Study On Compressive And Fracture Behaviors Of Crumb Rubber And Steel Fiber Reinforced Recycled Aggregate Concrete

In this paper, a new type of recycled concrete material, crumb rubber and steel fiber reinforced recycled aggregate concrete (RSRAC), is proposed and researched by the author. The RSRAC is produced mainly based on the recycled use of waste concrete and junked tire rubber, meanwhile taking the advantage of the superior mechanical mechanism of crumb rubber and steel fiber to improve some drawbacks of concrete, such as the lower tensile strength and the larger brittleness et al. There fore, RSRAC is a newly recycled concrete material which gives consideration to compressive strength, toughness and environmental protection and possesses a nice research value and promotion prospect.Thispaper,throughtheuniaxialcompressionexperimentoncylindersof Φ150×300mmand the three-point bending test on notched beams of100×100×515mm, respectively, focused on study of the effects of rubber content(0%,4%,8%,12%and16%) and target temperalure(25℃,200C,400℃. and600°C) on the compression behaviors along withthe fracturepropertiesat25℃, preliminarilydiscussed thecompression failure mechanism after exposure to elevated temperatures and fracture failure mechanism at room temperature. The research contents mainly include3parts as follow:(1) A total of72cylinder specimens, each group of three, were subjected to high temperature by an electric furnace. The appearance change and mass loss of specimens were measured after different high temperatures treating, thus the effects of rubber content and target temperature on the appearance change and mass loss of specimens were analyzed. Together with the present research results and the experiment results in this paper, the author has preliminarily discussed the high temperature damage mechanism on RSRAC and the mechanism of crumb rubber relieves explosive spalling.(2) By means of a compression experiment on a total of72cylinder specimens, each group of three, after exposure to elevated temperature, the compressive behaviors including compressive strength, Young’s modulus (stiffness), stress-strain curves and energy absorption capacity (toughness) of mixes were obtained and analyzed in accordance to ASTM standards. The results show that the compressive strength and stillness of RSRAC mixes decreased with the increase of rubber content, while increasing the rubber content from4%to16%by volume of sands leads to the decrease of compressive strength from4.57%to30.21%(with respect to the compressive strength of RC-RO), with the largest strength loss occurring between the rubber contents of4%and8%; A suitable rubber content and target temperature made contribution to the improvement of compressive toughness of RSRAC mixes, with the larger toughness appeared between the rubber contents of8%and12%.(3) Three-point bending test were carried out on a total of18notched beam specimens, each group of three, at room temperature. The load-deflection (P-δ) curves and load-crack mouth opening displacement(P-CMOD)curves were all measured during the tests, and thus the effects of rubber content on fracture energy and stress intensity factor of RSRAC mixes were also discussed and analyzed. The results show that a full replacement of NCA by RCA leaded to a decrease of46.78%in the fracture energy, while the rubber content is increased from4%to16%, the GF and KIC is first increased and then decreased with increase of rubber content, with RC-R8mixes having the highest fracture properties, indicating that an appropriate amount of rubber content increases the fracture properties of the concrete but too much rubber content may has a negative effect on the fracture properties of the concrete.