pulmonary artery banding or aortopulmonary shunts and after superior and total cavopulmonary anastomoses. There are significant intrinsic limitations to the applicability of these data, since they are invariably limited to descriptive studies of the outcome for a constantly evolving treatment strategy. The majority of these studies involve patients managed according to a management scheme that has now been abandoned. Until the pulmonary and systemic circulations are separated, a volume load is imposed on the ventricle that carries a long-term risk of progressive loss of myocardial contractility. As in the case with other forms of ventricular volume loading, the risk for and the pace of deterioration is proportional to the magnitude of the volume overload. This observation, coupled with the demonstration that the superior cavopulmonary anastomosis can be successfully performed by 6 months of age, has resulted in dramatic reduction in the duration of volume overload to which these patients are generally exposed. Despite the reduced incidence of impaired myocardial contractility that has been realized, the total cavopulmonary anastomosis circulation still imposes an increased workload on the single ventricle. Data on late outcome in patients managed with early volume-reduction therapy are not yet available. Although there is considerable concern about the relative durability of single ventricles of right ventricular morphology, the available data on this issue are contradictory. The energy requirements to fill the heart are particularly critical in patients who have previously undergone a Fontan operation because of the absence of a pulmonary pumping chamber. Compared to systolic function, the diastolic ventricular and myocardial outcome in these patients has been evaluated much less frequently and generally by less reliable methodologies. The utility of noninvasive techniques in the measurement of relaxation and compliance in single ventricle hearts is unproven and highly suspect, particularly when compounded by chronic volume overload or acute preload reduction. The available data do not document a verifiable impairment in ventricular or myocardial compliance, although there are suggestive data indicating that impaired relaxation may be present. Again, late outcome with regard to diastolic function are not yet available in the patients who have been treated according to present day management practices.

Effect of melting time on the properties of Sn-P-O-Cl glasses

Phosphate glasses with low melting temperature, high thermal expansion coefficient (α), low glass transition temperature (Tg) and softening temperature (Td) are of increasing interest and desirable for many applications, e.g. the molding of optical elements, glass to metal seals, thick film paste and low temperature enamels for metals [1–5]. Unfortunately, their poor chemical durability makes them generally unsuitable for practical applications [5, 6]. However, many authors have reported the ultra-low Tg glasses based on the stannous fluorophosphate (Sn–P–O–F) glasses have improved chemical durability [7–10]. It was suggested that the addition of SnO, PbO, and PbF2 results in the formation of Sn–O–P and Pb–O–P bonds, which replace the P–O–P bonds, and leads to dramatic improvement in the chemical durability of the stannous fluorophosphate glasses [8–10]. Although stannous fluorophosphate glasses offer possibility for the commercial applications where low melting point is required, they have some potential problems. During melting, it was found that there was considerable change in composition due to volatilization losses. This was found to result in variation in property [5]. Hu and Jiang have indicated that stannous chlorophosphate (Sn–P–O–Cl) glasses exhibit higher chemical durability than that of fluorophosphate system [11]. The results offer a new glass system with low melting points and good relative chemical durability for commercial development. The effects of additives on the properties and structure of Sn–P–O–Cl glasses also were studied [12–13]. However, the volatilization effects during melting on the properties of Sn–P–O–Cl glasses have not been studied in detail previously [11– 13]. The paper was undertaken to examine the effect of melting time and the volatilization of chlorine on the properties, including thermal expansion coefficient, Tg, Td and chemical durability of Sn–P–O–Cl glasses. Glasses with composition 40P2O5–60SnCl2 were prepared from reagent grade ammonium dihydrogen phosphate (NH4H2PO4) and stannous chloride (SnCl2 · 2H2O) by a two-step process. First, NH4H2PO4 were preheated slowly to 500 ◦C in alumina crucible for 30 min. Then the crucible was removed from the furnace and stannous chloride was added. The crucible was then transferred in to a furnace which was keeping at 500 ◦C and melted for 5–40 min. The melt was cast and annealed for 1 h immediately for stress relieving. Powder X-ray diffraction (XRD) analysis of the asquenched melt was used to verify the amorphous state. The thermal expansion coefficient (α) and dilatometric softening temperature (Td) were determined by a dilatometer, using a heating rate of 5 ◦C/min. Td was defined as the temperature of maximum thermal expansion. Glass transition temperature (Tg) was determined by the differential thermal analyses (DTA; Perkin Elmer DTA7 Analyzer) at a heating rate of 10 ◦C/min. Relative chemical durability was determined by measuring the weight loss of the polished glass sample after immersion in deionized water at 30 ◦C for 24 h. All sample were polished to 1000 grit finish prior to test. The dissolution rate was defined as weight loss per unit surface area per unit time (g/cm2-min). The chlorine content of the glass was measured at 25 ◦C by an ion analyzer (model 3045; Jenway/U.K.) with a Cl− ion-selective electrode (ISE). The sample solutions were prepared by dissolving small quantity of glass sample in 0.5 N HF solutions. About 2 parts of ISA (ionic strength adjuster) solution (5 mol/l NaNO3) was added to 100 parts of the sample solution for adjustment of total ionic strength. The electromotive force of this solution was measured and the chlorine content was determined using a calibration curve that was made by using a NaCl solution (Orion Research, Inc., USA) as chloride standard. The glassy state was confirmed by XRD and all glasses are transparent. The properties and chlorine content of the glasses are listed in Table I. During melting, volatilization occurs and the chlorine content in the glass decreases with increasing the melting time (see Table I and Fig. 1). First, the chlorine content decreases rapidly with melting time and then decreases slowly to about 2.6–3.2 wt% as the melting time is greater than 20 min. The effect of melting time on Tg, Td, thermal expansion coefficient, and dissolution rate of the investigated stannous chlorophosphate glasses are shown in Figs 2 and 3, respectively. Both Tg and Td of the glass increase with melting time. Tg increases

