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This study investigated the mechanical properties and durability of mortar specimens containing various quantities of waste limestone powder (0%, 10%, 20%, and 30% of the weight of cement). The mechanical properties were evaluated in terms of flowability, compressive strength, and splitting tensile strength. Permeability was evaluated in terms of resistivity, absorption, and rapid chloride penetration (total charge- passed). Test results revealed that replacing 10% of the cement with limestone powder improves both mechanical performance and durability. However, reducing the cement content reduced the availability of hydration products to fill the pores in the microstructure. The hydration product of limestone powder was mainly calcium hydroxide, which undermines the development of strength in the paste. Nonetheless, our results indicate that waste limestone powder is suitable for the partial replacement of cement.

Asbestos is widely known as a hazardous material and can contribute to many diseases. Its removal and neutralization are complicated, it requires proper preparation and the use of appropriate technology. Immobilization of asbestos materials in geopolymers seems to be one of the alternatives to its storage in landfills. However, this requires several studies confirming the possibility of asbestos immobilization in geopolymers. Also, asbestos dust contains silicon and aluminum, which may prove useful in the production of geopolymers. The paper presents research results regarding the possibility of using geopolymers based on fly ashes for neutralizing asbestos. An up-to-date literature review on the technology of managing asbestos-containing products is presented. As a result of the research, partial usefulness of geopolymerization technology for binding and neutralizing waste with asbestos was found. The research was carried out using waste asbestos-cement composites. Mixtures based on geopolymers were made in which ground asbestos material was introduced in an amount of 30, 50 and 70% by weight. Compressive strength tests have shown that geopolymers with the addition of asbestos have compressive strength: over 34 MPa for a composition containing 30% of asbestos material and about 14 MPa for a composition containing 70% of asbestos material. SEM observations have shown that asbestos fibers do not dissolve in the geopolymer production process and they can still be a threat if the geopolymer matrix is damaged.

Concrete production unfavourably affects the environment due to high energy demands of cement production and consumption of limited natural resources. Therefore, waste utilization in fabrication of cementitious material is beneficial and legitimate. Significant reduction of environmental impact can be secured by utilization of various types of wastes or byproducts used for a partial substitution of cement binder or aggregates. However, the use of waste materials usually leads to deterioration of material properties of the designed composites. Therefore, it is very important to thoroughly investigate important materials properties to verify performance and practical usability of the newly designed materials. In this paper, three types of concrete mixes were designed. The reference concrete involved fine and coarse natural riverbed aggregates and two other mixes were designed using both, natural and recycled aggregates represented by crushed concrete paving cobbles. Concretes were tested in terms of basic physical properties (bulk density), mechanical properties (compressive strength), thermal properties (thermal conductivity, specific heat capacity, thermal diffusivity), and hygric properties (water vapour diffusion resistance factor, water vapour sorption at 97% RH, water absorption coefficient, moisture diffusivity) and experimentally determined data were compared and discussed. It was observed that materials properties of concretes with recycled aggregates are comparable with those of the reference concrete which is a promising fact from the environmental point of view.

This study aims to investigate the binding properties of co-fired fly ash (CFFA) in paste and mortar specimens. Paste specimens containing various CFFA proportions (25%, 50%, 75%, 100% by weight of cement) were conducted and evaluated using setting time tests, water demand tests and compressive strength tests. Mortar specimens containing various CFFA and Pulverised coal fly ash (PCFA) proportions (10%, 20%, 30% by weight of cement) were also conducted and compared with regard to flowability and compressive strength. The test results indicated that the water demand increased as the amount of CFFA replacement increased on the flow level at 110±3%; this is due to the higher ignition loss (L.O.I.). Higher L.O.I. values mean that there are more unburned carbon particles in the CFFA and that most of these carbon particles are porous. The compressive strength of mortar specimens decreased as the amount of CFFA replacement increased. Compared to the chemical compositions of cement (C3S, C2S), the main components of CFFA (Ca(OH)2, CaCO3, CaO) have lower crystalline strength and compactness. Therefore, the higher amount of CFFA replacement would inevitably cause a reduction of the cement contents of specimens, thereby reducing the compressive strength of the mortar specimens. Thus, an appropriate amount of superplasticiser and CFFA replacement in the mixture is useful with regard to the binding properties of cementitious materials.

