Investigation on microstructure and mechanical properties of FA/GGBS -based geopolymer after exposure at elevated temperature

Fly ash (FA) and ground granulated blast -furnace slag (GGBS) are industrial wastes and have been widely utilized as construction material due to the environmental impacts. The use of these by-products is not only for the sustainable construction but also for reducing the emission of CO2 due to the use of Portland cement. This study presents the microstructure and mechanical properties of geopolymer paste made from different ratios of low -calcium FA and GGBS after exposure at elevated temperature (500- 950oC). Compressive strength tests for both heated and unheated cylindrical specimens (using 50 mm x 100 mm mold) after the age of 28 days have been carried out. The results showed that the compressive strength of unheated specimens is increasing with increasing amount of GGBS in the mixes (up to 84 MPa). However, exposure at high temperature caused dehydration of water inside the specimen, resulting in strength loss. It was also found that exposure at 500oC caused a shrinkage, while a thermal expansion event was observed to occur at approximately 750oC. Moreover, scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) methods have been used to investigate the microstructure, phase composition, and pore distribution, respectively

Effect of Sodium Sulfate Activator on Compressive Strength and Hydration of Fly-Ash Cement Pastes

In the study, the effect of 4% sodium sulfate (Na2SO4) as an activator on cement pastes with 0%, 20%, and 40% fly-ash replacements and a low water-to-cementitious materials ratio of 0.30 was investigated. The investigation was conducted to evaluate the effectiveness of the technique for the utilization of fly ash in developing sustainable concrete. The use of Na2SO4 decreased setting times of the fresh pastes and increased compressive strength of the hardened pastes up to 28 days irrespective of fly-ash replacement. The use decreased Ca(OH)2 content in the hardened pastes irrespective of fly-ash replacement. Meanwhile, it increased Ca(OH)2 consumption by the pozzolanic reaction of fly ash and content of calcium silicate and aluminate hydrates in the hardened fly-ash–cement pastes. Consequently, the use of Na2SO4 negatively affected cement hydration in the hardened cement pastes without fly ash, while it accelerated ettringite formation and pozzolanic reaction of fly ash in the hardened pastes

Prediction of lowest nocturnal blood glucose level based on self-monitoring of blood glucose in Japanese patients with type 2 diabetes

Available online 13 September 2018Aims: Continuous glucose monitoring (CGM) is not available for all patients with type 2 diabetes (T2D) at risk of nocturnal hypoglycemia (NH).This study was performed to predict the lowest nocturnal blood glucose (LNBG) levels. Methods: An LNBG prediction formula was developed by multivariate analysis using the data including self-monitoring of blood glucose from a formula making (FM) group of 29 insulin-treated T2D patients with CGM. The validity of the formula was assessed by nonparametric regression analysis of actual and predicted values in a formula validation group consisting of 21 other insulin-treated patients. The clinical impact on prediction was evaluated using a Parkes error grid. Results: In the FM group with a median age of 64.0, the following formula was established: Predicted LNBG (mg/dL) = 127.4-0.836 x Age (y) + 0.119 x Self-monitored fasting blood glucose (mg/dL) + 0.717 x Basal insulin dose (U/day) (standard error of calibration 17.2 mg/dL). Based on the validation results, standard error of prediction was 31.0 mg/dL All predicted values fell within zones A (no effect on clinical action) and B (little or no effect on clinical outcome) on the grid. Conclusions: LNBG could be predicted, and may be helpful for NH prevention. (C) 2018 Elsevier Inc. All rights reserved.ArticleJOURNAL OF DIABETES AND ITS COMPLICATIONS. 32(12):1118-1123 (2018)journal articl

An investigation on moisture and water absorption in cement paste with electrical resistance method