Experimental salt weathering of limestones in relation to rock properties

A total of 21 different types of British and European Mesozoic limestones have been subjected to simulated salt weathering using sodium sulphate (Na2SO4) with the following aims: assessment of the relative durabilities of different types of limestone; assessment of the importance of modulus of elasticity and other factors in affecting durability; and assessment of the use of impulse excitation techniques to monitor changes in rock modulus of elasticity. The rocks showed a wide spectrum of durabilities; while rocks with high values of modulus of elasticity, lower water absorption capacities, high densities and low salt uptakes tended to be durable, there were anomalies, the explanation for which probably lies in their pore structures. Non-destructive testing techniques showed that, although the more durable rocks failed to lose weight or to show visual signs of disintegration, their modulus of elasticity values did tend to decline, indicating a loss in strength. Copyright © 1999 John Wiley & Sons, Ltd.

Experimental salt weathering of limestones in relation to rock properties

A total of 21 different types of British and European Mesozoic limestones have been subjected to simulated salt weathering using sodium sulphate (Na2SO4) with the following aims: assessment of the relative durabilities of different types of limestone; assessment of the importance of modulus of elasticity and other factors in affecting durability; and assessment of the use of impulse excitation techniques to monitor changes in rock modulus of elasticity. The rocks showed a wide spectrum of durabilities; while rocks with high values of modulus of elasticity, lower water absorption capacities, high densities and low salt uptakes tended to be durable, there were anomalies, the explanation for which probably lies in their pore structures. Non-destructive testing techniques showed that, although the more durable rocks failed to lose weight or to show visual signs of disintegration, their modulus of elasticity values did tend to decline, indicating a loss in strength. Copyright © 1999 John Wiley & Sons, Ltd.

