Leca Lightweight Aggregate was recently specified by Perth & Kinross Council’s design consultants CH2M to provide an innovative solution to a brand new infrastructure development in Scotland. The A9/ A85 project was delivered by the Scottish Council in order to alleviate current and future traffic congestion, and to provide essential infrastructure to support economic growth in the surrounding area.
The poor ground conditions meant the use of traditional dense fill material to make up levels and backfill behind the new bridge abutments was not considered to be an acceptable solution, because a dense fill would have imposed loads resulting high settlement on the poor ground and unacceptable loadings against the A9 highway embankment. Leca LWA was selected to reduce settlement and to alleviate the risk of possible movement as a result of the new A9 overbridge.
More than 20,000m3 of Leca 10-20mm was specified for this project and was shipped by boat to Perth harbour between January 2017 and January 2018 using Articulated Walking Floor Trailers, with around 70m3 per load. Leca was specified for many reasons and this included its lightweight properties in comparison to traditional fill material. The reduced settlements as a result of using Leca LWA allowed for potential damage to surrounding road infrastructure was mitigated and the stability of Leca LWA reduced the risk of deformation and landslide. Leca was used in both sides of the bridge development and this was to back fill the bridge abutments and to build up levels.
Leca also provided an additional benefit through the ability to be shipped directly to Perth from the manufacturing kilns in Denmark. The flexibility offered by Leca limited the amount of transportation required for the project and intentionally reduced the environmental impact. This also reduced manpower and financial costs with much shorter haulage distances and the customer experienced more flexibility, increased daily volume potential, increased revenue for Calport Limited, who managed the offload and storage of the material at Port, this reduced material handling and eliminated any risk of potential project delays due to transportation.
Balfour Beatty Construction Manager provided some thoughts on this project, “There were a few factors involved with the decision to place the order with Leca, such as the price of the material and compliance with the specification. Based on alternative quotes that we received there was a cost saving in purchasing the Leca product”
Balfour Beatty Construction Manager went on to discuss some of the highlights from this huge project in Perth, “The specification issued to us asked for a class 1E lightweight expanded aggregate and certain grading limits were also detailed so there were a few potential suppliers of products that would comply.”
He goes onto explain how Leca provided flexibility and problem solving solutions in logistical process, “Other potential suppliers were proposing to use either Dundee or Aberdeen harbour and then road haulage from there to the site in Perth. However, Leca’s proposal was to use Perth harbour. This was attractive from the point of view of sustainability with reducing the sites carbon footprint, our client PKC own the harbour at Perth so harbour fees etc were being kept local to the area and less road haulage would be required due to the proximity of the harbour to the project.”