Compressive and free vibration response of fiber reinforced rubberized recycled concrete columns

Abstract

The production of sustainable green concrete is getting popularity in concrete industries. The increasing amount of waste tires and construction and demolition (C&D) wastes mounting up in the landfills create a concern for environmental sustainability. The construction industries are nowadays thinking of ways to reduce and reuse these waste materials. The use of recycled coarse aggregate (RCA) produced from the demolition of old concrete infrastructures and waste tires of vehicles in the concrete mixture can play a vital role in providing an economical solution. Thus, this study investigates the compressive behavior of steel-reinforced concrete columns that are made of RCA and waste tire-derived crumb rubber (CR) along with polypropylene (PP) fiber. A total of twenty-six short columns (kL/r = 11) having a size of 150 × 150 × 950 mm were cast and tested under uniaxial loading up to failure. Besides, from those twenty-six columns, nine columns were used for free vibration testing before applying compressive force. Different mechanical properties of rubberized recycled concrete (R2C) and fiber-reinforced rubberized recycled concrete (FR3C) were also evaluated by compressive strength test, tensile strength test, flexural test, ultrasonic pulse velocity test, surface resistivity test, and hardened density test. Test parameters included longitudinal reinforcement ratio (1.4% and 2.0%), tie spacing (75 mm and 150 mm), and content of CR (0%, 5%,10%, and 15%). However, the RCA and PP percentages were fixed at 30% and 0.5%, respectively. The axial capacity, failure mode, influence of longitudinal and transverse reinforcement, effect of RCA, CR, and PP fiber, strain and deflection characteristics, dilation ratio, curvature, toughness, and ductility were examined. The free vibrational responses of columns are presented in terms of damping ratio, time period as well as frequency. Besides, an extensive regression analysis has been carried out based on the experimental data and a number of equations have been proposed for predicting different mechanical properties by considering the effect of CR and fiber. Furthermore, a cost analysis was conducted to examine the cost-effectiveness of these new types of concrete. The axial capacity of columns decreased with increasing CR content by up to 39.6% and 35.5% for R2C columns and FR3C columns, respectively. However, the FR3C columns exhibited higher axial capacity compared to the recycled aggregate concrete (RAC) column and R2C columns. The ductility increased with increasing the CR percentage and the addition of fiber content. Approximately 167% and 70% higher ductility was achieved in 75 mm and 150 mm tie spaced columns by using 0.5% fiber content in the R2C mixture with 15% CR content. The toughness value of R2C columns was initially decreased for 0%, 5%, and 10% CR content but then increased for 15% CR content. However, all FR3C columns exhibited a higher toughness value compared to the conventional column. From the free vibration test, it was found that the damping ratio of all RAC, R2C, and FR3C columns were higher than that of the conventional column. Up to 131% and 301% damping ratio was increased for R2C columns and FR3C columns depending on the percentage of CR content. The cost analysis showed that both the R2C and FR3C mixtures saved more energy costs and decreased fuel consumption. Considering all the parameters, it is recommended to use up to 5% CR content with 30% RCA and 0.5% fiber content. Finally, this study will help to develop sustainable and resilient fiber-reinforced recycled rubberized concrete for the application in structural members.