Central Link Light Rail – Beacon Hill

Produce, heat-cure, and test high-performance concrete mixtures that would be used to produce precast concrete tunnel lining elements for the construction of the Central Link Light Rail

Beacon Hill Station and tunnel construction was part of building Seattle’s Central Link light rail. The Central Link opened in July 2009, offering the city its first light rail. The Beacon Hill contract included the construction of a one mile tunnel under Beacon Hill, the west and east portals, a half mile of elevated trackway, and the Beacon Hill and Mount Baker stations. The light rail link was built by Seattle’s SoundTransit, which also operates the city’s express buses and commuter rail.

SIMCO’s concrete materials’ experts were called upon in order to conduct a testing program on candidate mixtures that would be used to produce precast concrete tunnel lining elements of the Central Link Light Rail – Beacon Hill Project.

The specific objective of this project was to provide concrete mixture formulations that would meet all the strength and durability requirements specified for this project.

Each candidate concrete mixture was tested under controlled laboratory conditions and included the following tasks:

• The selection of proper chemical admixtures dosage (i.e. superplasticizer and air-entraining admixtures) to produce concrete mixtures with acceptable rheological properties and good frost durability
• The selection of the heat-curing cycle characteristics (i.e. temperature rise, maximum curing temperature and cooling rate of the material) required to produce high strength and durable concrete mixtures.
• The production of 6 heat-cured concrete mixtures and the measurement of the compressive strength of each of those mixtures at various maturity levels
• The determination of the frost resistance of concrete mixtures (according to ASTM C 666 – Method A)
• The determination of the water permeability coefficient of selected concrete mixtures (according to the procedure of Lawrence, 1986)