Construction World February 2015

PROJECTS AND CONTRACTS

RE-USED in extensive upgrade Murray & Roberts Infrastructure was awarded a construction contract by Transnet Capital Projects for new concrete paving, civil services and electric lighting at its City Deep Container Terminal in Johannesburg, claimed to be the largest dry or inland port in the world. Transnet’s refurbishment vision for the City Deep Terminal fitted Murray & Roberts Infrastructure to a tee from the outset. MATERIAL Murray & Roberts Infrastructure as part of the Construction Platform is a civils, roads and bulk earthworks contractor. As such its primary input materials into its products include cement, flue ash, aggregates, soil and water. Increasingly these input materials have either legal or financial restrictions placed upon them. As an added restriction, not all projects have these mate- rials, in quantity and quality, readily available from close markets. Finally an ever increasing number of clients who have Brownfield sites (existing but aged facilities) require Murray & Roberts Infrastructure to find innovative ways to recover used materials and feed them into the new product. As such Murray & Roberts Infrastructure and Murrays & Roberts Buildings, which have similar challenges with regard to green build- ings, have been developing innovative products at its Concrete Centre of Excellence (CCE) over the past few years that use large quantities of recycled product at exacting quality and performance standards. The major challenge has been to show clients that recycled materials are not substandard and will meet quality criteria and cost. Scope The specific scope of the City Deep Container Terminal project required the demolition and removal of +/-144 000 m 2 of existing concrete floor (250 mm thick), a 100 mm stabilised floor and 350 mm of on-site mine sand. This was then replaced with 300 mm of new layer works (150 mm G5 and 150 mm G3) and a 450 mm concrete pavement. The original job specification required the reuse of about 10 600 m 3 of old concrete as G5 for layerworks, after breaking it out and crushing it to a G5 specification. The remainder of the 25 400 m 3 generated from the demolition as well as the 64 800 m 3 (on site mine sand and stabilised layer) would then be disposed of at various landfill sites in the area. However, this was amended with the permission of Transnet, with the remaining 25 400 m 3 of removed old concrete and 64 800 m 3 of layer works combined to be reused wherever possible on site (layer works, backfill around structures) with an approved G5 classification. The remainder would be sold as a commercial G5 for reuse on other projects. In total 140 000 t of material was crushed to a G5 specifica- tion. Of that, 60 000 t was used on site while the remaining 80 000 t was sold for reuse as a commercial G5. >

Innovation Transnet required that the old concrete paving broken out of the site be recycled into the newproject. Murray & Roberts Infrastructure proposed crushing this material to produce a G5 foundation aggregate to be used as the supporting structure in the new pavement design whereupon the new concrete paving would be laid. This strategy allowed either company to maintain its sustainability and acceptable risk profile. In addition Murray & Roberts Infrastructure presented two innova- tive concrete designs. In addition to the high volume pulverised flue ash concrete (HVPAC) design, a several slabs of geopolymer concrete were poured for Transnet Capital Projects for long term evaluation at City Deep, a first for South Africa. Geopolymer concrete Geopolymers are a type of inorganic polymer that can be formed at room temperature by using industrial waste or by-products as source materials to form a solid binder that looks like and performs a similar function to Portland cement. Geopolymer binders can be used in appli- cations to fully or partially replace Portland cement with important environmental, technical and often cost benefits, including an 80% to 90% reduction in CO 2 emissions and improved resistance to fire and aggressive chemicals. High volume pulverised fly ash concrete The specification for the Transnet City Deep Container Terminal was a maximum of 35% Pulverised Fly Ash (PFA) replacement. This is consid- ered a high replacement of clinker/cement. The concrete used on this project used approximately 63% to 70% replacement of raw milled clinker with siliceous PFA, almost double to the maximum specified limit on most construction projects. Through the deeper understanding of advanced re-crystallisation (ARC) technology attained at the Murray & Roberts’ Concrete Centre of Excellence (CCE), Murray & Roberts Infrastructure understood the capa- bilities and limitations of high volume PFA substitution. Time and costs Murray & Roberts Infrastructure broke up and reused about 86% of the old worn concrete pavements at the City Deep Container Terminal,

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CONSTRUCTION WORLD FEBRUARY 2015