A group of researchers from the Royal Melbourne Institute of Technology (RMIT), has succeeded in replacing the classic method of making concrete, which is made of gravel and crushed rock, with rubber from discarded tyres that are suitable for building codes.
According to the press release that has been published by the university, new greener and lighter concrete also promises to reduce manufacturing and transportation costs significantly. Small amounts of rubber particles from tyres are already used to replace these concrete aggregates. However, the previous process of replacing all concrete with aggregates had not been successful.
The study published in the Resources, Conservation & Recycling journal showed the tyres' manufacturing process.
Lead author and Ph.D. researcher from RMIT University’s School of Engineering, Mohammad Momeen Ul Islam, stated that this work was revolutionary because it showed what could be done with recycled rubber pieces.
“We have demonstrated with our precise casting method that this decades-old perceived limitation on using large amounts of coarse rubber particles in concrete can now be overcome,” Islam said.
“The technique involves using newly designed casting moulds to compress the coarse rubber aggregate in fresh concrete that enhances the building material’s performance," he added.
This advance builds on the breakthrough invention of this technique by fellow RMIT University Engineers Professor Yufei Wu, Dr. Syed Kazmi, Dr. Muhammad Munir, and Shenzhen University's Professor Yingwu Zhou.
Study co-author and team leader, Professor Jie Li, stated that this production process will greatly benefit the environment and the economy.
"The greener and lighter concrete could also greatly reduce manufacturing and transportation costs," Li said.
"This would benefit a range of developments including low-cost housing projects in rural and remote parts of Australia and other countries around the world.”
“As a major portion of typical concrete is coarse aggregate, replacing all of this with used tire rubber can significantly reduce the consumption of natural resources and also address the major environmental challenge of what to do with used tyres,” Prof. Li shared his thoughts.
"Manufacturing process could be scaled up cost-effectively within a precast concrete industrial setting in Australia and overseas," Islam said.
After successful tests in the workshop, the research team aims to strengthen the concrete further to see how the elements put into the concrete can work. The RMIT research team also includes Professor Yu-Fei Wu, Dr. Rajeev Roychand, and Dr. Mohammad Saberian.
End-of-life tires are a challenging waste because of their non-biodegradable properties, high production volume, and low utilization rate. Extensive research is currently being undertaken to look for various applications of waste tire rubber in the concrete industry to improve their utilization rate and significantly increase the uptake of this waste material. However, low strength and poor bond performance between rubber aggregates and cement matrix are hindering its application in the concrete industry. This paper introduces an innovative method of prestressing the coarser rubber aggregates (RAs) to address these challenges and limitations found in the critical literature review. Two steel mould rigs were newly designed for manufacturing the rubberized concrete (RuC). Three different mix designs containing 100% replacement of conventional coarse aggregates were prepared using (i) two different sizes of rubber particles and (ii) the addition of steel fibers. Density, SEM-EDS analysis, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity were undertaken to evaluate mechanical performances. The experimental results depict that this novel preloading method can bring a maximum of 97%, 59%, and 20% increase in compressive strength, flexural and tensile strength compared to that of the normal RuC, respectively. In addition, it provides a significant improvement in the interfacial transition zone between the matrix and RAs. This study demonstrates the efficient scientific recycling procedures in manufacturing the RuC with a maximum compressive strength of 18 MPa (density of 2000 kg/m3), which can be considered structural lightweight concrete as per ACI 213R-14 and Eurocode 2 recommendations.
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