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• Using PG excites the reactivity of FA and improves the hydration degree of cement. • Mechanical properties and permeability of steam-cured sample are investigated. • Using appropriate amount of PG reduces cost and environmental impact of steam-cured FA mortar. Incorporating proper amount of fly ash (FA) contributes to improve the long-term performance of steam-cured mortar. However, with the introduction of stringent environmental policies, the reserves of high-quality FAs are decreasing and the costs are increasing. In this study, phosphogypsum is used to replace part of FA to produce high-quality prefabricated components, and mechanical properties, water permeability, microstructure and environmental benefits of samples are investigated. The research results show that replacing FA with proper amount of PG can greatly increase mechanical properties of steam-cured FA mortar and improve its water impermeability. When 10% of PG is applied to the steam-cured FA mortar, the 1-d and 28-d compressive strengths of the samples increase by 11% and 5.37%, respectively, relative to the control mortar. The results of microstructure characterization show that this is due to the generation of swelling products and the increase of the reaction degree of FA. When PG and steam curing are applied in combination, FA is severely corroded and a gel phase product is generated, which contributes to increase the strength of specimen. In addition, using appropriate amount of PG also brings obvious economic and environmental benefits for prefabricated components. [ABSTRACT FROM AUTHOR]

• The iron-copper tailings are recycled in prefabricated elements. • The mechanical properties and durability of steam-cured mortars are investigated. • Adding an appropriate amount of tailings is beneficial to improve the performance of steam-cured mortar. With the development of construction industrialization, the use of steam curing to produce precast concrete is widely used. In order to recycle long-term stacked tailings waste, iron-copper tailings (ICT) waste is comprehensively utilized in steam-cured mortar (SCM). The effect of ICT substitution level on the mechanics and durability of steam-cured mortars is investigated in this study. The research results show that the use of appropriate ICT instead of river sand in the production of mortar is beneficial to the enhancement of the mechanics and durability of the mortar. When the replacement level of ICT is 10%, the 1-d and 28-d compressive strength of SCM are increased by 1.09% and 7.27% respectively compared with plain mortar. SCM mixed with 10–20% ICT has lower permeability compared to plain samples, and further increasing the substitution level of ICT is not benefit the development of mortar durability. Since ICT has better conductivity compared to river sand, it makes the resistivity of SCM decrease with the increase of ICT content. Microstructural studies show that the addition of a small amount of ICT reduces the porosity of SCM and refines its pore structure. Meanwhile, the ICT and cement matrix exhibits a more dense ITZ than the river sand and cement matrix. Recycling of ICT also shows better economic and environmental benefits in SCM. This study provides a theoretical basis for recycling composite tailings waste in prefabricated components. [ABSTRACT FROM AUTHOR]

This present paper focuses the main effort on the mechanical properties of ETFE (ethylene tetrafluoroethylene) foils during the form-developing process of inflated cushion structure through the forming design method of flat-patterning. To this end, an equilateral triangle ETFE cushion model with the side length of 2.5 m was designed and developed through flat-patterning. A multidisciplinary approach, combining the automatic pressure control, photogrammetry, laser measurement and graphics processing, was utilized to realize the form-developing process of the ETFE cushion model. The whole form-developing process included the inflating phase from 0 kPa to 4 kPa, the viscoelastic–plastic creep phase under 4 kPa within 25 min and the creep-recovery phase under 0.5 kPa within 24 h. Some original experimental data, such as the values of the internal pressure, shapes of the upper layer and rises of the lower layer, were obtained from the forming test of ETFE cushion model. Based on the measurement results, the stress distributions and strain distributions under different conditions were calculated by using the force finding method and triangular element method, respectively. Some profound material mechanical properties and structural behavior, such as the elastic deformation, viscoelastic creep, creep-recovery and strengthening, were revealed via the analysis of experimental results. These results demonstrate the applicability of the flat-patterning method, which will improve the popularization of ETFE cushion structure. [ABSTRACT FROM AUTHOR]

Abstract: The corrosion behavior of epoxy/zinc duplex coated rebar embedded in concrete is evaluated comparing with the black steel, galvanized and epoxy coated rebars for a long term in ocean environment. The effect of mechanical damages of epoxy coatings on the corrosion protection is examined. The epoxy coated and epoxy/zinc duplex coated rebars show the higher anti-corrosion performance than other types of rebars. However, once the epoxy coating is mechanically damaged, the more serious corrosion may occur in the damaged area of epoxy coated rebar in concrete. The epoxy/zinc duplex coating remains a good corrosion protection to steel in concrete even when suffering from some mechanical damages. [Copyright &y& Elsevier]

