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The alkali–silica reaction (ASR) can cause expansion, cracking, and degradation of the mechanical properties of affected concrete. Concerns about the safety of ASR-damaged reinforced concrete structures have driven the demand for studying the effects of ASR on residual load capacity of the deteriorated structure. Conventionally, field load testing methods are used to assess the residual load capacity of ASR-affected structures. In this study, a novel accelerated laboratory test using the LVSA 50/70 autoclave to accelerate ASR was applied to investigate the flexural and shear behavior of small-scale reinforced concrete beams affected by ASR. The specimens were subjected to three cycles of 80 °C steam curing at atmospheric pressure in the autoclave, with 60 h/cycle. Significant expansion and ASR damage were observed. Load carrying capacity tests on the small-scale reinforced concrete beams showed that, at the expansion levels achieved, the flexural capacity of the reinforced concrete beams was not significantly affected. Shear resistance of the reinforced concrete beams, however, was found to increase compared with their 28-day counterparts, which could be attributed to the prestressing effect due to ASR expansion. It appears that the multicycle 80 °C steam-curing autoclave test is suitable for investigating ASR deterioration of actual concrete mixes within a short period of time. ASR effects on the load carrying capacity of reinforced concrete elements at higher expansion levels, however, need further investigation. more...

Supplementary cementitious materials (SCMs) are widely used to reduce the cement content to achieve economic and environmental objectives. As a result, understanding the shrinkage of blended cement-based concrete is essential. In total, 21 concrete mixes were produced with type general purpose cement and with cement replacements of 30% by fly ash, 40% and 60% by ground granulated blast furnace slag (GGBFS). The concrete compressive strength ranged from 25 MPa to 100 MPa. Experimental results were also compared with the predictions by models. Additional tests on pastes with the same SCM content were conducted to investigate both autogenous and chemical shrinkage in relation to their time-dependent pore structure refinement. For concretes with strength below 50 MPa, no significant difference in autogenous shrinkage could be observed between the different blends up to 28 days. However, the autogenous shrinkage of GGBFS concrete increased significantly after 28 days, being about 50% higher than all other concretes at 100 days. This late increase in autogenous shrinkage between 28 and 100 days can be attributed to pore refinement processes. No clear difference was observed for GGBFS concretes with strength greater than 50 MPa. Autogenous shrinkage of fly ash concretes was overall equivalent to that of reference concretes. more...

Supplementary cementitious materials (SCMs) are widely used to reduce the cement content to achieve economic and environmental objectives. As a result, understanding the shrinkage of blended cement-based concrete is essential. In total, 21 concrete mixes were produced with type general purpose cement and with cement replacements of 30% by fly ash, 40% and 60% by ground granulated blast furnace slag (GGBFS). The concrete compressive strength ranged from 25 MPa to 100 MPa. Experimental results were also compared with the predictions by models. Additional tests on pastes with the same SCM content were conducted to investigate both autogenous and chemical shrinkage in relation to their time-dependent pore structure refinement. For concretes with strength below 50 MPa, no significant difference in autogenous shrinkage could be observed between the different blends up to 28 days. However, the autogenous shrinkage of GGBFS concrete increased significantly after 28 days, being about 50% higher than all other concretes at 100 days. This late increase in autogenous shrinkage between 28 and 100 days can be attributed to pore refinement processes. No clear difference was observed for GGBFS concretes with strength greater than 50 MPa. Autogenous shrinkage of fly ash concretes was overall equivalent to that of reference concretes. more...

Durability of concrete structures is an important issue in the modern world, with the performance of concrete as a construction material significantly impacting its environmental, economic, and social costs. Understanding of the chemical behaviour of concrete informs the prevention and mitigation of potential causes of durability loss. Delayed e ttringite f ormation (DEF) is a chemical process in concrete that can cause expansion, microcracking and strength loss. It is a known risk of durability loss, in particular with precast concrete. The primary mechanism of DEF is the dissolution of the sulfate mineral ettringite during early hydration and subsequent re-precipitation as an expansive phase in hardened cement paste. The major factors of DEF relate to the saturation of the pore solution with sulfate ions. Primary factors that influence sulfate solubility are alkalinity and temperature, particularly in the early stage of hydration. Factors that influence the ettringite formation are aluminate and sulfate, and their content ratios. DEF is mainly initiated in the manufacturing process of precast elements and is a consequence of phase development during hydration. Isothermal calorimetry provides a way to monitor cement paste hydration and to investigate the role of alkali and sulfate content in phase development. This paper present s the outcomes of a study on the influence of these chemical factors on the hydration process and correlate s this with phase development by characterisation of phases using XRD and TGA in paste compositions that are both DEF free and at-risk of deleterious DEF. more...

