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To enhance the cost-effectiveness and sustainability of engineered geopolymer composites (EGC), polyvinyl alcohol (PVA) fibres in EGC can be partially replaced with recycled tyre polymer (RTP) fibres. This paper presents a systematic experimental study on the effects of PVA fibre volume fraction (1.0%, 1.5% and 2.0%) and RTP fibre content (0.25%, 0.5%, 0.75% and 1.0%) on the dynamic compressive behaviour of EGC under various strain rates (54.43–164.13 s−1). Results indicate that the flowability, quasi-static compressive strength and elastic modulus of EGC reduce with the increase of PVA fibre content, where the reductions can be effectively mitigated by adding RTP fibres. The dynamic compressive properties of all investigated mixtures including dynamic compressive strength, dynamic increase factor (DIF) and energy absorption capacity show a pronounced strain rate dependency which can be well described using the proposed equations for DIF against strain rate ranging from 10−5 s−1 to 103 s−1 with R 2 values of mostly greater than 0.9. The dynamic compressive properties of EGC are enhanced with the increasing PVA fibre dosage under various strain rates while replacing PVA fibre with a certain amount of RTP fibre (0.25% and 0.5%) can result in better dynamic compressive properties compared to EGC with 2.0% PVA fibre. EGC containing 1.75% PVA fibre and 0.25% RTP fibre can be considered as the optimal mixture given its superior quasi-static and dynamic compressive properties in comparison with EGC with 2.0% PVA fibre. [ABSTRACT FROM AUTHOR]

• Role of recycled tyre steel (RTS) fibre in engineering properties of UHPC was estimated. • Replacing IS fibre with 0.5–1.0% RTS fibre improves mechanical properties of UHPC. • UHPC exhibits a significant strain rate sensitivity under dynamic splitting tension. • Material cost, carbon emission, energy consumption of UHPC decline when adding RTS fibre. • UHPC containing 0.5% RTS fibre and 1.5% IS fibre is the optimal mixture. Employing recycled tyre steel (RTS) fibres to replace industrial steel (IS) fibres in ultra-high performance concrete (UHPC) can improve its cost-effectiveness and sustainability. However, the lack of research on dynamic properties of such sustainable UHPC would hinder its application in concrete structures such as protective and defence structures which may experience different dynamic loadings. This paper experimentally investigates the effect of various RTS fibre replacement levels (0.5–2.0% by volume) on the flowability and quasi-static compressive, flexural and tensile strengths of UHPC as well as the dynamic splitting tensile behaviour under various strain rates (4.5–6.5 s−1). The conventional UHPC with 2.0% IS fibre was prepared as the reference. Results indicate that the flowability of UHPC containing RTS fibres is about 5–11% higher than that of reference UHPC. Rising the RTS fibre replacement level up to 1.0% increases the compressive, flexural and tensile strengths while after which, the strengths drop. The dynamic splitting tensile behaviour of all UHPC specimens is sensitive to strain rate in terms of failure pattern, dynamic splitting tensile strength, dynamic increase factor and energy absorption capacity. Using 0.5% RTS fibre to substitute IS fibre can bring the best synergy, leading to the highest dynamic splitting tensile properties of UHPC at a strain rate of approximately 4.5–6.5 s−1. The material cost, embodied carbon and embodied energy of UHPC are reduced by 9–57% in the presence of RTS fibres. The optimal RTS fibre replacement dosage for UHPC is 0.5% considering static mechanical properties, dynamic splitting tensile behaviour, material cost and environmental impact. [ABSTRACT FROM AUTHOR]

