Life cycle, sustainability and the transcendent quality of building materials

This paper explores the relationship between the life cycle of engineering works and their sustainable and transcendent qualities, and considers the possibility of creating durable works with ephemeral materials. This paper also studies the impact of urban growth and its infrastructures on the environment through the consumption of raw materials and energy. City metabolism is one of the main causes of environmental deterioration, and present-day tendencies make it foreseeable that both urban and infrastructure development shall continue to increase. Although the expression "sustainable construction" is being used more and more, it is necessary to distinguish between the sustainability of the construction activity and the sustainability of works constructed. Both the materials and technologies used since ancient times have allowed many past works to have lasted thousands of years. Some were made out of permanent materials such as stone while others were made out of more ephemeral materials such as adobe bricks or cob walls. Structures built with Roman cement are still standing after 20 centuries. The overall durability of built structures depends on the durability of their materials. Transcendent construction was made possible either using permanent materials or more ephemeral materials, providing the project had taken the need for maintenance into consideration. The development of building works in a modular fashion makes the repairing action of modifying materials or parts of works possible without destroying its basic structure. With our present-day knowledge, plain concrete permits to create transcendent structures that could last several centuries. (c) 2005 Elsevier Ltd. All rights reserved.