Construction World December 2017

Category B: Specialist Contractors or Suppliers

CONCRETE FOR VAN ZYL SPRUIT BRIDGE Van Zyl Spruit Bridge is the first long integral bridge in South Africa and, at 90 m, it is one of the longest integral bridges in the world.

siliceous fly ash from Ash Resources’ Lethabo plant. Verification of the quality of outgoing product is undertaken on each tanker leaving the Works. To ensure the exact same percentage of fly ash extender in each production run, the rigorous quality management includes determination of fly ash content using an XRF testing method. Significant factors in favour of using Powercrete Plus were that it is a Low Heat Cement, reducing the potential for thermal cracking in mass pours; and its unique formulation allows contractors to extend it further on site with additional DuraPozz ® fly ash, to customise mixes for the differing needs of the works. The CEM II Powercrete Plus formulation creates mixes with: • Early strength performance on a par with traditional CEM I products but higher ultimate strength • Reduced heat of hydration • Better workability • Versatility on site through being able to be blended further with fly ash • Better flowability and finishes • The ability to form denser, more durable and impermeable concrete.

Constructing the bridge on the N1 Freeway, at a remote site, required close collaboration between the main contractor and the specialist concrete supplier.

In view of the importance of the innovative bridge design for future bridge construction policy in South Africa, the University of Pretoria, in collaboration with the UK’s Cambridge University, was commissioned by SANRAL to undertake a detailed assessment of the integral concrete bridge. This involved designing, installing and operating over 500 sensors, which are being logged every 15 minutes to detect and quantify trends in strain, temperature, tilt and earth pressure. Lafarge South Africa provided a unique ‘One Lafarge’ integrated offer to supply all of the main building materials and mitigate the contractor’s risk completely by providing the ‘durability concrete’ on their behalf from an on-site

Lafarge mobile concrete batching plant. Continuity of concrete supply to ensure uninterrupted pours and the consistency of a durable quality concrete mix were especially important for the construction of the integral bridge structure. Lafarge was able to guarantee to meet these requirements in the absence of any nearby fixed commercial ready-mixed concrete plants, by positioning a mobile concrete batching plant on site, equipped with basic quality control testing facilities. The company also standardised on the use of its premium technical cement, Powercrete Plus CEM II 42,5R, for all the concrete production. This pioneering project will significantly influence the future design of bridges in South Africa by introducing a largely maintenance-free concrete structure without bearings or expansion joints. Tight quality and durability specifications were a major challenge for the contractor as the site is some 120 km from the nearest fixed commercial ready-mixed concrete plant, and undertaking their own on- site batching represented a significant compliance risk. Manufactured exclusively at the

PROJECT INFORMATION

• Company entering: Lafarge South Africa • Client: Aveng Grinaker-LTA • Start date: 2015 • Project end date: August 2016 • Main contractor: Aveng Grinaker-LTA • Principle agent: Mott MacDonald • Research: University of Pretoria

Lafarge Lichtenburg Cement Works, Powercrete Plus is formulated with high quality DuraPozz® classified

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