Avaliação de um compósito cimentício piezoresistivo com resíduos siderúrgicos

Abstract

Structural Health Monitoring (SHM) has become an essential tool for preventing failures in civil structures, particularly in light of recent structural collapses that highlight the need for more efficient and continuous performance monitoring solutions. In this context, self-sensing cementitious composites based on the piezoresistive effect have emerged as a promising alternative to conventional monitoring systems, which present limitations related to durability, cost, and integration with cement-based materials. However, most of these solutions still rely on carbon-based conductive materials, whose application is limited by high cost and the complexity of dispersion within the cementitious matrix. In this regard, this study evaluates the potential of steelmaking by-products—Basic Oxygen Furnace (BOF) slag and Kambara Reactor (KR) desulfurization powder—as conductive aggregates in self-sensing cementitious composites. The materials were obtained from a steel plant located at the Pecém Port Industrial Complex (CE, Brazil) and subjected to processing procedures, including particle size adjustment and volumetric stabilization through accelerated weathering for BOF slag. Three mortar mixtures were produced: a reference mixture and two others with total replacement of conventional fine aggregate by steelmaking residues, using a 1:3 mix proportion and a waterto- cement ratio of 0.55. The mortars were characterized in terms of physical, mechanical, and microstructural properties through water absorption, void index, compressive strength, ultrasonic pulse velocity, and scanning electron microscopy. The electrical and piezoresistive behavior was evaluated using the four-probe method, with current monitoring in specimens subjected to cyclic loading. The results showed that the incorporation of steelmaking residues significantly influenced the electrical behavior of the composites. The mixture containing KR slag exhibited the lowest electrical resistivity and the highest piezoresistive sensitivity, demonstrating a strong ability to respond to applied loading, although it presented lower mechanical performance. In contrast, the BOF slag mixture showed a more balanced behavior, combining satisfactory mechanical performance with a consistent electrical response, indicating its potential for application in integrated structural sensing systems. Therefore, the findings demonstrate that steelmaking residues can act as active functional phases in selfsensing cementitious composites, contributing not only to the development of smart materials but also to the valorization of industrial by-products. Their incorporation promotes the reduction of conventional material consumption, supports circular economy strategies, and expands the applicability of cementitious composites in structural health monitoring.