1. Introduction
Concrete is one of the most prominent materials that has been used in the construction industry for more than a century since it provides the appropriate strength at the lowest cost when compared to other materials available. Due to the inability to use vibrating tools, casting and compaction of concrete can be exceedingly challenging in some concrete buildings, such as those with dense reinforcing and complex molds. Consequently, this exerts a negative impact on both the performance and longevity of concrete. Self-compacting concrete (SCC), a type of non-compacted concrete, stands out as a pivotal advancement in concrete technology, enhancing both the quality and durability of concrete structures. SCC has been widely employed to elevate concrete properties, durability, and workability conditions.
SCC was initially created in Japan in 1988 to produce more durable concrete structures, and it was brought to Europe in the middle of the 1990s via Sweden [
1]. Even in the presence of heavily reinforced, narrow, and deep sections [
2,
3,
4,
5], SSC is a new type of concrete mixture that can flow and fill every corner of the formwork by its own weight without requiring external vibration. In addition to these advantages, SCC offers the construction industry several other advantages, such as improved surface finish, decreased noise pollution, and health issues related to the use of vibration devices. SCC also decreases labor costs and construction time, which increases efficiency and effectiveness on site.
The ingredients for producing SCC mixtures are identical to those used in conventional concrete, comprising Portland cement, fine aggregate, coarse aggregate, water, and admixtures. However, SCC stands out due to the incorporation of supplementary fine components, such as filler materials like limestone powder and very fine sand, along with high water-reducing admixtures containing viscosity-modifying agents, which help regulate its rheological properties.
Concrete is generally known as a brittle, low ductility material that is strong in compression but weak in tension. In the field of concrete technology, incorporating fibers into self-compacting concrete creates a new composite material that combines the advantages of both SCC and fibers. The amount of fibers, length, aspect ratio, and shape all have a part in the improvement of concrete properties [
3,
6]. In general, fiber-reinforced self-compacting concrete (FRSCC) is a new construction material that combines the advantages of SCC with the positive benefits of fibers [
2,
4,
7].
Numerous research studies have explored the properties of concrete with the incorporation of basalt fibers [
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18].
Shoaib et al. [
8] studied the fresh and hardened properties of normal- and high-strength concrete (NSC and HSC) reinforced with basalt fibers (BF), ranging from 0.5 to 1.5% by volume. The findings revealed that the addition of BF decreased the workability of both NSC and HSC at a similar rate. An average maximum slump reduction of 78% was observed at 1.5% BF. The influence of BF on the compressive strength of NSC and HSC was found to be insignificant. However, significant enhancements were noted in the splitting tensile strength, ranging from 10 to 52% in NSC, and in flexural strength, ranging from 18 to 56%. Ref. [
9] studied the impact of chopped basalt fibers, measuring 32 mm in length, on concrete properties. They observed a reduction in concrete slump ranging from 5 to 34% with varying volumes of basalt fibers (BF) between 0.04 and 0.11%. This decrease in concrete workability due to the addition of BF was attributed to the larger surface area requiring more cement paste, consequently reducing workability. Ref. [
10] reported a minor improvement in the concrete compressive strength (up to 7%) by the addition of BF at 0.02 to 0.11%, while [
11] reported no notable change in strength at 0.2% and 0.3%, and the highest flexural strength was achieved with a 0.1% volume of fibers.
Ref. [
12] studied the use of basalt fiber in the production of self-compacting concrete (SCC). Basalt fibers of 3, 6, 12, and 24 mm in length were incorporated into the SCC mixtures at a replacement ratio of 0%, 0.1%, 0.3%, and 0.5% of concrete volume. Results show that the highest compressive strength result is obtained from the mixtures containing a fiber content of 0.1% for the fiber lengths of 12 mm and 24 mm. The highest flexural and splitting tensile strength results are obtained from the concrete mixtures incorporated with a content of 0.5% fibers having a length of 24 mm. The optimum volume fraction and basalt fiber length are determined as 0.49% and 21.12 mm. Ref. [
13] added BF to SCC by a fraction of 0.1% to 0.5%. According to the research findings, BF has reduced the diameter of the flow (695–663 mm) and increased the time of the flow (3–5.6 s). Also, SCC containing 0.1–0.4% volume fraction of BF improve the compressive strength in ranged from 2.22% to 8.43% at 28 days. Ref. [
14] examined various basalt fiber contents of 0.90, 1.35, and 1.80 kg/m
3, along with different fiber lengths of 24, 19, and 40 mm, respectively, in investigating SCC. Their findings indicated that the highest compressive and flexural strength values were achieved in SCC mixtures containing 0.1% and 0.5% BF by volume, with a fiber length of 24 mm, respectively. Compared to the control concrete, samples reinforced with basalt fiber showed an increase in compressive strength by 2.43%, 3.58%, and 4.20% for fiber contents of 0.90, 1.35, and 1.80 kg/m
3, respectively.
