M7 High Speed Framework Pavement Scheme – Trialling RAP in HRA
Major Initiative to HRA Design
We are excited to share through collaboration and engagement with our specialist paving sub-contractor, Kilsaran Road Surfacing and Contracting, and our client TII ground breaking changes to HRA (Hot Rolled Asphalt) design have been made.
The M7 High Speed Framework Pavement Scheme is the first project to be part of the CO2 Performance Ladder pilot in Ireland. The aim being to reduce carbon emissions while taking a transparent and collaborative approach.
The forecast of expected carbon usage on the project confirmed the largest carbon contributor and where we stood to make the greatest carbon reduction, raw materials . It was the clear view this should be the focus of any potential measures to reduce the carbon emissions whilst still looking at all possible measures.
Various early-stage exploratory discussions between TII/Jons/Kilsaran highlighted an opportunity/option to possibly use some of the fine milled plannings (which would have otherwise been a waste product) from this project as RAP to be used in the manufacture of Asphalt , thus reducing the virgin aggregate and bitumen required. When RAP is recovered from site it is processed into two grades, coarse and fine and stored under cover to control moisture content.
Further close coordination with Jons, Kilsaran and TII technical departments resulted in agreement to incorporate 15% RAP, using the fine grade, in all the HRA material on the project apart from a 5000m2 area which received incorporation of 35% RAP using the coarse grade and a 5000m2 area with the standard HRA mix to act as a control.
Ongoing monitoring/testing of these trial areas is being carried out to ensure its efficacy and to allow for the possibility of greater percentages to be used on future schemes.
The use of the 15% RAP in the HRA material results in a 6.4% reduction in Carbon (4.9kg Co2/Tonne) when compared with the Standard HRA.
The use of 35% RAP in the HRA results in a 12% reduction in the Carbon (9.1kgCo2/Tonne) when compared with the Standard HRA.
First indications from the project are positive and the goal is that the use of 15% RAP HRA becomes widely used on future projects with the possibility of greater percentages of RAP to follow.
