2.2. Concrete Mixes

Five concrete mixes have been designed for this study with a water-to-cement (w/c) ratio of 0.55. For all the mixes, the proportions of each concrete mix are 1: 3.1: 2.25 by the mass of cement, fine aggregate, and coarse aggregate, with the details of each concrete mix shown in Table 3.

Proportion of concrete mix design for 1 m^3.

The coarse aggregate has been prepared under full washing in case of sand’s adhesion on the surface. In addition, both coarse and fine aggregates are dried at the temperature of 105 °C for 48 h.

As demonstrated in a review of previous literature, limited studies on the mechanical properties of basalt fiber-reinforced concrete have shown that the optimal dosage of the basalt fiber roughly ranges within 0.5% of the total concrete volume. Hence, four different dosages are used for each type of basalt fiber reinforcement, ranging from a low dosage to the maximum mixable dosage. In addition, the chopped basalt fiber is added at 0.125%, 0.25%, 0.375%, and 0.5% of content by the total volume of the concrete mix. Finally, the concrete mixes were labelled as M₀ (plain concrete), M₁ (0.125%), M₂ (0.25%), M₃ (0.375%), and M₄ (0.5%).

According to the standard test method for fundamental transverse, longitudinal, and torsional resonant frequencies of concrete specimens (ASTM C215-19), to test the hardened concrete, two sizes of concrete specimen have been prepared for compression testing (Cube: 150 mm × 150 mm × 150 mm). This study employs the modal test and the three-points load bending test (rectangular prism: 150 mm × 150 mm × 600 mm), while three beams and five cubes have been made for each mix to ensure enough sample size and avoid errors. Hence, each concrete specimen is labelled as M_xC/B_x. For example, M₁C₂ means that the concrete specimen is the second cube containing 0.125% of basalt fiber reinforcement. Similarly, M₂B₃ shows that the concrete specimen is the third beam containing 0.5% of basalt fiber reinforcement.