Climate Change Corner

Climate Change Calls for More High-performance Concrete

Concrete is the most widely used construction material. Cement used in concrete contributes about 5 percent of global greenhouse gas emissions. Concrete accounts for more than 74% of the total material weight of a building in Hong Kong. The production of concrete for new buildings and the eventual demolition of old buildings generate a large carbon footprint that causes global warming and a large volume of solid waste that uses up valuable landfill space.

There is a pressing need to reduce the consumption of concrete and extend the service life of concrete buildings. In response, the concrete industry has been advocating the usage of more high-performance concrete (HPC), which usually has higher workability, strength and durability than normal concrete. Higher workability could significantly improve the buildability of new construction projects; higher strength could reduce the volume of concrete needed; higher durability could extend the service life of concrete buildings.

It is a misunderstanding that HPC, which usually contains more cementitious materials, would generate a larger carbon footprint. In fact, the cement used in HPC is not necessarily higher than normal concrete because of the extensive use of industrial by-products such as pulverized fuel ash, silica fume and ground granulated blast-furnace slag. Further, the life-cycle analysis of the carbon footprint of concrete construction shows that although HPC tends to have a higher cementitious content per unit volume, due to the reduced volume of concrete needed and the extended service life of buildings, its carbon footprint is actually much lower.

Although there may be some hurdles in application of a particular kind of HPC (i.e. the grade 60 MPa tremie concrete), the development and applications of various high-performance concretes will have considerable implications for the future development of the industry.

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This article is contributed by Ms Shirlee May Algire: Group Sustainability & CSR Manager and Dr Herbert Zheng: Assistant General Manager, Concrete Technology Department of Gammon Construction Ltd. with the co-ordination of the Environmental Division.