Long-term behaviour of particulate-filled epoxy-based polymers

Epoxy-based polymers are now widely used in civil engineering applications including bonding of structural elements, filling for structural repair, and coating for railway sleepers. Recently, different particulate fillers were introduced to reduce the cost of epoxy-based polymers. While the optimum amount of fillers was found to enhance the short-term properties of epoxy-based polymers, their effect on the long-term properties is still unknown. Understanding the long-term behavior of epoxy-based polymers is important as this material is subject to different environmental conditions, which can limit their application range. This study systematically investigated the long-term durability through deep understanding of the mechanistic response of particulate-filled epoxy-based polymer coating containing fire retardant (FR) and fly ash (FA) fillers. It focused on the weathering effects of high moisture, elevated in-service temperature, and solar ultraviolet (UV) radiation, and the synergistic effects of these severe environmental conditions on the mechanical, physico-chemical and microstructure behavior of particulate-filled epoxy-based polymer. New empirical models were also developed to predict the changes in the mechanical characteristics of epoxy-based polymers when exposed to harsh environmental conditions. The effect of in-service elevated temperature (from room temperature to 80°C) was evaluated as the first study. FR and FA filler materials were increased from 0% to 60% (with an increment of 20%) in the epoxy based matrix. The physical, mechanical and microstructure of particulate-filled epoxy polymers epoxy-based polymer matrix was examined. The results showed that sensitivity of epoxy resin against in-service temperatures can be significantly improved by the inclusion of fillers by up to 60% by volume. A simplified prediction equation based on power function showed a strong correlation to the experimental strength properties of particulate-filled epoxy based resin at different levels of in-service elevated temperature. The effect of the combined moisture and temperature (hygrothermal conditioning) on the durability of particulate-filled epoxy resin was investigated as the second study. The epoxy resin was conditioned for up to 3000 h at temperatures up to 60ºC and a relative humidity of 98%. Inclusion of fillers was found to decrease the moisture absorption, increase the glass transition temperature and slightly reduce the mechanical properties after hygrothermal conditioning. Based on the Arrhenius model, the filled epoxy polymers can retain more than 70% of their mechanical properties at 100 years of service in the Australian environment. The behaviour of the particulate filled epoxy polymer coating when exposed to UV was investigated as the third study. Epoxy-based resin system filled with FR and FA was exposed to UV for up to 2000 h. It was found that adding up to 60% by volume of FR and FA reduced the UV degradation to 0.5 mm, which is 5 times less than that of the neat epoxy resin. The developed prediction equation showed that providing a polymer coating of 11 mm will result in up to 100 years UV resistant materials. Finally, the synergistic effect of temperature, moisture and UV on the long-term performance of the particulate filled epoxy polymer coating was evaluated. The polymer coating was conditioned at a relative humidity of 98% and temperature of 60ºC for 2000 h (HG). These specimens were then exposed to UV for 2000 h. It was found that not all environmental conditions were detrimental to the properties of particulate filled epoxy, indicating its suitability as a protective coating material. An in-depth understanding of the long-term behaviour of particulate filled epoxy polymer coating was the significant outcome of this study. The results from this work provided a good representation and comparison of the long-term properties and durability performance of particulate filled epoxy polymer coating in different harsh environments. The experimental data, theoretical models and predictions equations derived from this study are critical for a safe mix design and use of epoxy-based polymers as coating for civil infrastructure

Polypropylene fibre reinforced cement mortars containing rice husk ash and nano-alumina

This paper presents the effects of incorporating two supplementary cementitious materials: rice husk ash (RHA) and nano-alumina (NA) in polypropylene fiber (PPF) reinforced cement mortars. RHA is an agricultural waste material and thus recycling of this material has substantial economic and environmental benefits. Compressive strength, flexural strength, water absorption and drying shrinkage of the hardened composites were investigated. The interfacial transition zone and the microstructures were studied by using scanning electron micrograph (SEM) and X-ray diffraction (XRD) analysis. A slight increase in compressive strength of mortar was observed by using up to 10 wt% of RHA as a replacement of cement. However, addition of nano-alumina helped the compressive strength of mortar remain approximately equal to that of the control specimen even when 20 or 30 wt% RHA was used. Addition of polypropylene fibers resulted in significant increase in the flexural strength of the mortar specimens. It was also observed that NA and PPF could reduce water absorption by pore blocking effect. The positive interactions between polypropylene fibers and RHA resulted in the lowest drying shrinkage of the fibrous mortar containing RHA. XRD analysis showed that the intensity of Alite and Belite phases decreased and new peak of portlandite produced with the addition of NA. The addition of RHA enhanced the late strength of the cement composites. Consequently, the combined addition of RHA, NA and PPF has resulted in increasing of flexural strength and reduction in both water absorption and drying shrinkage of mortars

Effect of elevated in-service temperature on the mechanical properties and microstructure of particulate-filled epoxy polymers

In civil engineering applications, epoxy-based polymers are subject to different environmental conditions including in-service temperature, which might accelerate their degradation and limit their application ranges. Recently, different particulate fillers were introduced to enhance the mechanical properties and reduce the cost of epoxy-based polymers. This paper addresses the effect of in-service elevated temperature (from room temperature to 80o C) in particulate-filled epoxy based resin containing up to 60% by volume of fire retardant and fly ash fillers through a deep understanding of the microstructure and analysis of their mechanistic response. An improvement in the retention of mechanical properties at in-service elevated temperature was achieved by increasing the percentages of fillers. The retention of compressive and split tensile strength at 80o C for the mix containing 60% fillers was 72% and 52%, respectively, which was significantly higher than the neat epoxy. Thermo-dynamic analysis showed an increase in glass transition temperature with the inclusion of fillers, while these mixes also experienced less weight loss compared to neat epoxy, indicating better thermal stability. Scanning electron microscopy images showed the formation of dense microstructures for particulate-filled epoxy based resin at elevated temperatures. This indicates that the particulate filled epoxy resin exhibits better engineering properties at in-service elevated temperatures, increasing their durability and therefore their suitability for civil engineering applications. A simplified prediction equation based on power function was proposed and showed a strong correlation to the experimental compressive and splitting tensile strength at different levels of in-service elevated temperature

