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This paper evaluates the potential of crushed waste calcined clay brick 3s cement replacement material. The crushed waste was characterised physically, chemically and mineralogically through fineness test, density, chemical composition and X-ray analysis and the consumption of calcium hydroxide determined using differential thermal analysis. The influence of the partial replacement of portland cement by calcined clay on the strength development was eAtrated until the age of 365 days. The pcrcentagc of ccmcnt replacement, by weight, ranged from 20 to 42% whereas the water/cement ranged from 0.37 to 0.45. The CO? emissions associated with portland cement production were determined as well as the emissions that can be avoided replacing portland cement by the calcined-clay brick. The results show that the crushed waste presented a good pozolanic activity and that the compressive strength of the blended mortars was higher than that observed for the control mixture for all ievels of cement replacement. The reductions in CO2 emissions can be achieved if pozzolanic materials such as calcined-clay brick is adequately used as cement replacement.

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.

This paper presents an experimental analysis of recycled concrete (RC) in which the natural aggregates are replaced by recycled concrete aggregates (RCA). This experimental program covers the specifications of the aggregates employed, together with that of the concrete that is manufactured with them. The considerable effect on the permeability of RC that is produced by the use of RCA is described and discussed. Tests reveal considerable increase in permeability of RC in comparison with the reference concrete. Both the water penetration depths and the permeability coeffkients are increased in a manner that may be correlated with the increase in the replacement of natural aggregates by RCA. These increments are attributed to the high porosity of RCA.

As a result of the Chi-Chi earthquake, which occurred in middle Taiwan on September 2 1, 1999, numerous buildings and bridges were seriously damaged. How to reuse a huge amount of building debris collected from the damaged structures became an important issue. After being crushed and screened, this debris could be served as recycled aggregate in concrete. Such recycled concrete is recommended to be used for sub-structures or other applications. Therefore, the production of fish reefs became one of the possibilities. In the study, treatment and measurement of the basic properties of the recycled aggregates were firstly studied. Then manufacture fish reef with the recycled concrete were undertaken. Test results show that the properties of recycled aggregate can meet the requirements of natural aggregate. The fish reefs produced by using the recycled concrete were satisfactory and conformed to the demands of the Fisheries Administration in Taiwan.

The crushing of reclaimed concrete-based demolition waste in the production of recycled aggregate produces a large volume of fine material which is rich in hydrated cement paste phases, the coarser fraction being predominantly composed of aggregate. It is the coarse fraction which is of use in construction and the fine fraction which is destined for landfill. Heavy metal-bearing wastewater and sludge arise from a number of industrial processes including; electroplating, galvanising, metal finishing and battery production. Treatment procedures for aqueous heavy metal-contaminated waste streams include; precipitation, adsorption, ion exchange, membrane filtration and soliditication/stabilisation using cement or lime-based materials. The removal of heavy metal species from aqueous media by the cement-rich fraction of ordinary portland cement-based waste concrete is demonstrated herein. Crushed concrete waste in the particle size range 1 - 2 mm is shown to be effective in the exclusion of a range of heavy metal nitrates (Pb2’, Cr3+, Cu’+, NiZf and Zn*‘) from solution. The leaching characteristics of the metal-impregnated cement matrices are also reported.