• Viscoelastic properties of ETFE foils were tested at 1–1000%/min strain rates. • Test result shows that strain rates affect mechanical properties of ETFE foils. • A nonlinear stress–strain constitutive model was proposed for ETFE foils. • Two models simulated first 15% and 30% strain stage curves well with 7.2% error. • Continuum models were got to predict rate-dependent viscoelasticity of ETFE foils. Apart from the well-known excellent basic properties, the mechanical behaviors of ETFE (ethylene tetrafluoroethylene) foils are more fundamental for the refined design and analysis of ETFE membrane structures. This paper investigates the nonlinear mechanical properties of ETFE foils at varying strain rates (0.01 to 10 min−1) through a combination of experiments and modeling. First, the uniaxial tensile tests at nine loading strain rates were completed on ETFE foil dumbbell specimens. The analysis of experimental results shows that ETFE foils exhibit the rate-sensitive and viscoelastic-plastic behaviors with two distinct yield points. Next, to simulate the nonlinearity of ETFE foils at the former deformation stage, the stress–strain constitutive equations at certain strain rates are established based on the generalized Maxwell model comprising one basic spring element and several basic Maxwell models. After identifying the model parameters, it is observed that the proposed model can accurately describe the viscoelastic-plastic mechanical behaviors of ETFE foils since good agreement is gained from the comparison between experimental results and model predictions. Finally, through establishing the relationship functions between model parameters and strain rates, the continuum constitutive model can be extended to predict the rate-dependent viscoelastic-plastic behaviors of ETFE foils. The experimental observations and constitutive model concerning the rate-dependent mechanical properties of ETFE foils would be helpful for the refined design, optimization and analysis of ETFE membrane structures. [ABSTRACT FROM AUTHOR]

• 30-day creep test of ETFE foils at varied stresses was done with a novel method. • Long-term results can be validated with short-term results of commercial machine. • Lading stress and time have proportional effects on creep properties of ETFE foils. • Post-creep mechanical properties of ETFE foils shows the rising elastic modulus. • Studying creep effects can prevent extreme deformation to ensure structure safety. As a typical fluorine-based copolymer with excellent chemical, thermal, electrical and physical properties, ETFE (ethylene tetrafluoroethylene) is usually produced into thin films as an essential building and construction material especially for constructing the permanent membrane structures in civil engineering. This paper is thus aimed to investigate the uniaxial tensile time-dependent behaviors of ETFE foils with applying long loading period and various creep stresses experimentally. To this end, 30-day and 1-day uniaxial tensile creep tests were accomplished for the dumbbell specimens of the original ETFE foils by employing a new method and the traditional method, respectively. High efficiency, feasibility and precision of the selected new method could be firstly confirmed while comparing the 1-day creep curves of the original ETFE foils between two results from different methods. The experimental results of creep tests demonstrate that the creep curves of the original ETFE foils are strongly nonlinear with the faster strain during the initial stage and the slower strain during the final stage, and also prove that the creep stress is an essential factor in influencing the time-dependent behaviors. Meanwhile, it could be found that the ETFE foils subjected to the larger creep stresses were still deformed slowly even after the 30-day creep test. Additionally, uniaxial tensile stress-strain test was performed on the deformed ETFE foils that have undergone the 30-day creep test to evaluate the post-deforming mechanical properties. The experimental result of the additional stress-strain test shows that the elastic modulus of the deformed ETFE foils would increase with enlarging the creep stress. These findings would be significant in understanding the time-dependent behaviors of ETFE foils and especially for estimating the structural safety of ETFE membrane structure during the long-term service condition. [ABSTRACT FROM AUTHOR]

Buildings with ethylene tetrafluoroethylene (ETFE) foils have attracted considerable attention due to excellent material properties, good architectural performance and structural behavior in comparison with glass structures. Generally, analyzing overall performance of ETFE structures is an interdisciplinary subject in terms of active control, environmental performance and sustainability. To identify typical and essential features of ETFE structures, this paper reviews and compares available theoretical, experimental and numerical studies on material properties of ETFE foils, architectural performance and structural behavior of ETFE structures. The achievements and gaps of the use of ETFE foils as building materials for public buildings are summarized and concluded. Moreover, reasonable recommendations on performance enhancement of ETFE buildings are made for future study. [ABSTRACT FROM AUTHOR]

