Following changes to the TII Series 800 Specification (CC-SPW-00800) the inclusion of recycled materials in granular fills is now permitted in UGM A materials up to 30% content and UGM B materials up to 100% content.
The following materials are now contained in CC-SPW-00800
| UGM A – Unbound Granular Mixture A | Previously Cl804 | Max 30% recycled content |
| UGM Ac – Unbound Granular Mixture A adjacent to cementitious materials | Previously Cl808 | Max 30% recycled content |
| UGM Am – Unbound Granular Mixture A adjacent to metallic materials | Previously Cl809 | Max 30% recycled content |
| UGM B – Unbound Granular Mixture B | Previously Cl804 | Max 100% recycled content |
| UGM Bc – Unbound Granular Mixture B adjacent to cementitious materials | Previously Cl808 | Max 100% recycled content |
| UGM Bm – Unbound Granular Mixture B adjacent to metallic materials | Previously Cl809 | Max 100% recycled content |
In light of these changes Roadstone in collaboration with TII undertook a research project to examine the effects of the inclusion of recycled returned concrete aggregate on the performance of a Cl804 type granular fill layer. As per the TII requirements for UGM A materials, 30% recycled returned concrete was added to a 0/31.5mm natural crushed rock material(previously known as Cl804). The material was placed and compacted as per standard industry practice with samples taken for testing to demonstrate compliance with the mechanical and chemical requirements of Series 800. In situ, a Falling Weight Deflectometer and compact density tests were carried out on the finished layer to demonstrate the pavement's ability to distribute loading as required.
It was demonstrated that granular fill with 30% recycled returned aggregate had equivalent performance to granular fills made solely from natural aggregates. The use of RCA in granular fills reduces CO2 emissions in the manufacture of the natural granular fill as the requirement for drilling and blasting of natural rock and transport to the crushing plant is eliminated.
The successful use of RCA as a natural aggregate replacement confirms that this material is a viable alternative that must be considered appropriate for use in unbound granular fills. In our Model Roadbase field trial, granular fills containing RCA were capable of achieving a performance level comparable to natural aggregates. The use of RCA in unbound granular fills represents a significant move towards greater sustainability in line with Ireland’s construction industry’s commitment to the circular economy.
Take a look a this case study on a UGMA Field Trial at Belgard quarry.