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Concrete In Australia : March 2013
Concrete in Australia Vol 39 No 1 51 New method of pavement construction and encapsulation of hazardous wastes Dr Aleksander Samarin Visiting Professor, Centre for Built Infrastructure Research, University of Technology Sydney e difficulty of safe disposal of hazardous wastes and particularly of low and intermediate level radioactive wastes is well recognised. In most cases it involves relocation of waste from one residential or industrial site to another, which is usually located in close proximity to the built-up areas. e paper proposes a new method of "highway construction-waste disposal" of hazardous wastes, which should guarantee not only a long-term safe removal of harmful materials, but also a significant improvement in the long term maintenance with defect-free surfaces of highway pavements. e theory and practical development of special highly durable concrete is founded on the principle of thermodynamic systems far from equilibrium. It should ensure safe long term encapsulation of hazardous wastes, including low and intermediate level radioactive wastes. Although the initial cost of highway construction using this method is somewhat higher than the conventional technique, if the cost of waste disposal is taken into consideration, the total expenditure, in most cases, should be actually lower than the combined cost of individual construction and disposal. 1.0 INTRODUCTION Waste, in general, can be defined as a not readily avoidable by-product for which there is no economical demand and for which disposal is required. Hazardous waste can be defined as a waste which is potentially harmful to humans, to the living organisms and to the environment. At present the proposal to relocate some 600 t of hazardous waste from Sydney s Hunters Hill to Lidcombe resulted in protests and petitions to parliament, with the rejection of this relocation. e waste was generated from the uranium ore processing plant at Hunters Hill. e process of waste encapsulation described in this article should provide a safe and economical method of hazardous waste disposal. In the conventional contemporary methods of pavement design and construction successive layers of paving materials are selected in accordance with their ability to safely withstand stresses and strains imposed on them by the traffic loads. us, the strongest materials, such as asphalt or concrete form the pavement surface, with stabilised soil placed as a sub-base and with the base composed of naturally occurring material. However, when base materials contain clay, the ingress of water from the shoulders after heavy rain, or from the rise in water table, can cause increase of the plasticity of soil, or even cause its liquefaction. is often leads to the formation of cracks or "potholes" on the pavement surface. At best, this results in high maintenance cost and at its worst in traffic accidents, injuries and even deaths of the road users. e "highway construction-waste disposal" technique investigated in this paper is similar, although not identical to, the via munita method of pavement design and construction used by Romans some 2000 years ago. As in Roman roads, it employs a "raft foundation". e fact that some of the Roman roads are still remaining functional to this day should serve as an endorsement for the proposed method of "highway construction-waste disposal". is method, as applied to the low and intermediate nuclear waste was proposed by Samarin to the Australian Senate Select Committee on the Danger of Radioactive Waste in 1995. It is my understanding, however, that this committee made no specific recommendations to the relevant authorities to evaluate and implement it. us, it may be appropriate to bring this technology to the public attention again, in a form of a paper in this journal. 2.0 THEORETICAL ASPECTS OF HAZARDOUS WASTE ENCAPSULATION 2.1 Theoretical concepts of cement solidification Durability can be defined as the ability of a product, assembly or construction to maintain its serviceability over a specified period of time in a specified environment, and serviceability can be defined as the ability to preserve desirable condition, again over a specified period of time. Most concretes, which contain hydraulic cements, exhibit good durability in natural environments, that is when they are subjected to cycles of wetting by water which is not too acidic, and then to a subsequent drying. Composition, which is constituents and their proportions, of hydraulic cement concretes must be properly selected and designed in order to achieve its durability in a particular environment over a specified period of time. Mixing, placing and compaction of concrete must also be at an optimum in order to achieve its required durability. e process of hydration of hydraulic cements in essence can be envisaged as a formation of order out of a chaotic state. e general theory of creation of order in thermodynamic systems which are in the state "far from equilibrium" was developed by Viscount Ilya Prigogine, an achievement for which he received