The Legibility Efficacy of Historical Neighborhoods in Creating a Cognitive Map for Citizens

Nowadays, historical neighborhoods in Iran are in a state of decay due to the lack of spatial legibility with respect to their organic spatial layout. Hence, the level of interaction among people and their perception of the environment has gradually diminished. Historical neighborhoods no longer possess their former prosperity and function, and citizens prefer to inhabit neighborhoods with newer configurations to meet their demands. The aim of this study was to investigate the role of the spatial legibility of historical neighborhoods in creating a suitable cognitive map for citizens. Quantitative and qualitative methods were applied using a questionnaire and simulation test instruments. In addition, in order to analyze the spatial configuration of the target areas, the Space Syntax method was implemented using Depthmap 10. The findings indicated that landmarks and navigation signs were identified as the most important factors affecting legibility from the viewpoint of users. Furthermore, the correlation between integration and connectivity illustrated that the studied areas possessed poor spatial legibility due to the organic texture of their spatial configurations. Accordingly, solutions such as enhancing the interaction between highly integrated streets and identified landmarks were emphasized to ameliorate the legibility of these spaces. The present study contributes to sustainable urban design with respect to the rejuvenation of historical districts by proposing a set of pragmatic alterations of urban spatial configurations. This research may be fruitful for urban designers, planners and managers seeking to revitalize historical neighborhoods

Effect of nano-CuO on engineering and microstructure properties of fibre-reinforced mortars incorporating metakaolin: experimental and numerical studies

In this study, the effects of nano-CuO (NC) on engineering properties of fibre-reinforced mortars incorporating metakaolin (MK) were investigated. The effects of polypropylene fibre (PP) were also examined. A total of twenty-six mixtures were prepared. The experimental results were compared with numerical results obtained by adaptive neuro-fuzzy inference system (ANFIS) and Primal Estimated sub-GrAdient Solver for SVM (Pegasos) algorithm. Scanning Electron Microscope (SEM) was also employed to investigate the microstructure of the cement matrix. The mechanical test results showed that both compressive and flexural strengths of cement mortars decreased with the increase of MK content, however the strength values increased significantly with increasing NC content in the mixture. The water absorption of samples decreased remarkably with increasing NC particles in the mixture. When PP fibres were added, the strengths of cement mortars were further enhanced accompanied with lower water absorption values. The addition of 2 wt % and 3 wt % nanoparticles in cement mortar led to a positive contribution to strength and resistance to water absorption. Mixture of PP-MK10NC3 indicated the best results for both compressive and flexural strengths at 28 and 90 days. SEM images illustrated that the morphology of cement matrix became more porous with increasing MK content, but the porosity reduced with the inclusion of NC. In addition, it is evident from the SEM images that more cement hydration products adhered onto the surface of fibres, which would improve the fibre–matrix interface. The numerical results obtained by ANFIS and Pegasos were close to the experimental results. The value of R2 obtained for each data set (validate, test and train) was higher than 0.90 and the values of mean absolute percentage error (MAPE) and the relative root mean squared error (PRMSE) were near zero. The ANFIS and Pegasos models can be used to predict the mechanical properties and water absorptions of fibre-reinforced mortars with MK and NC

Multifactorial e- and mHealth interventions for cardiovascular disease primary prevention: Protocol for a systematic review and meta-analysis of randomised controlled trials

Objective: Cardiovascular diseases (CVD) are a leading cause of mortality and disease burden. Preventative interventions to augment the population-level adoption of health lifestyle behaviours that reduce CVD risk are a priority. Face-to-face interventions afford individualisation and are effective for improving health-related behaviours and outcomes, but they are costly and resource intensive. Electronic and mobile health (e-and mHealth) approaches aimed at modifying lifestyle risk factors may be an effective and scalable approach to reach many individuals while preserving individualisation. This systematic review aims to (a) determine the effectiveness of multifactorial e-and mHealth interventions on CVD risk and on lifestyle-related cardiometabolic risk factors and self-management behaviours among adults without CVD; and (b) describe the evidence on adverse events and on the cost-effectiveness of these interventions. Methods: Methods were detailed prior to the start of the review in order to improve conduct and prevent inconsistent decision making throughout the review. This protocol was prepared following the PRISMA-P 2015 statement. MEDLINE, CINAHL, Embase, PsycINFO, Web of Science, Cochrane Public Health Group Specialised Register and CENTRAL electronic databases will be searched between 1991 and September 2019. Eligibility criteria are: (a) population: community-dwelling adults; (b) intervention/comparison: randomised controlled trials comparing e-or mHealth CVD risk preventative interventions with usual care; and (c) outcomes: modifiable CVD risk factors. Selection of study reports will involve two authors independently screening titles and abstracts, followed by a full-text review of potentially eligible reports. Two authors will independently undertake data extraction and assess risk of bias. Where appropriate, meta-analysis of outcome data will be performed. Discussion: This protocol describes the pre-specified methods for a systematic review that will provide quantitative and narrative syntheses of current multifactorial e-and mHealth CVD preventative interventions. A systematic review and meta-analysis will be conducted following the methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions and reported according to PRISMA guidelines