Economical, technical and ecological utilisation of treated steel slag in civil engineering of high quality demands

Projektinformationen

ID Finanzhilfevereinbarung: BRPR970446

Projekt abgeschlossen

Startdatum 1 August 1997

Enddatum 31 Juli 2000

Finanziert unter

• Specific research and technological development programme in the field of industrial and materials technologies, 1994-1998

Gesamtkosten

Keine Daten

EU-Beitrag

Keine Daten

Koordiniert durch

Forschungsgemeinschaft Eisenhüttenschlacken
Germany

CORDIS bietet Links zu öffentlichen Ergebnissen und Veröffentlichungen von HORIZONT-Projekten.

Links zu Ergebnissen und Veröffentlichungen von RP7-Projekten sowie Links zu einigen Typen spezifischer Ergebnisse wie Datensätzen und Software werden dynamisch von OpenAIRE abgerufen.

Leistungen

New products produced from treated steel slags; armourstones for waterway constructions, aggregates for road's base court, for asphalt, for lean concrete and aggregates for paving-stones

By treatment and special cooling techniques in the pit-the amount of stones suitable for water way construction purposes have been increased. Thus about 8000 t of the fraction class 0 (50/150 mm) have been produced to be built into two tests fields at the Rhine river. The technical behaviour of the stones in the test fields are good. Owing to the high specific weight the resistance against breaking waves is higher compared to natural stones. No disintegration has been observed. Aggregates for road construction: The technical properties of the slag have been improved by the treatment. The slag can be processed to aggregates for specified road construction. Due to high volume stability of the treated slag aggregates as an addition to concrete paving-stones as well as for asphalt have been produced. For both applications test fields in roads have been prepared and built. These test fields are still in the observation phase. There are no negative effects limiting the use of treated slag for these applications. The aggregates have been investigated for the use in lean concrete, too. Best results have been gained with EAF slag. No additional treatment seems to be necessary for EAF slag since their volume stability and their technical properties are good. As a result it has been shown that the treated slag is well volume-stable. No problems concerning insufficient volume stability have been encountered. The properties of the products fulfil the demands due to standards and regulations. The profits gained by selling treated slag are higher than for untreated slag with the lack of sufficient volume stability. Thus the costs for the investment and the higher treatment costs will be proceeded. The results achieved are necessary for the processors of slag, which are mainly SME's. The results are published, so that European processors can use them to have benefits for the steel industry in Europe.

Improvement of the internal recycling and minimising of residues to be utilised on other fields of application

The zinc content of BOF dusts is in a range too high for recycling into the BF, too low for recovering of zinc. Therefore the dust recycling into the converter has been investigated within this project to increase the zinc content to amounts suitable for recovering and due to higher iron contents in the slag to bind free lime contents. The target of this research has been to investigate the metallurgy of steel and slag during recycling. The quality and properties of the slag, mostly used as aggregates for road construction, must not be influenced negatively. As a result the tests show that it is possible to recycle BOF dust into the BOF vessel. Zn and other elements easy to be vaporised at steel temperatures will be transferred into the gas atmosphere and will be enriched in the dust. Thus, recycling the dust will increase the contents of valuable elements in the newly formed dust. The steel quality is not influenced by this recycling. Owing to high bad stirring during the BOF process, all the zinc introduced by the dust briquettes is vaporised during the process. No problems have been encountered during the casting. Also the quality of the steel slag has not been influenced negatively. The properties of the slag fulfil the demands on aggregates for road construction. Due to higher iron contents in the slag the free lime is bound into calcium ferrites. The results have advantages for all European steel producer and their processors for the slag. This technique is a further step to produce steel with minimum of residues.

Treatment of liquid steel slag with sand and oxygen in order to improve their volume stability and their environmental behaviour

Slag from BOF steel making have good mechanical and environmental properties. Their lack is their (sometimes) insufficient volume stability. The volume stability is mainly affected by the free lime content in the slag. This free lime can react with water or humidity by increasing its volume. Thus the slag matrix will be destroyed and cause problems in the application. A process has been developed to treat the liquid BOF slag with SiO2 containing materials, like sand, and oxygen to overcome the problems of insufficient volume stability. The free lime is solved into stable slag phases. The process is applicable to all steel works to treat their steel slag in order to reduce the free lime content in slag and to produce a volume stable slag with good technical and environmental properties. Furthermore a reduction in free MgO in the slag is expected. The benefits of the treatment are the production of a slag with higher quality which can be used on fields of application with high quality demands, which cannot be fulfilled by other residues or wastes from other industries. The use of the treated slag will help to save dump space and will save natural resources. The slag is a raw material for road construction as aggregates as well as aggregates for asphalt layers. It can be used in civil engineering for concrete additions. Owing to high investment costs the production of the slag is limited, today. But there are demands for the future with closing dump spaces in Europe as well as in the USA and Canada.

Treatment of liquid steel slag with glass cullets and oxygen in order to improve their volume stability and their environmental behaviour

On the base of the results from the slag treatment unit reported under point 3 in 1.2, additional treatment tests have been carried out by the partners SIDMAR and CRM. A process has been developed to treat the liquid BOF slag with glass cullets instead of sand and oxygen to introduce SiO2 containing materials into the liquid slag in order to bind the free lime. The process design for the SIDMAR tests is similar to the design of the Thyssen plant. However, the additions have been limited to 750kg glass culets in the first test runs and has proved to be insufficient. The injection of glass cullet achieved the same results as gained by using the same amount of sand injection. Additional tests (2000 to 3000kg glass cullets) are foreseen considering the slag ratio CaO/SiO2 in the slag. This process design is applicable to all steel works to treat their steel slag in order to reduce the free lime content in slag and to produce a volume stable slag with good technical and environmental properties. Since the tests have not shown results as expected, additional trials are necessary. Especially the amount of glass cullets has to be increased, to produce volume stable slag. Therefore additional tests will be carried out after the project will be terminated.