# Effect of Metallic Waste Addition on the Physical and Mechanical Properties of Cement-Based Mortars
###### Abstract  
This paper investigates the influence of the type and amount of recycled metallic waste on the physical and mechanical properties of cement-based mortars. The physical and mechanical properties of cement mortars, containing four different amounts of metallic waste (ranged 4 to 16% by cement weight), were evaluated by measuring the bulk density, total porosity, flexural and compressive resistance, and dynamic elastic modulus by ultrasonic tests. All the properties were measured on test specimens under two curing ages: 7 and 28 days. Additionally, the morphological properties and elemental composition of the cement and metallic waste were evaluated by using Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and X-ray fluorescence (XRF). Main results showed that the addition of metallic waste reduced the bulk density and increased the porosity of the cement-based mortars. Furthermore, it was observed that flexural and compressive strength proportionally increased with the metallic waste addition. Likewise, it was proven that elastic modulus, obtained by compressive and ultrasonic tests, increases with the metallic waste amount. Finally, based on a probability analysis, it was confirmed that the addition of metallic waste did not present a significant effect on the mechanical performance of the cement-based mortars. c 2018 8 May 2018; Published: 5 June  
The most commonly used particle-shaped reinforcements to improve the mechanical properties of cement-based materials are steel powder, carbon powder, and crushed steel shavings [6; 7; 8]. Likewise, organic fibres (palm, cellulose, hemp, etc.) [9], carbon fibres [10], synthetic fibres (e.g., polypropylene, polyethylene, polyvinyl alcohol, etc.) [11], and metallic fibres ([12; 13; 14; 15; 16; 17]) are amongst the most used fibre-shaped reinforcements. Nevertheless, over the last few years, the high cost of the commercial fibres has promoted the use of recycled metallic waste [10; 18] to develop new cement-based materials that are more resilient [12], environmentally friendly [13], and with advanced properties [18]. In this context, authors like [PERSON] et al. [8], [PERSON] et al. [12], [PERSON] [13], and [PERSON] et al. [14] used recycled steel particles and steel fibres from End of Life Tyres (ELTs) with the aim of mechanically reinforcing mortars and concrete. [PERSON] et al. [8] partially replaced fine aggregates with recycled steel particles in concrete. As the main result, flexural resistance of concrete reinforced with steel particles was 38% higher than that of a conventional concrete. Additionally, [PERSON] et al. [12] studied concrete samples reinforced with two different types of fibres, commercial and recycled steel fibres, in different contents. In this research, they observed that the test samples with higher percentages of recycled fibres presented lower mechanical resistance. Besides, commercial fibres cannot be totally replaced by recycled fibres, due to the significant reduction of their mechanical properties. Moreover, [PERSON] [13] demonstrated that recycled steel fibres from ELTs (diameter 0.1-2 mm) could be used to reinforce cement-based materials, although their compressive and flexural properties were lower in comparison with materials reinforced with commercial metallic fibres. [PERSON] et al. [17] highlighted that one of the disadvantages of the addition of fibres in cement-based materials is the reduction of their workability, which can affect the microstructure and physical properties of cement-based materials. In this context, [PERSON] and [PERSON] [19] evaluated the microstructure of mortars with steel fibres using Scanning Electron Microscopy, concluding that the porosity present in the interface matrix-fibre increases the total porosity of the mortar. Therefore, this increase of the total porosity can cause a decrease in the mechanical properties of the mortars.