Properties of concrete

Book review / Critique de livre 619 Like the three earlier editions of this bo k produced between 1963 and 1981, this fourth and final edition seeks to communicate a comprehensive knowledge of the technology of Portland cement concrete to its reader. Unlike many other classic texts on the same subject which have become somewhat dated, the periodic updating of this book culminating in the fourth edition has kept it alive and current with the concrete technology of the eighties and nineties in most respects. Consistent with this process, the comprehensive list of selected references spanning a wide range of sources worldwide, which was a particularly valuable feature of the previous 1981 edition, has been extended to include many items published between 1981 and 1995. Despite its title, this book is about much more than simply the properties of concrete. It is really a synthesis of the knowledge required to select suitable materials for a concrete mixture, how to proportion and mix these materials properly, and how to place and consolidate the resulting mixture to ensure that both the shortand long-term properties in the hardened state are satisfactory for the application in question. As the author correctly asserts, the primary property requirements in the hardened state are satisfactory compressive strength and adequate durability, but the former has always tended to preoccupy engineers responsible for specification development and construction much more than the latter because of the still widely held perception that concrete is a low-tech material consisting simply of water, cement, and inert aggregates. While many of the fundamentals of making good concrete have not changed, the variety of ingredients available for doing so has broadened greatly with respect to chemical admixtures and supplementary cementing materials or mineral admixtures, so the new chapter title highlighting chemical admixtures is welcome, as is the greater attention given to discussion of concretes made with supplementary cementing materials such as pulverized fly ash, ground granulated blastfurnace slag, or silica fume. However, a logistically strange feature of the layout carried over from previous editions is that the discussion of mixture proportioning practices is left to the last chapter, instead of following the chapters on the raw material ingredients and preceding the chapters on properties of the concrete mixture which derive from and depend strongly on the proportions selected. Nevertheless, North American and British practices, including the 1988 update to British practice, are adequately covered. Unfortunately, European practice which, as the author states, may well supersede British practice within the European Union is barely mentioned. The coverage of hardened concrete with respect to curing, strength development, and properties other than durability has been extended and reorganized from two chapters in the previous 1981 edition to four in this edition, with the important issue of temperature effects in concrete highlighted in a new chapter. The topic of durability is also covered more fully with respect to alkali-aggregate reactivity and carbonation, and is rearranged into two chapters instead of the previous one, with the second devoted specifically to freezing and thawing and the effect of the presence of chlorides. However, discussion of alkali-aggregate related durability problems is confined mainly to the well-known relatively rapid form of alkali-silica reaction remedied by pozzolanic additives. Even though the author states that he regards the subject area as too vast for full treatment in his book, some mention of the problems created by slower reacting siliceous aggregates that have created serious concerns in recent years, and for which the remedies are uncertain or unknown, would have been welcome. The chapter on concretes with particular properties which are special in one way or another has been extended considerably beyond the scope of the previous edition to include flyash, slag, and silica fume concretes and retain coverage of the various forms of lightweight concrete. High-density concrete for radiation shielding has been dropped, perhaps reflecting the reluctance in the developed world to build more nuclear power stations. The author introduces the term “high performance concrete” which, as he acknowledges, infers an allegedly distinct product. It is unfortunate that he has used the term at all because of its currently overworked buzzword connotation, particularly in Canada, and the inevitable implication that all other concretes are necessarily in some way inferior for their intended purpose. Aside from this criticism, the chapter contains new and useful information on concretes which excel in performance with respect to one or other definable properties, for example, with respect to flowability, compressive or flexural strength, shrinkage, resistance to cracking, abrasion resistance, and (or) water permeability, or chloride ion penetration. Since 1969, this reviewer has used the three previous editions of this book as a primary reference in undergraduate civil engineering courses on construction materials and as Received July 11, 1997. Manuscript accepted October 1, 1997.

Comparative durability of materials in wear

From the analysis of the entropy equation of durability, a procedure is proposed of a comparative assessment of material durability in wear. The equation parameters are determined by sclerometric measurements. The relative durability is shown to be represented by the relation between the dispersions of the sclerometer beam oscillation for materials being compared. Our findings can be used for choice of friction couple materials, tool materials in particular.

