Search

Our environment is subjected to many hazards and pollutants which is expanding and polluting in a very serious manner. One such thing is disposal of non-degradable waste on the environment. It has been stated that volume of polymeric wastes like rubber tyres and PET bottles [Polyethylene Terephthalate] is rapidly increasing in recent times. Waste rubber tyres is one among the crucial environmental hazard due to rapid increase of automobile production, leading in accumulation of waste of used rubber tyres. They are recycled rarely and others are just land-filled or stockpiled. For this reason, various efforts have been made to recognize the unrealized, application of rubber obtained from the waste tyres in civil engineering innovations. Interestingly, these rubber materials are made into pieces and are used as an aggregate replacement. By incorporating them as building material, it has an added benefit of saving the aggregates obtained naturally which are used in greater amounts for producing concrete, creating scarcity of aggregates. On this note, our study aims in usage of rubber tyres as partial aggregate replacement. This paper reviews the performance of the hollow block made by integrating the pieces of discarded rubber tyres as aggregate replacement in various proportions. A great number of projects are available on aggregate replacement by rubber in concretes, but this paper deals with the rubber replacement in hollow block. Thus, different percentage of replacement of rubber are casted and tested for its compressive strength after they are cured for 3 days, 7 days and 28 days. The test results were recorded and analyzed when they are subjected to aggregate replacement by rubber. After series of examinations and discussions, their results are concluded. [ABSTRACT FROM AUTHOR]

End of life tyres are discarded at an alarming rate reflecting the strength of developing countries economy and the intensity of trade and transportation. Conversely, environmental concerns are increasing the need for alternative materials in steelmaking industries. The solution to this problem involves the development of environmentally-friendly technologies that would utilize these waste products. The present study investigates carbon/slag reactions, including slag foaming and FeO reduction, for a range of coke/rubber blends.

A broad spectrum of substances is used in the rubber industry, many of them being genotoxic and/or carcinogenic. Convincing evidence of an excess of certain forms of cancer among rubber workers has been provided. The objective of this study was to determine the genotoxic effects in a group of individuals engaged in the production of rubber tyres from a Portuguese factory. Peripheral blood samples were collected from 32 exposed workers and 32 controls, and micronucleus (MN) test, sister chromatid exchanges (SCE) and comet assay were performed. Urinary thioethers were measured as a general biomarker of exposure to electrophilic compounds, and genetic polymorphisms in metabolizing enzymes (CYP2E1 Dra I, EPHX1 codons 113 and 139, GSTP1 codon 105, and GSTM1 and GSTT1 deletion polymorphisms) were analysed as susceptibility biomarkers. Excretion of thioethers was found significantly higher in rubber workers. Also, a non-significant increase in MN frequency related to time of exposure and no effect in SCE were observed in the exposed. Comet assay data showed decreased TL values in the exposed population with respect to the control group, this might indicate the induction of crosslinks by the substances present in the workplace environment. Significant increase in MN frequency was obtained for GSTT1 null exposed individuals with respect to positive ones, and interaction with GSTP1 polymorphism was found. Higher levels of cytogenetic test frequencies were observed in epoxide hydrolase expected low activity donors with respect to medium and high activity individuals. No effect of CYP2E1 or GSTM1 variants was obtained in the biomarkers analysed. [ABSTRACT FROM AUTHOR]

• Thorough review on recycling waste rubber tyres (WRT) and properties of WRT products • Recycling WRT products in concrete, asphalt and geotechnical applications • Concerns about toxicity of WRT incorporated products due to leaching of chemicals • Inadequate research data on leachate analysis of WRT products for metals and PAHs Waste tyres and their accumulation is a global environmental concern; they are not biodegradable, and, globally, an estimated 1.5 billion are generated annually. Waste tyres in landfill and stockpiles are renowned for leaching toxic chemicals into the surrounding environment, acting as breeding grounds for mosquitoes, and fuelling inextinguishable fires. The properties of waste tyre rubber and engineering applications have been previously reported in a range of publications with respect to the environmental, economic, and technical factors. This study compiles and reviews this research with a focus on geotechnical engineering applications, such as earthworks and infrastructure construction. The applications of waste rubber in construction materials includes cementitious concrete, asphalt concrete, and granular materials for earth structures. Crumb rubber, when used as a sand replacement in flowable concrete fill, improved ductility and strength-to-weight ratio. A 40 MPa concrete mix with 0.6% rubber crumb content exhibited optimal strength and air entrainment capabilities, displaying minimal damage after 56 freeze/thaw cycles. Rubber, as a partial replacement for aggregate in road base and sub-base layers, adversely affected the California Bearing Ratio (CBR) of the graded aggregate base course. Rubber-soil mixtures as the interface of foundation and structure yielded a 60–70 % reduction in vertical and horizontal ground accelerations when subjected to earthquake simulation modelling. There is concern regarding the toxicity of waste rubber incorporated products due to leachates of heavy metals and other chemicals common in tyres. Further comprehensive studies in this area are needed. Leachate studies should be conducted under different pH and liquid to solid ratios. [ABSTRACT FROM AUTHOR]