Study on Eccentric Compression Mechanical Characteristics of Basalt Fiber-Reinforced Recycled Aggregate Concrete-Filled Circular Steel Tubular Column

Abstract

During this study, eight basalt fiber-reinforced recycled aggregate concrete-filled circular steel-tubular (C-BFRRACFST) column specimens were subjected to eccentric compression tests with different replacement ratios of recycled coarse aggregate (RCA), basalt fiber (BF) contents, length-diameter (L/D), and eccentricity. The whole process of stress as well as failure mode of the specimens were observed, and a load–displacement curve as well as a load–strain curve for the specimens were measured. The impacts of various parameters upon the bearing capacity, peak displacement, and ductility coefficient of the specimens were analyzed. Subsequently, a 3D finite element model of the C-BFRRACFST column was established, and the whole process of stress was simulated. Based on the finite element simulation results, the N/Nu-M/Mu correlation strength curve of the C-BFRRACFST columns was verified. The exploration demonstrated that under eccentric load, the C-BFRRACFST column eventually underwent destruction of the overall instability. The load–axial displacement curve was characterized as three stress stages: elastic, elastic–plastic, declining, as well as declining stages. The strain of the mid-span section for the specimens follows the plane section assumption, and the lateral deflection basically follows the sine waveform curve. The ultimate bearing capacity of the specimens exhibited little change as the replacement ratio of RCA improved, while the ductility progressively reduced. Furthermore, the ultimate bearing capacity of the specimens failed to be obviously changed as the BF content enhanced, while the ductility progressively rose. Increasing the L/D gradually reduced the specimen’s ultimate bearing capacity alongside its ductility. The corrected N/Nu-M/Mu curve agreed well with the findings of finite element simulation.

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.…”