The Challenge

The Luas Cross city project extended the Luas Green line from St. Stephens Green to Broombridge in Cabra. The project comprised the construction of 5.9km of new track and 13 new stops through the heart of Dublin city and proved to be a particular logistical challenge.

This was especially true when works commenced across O’Connell Bridge, a key crossing point of the Liffey for both traffic and pedestrians. To minimise disruption works were carried out over a Bank Holiday. Roadstone fast set concrete proved crucial in allowing for the tight schedule to be achieved.

The Solution

Two conflicting parameters of the concrete mix were required by the contractor.

Firstly the concrete had to maintain its workability for 2 hours following batching to allow for onsite operatives to place and finish the concrete. The concrete had to then achieve its hardened properties to allow for follow on works to commence and a re-opening of the bridge to pedestrians and traffic.

A suitable concrete was produced through the selection of a superplasticing admixture, an accelerating admixture and CEM II/A-L Portland Limestone cement. The superplasticing admixture ensured that the workability retention was achieved, while the accelerator and CEM II/A-L cement type ensured both rapid set and rapid strength development of the concrete.

The time-lapse video below illustrates the speed at which works were complete and the important part that the concrete played in allowing the project to progress with minimal disruption to business and the general public.

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Preview image for the video "Luas Cross City project at O'Connell Bridge".

With a tight window in which to complete works our real time traffic analysis system and close communication between our readymix concrete truck drivers and our concrete dispatch team proved essential in ensuring deliveries arrived onsite on time and that works were completed as scheduled.