Wear and Fatigue of Nylon and Polyester Mooring Lines

Wear and fatigue in synthetic fiber lines depend on a multitude of mechanisms, including cumulative creep to rupture, hysteretic heating due to cyclic loading of filaments or to relative displacement of structural rope elements, internal wear caused by relative movement between yarns or strands, and external abrasion against deck hardware or rough surfaces. Studies undertaken to evaluate fiber, yarn, and rope responses to each of these mechanisms, singly or in combination, vary significantly with the test conditions including cyclic load level (both axial and transverse), cyclic strain level, and ambient conditions, i.e., temperature and moisture content (whether dry or wet in fresh water or salt). Cyclic load limits depend on wave height, wind velocity, and mooring line dimensions and properties. The relative durability of nylon versus polyester lines is considered as the lines are subjected to tensile cycling under storm conditions. While tensile fatigue as a creep phenomenon is operative over the free length of the mooring line, the more critical location of rope deterioration is at its interactive contact with deck hardware. An ideal mooring system is composed of two segments. The one between the elements of deck hardware (cleats and chocks) should possess maximum abrasion resistance and high tensile stiffness. The other segment should possess high tensile compliance so as to minimize cyclic load levels induced by waves and wind. A review of yarn/yarn wear tests and rope abrasion tests is provided to form the foundation for recommendations.

Characterisation of Films Grown on Aluminium Immersed in Aerated Saline Solutions Containing Nickel

Small additions of nickel chloride to salt solution significantly reduce the corrosion of aluminium alloys. Films produced in these solutions produce a microrough topography which may be suitable for adhesive bonding. Techniques such as XPS, SEM, FTIR and SIMS were used to investigate the properties of the films. The results established that nickel is incorporated in the outer layer of a hydrated aluminium oxide film and is responsible for altering the film growth mechanism. Boeing wedge tests were conducted to assess the relative durability of bonds with adherends pretreated in the salt solutions. The durability performance of the film as a surface treatment for adhesive bonding compared favourably with the Forest Products Laboratory chromate etch. A comparison of the nickel salt treatment with a sodium chloride solution treatment indicated that durability differences were related to their respective hydrated oxide structures.

The Role of Coupling Agents in Composite Durability

ABSTRACTWe investigated the role of coupling agents with respect to the relative durability of glass fiber/epoxy matrix composites exposed to water, which degrades both glass fibers and the fiber-matrix interface. Interface chemistry was tailored by coating fibers with mixtures of different coupling agents. Single-fiber fragmentation test results showed little decrease in the strengths of the interface and a slight decrease in fiber strengths upon exposure to water. XPS results showed expected variations in surface composition. Contact angle measurements demonstrated variations in surface hydrophobicity as coupling agent mixtures were changed.

Gianturco self-expanding stents: Clinical experience in the vena cava and large veins: Irving JD, Dondelinger RF, Reidy JF, Schild H, Dick R, Adam A, Maynar M, Zollikofer CL. Cardiovasc Intervent Radiol 1992;15:328-33

