Tests to determine the reactivity of supplementary cementitious materials (SCMs) by using isothermal calorimetry and thermogravimetric analysis have been proposed. In one such test, the heat release ...and calcium hydroxide consumption of SCMs mixed with calcium hydroxide (3:1 ratio of calcium hydroxide and SCM) at 50 °C in a 0.5 M potassium hydroxide environment are measured. In this study, we show the results of such testing for a large variety of SCMs and fillers, ranging from conventional materials such as fly ash, slag, silica fume, quartz, and limestone, to alternative materials such as calcined clays, municipal solid waste incineration fly ash, basic oxygen furnace slag, ground lightweight aggregates, ground pumice, ground glass pozzolan, and basalt fines. A total of 54 SCMs are tested using this approach. Results show that even among SCMs of the same type, there is considerable difference in the heat release and calcium hydroxide consumption, likely due to differences in amorphous content, chemical composition, and fineness, leading to different reactivities. Based on the response in the test, SCMs are classified into inert, pozzolanic, and latent hydraulic; the pozzolanic and latent hydraulic materials are further classified into less reactive and more reactive. The relationship between heat release and calcium hydroxide consumption depends on the chemical composition of the SCMs, and SCMs with high calcium, high alumina, and high silica contents show different relationships (determined by the slope of the heat release vs. calcium hydroxide plot).
This book offers the students and researchers a unique introduction to Bayesian statistics. Authors provide a wonderful journey in the realm of Bayesian Probability and aspire readers to become ...Bayesian statisticians. The book starts with Introduction to Probability and covers Bayes’ Theorem, Probability Mass Functions, Probability Density Functions, The Beta-Binomial Conjugate, Markov chain Monte Carlo (MCMC), and Metropolis-Hastings Algorithm. The book is very well written, and topics are very to the point with real-world applications but does not provide examples for computing using common open-source software.
This paper examines the impact of wet curing with different durations on differential drying shrinkage of concrete beams. The work shows that in severe drying conditions the magnitude of curling ...increased with the duration of wet curing of concrete specimens. Testing results are presented along with an explanation for the mechanisms observed. These findings provide guidance for wet curing durations for concrete slabs that must be resistant to volume change from drying.
•Resistance of microstructure to limewater and chloride penetration is investigated.•Drying rate is higher in lithium cured spans of bridge decks than in wet cured ones.•Lithium cured samples have ...higher chloride concentration than wet cured samples.
This paper gives a quantitative comparison of how different curing methods impact the rate of drying and subsequent penetration of lime water and chloride penetration of concrete. Laboratory work is used to investigate a bridge deck concrete mixture cured by two different curing compounds, wet curing of different lengths, and then no curing. The results confirm that wet curing methods reduce the ingress of external chemicals more effectively. The wet curing for even one day provided significant improvement over both curing compounds and no curing. To confirm the findings in the field eight bridge decks were investigated that were cured with a curing compound and wet curing. The field investigation confirms the findings of the laboratory testing and emphasizes the importance of wet curing for long term durability of concrete. This paper provides important quantitative data that can be used to compare these methods and help with making decisions about different curing practices and the impact on the service life of concrete.
Paste beams with different water-cementitious material ratios (w/cm) were cured for different durations with wet and sealed curing methods, and then the impact on curling M'as observed. The results ...show that the samples that were cured showed greater curling deflection and these effects increased with the length of curing for the drying conditions investigated. These findings could impact construction techniques for volume-change-sensitive structures such as slabs-on-ground in drying environments.
Curing compounds are used to retain moisture which promotes hydration to develop a tight microstructure. Because of the large surface-to-volume ratio of these structures, differential moisture loss ...can cause unwanted deflections, reduction in ride quality, and cracking. This paper quantitatively compares the effectiveness of different curing methods with an emphasis on curing compounds to resist moisture loss and subsequent volume changes caused by differential shrinkage. This work provides a quantitative comparison between different curing compounds, wet, sealed and no curing not made in previous publications. A performance-based cost analysis over the different curing compounds is also included. The result shows that the poly-alphamethylstyrene curing compound causes the lowest mass loss and subsequent deflections compared to the water-resin and water-wax-based curing compounds at equal coverage rates at equal costs. The work also shows that a double application of curing compound shows greater benefit than a single layer with the same volume for water-wax-based curing compounds. The results show that if adequate amounts of curing compounds are used then they are a useful curing method for members sensitive to differential drying such as concrete pavements.
