The aim of this study is the valorization of magnesium slags in order to recycle them in construction block form. Two kinds of slag with hydraulic properties are obtained according to a l/3-2/3 ratio: powdered slag similar to cement, and granulated slag similar to sand. A previous laboratory study was curried out in order to obtain sufficient mechanical strength for construction blocks and setting kinetics compatible with an industrial process. The present paper deals with the consecutive implementation of life size tests on an industrial scale. Two pre-industrial tests were carried out in extremely different temperature conditions 7°C for the first test and 22°C for the second one. Furthermore, the second test benefited from the new casting conditions resulting from updating of the manufacturing unit. The first test showed that the laboratory study permitted to adjust the set kinetics to a level adequate for industrial casting, whereas the mechanical strength obtained was lower than expected when the powdered slag was used as a substitute for cement. The second test enabled us to obtain enough mechanical strength for mixtures entirely composed of magnesium slags and proved the possibility of total and simultaneous enhancing value of magnesium slags as construction blocks. More generally, these industrial tests show how difficult the transfer to the industrial scale is.

On the background of the need for reuse of building rubble and the saving of natural resources, a European Union research project was performed covering concrete technology and durability aspects. A very special precondition was the use of large-scale processed building rubble with unknown origin and the total replacement of aggregates above 2 mm. Comprehensive tests were carried out on the properties of the starting material from different processing plants and fresh concrete, particularly the interdependence of water addition and wor ability. Investigations on hardened concrete properties included strength devel-opment, creep and shrinkage, modulus of elasticity, capillary absorption, freezing and thawing resistance, and carbonation behavior over a long period. The results demonstrate that the industrial production of a high-grade, durable concrete is possible. The project is a promising contribution for sustainable development.

A large number of relatively new reinforced concrete structures may require intervention due to problems affecting their durability. Repair and replacement costs of structures account for a considerable share of the total cost of constructions. Rice-husk ash (RHA) concrete displays lower permeability due to changes in the concrete microstructure, which reduces the vulnerability of this material to the action of aggressive agents. This study assesses concrete durability properties to chloride ions, an aggressive agent. The effect of chloride ions was investigated with tests of compressive strength and chloride penetration. These tests were performed in high initial strength portland cement concrete (CPV-ARI) modified with the addition of rice-husk ash (RHA) and in pozzolanic portland cement concrete (CPIV). The input variables were the water/cimentitious ratio (0.30-0.35-0.45-0.60-0.80) and the contents of the rice-husk ash additions (0%-5%-lo%-IS%/,-20%). Results show that the addition cf rice-husk ash to CPV-ARI concrete had no significant effect on compressive strength properties when compared to the reference concrete. Results for chloride penetration show that the addition of RHA produces an average reduction of 126.6% on the charge passed. Comparative results of RHA CPV-AR1 concrete and CPIV concrete show that the compressive strength performance of the latter is poorer than the former. Chloride penetration results show that CPIV concretes displayed a better performance than CPV-ARI concretes with and without the addition of RHA.

SP-202 Alternative cementitious materials can play a major role in the concrete industry’s contribution to sustainable development by helping to reduce carbon dioxide emissions and ease the fly ash disposal problem. Some of the approaches to sustainable development are described in ACI SP-202, Third CANMET/ACI International Symposium on Sustainable Development of Cement and Concrete. Twenty-nine papers from international authors describe experiences with non-ferrous slag, steel slag, crushed waste calcined-clay brick, and rice-husk ash used as partial replacements for portland cement. Other topics include use of recycled concrete as aggregate, high-volume fly ash RCC for dams, and performance-based hydraulic cements.

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.