Transport infrastructure renewal is an area where sustainable construction concepts have been applied but not fully implemented.
To find out why, the Department of Transport, the Environment and the Regions asked the Transport Research Laboratory to study the factors which limit waste minimisation and recycling in this sector and to suggest ways of overcoming them.
Renewal of transport infrastructure involves a range of activities including replacing worn-out pavements on roads and airports, replacing ballast on railways, repairing failures on earthworks slopes for roads, railways and canals and dredging canals to keep them navigable.
These activities differ from new construction works in several ways:
they are extensive rather than confined to one site they may cause significant interference with the operation of the infrastructure there is economic and public pressure to complete them as quickly as possible they may be carried out at night in short possessions or in the winter to minimise disruption to users.
These factors tend to inhibit the use of innovative techniques, although in some cases they may stimulate innovation by contractors in order to win the tender.
The project, commissioned under the government's Partners in Innovation scheme, began in June 2000 and will conclude with publication of guidance documents and a major seminar in October 2001.
Policy and practical issues were examined at a consultation workshop in September. The project is proceeding with a series of interviews with key people in all relevant sectors of construction. It is also undertaking case studies of schemes involving different aspects of recycling.
Some of the factors identified in the consultation exercise as barriers to recycling are summarised in the box below. A major problem in many cases is the definition of waste and the implications of this in terms of requirements for a waste management licence or exemption from the licensing regime.
The legal definition of waste derives from the European Commission Directive on waste (91/156/EC), under which any material which is discarded, or is required to be discarded, is classed as a waste - this is the so-called 'Directive waste' It is the intention of the producer rather than the nature of the material which determines whether it is a waste or not. This means a material may be a waste in one situation but not in another.
Many specifications do not allow the use of alternative materials. This overlaps with another problem, the lack of awareness of recent developments. For example in 1995 the Highways Agency produced HD35, which outlines where a wide range of alternative materials may be used. The Aggregates Advisory Service, in Digest 101, gives a summary of where secondary and recycled aggregates are permitted to be used in road construction under existing specifications. The use of other materials can be allowed by obtaining a departure from the specification.
TRL has produced a design guide and specification for structural maintenance of highway pavements by cold insitu recycling (TRL Report 386, 1999) and BRE has produced Digest 433, Recycled aggregates, which gives specification requirements, a classification system and test methods for the use of these materials.
Other particularly useful publications are CIRIA's Reclaimed and recycled construction materials handbook (1999) and the series on waste minimisation in construction. While specifications will inevitably lag behind new developments, there is more guidance available than is perhaps generally realised.
The construction industry has always had a conservative culture, and the particular pressures of transport infrastructure renewal works may have reinforced this.
However, the best results are found when new attitudes, exemplified by the Egan report and sustainable construction, are embraced wholeheartedly. The change in culture also addresses other issues such as conditions of contract.
Where a partnering approach is adopted throughout the supply chain, the possibilities for recycling become much greater. It is also possible to balance supply and demand, by moving from a project-specific costing basis to global costing. The British Airports Authority, for example, has produced major savings and greatly increased the amount of recycling on its pavement renewals by adopting these principles in its Pavement Team.
Work to date has shown that solutions may already be available for most of the problems identified, suggestions on how to overcome others have been made.
Sustainable construction is an achievable goal, but will require action by all the stakeholders in the industry. The consultation exercise is still in progress and the project team would be pleased to hear from anyone with views on the topic, especially for case studies which illustrate the points.
Contact Murray Reid at TRL, tel:01344 770 283; email jreid@trl. co. uk or use the discussion group facility on the project website: www.trl.co.uk/waste.htm
Aggregates Advisory Service. Secondary and Recycled Aggregates in Road Construction under Existing Specifications. AAS Digest 101. Symonds, East Grinstead.
Building Research Establishment. Recycled aggregates. BRE Digest 433, November 1998. BRE, Watford.
Construction Industry Research and Information Association. The reclaimed and recycled construction materials handbook. CIRIA C513, 1999. CIRIA, London.
Department of the Environment, Transport and the Regions. Building a better quality of life. DETR, London, April 2000.
HD35/95. Conservation and the use of reclaimed materials in road construction and maintenance. Design Manual for Roads and Bridges, Vol. 7 Section 1.The Stationery Office, London.
Milton LJ and Earland MG. Design guide and specification for structural maintenance of highway pavements by cold in-situ recycling. TRL Report 386, 1999.TRL, Crowthorne.
The project is supported by a steering group with representation from DETR, infrastructure owners (Highways Agency, Railtrack and London Underground), contractors, aggregate suppliers, the Environment Agency, the Association of Geotechnical and Geoenvironmental Specialists, the Institution of Highways and Transportation and the Institution of Civil Engineers.
Financial support to balance the DETR funds is provided by Lafarge Aggregates and the Hanson Environment Fund. The involvement of representatives of all the major stakeholders is vital to the success of the project.
Definition of waste When is a material a 'waste'? If so, does it qualify for an exemption under the waste management licensing regime?
Specifications Many older specifications do not permit the use of alternative materials.
Lack of awareness Many people not aware of methods available for recycling, developments in specifications and successful projects.
Supply and demand Difficulty in balancing production of material on one project with requirement on others.
Risk Pperception of use of alternative materials and recycling as being a high risk activity.
Conditions of contract Traditional forms based on offsetting risk lead to low priority for recycling.
Regulatory issues Time to obtain licences, exemptions and approvals for new materials or methods are often longer than timescale of contracts; there are regional variations in approach by authorities.
Economics Where cheap natural aggregates are available, alternative materials may not be competitive.
Environmental concerns Leaching of contaminants from alternative materials.
Technical problems Practical difficulties with individual materials and methods, often site-specific.