Durability of concrete structures is an important issue in the modern world, with the performance of concrete as a construction material significantly impacting its environmental, economic, and social costs. Understanding of the chemical behaviour of concrete informs the prevention and mitigation of potential causes of durability loss. Delayed e ttringite f ormation (DEF) is a chemical process in concrete that can cause expansion, microcracking and strength loss. It is a known risk of durability loss, in particular with precast concrete. The primary mechanism of DEF is the dissolution of the sulfate mineral ettringite during early hydration and subsequent re-precipitation as an expansive phase in hardened cement paste. The major factors of DEF relate to the saturation of the pore solution with sulfate ions. Primary factors that influence sulfate solubility are alkalinity and temperature, particularly in the early stage of hydration. Factors that influence the ettringite formation are aluminate and sulfate, and their content ratios. DEF is mainly initiated in the manufacturing process of precast elements and is a consequence of phase development during hydration. Isothermal calorimetry provides a way to monitor cement paste hydration and to investigate the role of alkali and sulfate content in phase development. This paper present s the outcomes of a study on the influence of these chemical factors on the hydration process and correlate s this with phase development by characterisation of phases using XRD and TGA in paste compositions that are both DEF free and at-risk of deleterious DEF. more...

The Alkali Silica Reaction (ASR) is a deleterious reaction in concrete that poses significant durability concern worldwide. As a preventative measure, total alkali content of general purpose Portland cements can be limited. In Australia, like in other countries, general purpose cement is limited with a conservative alkali content of 0.6%, this may be unnecessary, as low risk non-reactive aggregates and SCM blends are effective in reducing ASR prevalence. Indeed there is a growing argument to transition to risk assessed methods in choosing cement alkali levels. ASTM in the USA has employed a prescriptive approach to selecting preventative measures that incorporates a variety of cement alkali contents without compromising on safety. Similar balanced alkali approaches such as those recommended in Europe, Canada and New Zealand may be applicable in Australia. Raising alkali limits to a level greater than 0.6% in cement used in conjunction with alternative mitigation techniques would reduce the economic and environmental impact associated with alkali removal during cement production. This literature review discusses the Australian approach to alkali limits in contrast to the methods used around the world and explores the continuing research into alkali’s mechanistic contribution to ASR. more...

The Alkali Silica Reaction (ASR) is a deleterious reaction in concrete that poses significant durability concern worldwide. As a preventative measure, total alkali content of general purpose Portland cements can be limited. In Australia, like in other countries, general purpose cement is limited with a conservative alkali content of 0.6%, this may be unnecessary, as low risk non-reactive aggregates and SCM blends are effective in reducing ASR prevalence. Indeed there is a growing argument to transition to risk assessed methods in choosing cement alkali levels. ASTM in the USA has employed a prescriptive approach to selecting preventative measures that incorporates a variety of cement alkali contents without compromising on safety. Similar balanced alkali approaches such as those recommended in Europe, Canada and New Zealand may be applicable in Australia. Raising alkali limits to a level greater than 0.6% in cement used in conjunction with alternative mitigation techniques would reduce the economic and environmental impact associated with alkali removal during cement production. This literature review discusses the Australian approach to alkali limits in contrast to the methods used around the world and explores the continuing research into alkali’s mechanistic contribution to ASR. more...

