Abstract
This paper mainly investigates the fracture parameters of Basalt Fiber Reinforced Concrete (BFRC) with various fiber lengths and dosages using Double-K fracture model. The model was developed by fracture criterion using ABAQUS Virtual Crack Closure Technique (VCCT), and the results of the model and experiments were compared. The basalt fiber with length of 6 mm and 12 mm was added into concrete in the dosage of 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by volume of concrete, respectively. Concrete specimens were cast into three dimensions, i.e., 60 mm × 180 mm × 480 mm, 80 mm × 240 mm × 640 mm, and 100 mm × 300 mm × 800 mm. Then, three-point bending test was conducted on precast-notched beams. The load versus cracking mouth opening displacement (P-CMOD curve) was developed in order to evaluate cracking and breaking load. The initial fracture toughness and unstable fracture toughness were derived from the Double-K fracture model aimed to optimize the fiber length and dosage. The results showed that the initial fracture toughness and unstable fracture toughness increased first and then decreased with the increase in fiber dosage, and basalt fiber with length of 6 mm and dosage of 0.2% performed the best toughening effect on concrete. The comparison results showed that numerical simulation can better simulate the initiation and propagation of BFRC fractures and achieve the dynamic propagation process of fractures.
Highlights
Base phase is a mixture of cement, water, fly ash, water-reducing agent, air entraining agent, and basalt fiber, while dispersed phase is the aggregate. e fracture failure of BFRC can be divided into three levels, the first level: the bonding surface of mortar and aggregate is a weak surface, and cracks are generated on the bonding surface of mortar and aggregate firstly; the second level: with the development of cracks between mortar and aggregate binding surfaces, cracks spread into mortar and the interface of sand and hardened cement slurry begins to crack; third level: as cracks between sand and hardened cement slurry develop, hardened cement slurry starts to crack, accompanied by the pulling-out failure of fibers
P-CMOD Curves. e effects of various basalt fiber dosage on P-CMOD curve were obtained from the tests as shown in Figures 3 and 4 for 6 mm fiber and 12 mm fiber, respectively
(2) e P-CMOD curves were established by experiments, and the initial crack load was obtained based on the state of crack propagation. e initiation toughness was calculated by initial crack load
Summary
Where KQIC is initiation toughness, MPa·m1/2; FQ is crack initiation load, kN; a0 is length of precast crack, m; t is thickness of specimen, m; h is height of specimen, m; S is midspan distance, m; m is mass of midspan specimen, kg; and g is acceleration of gravity, 9.81 m/s2. E fracture process of BFRC specimen is not all linear due to the bond strength between aggregates and binder and the bridging effect of basalt fiber after matrix cracking. Where KSIC is unstable fracture toughness, MPa·m1/2; Fmax is maximum load, kN; ac is critical effective crack length, m; t is thickness of specimen, m; h is height of specimen, m; S is midspan distance, m; m is mass of midspan specimen, kg; and g is acceleration of gravity, 9.81 m/s2. E initiation toughness and unstable toughness parameters of BFRC were calculated by using the Double-K fracture model. Erefore, VCCT technique was used to simulate the fracture performance of BFRC and analyze the entire process of BFRC fracture
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