Irving JD, Dondelinger RF, Reidy JF, Schild H, Dick R, Adam A, Maynar M, Zollikofer CL. Cardiovasc Intervent Radiol 1992;15:328-33. Background: The conditions of approximately 20% of patients with symptomatic superior vena cava and major upper extremity venous obstructions will either fail or be unresponsive to medical therapy. Because the majority of such patients have advanced malignancy and limited life expectancy, venous bypass is not an alternative. This study reports an experience with use of self-expanding Gianturco stents to manage refractory, symptomatic superior vena cava and upper extremity venous occlusions. Methods and Results: The study population consisted of 25 consecutive patients treated with Gianturco stents from seven different European hospitals. There were 18 strictures in the superior vena cava (72%), three in the inferior vena cava (12%), three in the subclavian vein (12%), and one in the inominate vein (4%). Bronchogenic carcinoma was the cause in 15 (72%) of 21 malignant obstructions. Benign obstructions were due to dialysis catheters in two, posttraumatic mediastinal fibrosis, and Budd-Chiari syndrome. Compressed stents were delivered to the obstruction from the femoral vein. The introduction system consisted of a wire-guided 10F Teflon sheath. Before stent placement, all strictures were dilated with an angioplasty balloon of 15 to 20 mm diameter to determine the exact location and length of venous narrowing. The stent configuration consisted of two Gianturco Z stents (stainless steel wire bent in a zigzag fashion to create a cylinder 2.5 cm in length), joined end-to-end by a wire strut, and fitted with a single barb at each end to prevent migration. Strictures longer than 5 cm were spanned by placing additional stents in tandem. Incorrect stent positioning was rectified by placement of a second stent within the first. An average of 1.6 double stents were required per procedure. Symptomatic relief was evident in all patients within 24 to 48 hours of stent placement. There were no major complications and two recurrences. The single early failure was associated with incorrect placement and occurred 24 hours after intervention in a patient with malignant subclavian vein obstruction. A second patient had redevelopment of symptoms from benign superior vena cava syndrome 2 months after stent placement but was then successfully treated with venous bypass. Thirteen patients (61%) with malignant venous obstruction died within 3 months of stenting, and only two patients with malignancy (9%) survived more than 1 year. Summary: This study suggests that placement of self-expanding Gianturco stents into the vena cava and large veins is a simple and safe procedure for the rapid relief of symptoms in patients with preterminal malignant venous obstruction. Comment: This series documents the feasibility, safety, and relative durability of stenting for malignant venous obstruction in a population of patients with very limited life expectancy. The truncated survival of the study population combined with small numbers of benign lesions does not allow conclusions regarding the efficacy of stenting in patients with benign obstruction who are expected to enjoy long-term survival. Charles L. Mesh, MD Case Western Reserve University Cleveland, Ohio

A REVIEW OF THE DURABILITY OF INHALED FIBRES AND OPTIONS FOR THE DESIGN OF SAFER FIBRES

The hazards associated with inhaled fibres are linked with fibre shape, size, composition and durability Durability includes susceptibility both to dissolution and to mechanical disintegration. Most fibre types dissolve incongruently with some elements being preferentially leached from the fibre to leave it mechanically weakened. Incongruent dissolution is also associated with hydration of fibre surfaces and the associated volume changes can lead to mechanical failure of fibres. In general the asbestos minerals are more durable than most man-made vitreous fibres (MMVF), although some ceramic fibres may be more durable than chrysotile. The most soluble of the MMVF have relatively high alkali (Na and K) and alkali earth (Ca, Mg) contents, and low alumina and boron contents The least soluble MMVF are the high alumina silicate glasses (the ceramic fibres). The relative durability of different fibre types is governed by the physical and chemical environment which contains the fibres. The value of existing published data in determining the relative durabilities of different fibre types has been limited by the lack of comparability between studies The effective assessment of fibre durability is an important aspect in fibre safety and requires the development of better and more co-ordinated experimental design. It may ultimately be possible to design vitreous fibres which have low durabilities in the lung but are adequately durable in the intended environment of use.

The Encapsulation of Salts by Consolidants Used in Stone Conservation

Stone has been used by man as a building material, and for sculpture, for thousands of years, because of its relative strength and durability. However, since the onslaught of industrialisation, the built environment has been subjected to increasing rates of decay. This has been met with a growth in conservation treatments. One of the aims of stone conservation is 10 prevent deterioration of the stone by the action of soluble salts present in the decayed stone. One approach is to encapsulate the salts in a consolidant, thereby suppressing their activity. This was one of the objectives when deeply penetrating consolidants were first investigated in the early 1970's. However, it transpired that some objects were still exhibiting efflorescence after consolidation. The aim of the work described in this paper was to undertake an investigation into the encapsulation of soluble salts by consolidants commonly used in stone conservation.

