TOTAL SIKA PACKAGE

High-Performance adhesives, mortar and admixtures to produce concrete with every required property: the solution is called "Total Sika Package". Therein Sika bundles its core competencies, coordinated customer contact and aligns all products and processes.

HIGH PERFORMANCE CONCRETE MIX DESIGN

The Hoover Dam Bypass Bridge, Nevada, USA, eliminates the bottleneck above the world-famous Hoover Dam crosses the canyon above and to the South of the Dam at a height of around 300meters above the river.

For the cast-in-place reinforced concrete foundations and ribs of the arch, a high performance concrete mix design was specified that had to achieve a compressive strength of 69 MPas (10,000 psi), together with strict limits on shrinkage and long term creep. This had to be developed and then adapted to provide consistent performance in the extreme temperature conditions, which can vary from below -20°C in winter, to higher than +40°C in summer.

UNIFORM SEALED AND WAERTIGHT JOINT

The precast concrete pier segments had to have an excellent visual finish and also required very high early strengths of up to 4,500 psi (30 MPas). The segmental pier assembly and post-tensioning process was undertaken in a similar way to segmental bridge construction and a proven adhesive / lubricant was required.

This was for application between the adjacent segments, to assist in their final positioning and tensioning, then to ensure a uniform sealed and watertight joint in service. Finally, after tensioning the cables also had to be sealed and protected in their ducts with a non-shrink, high flow grouting system to prevent any future corrosion and water ingress to the structure.

Sika® ViscoCrete® AND SikaRapid® TECHNOLOGIES

All of the engineers High Performance Concrete (HPC) requirements were met using Sika® ViscoCrete® Technologies. Sika’s concrete technicians worked closely with the engineers, the contractor and the concrete producer to ensure the specified consistence, performance and finish. SikaRapid® Technology was used for accelerated hardening to achieve the high early strengths of over 30 MPas within 16 hours where required, to enable the formwork to be stripped and accommodate early loading.

For the segmental adhesive the engineers selected Sikadur®-31 SBA (Segmental Bridge Adhesive), as Sika is the global leader in this field and has previously completed numerous projects with Obayashi and others in China, Japan, the USA and worldwide.

Finally the necessary cable grouting around the post-tensioning tendons in their ducts, was successfully completed using the well known SikaGrout® PT system, which was developed by Sika USA as members of the American PTI (Post Tensioning Institute).