Abstract
The mechanical properties, failure forms, and deformation characteristics of 10 beam-to-column joints under monotonic loads were compared and analyzed. The design variables were waste fiber content (0.08%, 0.12%, and 0.16%), waste fiber length (12 mm, 19 mm, and 30 mm), and replacement rate of recycled aggregates (0%, 50%, and 100%). The results indicated that, under an axial compression ratio of 0.4, all specimens underwent plastic hinge failure at the beam end under monotonic loading and experienced four stages of the initial cracking, full-cracking, limit, and failure stages. There was no shear oblique crack in the core area of the joint, and no shear failure occurred. When the replacement of recycled aggregates is 50%, the tensile strength of concrete mixed with a specific amount of fibers can be effectively improved. The ultimate bearing capacity of the beam end is improved when the length and volume of the waste fibers are 19 mm and 0.12%, respectively. The ratios between the calculated and tested ultimate bearing capacity of beam-column joints are in the 0.99–1.10 range, and the calculated and tested values are in good agreement.
Highlights
Introduction e construction industry inChina is facing two serious problems: the huge consumption of natural resources [1] and the quantity of construction and demolition waste [2]
To prepare the waste fiber recycled concrete, coarse aggregates, and waste fibers were mixed for 2 min in a forced concrete mixer, and the cement and water were added and stirred at low speed for 2-3 min to achieve good workability, according to the GB/T 50081 (Chinese standard)
With the increase in load, the specimen with recycled coarse aggregates (RCA) enters the yield stage faster than the NCJ. e ultimate bearing capacity of RCJ-5019-0.12 was 9.6% and 11.22% higher than those of RCJ-190.12 and RCJ-100-19-0.12, respectively, which are close to that of NCJ. e main reason is that there is better compatibility between RCA and fresh cement slurry, and each of these has the possibility of chemical reaction. e surface of the RCA is rough and the interface meshing ability is strong, thereby improving the performance of the interface to a certain extent
Summary
Fine aggregates were natural river sand with a fineness modulus of 2.8, the water content was 4.14%, and apparent density was 2620 kg/m3, following Chinese standard GB 50164. E properties of the coarse aggregates are shown, following Chinese standard GB/T 14685. E density of the waste fibers is 0.91 g/cm, which is tested by the liquid displacement technique, according to JC/T 287-2010 (Chinese standard). E mixing water consisted of free water and additional water in accordance with JGJ/T 443-2018 (Chinese standard). To prepare the waste fiber recycled concrete, coarse aggregates, and waste fibers were mixed for 2 min in a forced concrete mixer, and the cement and water were added and stirred at low speed for 2-3 min to achieve good workability, according to the GB/T 50081 (Chinese standard)
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