Mechanical Properties of Recycled Aggregate Concretes Containing Silica Fume and Steel Fibres

Soheil Jahandari; Masoud Mohammadi; Aida Rahmani; Masoumeh Abolhasani; Hania Miraki; Leili Mohammadifar; Mostafa Kazemi; Mohammad Saberian; Maria Rashidi

doi:10.3390/ma14227065

Mechanical Properties of Recycled Aggregate Concretes Containing Silica Fume and Steel Fibres

Materials (Basel). 2021 Nov 21;14(22):7065. doi: 10.3390/ma14227065.

Authors

Soheil Jahandari¹, Masoud Mohammadi¹, Aida Rahmani¹, Masoumeh Abolhasani², Hania Miraki³, Leili Mohammadifar⁴, Mostafa Kazemi⁵, Mohammad Saberian⁶, Maria Rashidi¹

Affiliations

¹ Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2751, Australia.
² Department of Civil and Environmental Engineering, Alaodoleh Semnani Institute of Higher Education, Garmsar 5815, Iran.
³ Department of Civil Engineering, Iran University of Science and Technology, Tehran 6846, Iran.
⁴ Department of Architectural Engineering, Kerman Branch, Islamic Azad University, Kerman 1167, Iran.
⁵ GeMMe Building Materials, Urban and Environmental Engineering, University of Liège, 4000 Liège, Belgium.
⁶ School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.

Abstract

In this study, the impact of steel fibres and Silica Fume (SF) on the mechanical properties of recycled aggregate concretes made of two different types of Recycled Coarse Aggregates (RCA) sourced from both low- and high-strength concretes were evaluated through conducting 60 compressive strength tests. The RCAs were used as replacement levels of 50% and 100% of Natural Coarse Aggregates (NCA). Hook-end steel fibres and SF were also used in the mixtures at the optimised replacement levels of 1% and 8%, respectively. The results showed that the addition of both types of RCA adversely affected the compressive strength of concrete. However, the incorporation of SF led to compressive strength development in both types of concretes. The most significant improvement in terms of comparable concrete strength and peak strain with ordinary concrete at 28 days was observed in the case of using a combination of steel fibres and SF in both recycled aggregate concretes, especially with RCA sourced from high strength concrete. Although using SF slightly increased the elastic modulus of both recycled aggregate concretes, a substantial improvement in strength was observed due to the reinforcement with steel fibre and the coexistence of steel fibre and SF. Moreover, existing models to predict the elastic modulus of both non-fibrous and fibrous concretes are found to underestimate the elastic modulus values. The incorporation of SF changed the compressive stress-strain curves for both types of RCA. The addition of steel fibre and SF remarkably improved the post-peak ductility of recycled aggregates concretes of both types, with the most significant improvement observed in the case of RCA sourced from a low-strength parent concrete. The existing model to estimate the compressive stress-strain curve for steel fibre-reinforced concrete with natural aggregates was found to reasonably predict the compressive stress-strain behaviour for steel fibres-reinforced concrete with recycled aggregate.

Keywords: compressive behaviour; elastic modulus; recycled aggregates; silica fume; steel fibres.