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 Lafarge Agilia™ was the solution to the concrete repairs for the challenging M2
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.
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: [email protected]
/ 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.
