A judicious use of resources. achieved by the use of by-products and waste materials. and a lower environmental impact. achieved through reduced carbon dioxide emission and reduced natural aggregate extraction from quarries, represent two main actions that meet sustainable building development. Recycled-aggregate concrete containing fly ash is an example of a construction material which is in harmony with this concept, whereby sustainable building development is feasible with satisfactory performance in terms of both safety and serviceability of structures. The structural properties of recycled-aggregate concrete containing fly ash were evaluated by means of compression tests, splitting tension tests and pull-out bond tests on concrete specimens, whereas structure serviceability was checked by means of drying shrinkage. Moreover, corrosion measurements with galvanized steel embedded in natural-aggregate concrete containing fly ash were analyzed in order to expect the use of galvanized steel reinforcement in fly-ash recycled-aggregate concrete.

Cement manufactured from incinerator ash has been developed in Japan. This cement contains 1520% of CjA and 0.02~0.1% of chlorine. Since the chlorine content of this ccmcnt is higher than that of normal portland ccmcnt in Japan, thcrc is a concern whether steel bars embedded in concrete using this cement would become rapidly corroded. In this study, the behavior of chlorine in cement hydrates is investigated in terms of the contents of chlorine accommodated by Friedel’s salt. The compositions of pore solution in cement hydrates at early ages and the water-soluble and acid-soluble compositions of cement hydrates are analyzed. As a result, it is found that the concentration of chloride ion in pore solution of cement hydrates using cement manufactured from municipal wastes is not too high. It means that many chloride ions could be accommodated by Friedel’s salt because of high CJA content.

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.

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.

For the practical use of granulated blast-furnace slag as a clinker substitute, the addition of an activator is neccessary, in order to ensure that a sufficient early and ultimate strength will be reached. Up to now, portland cement has been the most common type of activator for granulated blast-furnace slag. The addition of portland cement leads to the activation of the granulated blast-furnace slag either on an alkaline or, to a minor extent, on a sulphate basis. Materials which prevent the obstruction of the latent hydraulic reaction by a close gel layer of reaction products work as an activator. In this paper, the influence of different fine-grained additives, e. g. fly ash or cement kiln dust, on the granulated blast-furnace slag reaction and the strength development is discussed. The investigations showed that it is basically possible to manufacture composite cement with a high content of granulated blast-furnace slag by using industrially by-products. These cements shows particularly a higher early strength than the reference cement dependent on the composition respectively to the addition. The reactivity of the blast-furnace slag is strongly influenced by the chemical composition of the addition or activator but also by the mineralogical and chemical composition of the blast-furnace slag.