1 Introduction

Concrete is brittle in nature and when failure is initiated in concrete under the application of load, it experiences complete loss in the loading capacity (Ibrahim 2016). Concrete has the disadvantages of low tensile strength, energy absorption and strain capacity (Kizilkanat et al. 2015). To improve the characteristics of concrete, the inclusion of fibers has been practiced (Parra-Montesinos 2005; Kasagani and Rao 2018). The inclusion of fibers in concrete improves flexural strength, early-age cracking, toughness, ductility and impact resistance (Arslan 2016; Ibrahim 2016, Farooq and Banthia 2018). Steel fibers have been used worldwide to improve the mechanical properties of concrete because of their low cost and favorable bond with surrounding concrete and good mechanical properties (Farooq and Banthia 2018). However, the steel fibers are susceptible to corrosion and have the tendency to interfere with the electromagnetic field. The steel fibers also possess higher density and difficult handling. Therefore, the use of corrosion-free, electromagnetic field-resistive and lightweight fibers needs to be investigated in plain concrete.

The use of polymer fibers gains attention because of their low cost, easy handling, low density, resistance to corrosion and the tendency to resist interference with electromagnetic fields. The small size, hydrophobic nature and high surface area of glass and polypropylene fibers offer advantages in concrete (Milind 2015; Ibrahim 2016). This study experimentally investigated the compressive strength, split tensile strength and flexural strength of alkali-resistant-glass fiber reinforced concrete (AR-GFRC) and polypropylene fiber reinforced concrete (PFRC).

2 Experimental Program

The experimental program of this study was planned to investigate the compressive strength, split tensile strength and flexural strength of Plain Concrete (PC), AR-GFRC and PFRC. The specimens were divided into three groups based on the type of fiber inclusion. Group PC had plain concrete without the inclusion of any fibers. Group AR-GFRC had alkali-resistant glass fibers added to the concrete. Group PFRC had polypropylene fibers added to the concrete. The test matrix consisted of 27 cylindrical specimens and 9 rectangular specimens. The compressive strengths of PC, AR-GFRC and PFRC were determined at the age of 7 and 28 days. The split tensile and flexural strengths were determined at the age of 28 days.

2.1 Test Specimens

The specimens tested under compression and split tensility had cylindrical sections, while the specimens tested under flexure had rectangular sections. The dimensions and sections of the specimens were set as per the standards. The specimens that were tested under compression had a diameter of 100 mm with a height of 200 mm in accordance with AS-1012.9 (AS 2014). The specimens that were tested under split tensile strength had a diameter of 150 mm with a height of 300 mm in accordance with AS-1012.10 (AS, 2000). The specimens that were tested under flexure had a width and breadth of 100 mm and a length of 500 mm in accordance with AS-1012.11 (AS 2000).

2.2 Materials

Normal Portland cement concrete with a maximum aggregate size of 10 mm was used in this study. The PC, AR-GFRC and PFRC were transported from a local concrete batching plant. The fibers were added to the concrete at the batching plant. The glass fibers were added in a ratio of 1.5% by volume of concrete, while polypropylene fibers were added in a ratio of 0.15% by volume of concrete. The mix proportions of the PC, AR-GFRC and PFRC are shown in Table 1.

Table 1 Mix proportions of PC, AR-GFRC and PFRC (Hanson 2019)
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The glass and polypropylene fibers were supplied by Domcrete GFRC Supplies Pty LTD (Domcrete 2019) and Sika Australia Pty Limited (Sika Confibre 19F 2010), respectively. The glass and polypropylene fibers had a nominal diameter of 14 and 55 μm, respectively. The glass and polypropylene fibers had a nominal length of 19 mm. The glass fibers had a nominal density of 2540 kg/m3 and the polypropylene fibers had a nominal density of 920 kg/m3. The properties and shape of glass and polypropylene fibers are shown in Table 2.

Table 2 Properties and shape of glass and polypropylene fibers
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2.3 Test Setup

The specimens that were tested under compression and split tensile strength were cast in the steel cylinders as per the standards, while the specimens that were tested under flexure were cast in the rectangular wooden boxes as per the standard. The arrangement for casting the specimens is shown in Fig. 1.

Fig. 1
Two figures. The first shows several iron cylinderal specimens and the second shows a rectangular wooden box.

Arrangement for casting of the specimens: a Cylindrical; b rectangular

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The specimens were demolded after 24 h and placed in a temperature-controlled curing water tank. The specimens were cured in the water tank until the day of testing.