Prolonged wet curing is thought by many to provide only improvements in concrete performance. Also, because of the large surface to volume ratio of volume change sensitive structures such as slabs on ...grade, differential moisture loss can cause unwanted deflections, reduction in ride quality, and cracking. This work has shown that there is a potential increase in the amount of curling of these structures that are wet cured and then subject to 1-D drying in severe drying conditions. Experiments on paste beams with different water-to-cementitious ratios and cured for different durations with wet and sealed curing methods as well as alternative tests on concrete beams with different curing lengths suggested that the extended wet curing causes a pore structure refinement resulting in greater saturation and consequently greater shrinkage. A simplified 1-D, drying diffusion and shrinkage model was able to adequately predict experimentally measured peak curling deflections as well as the entire curling history after further adjustments to input parameters and confirmed the effect of saturation on curling. Also, the ability of this analytical model to capture the mechanistic sources of wet curing on peak deflections was evaluated by comparing its predictions to those acquired via a fully nonlinear diffusion model. It was shown the overall deflection predictions by the approximate linearized model were in greater agreement with the measured data than with the full, nonlinear solution. Curing compounds are used to retain moisture which promotes hydration to develop a tight microstructure. This work provided a quantitative comparison between different curing compounds, wet, sealed, and no curing not made in previous studies and showed that adequate amounts of curing compounds are a useful curing method for members sensitive to differential drying such as concrete pavements in severe drying conditions. However, it was shown in less severe drying conditions that the curling strains caused by drying were minimal since the drying rate was less significant. So, if the concrete pavements are to be used in a moist environment, the type of curing that is used on pavements will have very little impact on their curling deformations.
Scope and Method of Study: Reducing the deformation in concrete pavements through the use of curing at early ages was the main concern of this study. In this project, supported by the Oklahoma ...Department of Transportation (ODOT), results from the curling of the paste and concrete beams and the effects of curing techniques on them were discussed separately. Effectiveness of wet curing and how it changes the moisture gradient and surface properties, and also the efficiency of the curing compounds in reducing the moisture loss and curling deflections were investigated. Findings and Conclusions: The results showed that the wet curing process on the specimens investigated did not reduce the drying shrinkage effects. Wet curing on either a paste or concrete beam which is sealed from all sides except the exposed surface is not recommended if curling is a concern for that element such as a concrete pavement. Draining the pavement could reduce this one-sided moisture loss and consequently the moisture gradient, drying shrinkage, and finally the curling deflections. The curing compound, however, had the best efficiency among all methods investigated in this project; the poly-alphamethylstyrene-resin had a very low water loss and beam deflection on paste specimens, while the water and wax based in a medium coverage with a double application was the best curing technique on concrete beams. The current research shows that the curing compound application in double layers has more benefit, since it is easier to provide a more uniform coverage than a single layer in the same dosage.
Curling iron Ley, Tyler; Hajibabaee, Amir
Roads & bridges,
01/2018
Magazine Article
Today's modern concrete construction technologies and experienced personnel provide an opportunity to construct the smoothest concrete pavements and slabs in history. Smooth pavements and slabs are ...in high demand because they reduce cracking, improve ride quality, reduce noise and improve fuel efficiency. One contributor to smoothness is caused by differential drying in the concrete that in turn causes upward slab curvature, or curl. This article focuses on comparing different methods of curing and their relative ability to reduce this phenomenon. Mitigation strategies also are discussed. Designing concrete pavements with a lower potential for curling is the most cost effective mitigation strategy. The development of upward slab curvature has the potential to decrease slab smoothness, even when no distress is present. The use of high quality curing com pounds, careful selection of mixture proportions and intelligent design can reduce the occurrence of curling in new construction. Grinding of rough concrete pavements can result in an immediate reduction in roughness due to slab curvature.
Aim
The aim of this study was to investigate the relationship between organizational ethical climate and components of nursing error reporting in selected hospitals of Tehran University of Medical ...Sciences in 2020.
Background
Error reporting is considered as a strategic indicator for error prevention.
Method
This is a cross‐sectional and correlational study that was conducted on 336 samples who had been selected by stratified random sampling method. Data were analysed by SPSS‐16 software, using descriptive and inferential statistics such as Mann–Whitney U and Kruskal–Wallis tests.
Results
The results of this study showed a significant and direct relationship between the organizational ethical climate and components of nursing error reporting (p < .05).
Conclusion
It is imperative for nursing managers in all management levels to remove barriers to nursing error reporting by using ethical climate strategies.
Implications for Nursing Management
It is difficult to obtain accurate statistics on medical errors and their causes in developing countries; therefore, nursing managers should provide the necessary conditions for formal, principled, and complete reporting of nursing errors for nurses without causing fear of punishmnet.
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