Comportamento estrutural de pilares de aço preenchidos com concreto de agregado reciclado cerâmico submetidos à compressão axial

Abstract

Concrete-filled steel tubular columns are an efficient structural solution for compression members, since the interaction between the steel tube and the concrete core contributes to increased strength, stiffness, and ductility. At the same time, the growing demand for more sustainable solutions in the construction sector has encouraged the use of industrial waste as a replacement for natural aggregates. In this context, the feasibility of using recycled ceramic sanitary ware aggregate as a replacement for natural sand in self-compacting concrete for steel composite columns subjected to axial compression is assessed, considering its effects on material properties, structural behavior, and strength prediction by numerical and design code models. For this purpose, the constituent materials were characterized, and two self-compacting concrete mixes were analyzed, with natural fine aggregate replacement levels ranging from 0 to 100% in the first mix and from 0 to 50% in the second, in 25% increments. Subsequently, 24 experimental axial compression tests were carried out on circular concrete-filled steel tubular columns, comprising 16 short columns and 8 columns of intermediate slenderness. In addition, a finite element numerical model was developed in ABAQUS, validated against the experimental results, and used in a parametric study with 1,442 models, varying geometric and mechanical parameters as well as the recycled aggregate replacement level. The results indicate that the incorporation of recycled aggregate reduces the workability of the mixtures, without preventing the production of self-compacting concretes with satisfactory performance. It was found that increasing the replacement level does not necessarily lead to strength loss, with strength gains observed at certain replacement levels, depending on the mix composition. In the composite columns, the structural behavior was consistent with steel-concrete composite action, with efficient filling of the tube and mobilization of confinement in the short columns, whereas, in the slender members, the response was predominantly governed by global instability. Among the replacement levels evaluated, the 25% replacement level showed the most balanced performance for structural application, as it maintained a more stable response under different conditions. The numerical modeling satisfactorily reproduced the experimental response, and the parametric study confirmed global slenderness as the variable with the greatest influence on member efficiency. It is concluded that the use of recycled sanitary ware ceramic aggregate in self-compacting concrete for filling circular concrete-filled steel tubular columns is technically feasible and structurally promising, combining satisfactory mechanical performance, reuse of industrial waste, and potential application in structural concretes.