The utilization of recycled tyre polymer fibre (RTPF) into concrete production is feasible to promote sustainable development and mitigate environmental pollution of global landfilled waste tyres. This paper for the first time presents an experimental study on flexural fatigue behaviour of concrete reinforced with mixed RTPF considering different fibre dosages (i.e., 1.2, 2.4, 4.8 and 9.6 kg/m 3). Results indicate that with the presence of RTPF, the flexural strength of concrete was increased by 3.6-9.6%. The fatigue life of all mixtures followed the two-parameter Weibull distribution and can be accurately predicted using the developed double-logarithm fatigue equations. Concrete reinforced with 4.8 kg/m 3 of RTPF presented the longest fatigue life under different failure probabilities. RTPF and polypropylene fibre (PPF) reinforced concrete exhibited similar fatigue failure mechanisms. 0.2-0.4% Vf of RTPF could substitute around 0.1% Vf of PPF in concrete considering overall static, dynamic and fatigue performance.
The effect of recycled tyre polymer fibre (RTPF) on mechanical and durability performance of concrete has been increasingly studied in recent years, primarily because of the economic and sustainable feasibility of RTPF's application in construction industry. This paper presents an experimental study on workability, static compressive strength and dynamic compressive properties of concrete reinforced with RTPF with various fibre dosages (i.e. 1.2, 2.4, 4.8 and 9.6 kg/m 3 ) that have not been extensively investigated. Results indicate that the dynamic compressive properties including dynamic compressive strength, energy absorption capacity, ultimate strain and dynamic increase factor of all mixtures were highly sensitive to the strain rate. The optimal RTPF content was found to be 2.4 kg/m 3 (i.e. 0.2% fibre volume fraction (Vf)) considering fresh and hardened properties, as adding this content into concrete induced the most development in dynamic compressive strength (with the highest increase of 12.9%), fracture energy (with the highest improvement of 54.4%) and total energy absorption (with the largest enhancement of 26.4%). It was found from scanning electron microscope (SEM) image analysis that RTPF exhibits bridging performance with no obvious fracture on its surface, and 0.1% Vf of PPF could be replaced by 0.2% Vf of RTPF for concrete.
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%e0.9% V f ) and polypropylene fibre (PPF, 0.1% e0.5% 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%e66.7%. 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%e6.8% as compared with the mixture reinforced with only RTSF.
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% to 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.
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