Innovative concrete the solution for on-time repairs to M2 motorway
Monday 4 November saw Johannesburg motorists immensely relieved to see the end of widespread congestion after the closure of the vital M2 motorway over a year ago. The decision to close the route, in the interest of users’ safety, was made when the engineers determined that concrete structural sections of the aged motorway had severely deteriorated, and instigated an urgent Bridges Rehabilitation Project. Lafarge South Africa played a key role in ensuring high-quality, durable repairs by supplying innovative ready-mixed concretes.
Lafarge South Africa (Lafarge) is a member of the LafargeHolcim Group, a world leader in building materials and solutions. The company provides innovative solutions and high-tech cement and concrete materials for building sustainable infrastructure. The group has advanced research and development facilities that meet the needs of communities today and anticipate their future needs.
The deterioration of bridges on the motorway built in the 1960s, in particular the Selby Bridge, was largely due to alkali-silica reaction (ASR) in the materials used, causing swelling and cracking in the concrete and the subsequent ingress of moisture. Casting major replacement concrete sections presented construction challenges because of the heavily reinforced deep structural sections involved. A high density of reinforcing makes compacting difficult and laborious, adding to the time pressures associated with such a high-profile project. The client’s demanding durability specifications also ruled out the use of standard concrete mixes.
Unique global brands
The solution was provided by the LafargeHolcim Global Brands, a range of technically advanced products that have the same specification throughout the world with top-quality and guaranteed identical performance. They offer solutions specifically adapted and tested in the local market to reflect South African expertise.
Agilia™, a self-compacting ready-mixed concrete, was used for the bridge reconstruction works. The innovative formulation of this Global Brand product achieves an optimum balance between fluidity and stability to achieve better productivity, high strength and durability, as well as exceptional aesthetic finishes.
| Lafarge Agilia™ was the solution to the concrete repairs for the challenging M2 Motorway repairs |
The Lafarge Wynberg Readymix plant, with contingency backup provided by Cleveland, supplied over 1,000 m3 of Lafarge Agilia™Verticalfor casting heavily reinforced or highly congested sections of the bridge.
All-round benefits
The diameter and depth of each column made it clear that consolidating conventional concrete would be a significant challenge. Agilia™ allowed structures to be cast with certainty that the concrete would be soundly consolidated and reinforcement completely encased. There were sections where the density of reinforcement prohibited a poker vibrator from penetrating to an effective depth. Because compaction of concrete was not a necessary additional task, placement could proceed at a faster pace. Although not a contractual requirement, there was also a notable reduction in construction noise.
Agilia™ comfortably exceeded the minimum strength specification of 45 MPa, while the cement extenders and aggregates used in the formulation gave enhanced durability and minimised potential ASR problems.
Focusing on the contractor’s needs
With major structural works on the bridges finished and the contract completion deadline approaching, time was critical for the contractor, still having to repair various smaller sections of the motorway.
“We needed to have a concrete that could be transported and handled in the same way as conventional ready-mixed concrete, but would guarantee strength development when it optimally suited the contractor’s programme,” said Darren Jacobs, Technical Global Brands Manager of Lafarge South Africa. “This meant wanting to effect the repair far quicker than could be achieved with a normal concrete mix. Our innovative Chronolia™, another LafargeHolcim Global Brand product, was the solution to these seemingly contradictory requirements.”
The range of Lafarge Chronolia™ grades has the same workability as conventional ready-mixed concrete and can be used on all construction site applications. The formulations give at least two hours of slump retention followed by the selected rapid strength gain. For the motorway repair, Lafarge readily met the client’s stipulation of a minimum strength of 25 MPa guaranteed at 24 hours.
The high early strength of Chronolia™, makes it an ideal solution for repairing road surfaces and civil engineering structures, enabling them to be brought back into service with minimal disruption to users.
“Offering Lafarge’s innovative ready-mixed concrete solutions to address the huge challenges in this vital motorway project made a significant contribution to the successful on-time delivery of the rehabilitated structural works,” concludes Jacobs.
More information from Natalie Johnson, Tel: +27(0)11 657 2320 / email: Natalie.johnson@lafargeholcim.com / www.lafarge.co.za / www.lafargeholcim.com
Caption for pic 1945: Official opening of M2 Motorway, cutting the ribbon are JRA board chairperson Sipho Tshabalala, Prince Mangosuthu Buthelezi, Gauteng Premier David Makhura, City of Johannesburg Mayor Herman Mashaba, MMC for Transport councillor Nonhlanhla Makhuba and the JRA acting MD, Siyabonga Nodu. Photo: Southern Courier.