Heat waves (HWs) have killed more people in Australia than all other natural hazards combined. Climate change is expected to increase the frequency, duration, and intensity of HWs and leads to a doubling of heat-related deaths over the next 40?years. Despite being a significant public health issue, HWs do not attract the same level of attention from researchers, policy makers, and emergency management agencies compared to other natural hazards. The purpose of the study was to identify risk factors that might lead to population vulnerability to HW in Western Australia (WA). HW vulnerability and resilience among the population of the state of WA were investigated by using time series analysis. The health impacts of HWs were assessed by comparing the associations between hospital emergency department (ED) presentations, hospital admissions and mortality data, and intensities of HW. Risk factors including age, gender, socioeconomic status (SES), remoteness, and geographical locations were examined to determine whether certain population groups were more at risk of adverse health impacts due to extreme heat. We found that hospital admissions due to heat-related conditions and kidney diseases, and overall ED attendances, were sensitive indicators of HW. Children aged 14?years or less and those aged 60?years or over were identified as the most vulnerable populations to HWs as shown in ED attendance data. Females had more ED attendances and hospital admissions due to kidney diseases; while males had more heat-related hospital admissions than females. There were significant dose-response relationships between HW intensity and SES, remoteness, and health service usage. The more disadvantaged and remotely located the population, the higher the health service usage during HWs. Our study also found that some population groups and locations were resilient to extreme heat. We produced a mapping tool, which indicated geographic areas throughout WA with various vulnerability and res more...

Understanding how students and educators use social media, and their perceptions of its benefits, may lead to opportunities for successful integration of social media to benefit all those involved in medical education. We aimed to explore and describe how medical students use social media in countries across the world, including the extent to which they consume and contribute. 741 students from 8 institutions in 5 countries answered a 16-item questionnaire. The majority of students were using some form of social media, with the most popular application being Facebook. Social communication and entertainment were the most cited reasons for using social media. Students reported valuing social media for educational reasons and, in particular, information and resource sharing between peers. Institution-student interactions were not common amongst medical students and whilst some students reported wanting more of this, others reported that they did not. The paucity of student-institution interactions on social media did not vary across institutions. Although some students could see benefits to increasing use of social media by medical schools, others had concerns about this. Of particular concern were confidentiality and professionalism online and the perception that the medical schools might not do it well. Medical schools should have a clear rationale for engaging further in social media, mindful of what students want and of the need for the engagement to be conducted professionally. more...

Objective: To determine which measures of heatwave have the greatest predictive power for increases in health service utilisation in Perth, Western Australia. Methods: Three heatwave formulas were compared, using Poisson or zero-inflated Poisson regression, against the number of presentations to emergency departments from all causes, and the number of inpatient admissions from heat-related causes. The period from July 2006 to June 2013 was included. A series of standardised thresholds were calculated to allow comparison between formulas, in the absence of a gold standard definition of heatwaves. Results: Of the three heatwave formulas, Excess Heat Factor (EHF) produced the most clear dose-response relationship with Emergency Department presentations. The EHF generally predicted periods that resulted in a similar or higher rate of health service utilisation, as compared to the two other formulas, for the thresholds examined. Conclusions: The EHF formula, which considers a period of acclimatisation as well as the maximum and minimum temperature, best predicted periods of greatest health service demand. The strength of the dose-response relationship reinforces the validity of the measure as a predictor of hazardous heatwave intensity. Implications: The findings suggest that the EHF formula is well suited for use as a means of activating heatwave plans and identifies the required level of response to extreme heatwave events as well as moderate heatwave events that produce excess health service demand. more...

We aimed to determine the natural history of borderline increases in albuminuria in adolescents with insulin-dependent (Type 1) diabetes mellitus (IDDM) and factors which are associated with progression to persistent microalbuminura. Fifty-five normotensive adolescents with IDDM and intermittent microalbuminura (overnight albumin excretion rate of 20-200 mug min-1 on one of three consecutive timed collections, n = 29) or borderline albuminura (mean overnight albumin excretion rate of 7.2-20 mug min-1 on one of three consecutive timed collections, n = 30) were followed prospectively at 3 monthly intervals. The endpoint was persistent microalbuminuria defined as a minimum of three of four consecutive overnight albumin excretion rates of greater than 20 mug min-1. One hundred and forty-two adolescents with IDDM and normoalbuminura were also followed prospectively. Fifteen of the 59 patients (25.4%) with intermittent (9/29) or borderline (6/30) albuminura progressed to persistent microalbuminura (progressors) over 28 (1550) months [median (range)] in comparison with two of the 142 patients with normoalbuminuria at entry (relative risk = 12.6; p = 0.001). Progressors to persistent microalbuminura were pubertal and had higher systolic (p = 0.02) and diastolic (p = 0.02) blood pressure, and HbA(lc) (p = 0.004) than non-progressors. All patients remained normotensive. Glomerular filtration rate, apolipoproteins, dietary phosphorus, protein and sodium intakes, and prevalence of smoking did not differ between progressors and non-progressors. Total renin was higher in the diabetic patients without a difference between progressors and non- progressors. In conclusion there is a relatively high rate of progression to persistent microalbuminuria in pubertal adolescents with borderline increases in albuminura and duration greater than 3 years. These patients require attention to minimize associated factors of poor metabolic control and higher blood pressure in the development of in more...