Biological activity of respirable industrial fibres treated to mimic residence in the lung

The durability of fibres in the lung environment after deposition could be a key factor in determining whether they accumulate to a sufficient tissue dose to cause pathological change. There is a shortage of information on the relative durabilities of respirable industrial fibres of various types. We describe a strategy for assessing the ability of different fibre types to persist in the lung milieu and to retain their biological activity. This is particularly important for the development of mesothelioma, where the long latent time that characterises this disease would be expected to exclude, from culpability, fibres that are not durable. We have combined a pre-treatment step in pH 5.0 or 7.0 with an assay that relies on the ability of fibres to damage the mesothelium. The long-term aim is to assess the impact that treatment in various pH solutions has on (a) fibre size/number, (b) loss of key elements, (c) the ability to damage the mesothelium. Such information should enable us to better predict the potential of fibres to cause mesothelioma.

An Energy-Based Method for Testing Cushioning Durability of Running Shoes

A new method for quantifying shoe cushioning durability was developed. This method used a computer-controlled, closed-loop materials testing system to subject the shoes to force-time profiles that were indicative of running. The change in the magnitude of the maximum energy absorbed by a shoe and the change in the magnitude of the energy balance of the shoe were quantified after the shoe had been worn running for a given distance. A shoe that changed very little in these quantities had a small energy wear factor and was deemed to have durable cushioning. The test method was roughly validated through comparison of three shoes of different midsole constructions with known relative durabilities. The shoes were tested at four simulated running speeds for energy properties when they were new and after they were run in for 161 km. The relative durabilities of the tested shoes were consistent with expectations based on the shoes' materials and constructions, showing that the new method has promise in predicting shoe cushioning durability, and thus more complete studies of the method may prove useful.

Evaluation of primers for adhesively-bonded aircraft repair

This paper contains the results of an investigation to determine the effectiveness of primers in promoting adhesion and improving the environmental durability of epoxy adhesive bonds on grit-blasted aluminum substrates. The control for this study consisted of phosphoric acid anodization of substrates followed by the application of EC 3924 B primer. The following primers were evaluated on grit-blasted substrates: (1) EC 3924 B; (2) Metlbond 6726; (3) Dow Corning Z-6040; and (4) EA 9203. In addition, grit blasting followed by Alodine application was compared with the other primers. Studies include shear strength evaluations of each primer/adhesive system at 23 and 105°C. In order to assess the relative durability of each system, shear strength testing at 93°C of samples exposed for 2 weeks to a 93°C/condensing humidity environment and wedge crack extension testing of samples exposed for a 2-week period to a 60°C/condensing humidity environment were performed. The peel strengths of the systems were determine...

An investigation of a site in Coal Measures for brickmaking materials: an illustration of procedures

Mudrocks of Coal Measures age are used extensively in the United Kingdom for making bricks. When a new brick pit is to be developed in such mudrocks an assessment has to be made of their geotechnical properties, notably their strength and durability in relation to the evaluation of slope stability of the sides of the pit. The influence of discontinuities on the stability of slopes also has to be taken into account. Groundwater conditions are another factor which require assessment since flooding of the brick pit must be avoided. Mudrocks in the Coal Measures generally are interbedded with siltstones and sandstones. Hence, one of the factors which a site exploration must determine is the proportion of material to be worked that is available for brickmaking purposes as opposed to how much material represents waste. Obviously, not only must the quantity be determined but so must the quality. The quality of the mudrock can be ascertained by chemical and mineralogical analyses. In this instance mineralogical assessment was made by X-ray diffraction and Keeling's method. The carbon and sulphur contents of the raw material were determined, as were the physical properties of brickquettes made from it. The material appeared to be highly suitable.

Durability of adhesively bonded steel under salt spray and hydrothermal stress conditions

The relative durability of bonded joints made from steel substrates with five different surface conditions was assessed considering the effects of salt spray, humidity exposure and applied load. The surface conditions comprised degreasing, ligth oiling, two established pretreatments and an experimental pretreatment applied on top of oil. The results clearly show large differences in durability, with the oily joints demonstrating the worst performance. Simply removing the oil had little beneficial effect. The pretreated joints performed dramatically better, including those where the treatment was applied on top of oil. The effect of applied stress is discussed in light of the high retained strength of some of the stressed joints.