# Design Procedures for Sustainable Structural Concretes Using Wastes and Industrial By-Products
###### Abstract  
The protection of the environment must be a priority in our society, and the construction sector can contribute significantly to this goal. Construction, being one of the industrial sectors that is more demanding in terms of raw materials, must reinforce its effort to implement, in a more profound and systematic way, the paradigm of the circular economy. In this sense, in recent years several studies have been trying to contribute solutions aimed at retrotudoting industrial by-products or residues in new products for the construction industry. It should be noted that nowadays it is increasingly important to introduce a higher percentage of recycled materials in concrete. In this context, the present work addresses the appropriateness of a design procedure proposed to maximize the content of electric arc furnace slag (EAFS) and include recycled tire steel fibers (RTSF) in the production of more sustainable structural concretes. For this, the properties of various concrete mixtures at the fresh and hardened state, obtained by the substantial substitution of coarse and fine natural aggregates by EAFS and fly ash (FA), were investigated. The design of EAFS mixtures was based on two conventional reference mixtures (REF1 and REF2), and by using the modified Andreasen and Andersen particle packing model, these were optimized to achieve maximum packing density. Compressive strength, modulus of elasticity behavior, and fresh and physical properties were assessed in order to define the best mix proportions with respect to the predefined requirements of ordinary mixtures. Untreated recycled tire steel fibers (RTSF) were included in the developed sustainable concrete to perform a comparison of the physical properties with unreinforced concretes developed with natural aggregates (REF2) and with EAPS aggregates (EAFSSD1). This incorporation was intended to improve the physical behavior of unreinforced concretes with EAFS aggregates. Mixtures with high percentages of waste aggregates up to 70% (in weight), and 10% (in weight) of FA were obtained, showing competitive mechanical behavior compared to REF1 and REF2. These concrete compositions showed minimum and maximum compressive strengths between 9 MPa and 37 MPa, respectively. This study covered the two major classes of concrete used as structural material, namely structural concrete and fiber reinforced concrete. recycled materials; industrial by-products; electric arc furnace slag; fly ash; recycled tire steel fibers; particle packing model; mechanical properties; durability; technological properties +
Footnote †: journal: Applied Sciences  
paradigm of the circular economy in their activities [1; 2; 3]. A significant part of the current effort to pursue these more sustainable solutions involves research and innovation in the area of structural concrete. In fact, in recent years several studies have been carried out aiming at partially or totally replacing cement, natural aggregates, and fibers, or to replace natural supplementary cementitious materials (SCMs), by wastes, industrial by-products or recycled materials. Examples of wastes or recycled materials that were recently studied for incorporation into alternative structural concrete compositions as binders are fly ash, glycerol, cooking oil, ground granulated blast furnace slag (GGBS) and limestone powder, among others [4; 5; 6]. Additionally, there are other studies where recycled materials were introduced into concrete compositions as coarse and fine aggregates. Examples of these are electric arc furnace or blast furnace slag, plastics, quarrying, construction and demolition residues, textiles, ceramics, vegetable ash, pulverized fuel ash, municipal solid waste ash, silica fume and glass [7; 8; 9; 10]. Recent studies also show the reuse of tire rubber and recycled tire fibers, respectively, as aggregate or fibers in concrete [11; 12; 13; 14; 15; 16].