コンクリートの環境問題への取り組みに関する国内外の動向

抄録

The construction industry is essentially an industry with a high degree of locality. Socioeconomic infrastructure realized through construction activities has generally been developed by local people using local materials. Globalization has promoted internationalization in the construction industry as elsewhere, however the basics of the construction system have remained unchanged. What makes this possible is the existence of concrete as a construction material. Its primary component materials are aggregate, cement and water, with aggregate constituting approximately seventy percent of the total volume. Concrete is thus made from the most abundant substances on Earth, and this is one of the main reasons why its production has been able to expand to respond to growing construction demand. Concrete is nowadays the second most consumed substance on Earth after water. To state the case in extreme terms, we might say that contemporary society could not exist without concrete, and it is no exaggeration to say that the development of a nation has been directly proportional to the consumption of concrete. There are two problems concerning concrete and steel, which are necessary for the development of socioeconomic infrastructure. One is that, despite an abundant availability of their material resources, the volume of consumption is enormous. Another is that the production of cement and steel generates a large amount of carbon dioxide, known to be a greenhouse gas. However, there are no alternatives to concrete and steel as basic materials for the development of socioeconomic infrastructure. Mankind thus has no choice but to continue utilizing concrete and steel, while a significant increase in material consumption as well as the resulting carbon dioxide emissions due to growing population and socioeconomic expansion will most likely become a strong factor in hampering sustainable global development. As the concrete and construction sectors are expected to have such a great impact, they are required to precisely understand the degree of their involvement, and strive for reduction of their environmental load. In fact relevant research and study activities have intensified in recent years. The authors take pride in leading such activities both in Japan and overseas. Specifically, in the Japan Concrete Institution（JCI）, we have been engaged in researches conducted by the technical research committees on concrete related to the environment, and are presently focused on researches with the sustainability committee. In the Japan Society of Civil Engineers（JSCE）and the Architectural Institute of Japan（AIJ）, we have published guidelines regarding the environment and construction in concrete respectively. Internationally, the authors take a leading role in the Commission 3 of the International Federation for Structural Concrete（fib）, Concrete Sustainability Forum of the American Concrete Institute（ACI）, Sustainability Forum of the Asian Concrete Federation（ACF）, and TC71/SC8（Environmental management for concrete and concrete structures）of the ISO. In this article, the authors give an outline concerning environmental assessment tools, activities of international associations, and the present state of development of environmental standards, in relation to efforts concerning global environmental issues with respect to concrete, an enormous amount of which is used for the development of socioeconomic infrastructure.