Experimental investigation on the floating of rubber particles of crumb rubber concrete

Abstract

Crumb rubber concrete has been reported to possess many favorable qualities for engineering applications, such as higher ability of deformation, higher toughness, damping ratio and good performance of freeze-thaw, anti-cracking and resistance to water or chloride ion penetration. However, still there exists a major problem at this stage of applications of crumb rubber concrete, which is the floating of rubber particles when vibrating and compacting fresh Crumb rubber concrete. In order to investigate this “floating problem”, a series of experiments were conducted which utilize Crumb rubber concrete cube compressive strength, density and rubber particle distribution inside Crumb rubber concrete specimens as measures of floating of rubber particles. 20 groups of prismatic specimens were casted, among which 11 groups were proportioned with different slump values by adjusting content of water and water-reducing agent, 4 groups were proportioned on basis of one of the 11 groups mentioned above with different sand ratio and vibrating time and the last 5 were controlled groups with no rubber particles. The results show that the floating of rubber particles is not apparent when the slump test value of concrete is low. However, if the slump value is high, and keeps increasing, the floating effect tends to be more apparently and when the slump surpasses a certain value (near 18 cm), the floating develops sharply and abruptly. The floating is more evident with an increased vibrating time. With the sand ratio at a certain value, the floating phenomenon is well-controlled. Sand ratios that are too high or too low can lead to significant floating.