The specimens were tested in the MATEST (Matest, C095N-05) flexural and transverse multi-purpose testing machine of 320 kN capacity at the high bay lab of the University of Wollongong, Australia. The specimens were tested with different force-controlled loading rates. The top and bottom surfaces of the specimens tested under compression were caped with high-strength plaster for the uniform distribution of applied load. The specimens that were tested under compression were placed in the compression loading arrangement of the machine and were applied a loading rate of 20.0 MPa/min in accordance with AS-1012.9 (AS 2014). The specimens that were tested under split tensile strength were placed in the split tensile loading arrangement of the machine and were applied at the loading rate of 1.5 MPa/min in accordance with AS-1012.10 (AS 2000). The specimens that were tested under flexure were placed in the flexural loading arrangement of the machine and were applied a loading rate of 1.0 MPa/min in accordance with AS-1012.11 (AS 2000). The compressive, split tensile and flexural loading arrangement of the specimens are shown in Fig. 2a–c, respectively.

Fig. 2
Three photographs. The first machine is having a cylindrical base and a narrow cylindrical structure above it. The second figure has two machines. The third figure has a machine and a cuboidal cement block in the middle of it.

Loading arrangement of specimens: a Compression; b split tensile; c flexure

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3 Results and Discussion

The average experimental results of the PC, AR-GFRC and PFRC are shown in Table 3. The average 28-day compressive, split tensile and flexural strengths for the PC, AR-GFRC and PFRC are shown in Table 3.

Table 3 Average experimental results of PC, AR-GFRC and PFRC at 28 days
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3.1 Compressive Strength

The average compressive strengths of the PC, AR-GFRC and PFRC were determined in accordance with AS-1012.9 (AS 2014). The tabulated and graphical compressive strengths of PC, AR-GFRC and PFRC are shown in Table 3 and Fig. 3, respectively.

Fig. 3
The graph has compressive strength, M P a on the vertical axis ranges from 0 to 50, and age in days from 0 to 30 on the horizontal axis. Three increasing curves with an initial point as origin having points of P C , A R-G F R C , and P F R C are there.

Graphical representation of the compressive strength

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The PC achieved higher compressive strength than AR-GFRC and PFRC. The inclusion of glass fibers reduced the compressive strength of plain concrete by 20% at the age of 28 days. The inclusion of polypropylene fibers reduced the compressive strength of the plain concrete by 9% at the age of 28 days. However, the PFRC achieved 12% higher compressive strength than AR-GFRC at the age of 28 days.

3.2 Split Tensile Strength

The average split tensile strengths of the PC, AR-GFRC and PFRC were determined at the age of 28 days in accordance with AS-1012.10 (AS 2000). The tabulated and graphical split tensile strengths of the PC, AR-GFRC and PFRC are shown in Table 3 and Fig. 4, respectively.

Fig. 4
The bar graph has strength, M P a on the vertical axis from 0 to 5 and concrete type on the horizontal axis . The bars for split tensile and flexural for the P C, A R-G F R C, and P F R C are there.

Graphical representation of the split tensile and flexural strengths

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The inclusion of polypropylene fibers enhanced the split tensile strength of the plain concrete, while the inclusion of glass fibers reduced the split tensile strength of the plain concrete. The inclusion of polypropylene fiber enhanced the split tensile strength of the plain concrete by 11%. However, the inclusion of glass fibers reduced the split tensile strength of the plain concrete by 16%. Comparatively, the PFRC achieved 26% higher split tensile strength than AR-GFRC.

3.3 Flexural Strength

The average flexural strengths of the PC, AR-GFRC and PFRC were determined at the age of 28 days in accordance with AS-1012.11 (AS 2000). The tabulated and graphical flexural strengths of PC, AR-GFRC and PFRC are shown in Table 3 and Fig. 4, respectively.

The results showed that the flexural strength of the plain concrete enhanced with the inclusion of glass and polypropylene fibers. The inclusion of glass fibers enhanced the flexural strength of the plain concrete by 7%. The inclusion of polypropylene fibers enhanced the flexural strength of the plain concrete by 14%. Comparatively, the PFRC achieved 7% higher flexural strength than AR-GFRC.

4 Conclusion

This study experimentally investigated the compressive, split tensile and flexural strengths of AR-GFRC and PFRC. The results showed that.

  1. 1.

    The compressive strength of AR-GFRC and PFRC reduced by 20% and 9% than PC, respectively.

  2. 2.

    The split tensile strength of AR-GFRC reduced by 16% and the split tensile strength of PFRC increased by 11% than PC, respectively.

  3. 3.

    The flexural strength of the AR-GFRC and PFRC enhanced by 7% and 14% than PC, respectively.