The effect of different types of fiber on flexure strength and fracture toughness in SIFCON Metin Ipek a,⇑ , Mecbure Aksu b a Sakarya University of Applied Sciences, Technology Faculty, Civil Engineering Department, 54187 Sakarya, Turkey b Sakarya University of Applied Sciences, Vocational School of Adapazarı, Construction Department, 54187 Sakarya, Turkey highlights  The effect of different fibers on SIFCON was investigated.  Steel and polymer fibers in different combinations and mold heights were investigated.  The combination of polypropylene and steel fibers increased the flexural strength.  The highest flexural strength of 44.02 MPa has been obtained with proper fiber combination.  Durable and economical structural elements are producible with the use of Polypropylene fibers.  Polypropylene fibers reduced the cost and the unit weight of SIFCON. article info Article history: Received 31 October 2018 Received in revised form 5 April 2019 Accepted 8 April 2019 Keywords: SIFCON Polypropylene Fiber Flexural strength Fracture toughness abstract Slurry Infiltrated Fiber Concrete (SIFCON) is a special kind of steel fiber-reinforced cement composite which has extraordinary toughness values and surpassing mechanical characteristics like compressive, tensile, shear, and flexural strengths. In this study, steel and polypropylene fibers have been used by mix- ing in different combinations. 1/1, 1/3 and 2/3 of the beam molds have been filled with these fibers. In the study, the physical and mechanical properties and also the unit strength cost analyses of SIFCON have been examined. The use of the fibers with combinations has caused to an increase in the fiber volume. The highest flexural strength values have been reached with the beam samples completely filled with fiber respectively as 44.02 MPa and 41.23 MPa with the steel fiber at the length of 60 mm and 35 mm and with 60 mm steel and 50 mm polypropylene fiber combination. The combined use of polypropylene fiber and steel fiber has increased the flexural strength and fracture toughness. Consequently; it has been observed that the polypropylene fiber provides significant advantages for the use of SIFCON in terms of unit weight and cost due to the fact that its density and cost are lower when compared to those of the steel fiber. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Normal concrete is a very brittle material which has a very low bearing capacity in terms of tension and having only 0.10.01% tensile strength and 0.24% fracture toughness of the steel when compared to the structural steel. Axial transformation capacities increase in the concretes with high strength and the tension decrease occurs as sudden after exceeding the peak point and it is fractured in a more brittle way [1]. The problem of brittleness is tried to be exceeded by adding fiber to the concrete. Thanks to the fiber, both the flexural strength and the energy absorption capacities increase. Because the mixture of the fibers with the con- crete in high ratios negatively affects the processability of the con- crete, the fiber ratio to be added is limited [2]. The fact that it is not possible not to add fibers to the concrete in high ratios has revealed the idea of adding the concrete to the fiber. SIFCON (Slurry Infiltrated Fiber Concrete) technology has been developed as a result of filling the cement, sand, pozzolana, water and chemical additive mixture slurry in the mold containing fiber by 5–30% in volume [3]. SIFCON was firstly developed in 1983 by Lankard in New Mex- ico Engineering Research Institute (NMERI) [4,5]. The fibers in high ratios are placed by sprinkling inside the mold prepared during the production phase. Afterwards; the slurry containing cement, https://doi.org/10.1016/j.conbuildmat.2019.04.055 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: metini@sakarya.edu.tr (M. Ipek), maksu@sakarya.edu.tr (M. Aksu). Construction and Building Materials 214 (2019) 207–218 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat