LD slag with expansion reduction - ACERITA®
LD slag due to its volumetric expansion caused by free CaO and MgO content, which suffer hydrating reactions in presence of water, can present some application restriction.
ArcelorMittal Tubarão searched for partnership with a Road Work consulting company (KAEME Consultoria) to develop correct application methods.
Experiences were conducted to check which factors speed up slag stabilization so that free oxides are partially inertized reducing slag expansion capacity. The result of this study was the development of ACERITA®.
ACERITA® is a steel-making co-product that after crushed and screened into granulometric ranges is submitted to an expansion reduction treatment.
This process consists in stimulating the free oxides reaction to air and water through a repeated humectation and airing process.
During its expansion reduction treatment the LD slag is permanently monitored through laboratory testing according to DNIT (Road Traffic Dept) for its use as road base and sub-base paving.
Upon reaching expansion limits in compliance with technical regulations the process is interrupted and the material is made available to the market under the name ACERITA® - Expansion reduced LD slag.
The values required for expansion measured by CBR testing method are below 0.5%, which have been accomplished by ACERITA® through extensive monitoring. Besides that, it presents CBR values above stone aggregates; it is a very resistant material offering good paving structure.
Besides presenting LD slag usual characteristics such as: high load resistance, high wear resistance, high weight and cement properties, ACERITA® presents very low expansion values in CBR method expansion testing according to the tests required by DNIT allowing for its use in Roadworks.
PTM 130 (Pennsylvania Testing Method) modified by the state of Minas Gerais Road Traffic Dept - DNER-EM 262/94 and DNER-PRO 263/94 regulations.
DNER-EM 262/94 and DNER-PRO 263/94 regulations determine a maximum LD slag volumetric expansion of 3.0% for roadway use; ACERITA® has been complying with this regulation.
ACERITA® expansion reduction allows its use as sub-base, base, binder and asphalt concrete, that is, in all paving layers mixed or not with other materials. The great advantage of ACERITA® over other stone aggregates is that the layers using ACERITA® can be thinner than those of stone aggregates as the elasticity module of ACERITA® is superior to stone aggregates as per ELSYM5 method.
The ACERITA® research and development process is still under way with new investments aiming to improve its use. In May 2004, ArcelorMittal Tubarão signed a partnership with the state of Espírito Santo DNIT and KAEME to study the use of LD slag in road works and to review the existing regulations so as to ensure the quality of LD slag application, and to have enough monitoring tools to make the best use of the paving done with this material. This way, it will be possible to reduce paving layers thickness without jeopardizing their supporting capacity, diminishing the amount of material needed, thus making the use of ACERITA® a technically and economically viable alternative.
For all the positive characteristics presented in the tests and the performance monitoring carried out by ArcelorMittal Tubarão in the works using the material, ACERITA® can be seen as an ideal solution for low maintenance cost, long lasting and lower cost paving that contributes to the improvement of roadway paving quality.
Construction work using ACERITA®
Contact:Engineer Nocy Oliveira da Silveira