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.