ACERITA®
Steelmaking Slag with Expansion Reduction - ACERITA®
The Steelmaking Slag has always been considered a problem for the steel mills due to its volumetric expansion caused by the contents of free CaO and MgO, which undergo hydration reactions when in contact with water.
Considering this problem, in 1999 ArcelorMittal Tubarão sought a partnership with a road consulting firm (KAEME Consulting) in order to find a way to conform the use of Steelmaking Slag into road paving.
We carried out some trials for a few months in order to check what factors provided greater speed in stabilizing the slag, thus allowing the free oxides to become partially inert, then reducing the slag's capacity to expand. The result of this study was the development of the so-called ACERITA®.
ACERITA® is a steelworks co-products that after being crushed and separated into suitable granular ranges is submitted to a treatment of expansion reduction.
This process consists of "stimulating" the reaction of the free oxides with the air and water, through a process of moistening and aeration of the slag during a certain period of time.
During its treatment period and aiming at reducing its expansion capacity, the Steelmaking Slag is permanently monitored through laboratory assays and tests conforming to the DNIT standards (former DNER)*, to be further used in base and sub-base of road pavements.
Upon reaching an expansion value that conforms to the technical standards, the process is interrupted and the material is made available to the market under the name ACERITA® - Steelmaking Slag with Expansion Reduction.
* DNIT / DNER = Brazilian Department of Motor Vehicle
Main Features
- Granulometry range C of the DNIT
- Maximum dry specific mass: 2.350 g/dcm³
- Loose material density: 1,75 t/m³
- Los Angeles abrasion testing: 20 %
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Generation capacity: 15.000 t/month
In addition to the usual features of the Steelmaking Slag, such as high load capacity, high wear resistance, high dead-weight and cementing properties, it presents very low expansion values, when submitted to expansion assays via CBR method in accordance with the trial standards required by DNIT, which allows its application in Road Construction.
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CBR Testing Method
For the expansion measured by the CBR testing method for paving use, it is required expansion values lower than 0.5 %, which through considerable monitoring, have been achieved by ACERITA®. In addition, it presents CBR values higher than the stony aggregates, thus being a very resistant material and providing a good structure to the pavement.
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" PTM 130 Method (Pennsylvania Testing Method modified by DER-MG - Standards DNER ME 262/94 and DNER Pro 263/94).
The standards DNER-EM-262/94 and DNER-PRO-263/94 determine that the volumetric expansion of Steelmaking Slag, measured through the PTM 130 method (Pennsylvania Testing Method), presents an expansion of maximum 3.0 % for roadways applications, a figure that has been reached by ACERITA®.
The expansion reduction of ACERITA® allows for its application in sub-base, base, binder and CBUQ, that is, in all layers of a pavement, with or without the mixture of other materials. The greatest advantage of ACERITA® if compared to other stony aggregates is that the thickness of those layers can be reduced because the elasticity module of the layer built with ACERITA® is superior to the module of the stony aggregate, considering the measurement through the ELSIM-5 method.
The process of research and development of ACERITA® is still in progress, and with new investments aiming at improving its application even further; in May 2004, ArcelorMittal Tubarão signed a joint venture with DNIT-ES and KAEME Consulting for studying the application of the Steelmaking Slag in the roadway sector in addition to reviewing the existing standards with a view to promote and guarantee the quality of the Steelmaking Slag application, in order to have enough instruments to monitor and make a better use of the high performance of pavements built with this material. This way we are able to reduce the thickness of the pavement layers, without sacrificing the pavement's support capacity, thus decreasing the required amount of material and ultimately, turning the use of ACERITA® into an economically feasible technical alternative, also aggregating quality.
Due to all positive characteristics shown in the tests and performance monitoring routines carried out by ArcelorMittal Tubarão in construction works already accomplished, ACERITA® has proved to be an actual solution for construction material that provides the pavement with higher durability, lower final cost, lower level and cost of maintenance, also contributing to improve the quality of road paving.
Construction works accomplished with ACERITA®
Contact:
- Road Construction Works
Eng. Nocy Oliveira da SilveiraSales Executive
Tel: (+55 27) 3348-1082
E-mail: nocy.silveira@arcelormittal.com
ArcelorMittal Tubarão
Av. Brigadeiro Eduardo Gomes, 930
Jardim Limoeiro, Serra,
Espírito Santo
Zip Code 29163-970. PCE 41
Siderúrgica produtora de placas de aço, aços planos, bobinas e laminados a quente.