This paper reports the central slit tearing behaviors of laminated fabrics for airships from experimental investigation and analytical models. First, central slit tearing behaviors of laminated fabrics with different tear lengths were tested to obtain tearing stress–displacement curves and damage morphology. Then, an analytical model was established to simulate the central slit tearing behaviors of laminated fabrics. In the model, a new concept of equivalent yarn was introduced to simplify the model parameters, and an exponential stress distribution was used to refine the stress distribution in the vicinity of tear tips. The yarn stresses can be calculated to derive the tearing strength at different tearing displacements. Finally, the model was validated due to the high similarity between the calculated and experimental results. The breaking strain and elastic modulus of the yarns as well as the weaving density of the fabric were found to be the key factors affecting the tearing strength. [ABSTRACT FROM AUTHOR]

This study concerns the uniaxial tensile mechanical properties and model parameters determination of ethylene tetrafluoroethylene (ETFE) foils used in structural engineering for membrane structures such as roofs and claddings. On one hand, a series of uniaxial tensile tests under a wide range of temperatures and constant loading speeds were conducted. The experimental results were processed with mathematical methods to determine the mechanical properties, such as first yield stress and elastic modulus. It is obtained that the first yield stress and elastic modulus decrease with increasing temperature but increase with the increasing loading speed. In detail, for the elastic modulus, the dimensionless ratio of the difference between the maximum and minimum values to the maximum value are 91% and 27% for temperature and loading speed tests; for the first yield stress, the dimensionless ratio are 82.9% and 19.2%, respectively. This indicates that the effect of temperature on mechanical properties is greater than that of loading speed when considering the normal working conditions. On the other hand, a constitutive model based on viscoelasticity–plasticity of semicrystalline polymers is employed for ETFE foils. The material parameters are determined with a numerical method based on the Runge–Kutta and least squares methods. The numerical results are in good agreement with the experimental results with a maximum deviation of 6.2%, demonstrating that this model could correctly predict the stress–strain relation of ETFE foils. [ABSTRACT FROM AUTHOR]

• Detailed nonlinear characteristics of shear stiffness for warp-knitted NCF composites under shear-tension coupling loading were discussed. • Shear-tension coupling effects on stiffness nonlinearities were investigated. • A new method for determination of shear stiffness was proposed, and its feasibility was verified by FEA simulation using UMAT. • Differences in shear stiffness and micro-deformation mechanisms between NCF and PWF composites were revealed. In order to reveal shear deformation mechanisms of architectural non-crimp fabric (NCF) composites, detailed shear stiffness-nonlinearities for a typical coated warp-knitted NCF composite under shear-tension coupling loading were studied from experimental investigation and FEA models. Shear-tension coupling effects on shear stiffness of the NCF composite were investigated for different stress states. Its shear stiffness shows significant nonlinear characteristics which are highly tensile stress level (TSL) related, and therefore a critical TSL value was obtained for the studied material. Moreover, a new method for determination of shear stiffness was proposed, and its feasibility was verified by FEA simulation using UMAT. In addition, differences in shear stiffness and micro-deformation mechanisms between NCF and plain-woven fabric (PWF) composites were analyzed specifically. Apparently, the yarn-to-yarn compression on the yarns could contribute to the different stiffness variations between these two composites. [ABSTRACT FROM AUTHOR]

Highlights • Shear behavior of four kinds of architectural coated fabrics is studied. • The distribution of shear stress and shear strain was analyzed by finite element method. • The novel test method of biaxial bias-extension method was proposed. • Shear stress-strain relation was summarized in different loading stage. Abstract As two typical kinds of architectural coated fabrics, PVDF coated polyester fabrics and PTFE coated glass-fiber fabrics have been prevalently used in tensile structures. Shear behaviors of architectural coated fabric is generally regarded as an unneglectable factor when analyzing and simulating mechanical response of tensile structures. This paper employed two approaches to investigate the shear stress-strain characteristics to understand the shear properties of these two common coated fabrics. At first, a finite element model of the cruciform specimen was developed to calculate the shear stress-strain distribution. The results of finite element analysis showed uniform shear stress field and uniform shear strain field in octagonal core area. Then, biaxial bias-extension test was carried out to study the shear behaviors of architectural fabrics. Experimental results showed viscoelastic-plastic property of architectural coated fabrics and the shear stiffness of PTFE coated glass-fiber fabrics greater than that of PVDF coated polyester fabrics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Uniaxial cyclic tensile mechanical properties are investigated under eight loading cases. [•] Elastic modulus divided into three parts explains deformation discrepancy of ETFE foil structure. [•] Yield point is determined by the elastic modulus of 70MPa to minimize strain difference. [•] Ratcheting strain and hysteresis loop area at the 16th cycle are found to be approximate stable. [•] Obtained values are useful for analyzing structural stress, deformation and energy dissipation. [Copyright &y& Elsevier]