In this study, the different proportions of co-fired fly ash and ground granulated blast-furnace slag were used to fully replace the cement as non-cement blended materials in a fixed water-cement ratio. The recycled fine aggregates were replaced with natural fine aggregates as 10%, 20%, 30%, 40% and 50%. The flowability, compressive strength, water absorption and scanning electron microscope observations were used as the engineered indices by adding different proportions of recycled fine aggregates. The test results indicated that the fluidity cannot be measured normally due to the increase in the proportion of recycled fine aggregates due to its higher absorbability. In the compressive strength test, the compressive strength decreased accordingly as the recycled fine aggregates increased due to the interface structure and the performance of recycled aggregates. The fine aggregates and other blended materials had poor cementation properties, resulting in a tendency for their compressive strength to decrease. However, the compressive strength can be controlled above 35 MPa of the green non-cement blended materials containing 20% recycled aggregates.

The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.

Conventional cementitious materials as tunnel supporting materials are utilised in the construction of the final repository for spent nuclear fuel. However, the use of cementitious material releases alkaline ions from pH12 to pH13 plumed into groundwater. Such a high pH is detrimental to the performance of the bentonite functioning, which may possibly enhance the dissolution and alteration of the fracture buffer and filling materials. Instead, low-pH cementitious materials are being developed for use in geological repositories. This study is aimed at evaluating the usability of low-pH cementitious materials containing 40% silica fume or composites blended with 20% silica fume and 40% fly ash. Engineering properties were analysed and verified through experimental research using the flow, compressive strength, pH measurement and hydraulic conductivity. Test results show that the replacement level with 40% of silica fume or 20% of silica fume and 40% of fly ash was suitable for the mixture of low-pH cementitious. Compared to the compressive strength and water permeability of ordinary cementitious, those of low-pH cementitious enhanced better engineered performances at the age of 91 days. The information is contributed us to establish the long-term durability and environmental requirements of disposal repositories in Taiwan.

BACKGROUND: China is the largest tobacco producer and has the highest number of tobacco consumers in the world. Extensive research has demonstrated the utility of social media for smoking cessation. WeChat is the most commonly used social media platform in China, but has not yet been utilized for smoking cessation interventions. The objectives of this study are (1) to evaluate the efficacy of a WeChat-based smoking cessation intervention; and (2) to examine a possible additive effect of integrating oral health and smoking-related information into a tailored, Transtheoretical Model (TTM) guided smoking cessation intervention. METHODS: Eligible adults were recruited through WeChat from July 1 to August 6, 2019, to participate in a 3-arm, single-blinded, randomized controlled trial. We enrolled and randomized 403 participants into three groups: the Standard Group, Enhanced Group, or a Waitlist-Control Group. Participants in the Standard Group received 20 smoking cessation-related messages for 2 weeks; participants in the Enhanced Group received this same protocol plus 6 oral health-related messages over an additional week. Participants in the Control Group received smoking cessation-related messages, after the post-intervention assessment. The primary outcome was TTM Stage of Change, and the secondary outcomes were 7-day Point Prevalence Abstinence (PPA), 24-h PPA, daily cigarette use, and nicotine dependence at 4 weeks follow-up post intervention, comparing intervention groups with the control group. The overall program attrition rate was 46%. Paired t-tests, McNemar tests, and linear and logistic regression were used to examine differences in smoking cessation outcomes within and between groups. RESULTS: Participants in the Enhanced Group (β = -1.28, 95%CI: -2.13, -0.44) and the Standard Group (β = -1.13, 95%CI: -1.95, -0.30) reported larger changes in nicotine dependence scores, compared to participants in the Waitlist Group. No statistically significant differences were found between the Enhanced Group and the Standard Group. DISCUSSION: This WeChat-based intervention was effective for smoking cessation overall. The addition of oral health information did not significantly improve the intervention.