• Feasibility of developing ECC with recycled tyre polymer fibres was explored. • Effect of RTP fibre content on engineering properties of ECC was estimated. • ECC exhibits a significant strain rate dependency under dynamic compression. • Drying shrinkage, material cost and energy consumption of ECC drop when adding RTP fibre. • ECC containing 0.25–0.5% RTP fibre and 1.5–1.75% PVA fibre is the optimal mixture. To lower the material cost and environmental impact of polyvinyl alcohol (PVA) fibre reinforced engineered cementitious composite (ECC), recycled tyre polymer (RTP) fibres were adopted to partially replace PVA fibres in ECC in this study, with an overall aim to develop sustainable ECC with RTP fibres without significantly affecting the engineering properties. A series of tests were conducted to investigate the effect of RTP fibre content on the engineering properties of ECC, with special focus on tensile strain-hardening behaviour and dynamic compressive behaviour. Results indicate that the incorporation of RTP fibres can improve the drying shrinkage resistance of PVA fibre reinforced ECC by 5–13% at 28 d while no positive influences are found on the workability and quasi-static compressive properties. There exists clear strain-hardening behaviour for all studied ECC mixes even when 50% of PVA fibre is substituted with RTP fibre. Based on the results of the micromechanical investigation, all mixtures satisfy the criteria for achieving a robust strain-hardening behaviour. All ECC specimens are characterised by a pronounced strain rate effect under dynamic compression and ECC incorporating RTP fibres shows a stronger sensitivity as opposed to ECC with 2.0% PVA fibre. The material cost and energy consumption of ECC are reduced by about 11–45% and 5–18%, respectively, when RTP fibres are present. This study proves the feasibility of utilising RTP fibres in ECC to improve its sustainability and maintain acceptable static and dynamic mechanical properties while the incorporated fibre volume fraction should be limited to 0.5%. [ABSTRACT FROM AUTHOR]

Engineered cementitious composite (ECC) featuring extraordinary tensile ductility is a promising option for many structural applications but its large-scale manufacture is not eco-friendly due to its binding ingredient, Portland cement. One of the potential alternatives to ECC is engineered geopolymer composites (EGC) that have been increasingly studied in recent years. This paper presents a comprehensive review of the state-of-the-art of EGC in terms of design theory, mix design, fabrication process, engineering properties, durability and environmental benefit, with special focus on the effects of different material composition factors including precursor, activator, aggregate, additive and fibre on the critical material properties of EGC especially uniaxial tensile properties. The correlations between essential mechanical properties are discussed in depth. The unique tensile behaviour of EGC can be tailored by modifying the material composition that would change its internal microstructure and in turn alter the matrix properties and fibre-matrix interfacial behaviour. Compared to typical ECC, around 64% of EGC mixtures have higher tensile strain capacity (over 2.49%) and about 27% of mixtures exhibit larger tensile strength (over 4.86 MPa). Through adjusting the mix design of EGC, it holds promises as a cost-effective and sustainable material for applications against dynamic loadings, fire and chemical attacks, as well as 3D concrete printing. This review summarises the recent advances in EGC and identifies the remaining challenges in development of EGC with desired properties for practical applications. [ABSTRACT FROM AUTHOR]

Partial replacement of the widely used polyvinyl alcohol (PVA) fibre in engineered geopolymer composites (EGC) with recycled fibres can reduce the material cost and improve sustainability. This study investigates the effect of hybrid PVA and recycled tyre polymer (RTP) fibre content on the quasi-static and dynamic splitting tensile behaviour and microstructure of ambient-cured fly ash-slag based EGC through split Hopkinson pressure bar, scanning electron microscopy and X-ray computed tomography tests. Results indicate that the presence of PVA or RTP fibres can considerably improve the quasi-static and dynamic splitting tensile behaviour of geopolymers. All investigated mixtures are characterised by remarkable strain rate sensitivity within the considered test range, which can be well described using the proposed relationship between dynamic increase factor and strain rate for predictions of dynamic properties. Replacing PVA fibre with 0.25–0.5% RTP fibre can lead to better dynamic splitting tensile properties of EGC compared to that with 2.0% PVA fibre, which can be mainly ascribed to the improved synergistic effect of hybrid fibres in controlling the cracks. The microscopic images reveal that the failure mode of RTP fibres is not sensitive to the strain rate due to its hydrophobic surface feature, which could benefit the energy absorption capacity of EGC under dynamic loading. EGC containing hybrid PVA and RTP fibres holds promise as a cost-effective and sustainable material for applications against dynamic loadings. [ABSTRACT FROM AUTHOR]

