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International Concrete Abstracts Portal

Showing 1-5 of 30 Abstracts search results

Document: 

SP202-23

Date: 

August 1, 2001

Author(s):

D. D. Bui and P. Stroeven

Publication:

Symposium Papers

Volume:

202

Abstract:

Fly ash is increasingly used on a worldwide scale in cement and concrete because of reduced cost, material and energy savings, and improved resistance and durability of the fly ash concrete. One of the drawbacks of (Class F) fy ash concrete is its potentially relatively low early strength. Highly reactive pozzolanas such as silica fume and metakaolin can be used to enhance the properties of fly ash concrete. However, silica fume and metakaolin are relatively scarce and expensive. Rice husk ash is an active pozzolana produced by controlled burning of rice husks, hitherto an agricultural waste. This paper describes the combined use of rice husk ash (RHA) and fly ash in high-perfomrance concrete. The high-performance concrete was based on a gap-graded concrete aggregate with fine sand. Further, a superplasticizer was applied. These ternary blended cement concretes showed greater strength gain than the fly ash concrete.

DOI:

10.14359/10794


Document: 

SP202-18

Date: 

August 1, 2001

Author(s):

K. Kawai, E. Tazawa, S. Tanaka, and S. Yokoyama

Publication:

Symposium Papers

Volume:

202

Abstract:

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.

DOI:

10.14359/10789


Document: 

SP202-14

Date: 

August 1, 2001

Author(s):

N. J. Coleman, D. C. Johnson, 0.1. Shtepenko, and C. D. Hills

Publication:

Symposium Papers

Volume:

202

Abstract:

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.

DOI:

10.14359/10783


Document: 

SP202-08

Date: 

August 1, 2001

Author(s):

J. P&a, J. Ambroise, J. Biermann, and N. Voogt

Publication:

Symposium Papers

Volume:

202

Abstract:

CDEM, a group of four Dutch papermills, joined forces to develop a proprietary (patented) process that allows the production of a new type of admixture for use as building material. The process consists of a controlled thermal conversion of deinking paper residue in a fluidized-bed combustor. The resulting mineral product has both hydraulic and pozzolanic properties. The mineral product is mainly composed of metakaolin and calcium compounds. The mineral product composition depends upon the chemistry of the starting paper residue and the thermal conditions applied. When the raw paper residue is rich in kaolin and the thermal conversion preserves calcium carbonate, a very reactive pozzolan is obtained. When the calcium content increases and decomposition of calcium carbonate occurs, a self-cementing material appears which can replace normal cement in several applications like: masonry blocks, autoclaved products, and backfilling mortars.

DOI:

10.14359/10777


Document: 

SP202-04

Date: 

August 1, 2001

Author(s):

A. K. Chatterjee

Publication:

Symposium Papers

Volume:

202

Abstract:

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.

DOI:

10.14359/10773


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