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CONSTRUCTION WORLD
MARCH
2014
Lanxess Inorganic Pigments –
based in Germany – is one of the
largest pigment suppliers to the
global
construction
industry.
Chryso Southern Africa is the sole distributor
of Lanxess inorganic iron oxide pigments
for the South African construction industry
and has a colour laboratory in Jet Park
that can measure the colour strengths
of pigmentation, and provide customers
with specifications to colour-match avail-
able concrete masonry production lines at
competitive rates
Medelin’s 12 000 m
2
Plaza de la Libertad
features two towers (24 and 17-storeys
high) resembling tall tree trunks, designed
to blend in with the surrounding forest’s
trees and their trunks and barks. The design
concept of architect and interior designer,
Alejandro Toro Posada – which liberally
features concrete coloured with Bayferrox
pigments to add natural inspiration – also
employs the building’s wings as branching
structures emanating from the giant ‘trees’.
The structural elements of Plaza de
la Libertad are based on a temperature
-regulating and extremely weather resistant
concrete coloured with 60 metric tons of
Bayferrox 918 LOM yellow pigments in
the main building, and seven metric tons
Bayferrox 130 M (red) and 318 M (black)
pigments in the auditorium. A major
benefit of using integrally coloured con-
crete is that the façade will require no
follow-up maintenance.
“Furthermore, the façades have been
designed to conserve resources, reducing
conventional air conditioning and lighting
costs by around 40%,” adds designer Posada.
The avant-garde building accommo-
dates government institutions, a business
hotel, TV studios, businesses, cultural centre,
open-air theatre and exhibition halls.
Described as a ‘place of expressive
power’, it has won top prize in a major
international competition organised by the
National Association of Architects.
Hannes Engelbrecht, Chryso S.A. busi-
ness manager: concrete aesthetics, says
PROJECTS AND CONTRACTS
CREATING CONCRETE
‘TREE TRUNKS’
A range of Bayferrox
pigments, produced
by Lanxess Inorganic
Pigments, was extensively
used in the design and
construction of Plaza
de la Libertad, a new
landmark and iconic
structure in Medelin,
central Colombia.
there are some vital factors to consider when
producing pigmented concrete:
• Cement: Portland cement can vary
significantly in colour – from light to dark
grey. This change in colour can influence
the final colour of pigmented concrete.
“That is why it is important to use the
same cement throughout. The higher the
cement content, the more intense the
colour,” Engelbrecht explains.
• Aggregates: The colour of aggregates
also influences the ultimate colour so
it is important to ensure that the entire
surface area of the aggregate is coated
with the pigmented cement paste for
colour uniformity.
• Mixing water: Water dilutes the colour
of the pigments in the mix and excess
water evaporates from concrete, leaving
behind pores that scatter incidental light
and lighten the colour of the pigment.
• Formwork: The type, colour and
condition of formwork can influence
surface colour. Formwork with different
rates of absorption will create surfaces
with different colour shades.
• Dispersion: The pigment must be
mixed with the aggregate before
the cement is added.
• Temperature during drying: In higher
temperatures, fine crystals develop
in the cement matrix and determine
how the light that falls on the concrete
is scattered. Smaller crystals produce
lighter pigment.
• Efflorescence: Admixtures with high
levels of calcium chloride can cause
primary efflorescence.
All Bayferrox pigments are UV-stable and
comply with quality standards EN 878 (the
use of pigments for colouring building mate-
rials), and ASTM C979 (pigments for integrally
coloured concrete), and carry the CE quality
mark on their packaging. Lanxess operates
from sites in Germany, Brazil and China, as
well as additional mixing and milling plants
in Australia, China, Spain, the UK and USA.
ABOVE AND BELOW:
Two views of the imposing
twin-towered Plaza de la Libertad in Colombia
which, through the use of concrete coloured
with Bayferrox pigments, shows ‘human kind in
harmony with the environment’.
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