Push-out test of steel reinforcement from recycled plastic beams

Recycled plastic is a rather flexible material, thus the stiffness and load bearing capacity of beams is mainly provided by typical steel reinforcement. This steel reinforcement is fully submerged into the recycled plastic beam. In 2004, four point bending tests on steel reinforced recycled plastic beams have been conducted. These tests have shown that the beam capacity is conditioned by the bond between reinforcement and plastic, because the beams fail by slippage of the steel reinforcement. Therefore, investigation of the bond properties is crucial for modelling the failure mechanism and improving the capacity of steel reinforced recycled plastic beams. A standard method to examine these properties is the pull-out test. However, preparing pull-out test specimens from recycled plastic is complicated. Normal production of recycled plastic products requires heat and pressure thermal reprocessing. Chips of sorted plastic waste (mixture of polyethylene and polypropylene) need to be melted at a temperature around 200 C and pressed through extruder into a steel mould. The variability of these products is highly dependent on and limited by the size of moulds and available production machinery. Hence, making standard pull-out test specimens would require a design of new moulds, which is expensive and ineffective. In the present paper, we examine the bond properties through push-out tests. Beams with plain and ribbed steel reinforcement were cut into pieces of 50 mm, 100 mm, 150 mm and 200 mm height, and the steel reinforcement was pushed out. Force-displacement curves are presented to illustrate the test results.