We aimed to determine the natural history of borderline increases in albuminuria in adolescents with insulin-dependent (Type 1) diabetes mellitus (IDDM) and factors which are associated with progression to persistent microalbuminura. Fifty-five normotensive adolescents with IDDM and intermittent microalbuminura (overnight albumin excretion rate of 20-200 mug min-1 on one of three consecutive timed collections, n = 29) or borderline albuminura (mean overnight albumin excretion rate of 7.2-20 mug min-1 on one of three consecutive timed collections, n = 30) were followed prospectively at 3 monthly intervals. The endpoint was persistent microalbuminuria defined as a minimum of three of four consecutive overnight albumin excretion rates of greater than 20 mug min-1. One hundred and forty-two adolescents with IDDM and normoalbuminura were also followed prospectively. Fifteen of the 59 patients (25.4%) with intermittent (9/29) or borderline (6/30) albuminura progressed to persistent microalbuminura (progressors) over 28 (1550) months [median (range)] in comparison with two of the 142 patients with normoalbuminuria at entry (relative risk = 12.6; p = 0.001). Progressors to persistent microalbuminura were pubertal and had higher systolic (p = 0.02) and diastolic (p = 0.02) blood pressure, and HbA(lc) (p = 0.004) than non-progressors. All patients remained normotensive. Glomerular filtration rate, apolipoproteins, dietary phosphorus, protein and sodium intakes, and prevalence of smoking did not differ between progressors and non-progressors. Total renin was higher in the diabetic patients without a difference between progressors and non- progressors. In conclusion there is a relatively high rate of progression to persistent microalbuminuria in pubertal adolescents with borderline increases in albuminura and duration greater than 3 years. These patients require attention to minimize associated factors of poor metabolic control and higher blood pressure in the development of in more...

There were over 600 antibodies submitted to HLDA8, with many of unknown specificity. Of these, 101 antibodies were selected for a blind panel study that also included 5 negative controls and 27 positive controls of known CD specificity making a total of 133 antibodies in the final panel. Of the 101 unknowns, 31 antibodies were identified during the course of this blind panel study as being specific for known molecules and included some specific for MHC class II antigens, CD45 isoforms and the Dombrock antigen. Several antibody pairs among those in the blind panel were found to have very similar staining patterns and were therefore compared by immunohistochemical and/or Western blot analyses for identity. © 2005 Elsevier B.V. All rights reserved. more...

There were over 600 antibodies submitted to HLDA8, with many of unknown specificity. Of these, 101 antibodies were selected for a blind panel study that also included 5 negative controls and 27 positive controls of known CD specificity making a total of 133 antibodies in the final panel. Of the 101 unknowns, 31 antibodies were identified during the course of this blind panel study as being specific for known molecules and included some specific for MHC class II antigens, CD45 isoforms and the Dombrock antigen. Several antibody pairs among those in the blind panel were found to have very similar staining patterns and were therefore compared by immunohistochemical and/or Western blot analyses for identity. © 2005 Elsevier B.V. All rights reserved. more...

When a single-fibre composite test is performed to obtain information about the interfacial adhesion in a composite, a gradual strain increase often causes an opaque (black) cylinder to nucleate at, and grow from, the fibre failure sites. The nature of the opaque cylinder is difficult to ascertain using optical microscopy. This is the subject of the present note. To study the inside of the opaque cylinder we use several experimental methods based on imaging the failed region: optical microscopy, laser Raman spectroscopy and scanning electron microscopy. Mechanical models, including FEM analysis and analytic equations based on the shear-lag, approach, are used to discuss the experimental work. The nature and growth mechanism of the opaque cylinder are of importance in defining the parameters and/or contributions that appear in both the force balance and the. energy balance schemes., QC 20100525 more...

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