ICE - Institution of Civil Engineers - Virtual Library

‘Contraction and convergence’ is an ambitious yet widely supported plan to harmonise global greenhouse gas emissions to a safe and sustainable level per person within the next few decades. It was conceived in the mid-1990s by the Global Commons Institute (GCI) in London as an antidote to the expanding, diverging and climate-changing nature of global economic development. The plan is now at the core of the UN Framework Convention on Climate Change, has been approved by the European Parliament and many other governments and in July 2004 even received divine backing from the Church of England. GCI director Aubrey Meyer explains the background and defining characteristics of what could prove to be the ultimate sustainability initiative.

There is a growing recognition in developing countries of community-based infrastructure procurement and its potential to achieve sustainable development. The advantages of such an approach are that it encourages participative negotiation of activities and speedier implementation, the use of local resources, skills and appropriate technology, and entrepreneurship within communities. These wider socio-economic impacts arising from community-partnered micro-projects can lead to more sustainable infrastructure through meeting local stakeholders’ needs, community empowerment and capacity building. This paper describes the development and use of performance indicators for community-contracted urban infrastructure provision in low-income communities in India, Pakistan and Sri Lanka. In particular, these indicators refer to the dimensions of time and cost; some key performance yardsticks are also proposed. The urban infrastructure and services referred to in these cases are the facilities needed for water and sanitation provision, access roads, street lighting and solid waste management. In general, it was found that costs for community-contracted micro-projects were normally very close to being on target. The quality of infrastructure and service provision also tended to be superior to that envisioned by local government engineers. However, project duration generally exceeded the target but was still comparable to conventional contracts. The overall performance of the community-partnered micro-projects was found to be comparable or better than the conventional micro-contracts; in addition, the performance of these projects in terms of socio-economic elements was likely to far exceed that of the conventional micro-projects.

Breastshot waterwheels—that is, waterwheels where the water enters the wheel approximately at the level of the axis—were in widespread use in England and Germany during the nineteenth and early twentieth century. Although this type of wheel even today has the potential for the economical and environmentally acceptable exploitation of small hydropower with low heads from 1·5 to 2·5 m, very little is known about its performance characteristics. In order to assess the breastshot waterwheel for hydropower generation, a study of design methods and a series of model tests were conducted at Queen’s University Belfast. Sample calculations for a 4 m diameter wheel are given to explain the design principles. Tests on a 1:4 scale, 1 m diameter model gave efficiencies of 78·5% over a broad range of flows. Based on these measurements and observations, improved geometries for in- and outflow were developed, resulting in maximum efficiencies of 87·3%. An initial ecological assessment indicated that waterwheels may have a significantly reduced ecological impact when compared with turbines. The breastshot waterwheel was found to be an efficient and ecologically acceptable hydraulic energy converter with the potential for further development.

Slag from the imperial smelting furnace (ISF) method of zinc production is an industry by-product that has been investigated for its potential use as an aggregate in concrete. In the UK alone, there is currently a 2·5 million t stockpile of ISF slag that could potentially be used as aggregate in the construction industry. However, the presence of the heavy metals zinc and lead in the slag raises environmental concerns about its reuse. ISF slag is physically suitable for use as an aggregate, although there are several barriers that need to be overcome before it can be used in concrete. Issues relating to the metal ions present have been addressed in other publications. However, the glassy nature of the slag initially raised concerns regarding the potential for alkali–silica reaction (ASR) to occur in concrete. A comprehensive series of accelerated ASR tests have been carried out, which indicate that the material is not susceptible to this type of deleterious reaction. In addition, site trials on a concrete roadway containing ISF slag have proved successful.

Concrete bridges form significant links in most infrastructure schemes, but as a constructional material concrete faces major challenges concerning its sustainability performance. The paper seeks to identify and discuss significant themes in sustainability as they affect concrete bridges and to give a briefing on the subject to bridge owners, designers, constructors, maintainers and users. After introducing the challenge of sustainability to the concrete industry, a structured means of addressing sustainability issues is presented and the role of concrete in bridge construction is described. The four major aspects of sustainable thinking (natural resources, environment, societal issues and economics) are discussed in the context of concrete bridges. Examples of how sustainable principles have been applied to practical situations involving concrete bridges are then presented and discussed. In conclusion, the need for further research to provide practical sustainability assessment tools is identified together with the importance of increased awareness and involvement of all through education and training.