In the study conducted by [
15], the behavior of SCC produced with basalt fiber was investigated using fiber amounts ranging from 0.6% to 2.0%. It was stated that the addition of fiber into SCC increases the 28-day splitting tensile and flexural strength by 5% to 50% and 30% to 48%, respectively. It was revealed that the 7-, 14-, and 28-day compressive strength, splitting tensile strength, and flexural strength results from SCC mixtures produced with basalt fibers become highest for the fiber utilization of 0.3%, 0.4%, and 1.4%, respectively.
Concrete’s durability is a vital characteristic, irrespective of its compressive strength, as issues with concrete typically arise from durability failures rather than inadequate strength [
19]. In order to maintain its ideal engineering properties, original shape, quality, and serviceability, concrete must be able to survive weathering, environmental factors, chemical attack, fire, abrasion, and any other deterioration process. Elevated temperatures represent a significant environmental factor that could potentially compromise the mechanical and physical properties of concrete. Conversely, heightened temperatures result in increased internal pressure, a primary factor contributing to the reduction in concrete strength [
20,
21]. According to previous studies on polypropylene fibers (PPF), utilizing PPF in conventional and self-compacting concrete can prevent spalling in the event of a fire [
22,
23]. PPF melts at 160–170 °C while spalls at 190–250 °C. As a result, as the fibers melt, vacuous channels emerge, creating a new pathway for gas escape [
24].
Ref. [
25] studied the compressive strength of self-compacting concrete under elevated temperatures. After 28 days of curing, the specimens were kept at 200 °C, 400 °C, 600 °C, and 800 °C temperatures for two hours. It was established that compressive capacity decreased with an increase in temperature. Also, there was a drastic reduction in strength at both 600 °C and 800 °C. The percent variation of resilience strength of self-packing concrete at 200 °C, 400 °C, 600 °C, and 800 °C was found to be 3.15%, 10.88%, 43.39%, and 51.36%, respectively, relative to the controlled concrete. Ref. [
26] investigated the mechanical performance of self-compacting concretes (SCCs) under both room and high temperatures. Their findings revealed that the relative compressive strengths measured at 120 °C and 600 °C for all the SCCs studied were lower than those determined for conventionally vibrated concretes. Additionally, increasing the volume of cement paste resulted in a notable reduction in the relative compressive strength at 250 °C, 400 °C, and 600 °C. The water–binder ratio had minimal impact on the relative compressive strength of the SCCs studied at high temperatures.
Ref. [
27] studied experimentally the influence of high temperatures on the characteristics of self-compacting concrete. All specimens were subjected to high temperatures (20, 200, 400, 600, and 800 °C). Mixes were categorized into three groups based on types of concrete: high-strength concrete (HSC), self-compacting concrete (SCC), and self-compacting concrete with polypropylene fiber (SCCPPF). Moreover, several parameters were studied: concrete compressive strength (30 MPa and 60 MPa), water–cement ratio (0.28 and 0.64), and polypropylene fiber content (0% and 1%). Based on experimental results, the hot compressive strength of SCC reduces as temperature rises, except for high-strength SCC, which rises at around 400 °C. On the other hand, concrete’s strength loss is impacted by its strength grade, especially at temperatures under 400 °C. Another finding of the studies was that adding polypropylene fibers to the mix reduced the compressive strength and the possibility of explosive spalling as well as gave greater fire resistance than other HSC and good workability.
Ref. [
28] investigated the effects of basalt fibers on the workability and strength of fresh self-compacting concrete (SCC). The properties of hardened concrete, such as compressive strength, splitting strength, and flexural strength, were examined at temperatures between 25 °C and 500 °C. The results showed that workability decreased significantly with an increase in basalt fiber content. An average strength reduction of 11.43% was observed when the fiber content was increased. This result is attributed to the reduction in the workability and density of SCC caused by fiber introduction. The splitting tensile strength of the SCC mixtures was increased by the addition of 0.25% basalt fibers. However, a decrease in splitting tensile strength occurred when more than 0.25% basalt fiber volume fraction was added. The experimental results revealed that increasing the temperature up to 500 °C reduced the tensile and compressive strengths of SCC by over 20%.
Based on the literature, there is limited research on the behavior of self-compacting concrete (SCC) containing basalt fiber after exposure to high temperatures and freezing-thawing cycles. Therefore, this study extensively investigates the rheological and mechanical properties and the durability of self-compacting concrete, incorporating basalt fiber in various proportions under the influence of exposure to high temperatures and freezing-thawing cycles, making it the focal point of this research.