Waste Rubber for Road Repair
By TA News Bureau:
Building, repairing and maintaining road infrastructure pose unusual challenges to engineers who work under constant pressure to economise but are also compelled to ensure road safety, which is their top priority. Although conventional concrete roads are considered more durable than asphalt, engineers grapple with the issue of using recycled materials, particularly waste tyres, to press down the cost. Research by Dr Renga Rao Krishnamoorthy of the Centre for Studies in Structure and Material Engineering at Selangor (Malaysia)-based Universiti Teknologi Mara (UiTM), has shown that it is possible to upgrade standard concrete materials with recycled concrete and shredded rubber from end-of-life tyres. Explaining his research work, he said in an interview that the optimum percentage of recycled concrete material that can be used to get good value of indirect tensile strength is in the range of 10% to 30% of shredded tyre rubber and ground plastic polypropylene bottles
Research by Dr Renga Rao Krishnamoorthy of the Centre for Studies in Structure and Material Engineering at Selangor (Malaysia)-based Universiti Teknologi Mara (UiTM), has found that recycled rubber from waste tyre and polypropylene from used plastic bottle can be utilised as alternative materials for replacing either sand or coarse aggregate in concrete mix for building pavements.
The optimum percentage that he found, which is 10% of sand and coarse aggregate, could be replaced with recycled materials, including waste tyre rubber. This will also address the problems being faced in environment-friendly disposal of waste tyres.
Shredded tyre rubber can be used as a replacement for coarse aggregate by using an optimum percentage of 20% for repair of pavements. “The extend of my research to optimize the use of waste tyre for road pavement is an alternative method, which is to re-use the waste tyre material in the form of shredded tyre in a controlled mixture of concrete,” he told Tyre Asia.
There are many types of asphalt or flexible pavement failures, namely, ‘alligator cracking’, shear failure cracking, longitudinal cracking, formation of waves and corrugation and many more. Nevertheless, these road damage could be re-engineered and repaired using recycled concrete materials and shredded tyre material in certain proportions.
When asked what kind of granulated or chip of shredded waste tyre rubber is found useful in recycled concrete material, Dr Krishnamoorthy said his research has revealed that 6 mm coarse shredded tyre rubber is ideal. “This size was chosen to mimic the aggregate size used for mixture in concrete.”
He says in terms of economy, his research has indicated cost-effectiveness in using waste tyre rubber in pavement building and repair. “Well, to be mindful, a computational cost-effective study requires further research into practical implementation onsite. It should be like an apple to apple comparison between existing asphalt pavement vs. recycled waste tyre concrete pavement.”
Dr Krishnamoorthy suggests that using recycled material is definitely cost effective, and in addition, it paves the way for a greener and environmentally friendly construction. Currently there is no immediate data for a comparison. However, he said that future collaboration with industry will help develop more insight into the percentage of savings that can be achieved.
Referring to his work on ‘flexible pavement’ he explained that there are two types of pavement construction that engineers take into consideration while executing road projects. One is called flexible pavement and the other rigid pavement.
Flexible pavement is commonly used in Malaysian road construction. However, the ‘infamous’ rigid pavement has also been extensively used in the North-South Expressway. Flexible pavement is usually asphalt. It is laid with no reinforcement. It is normally designed based on load distributing characteristics in the component layers which include sub-grade and layers up to the surface.
In the case of rigid pavement, there is application of reinforced concrete slabs. The load is distributed in the extensive area of sub-grade soil. Concrete material consists of Portland cement, clean river sand, water and coarse aggregate.
Regarding his recommendation for optimum result, he suggests 10% – 30% of shredded tyre rubber for laying pavements.
The recommended percentage of 10% – 30% shredded tyre shows good agreement with existing pavement strength, he said adding that he is still sceptical to include pieces of shredded tyre rubber that contain steel cord. This could compromise the safety of the finished recycled concrete pavement.
“Protruding steel cords are dangerous for end-users and for the rubber wheels when they come in contact. However, a textile mesh steel reinforced cord can be placed to overcome the issue,” he feels.
Dr Krishnamoorthy said his research is aimed at upgrading the standard concrete material that come from industrial waste. Adding shredded tyre rubber and ground plastic bottles in place of coarse aggregates in place of clean river sand will also help preserve water bodies.