International Concrete Abstracts Portal

Sustainable development in the concrete and cement industry is achievable in the near future. This paper proposes the viability of a factor 10 reduction in the negative environmental effects of current cement/concrete production through the use of cement blends with minimum portland cement and maximum pozzolanic loading. Such cement blends substantially extend the longevity of concrete and avoid the enormous cost of several repair and replacement cycles. ‘l’he transition to sustainable concrete technology will be driven not by environmental imperative but rather by market forces pursuing economic advantage through more durable concrete. Market driven economics already in place will soon prove that concrete durability is worth a high premium but is available at a bargain. There is enormous leverage in improving concrete quality as a doubling of the price of highest quality cement would add only 2% to overall construction project costs while the extended service life of the structure would offer a many-fold return on the additional investment. In coming years, the consideration of CO2 emissions regulations and increasingly valuable internationally traded CO2 credits will assume an economic importance equal to or greater than capital and operating costs among cement producers. Those who do not move to sustainable concrete technologies will run the risk of losing substantial market share or business failure.

In 1995 the German cement industry committed itself to a 20 % reduction in it’s specific fuel energy consumption between 1987 and 2005. In 2000, this commitment has been adapted to the international agreements, particularly to the Kyoto Protocol. Now the voluntary agreement includes a reduction of the specific energy-related CG2 emissions from 1990 to 2008/12 by 28 %. As the burning and grindrng facilities have been widely optimized during the past years, the German cement industry is planning to increase the sub-stitution of fossil fuels by waste fuels and to promote the marketing of blended cements. From 1987 to 1999 the German cement industry’s efforts have led to a reduction of the energy related CO, emissions by 3,6 million ton-nes per year. The share of waste fuels has been increased from 4 to 23 % and the clinker portion in cement has been decreased from 86 to 80.6 % by using more granulated blast-furnace slag and unburned limestone as the main constituents in cement. To what extent other instrument like emission trading, joint imple-mentation or clean development mechanism can be used in the future to achieve further reductions, will depend on mutual arrangements and implementation by the international community.

A non-ferrous slag from the production of metallic zinc was studied as a new ingredient for concrete. It was used in two forms: ground and un-ground material. The ground slag replaced 15% of portland cement, whereas the un-ground slag replaced 20% of the natural sand. Five different concrete mixtures were studied, all with a water-cementitious materials ratio of 0.60: - reference mixture with portland cement and natural aggregates; - concrete mixture with ground non-ferrous slag replacing portland cement; - concrete mixture with un-ground non-ferrous slag replacing sand; - concrete mixture with ground non-ferrous slag replacing portland cement and un-ground slag replacing sand. Additionally, for comparative purposes, a ground granulated blast-furnace slag was used to replace 15% portland cement. The following properties were studied: compressive strength: heat development through change in temperature; and immobilisation of heavy metals of the non-ferrous slag through water-leaching tests. - The compressive strength development of the concrete with the ground non-ferrous slag was the same as that of the corresponding concrete with ground granulated blast-furnace slag; - When un-ground slag was used to replace sand there was a negligible decrease in the early compressive strength; - When both ground and un-ground non-ferrous slag were used there was a significant retardation in the development of compressive strength during the first 2 days; - The early heat development was slightly reduced due to the portland cement replacement and the temperature peak was significantly delayed when both ground and un-ground non-ferrous slag were used; - The leaching by water of heavy metals from the hardened specimens was negligible and then the immobilisation of zinc and lead of the slag into the cement matrix was very effective.

In the production of iron and steel, two different types of slags are generated - one, the blast- furnace slag obtained at the time of iron extraction and the other, the steel slag generated during the conversion of iron to steel in the steel melting shop. The blast-furnace slag, after proper granulation, is used extensively as a supplementary cementitious material in the cement and concrete industry. The steel slag, however, has not found much use and is mostly dumped as a waste material after removing scrap steel. In order to explore the avenues for economical utilisation of this slag in cement-making an extensive literature and patent survey has been carried out. Further, based on the steel slags available from some of the integrated steel plants in India, the material has been characterized in detail and its hydraulic behaviour has been studied. Studies relating to the potential use of this slag as a raw material in the production of portland cement clinker as well as in the manufacture of special cements like the calcium sulphoaluminoferrite type has been experimentally carried out at a pilot scale. Blended cement formulations with maximized incorporation of steel slag have been prepared and studied. Based on available literature and experimental findings, an attempt has been made to look at the potential scenario of steel slag usage in cement-making with specific emphasis on environmental amelioration and GHG reduction.

Because cement plants generate approximately one ton of CO, per ton of produced clinker the industry can play an important role in meeting the objectives of Kyoto Protocol. This paper presents Croatian experience in that field which includes: Production of cements with lower clinker content but with satisfactory development of strength in concrete owing to the proper choice of mineral admixtures. Application of alternative fuels derived fromindustrial and municipal waste in clinker burning process instead of burning that waste in specialized incineration plants without using the benefit of the energy expended.Use of solidificates made by agglomerating wastes from oil refineries by means of quick lime, as an alternative raw material and fuel at the same time. This reduces CO, emissions due to replacing part of limestone with Ca(OH), and due to the lower requirement of fuel for decarbonization process.