Partial replacement of the widely used polyvinyl alcohol (PVA) fibre in engineered geopolymer composites (EGC) with recycled fibres can reduce the material cost and improve sustainability. This study investigates the effect of hybrid PVA and recycled tyre polymer (RTP) fibre content on the quasi-static and dynamic splitting tensile behaviour and microstructure of ambient-cured fly ash-slag based EGC through split Hopkinson pressure bar, scanning electron microscopy and X-ray computed tomography tests. Results indicate that the presence of PVA or RTP fibres can considerably improve the quasi-static and dynamic splitting tensile behaviour of geopolymers. All investigated mixtures are characterised by remarkable strain rate sensitivity within the considered test range, which can be well described using the proposed relationship between dynamic increase factor and strain rate for predictions of dynamic properties. Replacing PVA fibre with 0.25–0.5% RTP fibre can lead to better dynamic splitting tensile properties of EGC compared to that with 2.0% PVA fibre, which can be mainly ascribed to the improved synergistic effect of hybrid fibres in controlling the cracks. The microscopic images reveal that the failure mode of RTP fibres is not sensitive to the strain rate due to its hydrophobic surface feature, which could benefit the energy absorption capacity of EGC under dynamic loading. EGC containing hybrid PVA and RTP fibres holds promise as a cost-effective and sustainable material for applications against dynamic loadings. [ABSTRACT FROM AUTHOR]

Strain hardening geopolymer composite (SHGC) processing superior tensile ductility and multiple cracking is a promising alternative to traditional ductile cementitious composites whereas the extremely high cost of polyvinyl alcohol (PVA) fibres limits its large-scale application. This paper presents a feasibility study of replacing PVA fibres with recycled tyre polymer (RTP) fibres to reduce the material cost of fly ash-slag based SHGC and ease the pressure on environmental impact induced by the vast amount of waste tyres, focusing on the influences of PVA fibre content (1.0–2.0% by volume) and RTP fibre replacement dosage (0.25–1.0% by volume) on the engineering properties especially uniaxial tensile behaviour, microstructure, material cost and environmental impact. Results indicate that the incorporation of RTP fibres into SHGC can lessen the loss in flowability and compressive strength due to the addition of PVA fibres. The drying shrinkage of SHGC containing RTP fibres is effectively reduced by about 35.69% and 17.33% as compared with the plain matrix and SHGC containing 2.0% PVA fibre, respectively. Although the presence of more RTP fibres diminishes the uniaxial tensile behaviour of SHGC, the cost and embodied energy of SHGC utilising RTP fibres are reduced by up to 34.52% and 16.23%, respectively. SHGC with 1.75% PVA fibre and 0.25% RTP fibre can be considered as the optimal mixture as it provides adequate engineering properties including a tensile strain capacity of around 2.5%, lower material cost and lower environmental impact compared to the typical SHGC with 2.0% PVA fibre. [ABSTRACT FROM AUTHOR]

To provide an eco-friendly disposal way of increasingly accumulated waste tyres and reduce the environmental impact caused by the production of industrial fibres, this study explores the feasibility of using recycled tyre materials as substitutes for natural fine aggregates and manufactured fibres in cementitious mortar. The effects of crumb rubber (CR) replacement ratio (5%–15% by volume of fine aggregates), recycled tyre steel (RTS) fibre content (0.5–1.5 vol%) and recycled tyre polymer (RTP) fibre content (0.5–1.0 vol%) on the engineering properties of fibre reinforced cementitious composite (FRRC) were experimentally investigated. Results indicate that the pre-treated CR using NaOH solution is feasible to combine with a high dosage of recycled fibres without considerably weakening the workability, bulk density, ultrasonic pulse velocity and compressive strength of FRRC. The incorporation of CR, RTS fibre and RTP fibre together can reduce the drying shrinkage by up to 41.6% and enhance the flexural strength by at most 174% as compared to the plain mortar. The production cost, embodied carbon and embodied energy of FRRC are decreased by 13.3%–68.2% when replacing the manufactured fibres with recycled tyre fibres. The optimal content of CR and RTS fibre and RTP fibre is 5%–10%, 1.0 vol% and 0.5 vol%, respectively, considering the engineering properties, cost and environmental impact. [ABSTRACT FROM AUTHOR]

