Substitution of Recycled Plastic Aggregates (RPA) in concrete and its influence on pullout capacity of mechanical and chemical anchors
There is a lot of plastic going to land fill or entering environmentally sensitive systems, that could ideally be converted into a form or material that would be considered as a resource. Much of this plastic waste is not suitable for re-cycling or use, where exposed to sun light or weathering elements. Some of these materials have been converted to granular materials and used in sub-soil drainage systems as free draining materials and as substitute for aggregates in concrete pavements. There is significant enthusiasm for utilising ‘environmentally friendly’ construction systems and materials. Unfortunately, that enthusiasm can result in them being utilised in in-appropriate situations that can have a negative result to the reputation of the material or system. The aim of this project was to determine if anchors and fixings inserted into Recycled Plastic Aggregates (RPA) concrete elements will perform as expected and required. Proprietary RPAs were procured from a commercial supplier to substitute for natural concrete aggregates in various proportions. Normal and RPA concrete cylindrical samples were manufactured in a controlled environment at USQ lab and subsequently cured for 28 days. The purpose of manufacturing and testing normal concrete samples, involving standard concrete blends, was to provide a reference point when comparing the performance of the RPA concrete systems. Compression tests were performed on both normal and RPA concrete samples using the universal load test machine. On the other larger samples, holes were drilled in the normal and RPA concrete samples to install proprietary mechanical and chemical anchors so pull-out tests could be performed to simulate real life scenario. These pull-out tests were also performed on universal load test machine. The 50% RPA concrete demonstrated significant capacity reduction and to the extent that these rates cannot be sustainable. The 20% RPA concrete has demonstrated reduction in capacities that could conceivably be tolerated in the construction industries. The mechanical anchors were noticeably more affected by the RPA substitution than the chemical anchors. The substitution of recycled plastic provides a sustainable option for offsetting waste plastic going to landfill, thereby reducing environmental pollution. This study develops confidence in the performance of post fixed anchors inserted into low percentage RPA concrete, creates awareness in the industry and supports recycling through buying products which include recycled content in line with Australian Government National Plastic Plan 2021.
Raza Akhtar, Graham Skellern and Ali Mirzaghorbanali, Investigation of the effect of using fly ash in the grout mixture on performing the fully grouted rock bolt systems, Proceedings of the 2023 Resource Operators Conference, University of Wollongong - Mining Engineering, February 2023, 302-310.