Avaliação da adesividade ligante-escória sob aspectos físicos, químicos e termodinâmicos e correlação com desempenho mecânico de misturas asfálticas contendo diferentes fíleres melhoradores de adesividade

Abstract

The implementation of road pavements is a practice that requires great exploitation of natural resources. Any possibility of replacing material required in this process deserves attention, especially if this is also a solution for another issue: destination of intermediate industrial products. In this line, a steel industry presents itself as a great option in the supply of aggregates from different stages of the steelmaking process. Among them, the air-cooled blast furnace slag (ACBFS or EFRA) and steel slag (LD) are highlights for use in the asphalt pavement due to its favorable characteristics such as resistance, abrasion resistance and shape. LD has a limiting factor to its implementation, which is a tendency for the volumetric expansion of this co-product when in contact with humidity and heat. However, it shows excellent recovery by asphalt binder. On the other hand, blast furnace slag does not have good adhesion to the bituminous material when subjected to a usual adhesion test. In order to verify the adhesion mechanisms and understand which characteristics of the aggregates collaborate for a better adhesion to asphalt binders, in this study a characterization of form, thermodynamics and chemistry was carried out in EFRA and LD tests. It was found that LD has favorable characteristics to good adhesion to the binder in relation to EFRA, such as highersurface free energy, low silica content and high iron content, more basic pH, in addition to better resistance to abrasion, hardness and greater modulus of elasticity. In order to verify the performance of the two steel aggregates in asphalt mixtures, Marshall stability and creep test, diametral compression tensile strength and damage by inhaled moisture carried out in asphalt mixtures with partial replacement of 25% at natural aggregate by co-products (EFRA or LD). Furthermore, the mixture with EFRA was dosed by adding 1.5% additive to improve adhesion, being hydrated lime, Flue Gas Desulfurization powder and Eletrostatic Precipitator powder (both also intermediate products of the steelmaking process, whose chemical compositions are rich in calcium and iron, respectively) and natural aggregate powder. Even with the improvement that the additives provided in relation to the mixture of EFRA without additive, the LD performance was more satisfactory than that of mixtures containing EFRA. Considering only the mixtures with EFRA, it was possible to notice an improvement relationship in the group with the addition of lime and EP powder, mainly. Despite this, EFRA should not be discarded, as it is better than the natural aggregate in many ways.