Recycled tyre polymer (RTP) fibre has recently been gaining ever-increasing attention from the scientific community as a promising substitute to synthetic fibres for cementitious composites to improve sustainability. This paper, for the first time, investigates the behaviour of RTP fibre reinforced concrete (FRC) under dynamic splitting tension, focusing on the effects of fibre content (0.1, 0.2, 0.4 and 0.8 vol%) and strain rate (0.88–3.54 s−1) and the feasibility of replacing polypropylene (PP) fibre with RTP fibre for FRC. Results indicate that the inclusion of RTP fibres is favourable in enhancing the splitting tensile properties of concrete under various strain rates (10−1 to 101 s−1), where the dynamic splitting tensile strength and dissipated energy of concrete mixture containing 0.2 vol% RTP fibre are improved by 5.5%–14.2% and 24.9%–36.7% respectively compared to the plain mixture as a result of fibre bridging effect. Fibre pull-out process considerably contributes to the enhancement of energy dissipation capacity. The splitting tensile properties of all mixtures are sensitive to strain rate, where the developed empirical equations well describing the relationship between dynamic increase factor (DIF) and strain rate provide insight into this rate sensitivity. A comparison between RTP-FRC and PP-FRC confirms that RTP fibre can be used as a sustainable and cost-effective alternative to PP fibre for cementitious materials considering engineering properties and potential economic benefit of the composites. [ABSTRACT FROM AUTHOR]

Recycled tyre steel fibre (RTSF) is considered as a potential and sustainable alternative to manufactured steel fibre (MSF), while RTSF resulted in lower energy absorption capacity and more serious corrosion problem in concrete compared to MSF. This paper presents an experimental study on engineering properties of concrete reinforced with hybrid RTSF (0.5%–0.9% V f) and polypropylene fibre (PPF, 0.1%–0.5% V f). Results show that combining RTSF with PPF could compensate the serious workability loss caused by RTSF and the workability was improved by 38.9%–66.7%. However, the compressive, splitting tensile and flexural strengths were weakened significantly when PPF was over 0.3% V f in hybrid fibre reinforcement (total content of 1.0% V f). The strain field shown in digital image correlation images suggests that hybrid RTSF and PPF can create a synergistic effect in restraining the crack growth and the post-cracking behaviour of concrete especially toughness that was enhanced with the presence of PPF. RTSF was more effective in restraining shrinkage of concrete than PPF. With the increase of PPF content in hybrid fibre reinforcement, the chloride migration coefficient of concrete was reduced by 4.9%–6.8% as compared with the mixture reinforced with only RTSF. [ABSTRACT FROM AUTHOR]

To mitigate the potential problems of waste tyres and Portland cement greenhouse gas emissions while further promote the sustainable development of construction industry, this paper, for the first time, explores the workability and mechanical properties of crumb rubber alkali-activated fly ash-slag mortar reinforced with recycled tyre steel fibre (RSFRAM) considering different contents of crumb rubber (CR, i.e. 5%, 10% and 15% replacement by volume of fine aggregate) and recycled tyre steel fibre (RTSF, i.e. 0.5% and 1.0% by volume). The results indicate that the inclusion of CR led to a 4.7%–26.7% improvement in workability of RSFRAM when the RTSF content was low, while the addition of RTSF compensated the strength loss caused by the addition of CR. The combination of CR and RTSF created a synergistic effect on the flexural behaviour of RSFRAM. The optimal mixture was regarded as R5F1.0 (5% CR replacement and 1.0 vol% RTSF) exhibiting comparable compressive strength, and superior flexural strength (around 171.1% higher), toughness indices (highest among all RSFRAMs) and residual strength factors (higher than 100) compared to the reference mixture without CR and RTSF. In addition, R5F1.0 can meet the strength requirement of concrete (i.e. 28 MPa for basic construction application) and thus suitable for structural applications as a sustainable material. [ABSTRACT FROM AUTHOR]

We present a single-fiber dark trap for trapping low-refractive-index (LRI)biological cells, which consists of a single-mode fiber stretched by a hot-melt method. The prepared single-mode fiber tip is a flat-tipped tapered structure with a tip taper angle of 0.55 ° at a stretch length of 44 um. With this structure of the single-mode fiber, the focused beam of different modes interferes to form a dark trap after the 650 nm laser is passed through, and three-dimensional trapping of LRI biological cells in a high refractive index (HRI) solution is achieved. Its all-fiber structure can be used as a micro-optical probe for in-situ characterization and manipulation of biological cells with a lower refractive index than the base solution. • The focused beam of different modes interferes to form a dark trap is passed through, and three-dimensional trapping of low-refractive-index biological cells in a high-refractive-index solution is achieved. • Its all-fiber structure can be used as a micro-optical probe for in-situ characterization and manipulation of biological cells with a lower refractive index than the base solution. [ABSTRACT FROM AUTHOR]