Project Reference: Marina Coastal Expressway
Location: Singapore
Products used: MasterRheobuild 1000, MasterPozzolith R138
Project background
Marina Coastal Expressway (MCE) runs a total length of approximately 5 km, connecting the Kallang-Paya Lebar Expressway (KPE) and the East Coast Parkway (ECP) in the East to the Ayer Rajah Expressway (AYE) in the West.
The scope includes the design, construction and completion of 360m of dual carriageway depressed road structure, 640m of dual carriageway vehicular tunnel structure, slip tunnels, at-grade roads, and a 280m section of future transit tunnel undercrossing the MCE tunnels, trunk link sewer and associated manholes, waste water pump sump, storm water pump sump and future tunnel stub.
The challenge
This project is the largest contract ever awarded by the Land Transport Authority. Under this project, the mass castings to the base slabs and top slabs of the tunnels present huge challenges, with six hours of retardation needed along with a concrete placement temperature not higher than 32 degrees Celsius. Singapore’s hot weather often induces a loss of workability in concreting tasks.
To ensure sufficient compaction of fresh concrete, it is critical to extend the time for fresh concrete to remain plastic. In addition, a rapid hydration process can lead to loss in concrete strength since the resultant concrete will have a poorer structure with a higher gel/space ratio. During the hydration process, a substantial heat would be produced. If the hydration process is performed too swiftly, it will lead to a rapid increase in temperature, thereby causing considerable early thermal movement in the concrete.
Our solution
Several trial mixtures were carried out in consultation with Master Builders Solutions as the supplier of concrete admixtures, in line with the project’s key requirements. As the peak temperature of concrete administration must be controlled at a temperature of not higher than 75 degree Celsius, MasterPozzolith R 138, a ready-to-use, chloride free admixture designed for hot weather concreting, was adopted.
MasterRheobuild 1000, a super-plasticising admixture containing a sulphonated polymer with chloride-free properties to impart rheoplastic attributes to concrete, was also adopted. The benefits it brought to the project were substantial. These included very high workability, high water reduction, superior cohesion, high early strength as well as low shrinkage and creep.