Environmental impacts - Sustainability

In the table below, several topics regarding sustainability in concrete production are outlined. These topics are elaborated further in the following in order to provide the reader with an overview of the concrete production industry. It is generally accepted that most sustainability aspects of concrete production may be considered under one of these categories.

Category 1 mainly concerns the production and processing of raw materials for concrete production. Since this topic is treated by the aggregate part of this baseline report and from Cluster 1 and 2, it is not dealt with in the present chapter.

Category 2 is often dealt with by means of:

• Reusing waste generated from within the concrete production, e.g. washing water or rejected concrete batches.
  
• Reusing waste products from other industries, e.g. fly ash, slag, silica fume, waste glass, manufactured sand.

Category 3 is often dealt with by means of minimising the use of Portland cement clinker by:

• Blending cement with supplementary cementitious materials such as e.g. fly ash, silica fume, slags, limestone etc. Blending during cement production or at the concrete plant depend on local traditions and level of technology. In some parts of the world addition of local supplementary materials, such as rice husk or bamboo fibers are added to concrete also.
  
• Optimising the concrete mix design, so that its performance fulfils the specifications with the lowest possible clinker content in the concrete.

Finally, category 4 is often dealt with by improved automation of concrete batching and casting. However, this again may lead to societal side effects such as reductions in the labour force.

The use of fibre reinforced concrete also leads to improved working environment as the traditional reinforcement work involves extensive impact on the workers.

A relatively new way of improving the working environment for the concrete workers during casting is by using Self-Compacting Concrete (SCC), a high-performance concrete that flows into the formwork under its self-weight only, without the need for vibration and compaction.

The most popular tools for the authorities in order to implement environmentally friendly actions are economically based instruments such as landfill, energy and CO₂ emission taxes.

Finally, it should be mentioned that sustainability issues in concrete production are often governed by simple short-term economical considerations such as:

• Changes in the production facilities being very costly, it takes time to adopt new technologies requiring alterations in mixing equipment, storage facilities and so forth. Furthermore, the manufacturer needs to establish documentation that the green choice of materials is in agreement with the standards and codes of practice, which may be costly.
• The competition on concrete is very focused on price. The costumers are not (yet) prepared to pay an increased cost for environmentally friendly concrete.
  

Figure 1: Total cement consumption in 16 European countries.
Source: ERMCO 2001 Statistics

The annual cement consumption of almost 200 million tonnes Portland cement clinker in 16 European countries (Figure 1) equals an average of about 500 kg per capita. Since the production of 1 kg cement generates approximately 1 kg CO₂ emission this corresponds to 500 kg CO₂ annually per capita. Comparing total CO₂ emissions per capita (listed on various web sites, e.g. http://millenniumindicators.un.org) with the cement consumption figures in Figure 2 it is seen that cement production counts for about 2-3 % in Scandinavia up to about 15 % in Spain and Portugal.

Figure 2: Total annual cement consumption per capita.
Source: ERMCO 2001 statistics

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