Moisture in concrete is one of main factors related to degradation and deterioration of concrete structure, and there are various moisture transport phenomena in concrete such as drying and absorbing. There are a lot of previous studies on the drying process of concrete to clarify the mechanisms of creep as well as shrinkage. However, few studies have been reported on the process of water absorption and moisture absorption although carbonation and chloride attack are strongly related to moisture and water absorbing. It is necessary to investigate moisture transfer in concrete in detail. This study investigated the moisture transfer in moisture and water absorbing processes in cement paste by using electrical resistance method to understand how moisture and water transfer into concrete. Cement paste specimens with water-to-cement ratios (W/Cs) of 0.35 and 0.55 were prepared in this study. Stainless steel rods of 0.9 mm in diameter were arranged at an interval of 4 mm in the specimen for measuring the electrical resistance. The specimens for moisture and water absorbing test were cured in water at 20 ºC for 28 days and stored at 20 ºC and a relative humidity of 0% and 70% as reference and the national average of the annual average relative humidity in Japan, respectively. The electrical resistances were measured through the stainless-steel rods and converted to electrical resistivity. The calibration test was also conducted to obtain the relationship between the electrical resistivity and the internal relative humidity (IRH), which was used to know IRH in cement paste specimen. As a result, the rate of moisture transfer in the specimen at initial internal relative humidity (IIRH) of 0% was higher than that at IIRH of 70%. Additionally, the rate of moisture transfer in the specimen at any IIRH depends on the total pore volume in the specimen

Contribution of fly ash to mortar strength development under steam and internal curing

The purpose of this study is to quantitatively evaluate the effects of steam curing and internal curing on contribution of fly ash to strength development of mortar by using cementing efficiency factor (k-value) that represents strength development performance as a binder of fly ash. In addition, the pozzolanic reaction of fly ash was evaluated from the viewpoint of calcium hydroxide consumption by using thermogravimetry and differential thermal analysis as well as the degree of fly ash reaction by using selective dissolution method. The result indicated that steam curing improved early compressive strength and internal curing improved compressive strength and k-value at all ages. Also, a linearrelationship between the degree of fly ash reaction and the k-value was shown regardless of the age and the replacement ratio of fly ash

Fermented persimmon extract (kaki-shibu) is useful as a standard for component analyses of persimmon phytobezoars

The definite diagnosis of persimmon phytobezoar (i.e., diospyrobezoar) is often accomplished by a component analysis using infrared spectroscopy. However, no studies have been conducted to investigate which substance is the best as a standard for the component analysis. Here we analyzed tannic acid, Japanese persimmon (kaki), fermented persimmon extract (kaki-shibu), conventional dried persimmon, and dried persimmon smoked in sulfur (ampo-kaki) by infrared spectroscopy to determine which would be optimal as a component analysis standard. The spectrum between 1,600 to 600cm－1 of a persimmon phytobezoar was quite similar to the spectrum of kaki-shibu rather than that of tannic acid. Consequently, we conclude that kaki-shibu should be used as a standard for infrared spectroscopy analyses of persimmon phytobezoars

日本の保健師が期待する発達障害児とその家族を支援する民生委員の役割と能力

Background: Public Health Nurses (PHNs) collaborate with community volunteer welfare commissioners to support children with developmental disorders and their families lead a life without isolation. Objective: This study aims to clarify the roles and competencies that PHNs expect of welfare commissioners in supporting children with developmental disorders and their families. Methods: An online survey was administered through Survey Monkey© to 220 PHNs working in Japanese municipalities using an independently developed questionnaire regarding the roles and competencies of welfare commissioners supporting children with developmental disorders and their families expected by PHNs. Exploratory Factor Analysis (EFA) was performed to simplify the data structure and enhance understanding. The reliability of the scale was confirmed using Cronbach’s α. Differences due to PHN attributes (e.g., experience collaborating with welfare commissioners) were analyzed using Welch’s t-test. This study was conducted between April and September 2021. Results:The highest scoring items were, for the role, “a welfare commissioner’s role is to pass on accurate information to their successor,” and for competencies, “a necessary competency for a welfare commissioner is to protect the information about children with developmental disorders, and their families learned during one’s work.” The EFA results revealed a two-factor structure for role items: Factor 1, “Supporting children with developmental disorders and their families and preventing abuse,” and Factor 2, “Connecting to social resources.” Competency items were also found to have a two-factor structure: Factor 1, “Understanding the position of children with developmental disorders and their families and connecting with local residents,” and Factor 2, “Understanding developmental disorders and supporting them based on assessment.” A comparison of the attributes of PHNs showed no significant differences. Conclusion: PHNs feel welfare commissioners should pass on the information and protect confidentiality when supporting children with developmental disorders and their families. Furthermore, PHNs expect welfare commissioners to connect children with developmental disorders and their families to the community, prevent abuse, and provide support based on assessment. PHNs had the same expectations regarding the roles and competencies of welfare commissioners regardless of their own attributes