The Axial Compression Behavior of Basalt Fiber-Reinforced Recycled Aggregate Concrete-Filled Circular Steel-Tubular Column

Abstract

Recycled aggregate concrete (RAC) technology has received a lot of attention as a green environmental protection technology. However, the unsatisfactory mechanical behavior of RAC restricts its application in engineering practice. The structure of basalt fiber-recycled aggregate concrete-filled circular steel tubes (C-BFRACFST) can dually improve the mechanical behavior of RAC. To observe the axial compression behavior of the C-BFRACFST column, seven specimens were designed with recycled aggregate replacement ratio (0%, 50%, 100%), basalt fiber (BF) content (0 kg/m3, 2 kg/m3, 4 kg/m3) and length–diameter (L/D, 5, 8, 11) as variable parameters for axial compression tests. The failure mode, load–displacement/strain curve, axial compression deformation, ultimate bearing capacity, energy dissipation, and ductility of specimens have been analyzed. The derived constitutive relation of core basalt fiber-reinforced recycled aggregate concrete (BFRAC) constrained by the circular steel tube and the 3D finite element model of C-BFRACFST column have been established to simulate the whole process of compression. It is observed that instability or shear failure occurs in specimens under axial compression load. When the recycled aggregate replacement ratio was increased from 50% to 100%, the change in the energy-dissipation capacity of the specimens was not significant but the ultimate bearing capacity and displacement ductility coefficient decreased by 3.45% and 8.91%, respectively. When the BF content was increased from 2 kg/m3 to 4kg/m3, the change in the ultimate bearing capacity of specimens was not significant; the energy-dissipation capacity at the later stage of bearing increased, and the displacement ductility coefficient was noted to increase by 13.34%. When the L/D was increased from 8 to 11, the energy-dissipation capacity of specimens was decreased, and the ultimate bearing capacity and displacement ductility coefficient declined by 1.37% and 43.52%, respectively. The finite element simulation results are in agreement with the test results.

Influence of Polymer Fibers on the Structure and Properties of Modified Variatropic Vibrocentrifuged Concrete

“…Accordingly, when stresses arise in the structure of a vibrocentrifuged composite, these fibers absorb part of the stresses and prevent microcracks from forming in the structure of the composite. Also, basalt fiber has better adhesion to cement–sand mortar than polypropylene fiber [ 11 , 12 , 13 , 14 , 77 ].…”

“…And first of all, this is due to the fact that polypropylene fiber itself has lower strength and deformation characteristics than concrete itself, and cannot properly perceive the stresses arising in concrete and redistribute them [ 8 , 31 , 32 ]. Modification of VCC with basalt fiber is more effective, since basalt fiber has a higher elastic modulus, tensile strength, and when stresses occur in the composite structure, it prevents microcrack formation [ 11 , 12 , 13 , 14 , 69 ]. Modification with microsilica improves physical and mechanical characteristics due to processes occurring at the microlevel, promotes the formation of additional calcium hydrosilicates and reduces the capillary porosity of the composite [ 28 , 29 ].…”

“…Such scientific deficiencies are especially pronounced in non-traditional types of fibers for normal-density concrete and, first of all, for variatropic concrete [ 7 ]. Note that in the technology of normal-density concrete, durable types of fibers, such as steel and basalt, are often used, and polypropylene polymer fibers are used much less frequently [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. However, in our opinion, an interesting direction that can lead to a number of new results is dispersed reinforcement of variatropic concrete with polymer fibers, namely polypropylene fiber.…”

“…Polypropylene and basalt fibers are the most popular and most often used in the technology of normal-density concrete, and the effectiveness of their use has been confirmed by many scientific studies [ 8 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. Basalt fiber is of inorganic origin, obtained by melting basalt rock in smelting furnaces and drawing continuous threads from this melt through special dies, which are subsequently dried and chopped into fibers.…”

“…In [9], the introduction of basalt fiber in an amount of 0.2% increases the crack resistance and bearing capacity of concrete beams. The use of basalt fiber in [12,13] during the Polymers 2024, 16, 642 3 of 27 manufacture of concrete-filled round steel tubular columns with recycled aggregate can improve their strength characteristics. In works [14][15][16][17], the introduction of basalt fibers in dosages from 0.5% to 1.5% is the most effective and improves such characteristics of cement composites as compressive strength, bending strength and impact strength.…”