## 1 Introduction  
Self-compacting concrete (SCC) has different properties compared with the ordinary concrete regarding its fresh and mechanical behaviour. A number of studies have been carried out to determine the benefits of incorporating various cement replacement materials into SCC. These materials reduce the cost of SCC resulting from the significant amount of cement that is necessary to provide the required filling and passing ability. Decreasing or eliminating the use of cement in SCC seems imperative for both environmental and economic reasons. Ground granulated blast furnace slag (GGBS) is used in SCC as a replacement for cement due to its natural binding properties. The addition of GGBS reduces the permeability and increases the chemical stability of SCC due to the reaction of blast furnace slag with an excess of soluble calcium hydroxide [1]. As a consequence, it has an impact on the overall improvement of the durability of reinforced concrete structures [2]. The dense microstructure of high-performance concrete (HPC) warrants an increase in the compressive strength and permeability, but at the same time it has a negative impact on the brittleness and fire resistance [3]. Fibres are widely applied to strengthen HPC in order to improve the strength and energy absorption capacity, as well as to reduce explosive spalling in a fire [4]. To delay the development of micro-cracks and to enhance the toughness in HPC, nanomaterials such as multi-layer graphene, carbon tubes, and carbon nanofibres can be successfully added [5]. On the other hand, in order to monitor the crack growth process in HPC, embedded piezoelectric aggregates described in [6] can be used for the evaluation of the degree of damage of brittle materials in HPC. However,steel fibre is most commonly used to prepare HPC and ultra-high-performance concrete (UHPC) [7; 8; 9]. In this investigation, polypropylene (PP) fibre was used to produce environmentally friendly and cost-effective HPC. It should be noted that steel fibre is more expensive, is not environmentally friendly, corrodes easily, is affected by magnetic and electric fields, and can be harmful to workers [10]. The use of PP fibres does not raise any objections as to thermal conductivity, fire resistance and corrosion of fibres enclosed in a concrete matrix [11]. Due to the long-term durability of PP fibres in an aggressive environment due to excellent chemical stability and hydrophobicity, scientists turned their attention to their use in HPC [12; 13]. It has been found that PP fibres are effective in reducing plastic shrinkage, delaying the formation of first cracks and controlling crack development [14; 15; 16; 17]. However, PP fibres are most commonly used to control plastic shrinkage cracks due to its relatively low tensile strength [18; 19; 20]. In addition, several studies have reported that polypropylene fibres can hold a stable concrete mix without settling its constituents [21; 22], which can be extremely important in self-compacting concrete mixes. On the other hand, the influence of PP fibres on the mechanical properties of HPC is not entirely clear, which is presented in the literature review below. [PERSON] et al. [23] examined the compressive strength, splitting tensile strength and flexural strength of normal strength concrete without fibres and with the addition of PP fibres up to 0.3% volume content. Their results indicated that the presence of fibres had a negative effect on the compressive strength, while the flexural and splitting tensile strengths slightly increased with increasing fibre content. Similar results were also observed by other researchers [24; 25]. [PERSON] et al. [26] reported a 3% decrease in the 90 day compressive strength of PP-fibre-reinforced, normal-strength concrete with compared to the reference one. [PERSON] et al. [27] noted that the PP fibre has no significant effect on the compressive strength of concrete. [PERSON] and [PERSON] [28] stated that the compressive strength of ordinary concrete increased by 25% with a 0.5% PP fibre volume fraction.