Greater building sustainability with Holcim Optimo

(Switzerland) — Holcim (Switzerland) has already massively reduced CO2 emissions by making changes to cement production and composition. With its new cement, Holcim Optimo, Holcim takes its achievements to a new level. Holcim Optimo is a sophisticated product for all applications in all respects, delivering an effective contribution to more sustainable building.

In cement manufacturing, natural raw materials such as limestone and clay are fired at a temperature of around 1450 C to produce clinker. So the production process is very energy-intensive. In addition, heating the limestone triggers a chemical reaction that also releases large quantities of CO2, making the cement industry a leading source of greenhouse gases.

Optimized manufacturing process
For decades Holcim (Switzerland) has pioneered efforts to make cement production as environmentally compatible as possible by reducing CO2 emissions. State-of-the-art filter plants reduce emissions of nitrous oxides, and optimizing firing processes down to the smallest detail has minimized emissions of harmful gases. Moreover, to reduce the use of fossil fuels alternative materials such as waste oil, car tires, and solvents are also combusted. Together these measures have had a considerable effect: In the past 20 years Holcim (Switzerland) has cut CO2 emissions per tonne of clinker produced by almost 40 percent.

Partial substitution of clinker
It is also possible to save CO2 by using less clinker. Thus, by 2009 the proportion of Portland cement had been reduced to 22 percent. The entry into force of standard SN EN 197-1 made this development possible, as in addition to “pure” cement, it allows for cements with additives. Aside from the technological advantages for concrete, which extended the range of applications, this advance also enabled significant reductions in CO2 emissions. In recent years, the most popular cement has been a type of Portland limestone cement, which contains ground limestone as additive. Other cements have admixtures of blast-furnace slag, and in the manufacture of concrete, fly ash replaces part of the cement. These materials are suitable additives on account of their chemical reactivity; however, they are not always available in the same quantities or in a constant quality, which causes serious production problems. What is more, they have to be transported long distances.

Burnt shale
Holcim embarked on a crossborder cooperation to improve the uncertain supply situation, replace the proportion of clinker in cement with a hydraulically effective additive of constant high quality, and shorten transport routes. Holcim’s Dotternhausen cement plant near Rottweil in southern Germany has deposits of shale in the immediate vicinity that are unique in Central Europe. This shale contains combustible components that are used to produce electricity; in the process the shale is chemically transformed. The burned shale is chemically reactive, i.e. it is capable of hydraulic and pozzolanic reactions. It is an ideal clinker substitute, to which shale cements already used in Germany impressively testify. Nevertheless, the properties of Holcim Optimo, a mixture of clinker, limestone and burned shale, were meticulously studied in a comprehensive range of pilot tests. These showed that very finely ground shale has a positive impact on several properties of concrete. The new Nano-T® technology increases the effective packing density, and thereby the density of the concrete structure. Certified to SN EN 197-1 for all applications of concrete, Holcim Optimo is the perfect all-rounder and the answer for those looking for a new standard cement with strong eco-compatible properties.

Transport by rail
Simply adding shale is not enough to permanently reduce CO2 emissions. The transport of shale from the Swabian Alb to Holcim’s Swiss plants also needs to be environmentally sustainable. In recent years considerable sums have been invested in expanding the railway infrastructure, including a new loading silo in Dotternhausen, the upgrading of an entire section of railway line to connect the plant to the national railway network, the purchase of new rolling stock, and a number of structural adjustments and extensions at the Swiss plants.

The cement industry sets an example
The Swiss cement industry has already made a disproportionately large contribution to meeting the goals of reducing CO2 emissions as laid down in the Kyoto Protocol – voluntarily. Holcim (Switzerland) is proud of the fact that the introduction of its new cement will reduce its CO2 emissions – measured on the basis of its total cement production – by a further 10 percent, without in any way affecting sales to clients. Furthermore, Holcim Optimo can be used with all common additives. However, the main distinction between Holcim Optimo and all other products on the market is its high contribution to sustainability. This should serve as a catalyst for everyone involved in construction to raise their eco-awareness and take responsibility themselves – at all levels, from planning to decommissioning and renaturation.

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