The use of ductile iron pipes with a cement mortar coating is to be considered sustainable for several reasons:
1. The reuse of trench excavation material saves both its transport away from the site and the delivery of bedding sand to the site, which means that additional HGV traffic, including the CO2 emissions, is avoided. When constructing water pipelines in Alpine areas for turbine pipelines and snow-making facilities, the transport of material is very much restricted and often well-nigh technically impossible. In these cases, the coating according to EN 15542 is so robust that bedding the pipes in the existing rocky screen has become common practice.
2. Bedding in coarse ballast opens up an entirely new application option for the ductile iron pipe with a coating of fibre cement mortar: with the sponge city principle, a pipe trench filled with coarse ballast can be used as linear intermediary storage for rainwater at times of heavy rainfall which is available to trees in urban areas for a longer period. The proven root resistance of the cast iron pipe joint means that a tree can be planted directly on the route of the pipeline. This application offers two simultaneous climate-related effects:
– Avoidance of flooding by the intermediate storage of rainwater.
– Improved growth conditions for street trees with the associated improvement of the microclimate because of the increased evaporation performance of their healthier crowns.
3. The development of trenchless installation and replacement techniques has been significantly influenced by ductile iron pipes with restrained joints. Here one can really talk about a bedding with more or less unknown properties. In a borehole strengthened with bentonite there can actually be anything which a pipe pulled through it might come up against, such as sharp stones, sharp-edged remains on foundations, fragments of grey iron in the case of burst lining etc. The list can easily go on. Ductile iron pipes with cement mortar coating have won through for these techniques with “unknown bedding” right along the pipeline.
