2010
Colorado, USA

The Hoover Dam and Lake Mead are located in Black Canyon on the Colorado River in the USA on the borders of Arizona and Nevada. Construction of the 220m high dam began in 1931 and more than 4 million m³ of concrete were placed by the time it was completed in 1936. Highway 93 is built into the top of the dam to cross the canyon, but the sharp bends and narrow widths of the highway, combined with the number of tourists and necessary security, led to an astronomical increase in traffic, so that long delays and bottlenecks had become the norm.

Project Requirements

After a long debate due to the sensitive environment, the final decision was for a composite bridge structure with a reinforced concrete deck, over steel box girders, supported on concrete piers from twin concrete rib arches. 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 longterm 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.

Sika Solutions

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.

Sika® Rapid 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 Sika-Grout® PT system, which was developed by Sika USA as members of the American PTI (Post Tensioning Institute).

Products Used

Sikadur®-31 SBA
SikaGrout®-328
SikaGrout®-300 PT
Sikament® MP
Plastiment®
Sika® ViscoCrete®-2100
Sika® ViscoCrete®-4100
Sika® ViscoCrete®-6100

Sika® ViscoCrete®-2100

HIGH RANGE WATER REDUCING ADMIXTURE
Water Reduction: Sika® ViscoCrete®-2100 can be dosed in small amounts to obtain water reduction from 10−15 % and will achieve water reduction up to 45 % at high dosage rates. Sika® ViscoCrete®-2100 is suitable for all levels of water reduction. High Plasticity: The superplasticizing action of Sika® ViscoCrete®-2100 provides high-slump, flowing concrete that maintains excellent workability and may be placed with minimal vibration even at very low water cement ratio’s as low as 0.25.
Sika® ViscoCrete®-2100 plasticized concrete is highly fluid while maintaining complete cohesion within the concrete matrix to eliminate excessive bleeding or segregation.  
Extended Slump Life and Set Control: Sika® ViscoCrete®-2100 has been formulated to provide controlled and predictable extended slump life for periods of 60 to 90 minutes with normal set times.  
The combined high range water reduction and superplasticizing action of Sika® ViscoCrete®-2100 provide the following benefits in hardened concrete:   
  • Higher ultimate strengths allow for greater engineering design flexibility and structural economies
  • Reduced water cement ratios produce more durable, dense concrete with reduced permeability
  • Highly effective plasticizer reduces surface defects in concrete elements and improves aesthetic appearance
  
Sika® ViscoCrete®-2100 has been formulated to provide maximum water reduction and extended slump retention at low dosages.
Sika® ViscoCrete®-2100

Sika® ViscoCrete®-6100

HIGH RANGE WATER REDUCING ADMIXTURE
Water Reduction: Sika® ViscoCrete®-6100 can be dosed in small amounts to obtain water reduction from 10−15 %, and will achieve water reduction up to 45 % at high dosage rates. Sika® ViscoCrete®-6100 is suitable for all levels of water reduction. High Plasticity and Cohesion: The superplasticizing action of Sika® ViscoCrete®-6100 provides high-slump, flowing concrete that maintains excellent workability, and may be placed with minimal or no vibration even at very low water cement ratios as low as 0.25. Sika® ViscoCrete®-6100 maintains excellent cohesion within the concrete matrix, and eliminates excessive bleeding or segregation. The unique plasticizing effect of Sika® ViscoCrete®-6100 provides excellent formed surface finish.   The combined high range water reduction and superplasticizing action of Sika® ViscoCrete®-6100 provide the following benefits in hardened concrete:
  • Higher early compressive strengths for earlier removal of forms and structural use of concrete
  • Higher ultimate strengths allow for greater engineering design flexibility and structural economies
  • Reduced water cement ratios produce more durable, dense concrete with reduced permeability
  • Highly effective plasticizer reduces surface defects in concrete elements and improves aesthetic appearance
  • Ideal for the production of Self-Consolidating Concrete (SCC)
  • Ideal for ready-mix trucks
  • Formulated to provide maximum water reduction, increased early strength, improved finishing characteristics, especially when a broom is desired
  • Sika® ViscoCrete®-6100 does not contain formaldehyde, calcium chloride or any other intentionally added chlorides, and will not initiate or promote the corrosion of steel present in the concrete
Sika® ViscoCrete®-6100

Project Participants

Owner
USA Government, Federal Highways Department

Engineers

HDR Services Inc. & T. Y. Lin International

Contractor

Joint Venture of Obayashi Corporation and PSM Construction

Concrete Producer – Ready-mix

Casino Readymix Inc.