Abstract Background Second-hand Smoke (SHS) exposure is a significant public health problem that may be responsible for serious health hazards for child. This study aimed to examine the exposure status of SHS and the factors associated with SHS avoidance behavior among the mothers of pre-school children. Methods A cross-sectional study was used to obtain a sample of the mothers of pre-school children (n = 1,020) in 30 registered kindergartens in eastern Taiwan. Overall, 919 (a response rate of 90%) completed the questionnaires. Regression models were used to identify factors with respect to the avoidance behavior of SHS. Results The prevalence of exposure to SHS was 70% and 50% for the mothers and their children, respectively. After adjusting for other variables, mothers who were current smokers (β = -0.260, p < 0.001), had spouses who smoked (β = -0.060, p < 0.05), SHS exposure (β = -0.138, p < 0.001), and/or children with exposure to SHS (β = -0.084, p < 0.05) were found to be less likely to avoid SHS, whereas mothers with a high knowledge score about SHS (β = 0.082, p < 0.01), positive attitudes (β = 0.274, p < 0.001) and a high self-efficacy level in regard to the avoidance of SHS (β = 0.397, p < 0.001) were observed to be more likely to avoid SHS. Regression analyses confirmed that the significantly factors associated with the avoidance behavior of SHS were self-efficacy, being a current smoker, and the attitude toward the avoidance of SHS to be that of 55.5% of the total variance explained (p < 0.001). Conclusions The high prevalence rate of exposure to SHS for mothers and their children suggests that a well-designed future intervention program should be implemented in regard to pre-school children's mothers in order to prevent these mothers and their children from SHS exposure hazards, more particularly, to strengthen the knowledge base, to enhance self-efficacy and to foster a more positive attitude toward the avoidance of SHS in the mothers.

Summary: Background: Uric acid (UA) and homeostatic model assessment of insulin resistance (HOMA‐IR) are endogenous biomarkers implicated in metabolic disorders and dysfunction. Objectives: To investigate the structural associations between sugar‐sweetened beverage intake (SSB), UA, HOMA‐IR and adolescent latent MetS construct (MetsC) representing paediatric metabolic syndrome (MetS). Methods: A population‐based representative adolescent cohort (n = 1454) was evaluated for risk profiles of MetS. Structural equation modelling was performed to identify multifactor structural associations between study parameters and evaluate mediating effects. Results: Adolescents had a single‐factor latent construct representing MetS. Increased SSB intake was associated with higher UA and HOMA‐IR levels, and the two biomarkers were positively associated with the MetsC score. UA and HOMA‐IR exerted three mediating effects on the association between fructose‐rich tea beverage (FTB) intake of >500 mL/day and MetsC: adjusted standardized coefficient and mediating effect (%), FTB → UA → MetsC: 0.071, 23.1%; FTB → HOMA‐IR → MetsC: 0.034, 11.0%; FTB → UA → HOMA‐IR → MetsC: 0.010, 3.1%. The UA‐associated pathways accounted for 31.1% of the overall mediation on the association between bottled sugar‐containing beverage intake and MetsC. After accounting for the UA‐ and HOMA‐IR‐derived detrimental effects, the fructose‐rich tea beverage intake of >500 mL/day had a tea‐related beneficial effect on MetsC, with an adjusted standardized coefficient of −0.103. Conclusions: UA and HOMA‐IR individually and jointly mediate the adverse effects of high fructose‐rich SSB intake on the mechanisms underlying paediatric MetS. Fructose‐free tea‐based beverages may have a beneficial effect on latent MetS structure in adolescents. [ABSTRACT FROM AUTHOR]