PRODUCTION CColoring oloring systems - Davis Colors

PRODUCTION

Coloring systems

Powder, liquid or granules? A method that’s right for every producer

By Nick Paris and Michael Chusid

Producers have more ways to color concrete overview of the leading coloring products and
than ever before. In addition to powdered processes available today.
pigments and liquid colors, new granulated
pigments are growing rapidly in popularity. A Color has increased in importance to many
wide selection of color handling and dispens- concrete producers. For example, the availabil-
ing systems is available, ranging from manual ity of permanent colors has contributed signif-
weighing and dosing to highly automated col- icantly to consumer acceptance of concrete
oring equipment. pavers, roof tiles and segmental retaining
units. In competitive markets, many ready-
Selecting the best system for a particular mix concrete and concrete block producers
concrete plant requires the producer to consid- report that they make more profit from value-
er many factors, including current and antici- added features like color than they do from the
pated demand for color; cost of pigments, dos- concrete or block itself. The increased variety
ing equipment, financing and labor; plant of coloring options has made it easier for pro-
design and technical factors; concrete mix ducers to take advantage of the growing
requirements; product line and marketing con- demand for colored products by reducing
siderations; individual preferences; and man- costs, making it easier to retrofit existing plants,
agement attitudes toward plant hygiene and and making coloring operations cleaner, more
quality control. This article provides an convenient and reliable.

Granule

Liquid

Powder

Coloring concrete

Manual versus inventory. Producers with a limited Color is a value-added feature for
product palette may require fewer hues concrete products. A wide range of
automated coloring while others may also require a premi- coloring systems are available to meet
um color or customized blends in their the needs of all concrete producers.
Before picking a pigment type or han- system. (Photo of Unilock Chicago, Auroara, Ill.)
dling system, a concrete producer
should first consider the level of An automation system is pro- Disintegrating bags with powdered
automation appropriate for a plant. grammed to meter and blend just the pigments are increasingly popular
While manual methods of adding pig- right amount of each of the basic colors among ready-mix producers. The pre-
ment will always have their place, the to produce the shade specified for a par- measured bags can be thrown into
cost of automation equipment has ticular batch. While a manual operation mixers without opening or pouring and
dropped during the past decade. can use just the basic colors, the time are a clean and convenient way to color
Increasingly, the capital investment for required to weigh multiple colors and ready-mix concrete.
automation equipment is offset by the potential for mistakes generally
reduced manpower and inventory makes it impractical. Another benefit of
requirements plus other benefits, such on-site blending is that a producer can
as a cleaner plant environment and readily reprogram a system to match a
improved product quality. special color upon customer request.
This becomes an important advantage
Color automation systems generally in competitive markets, especially for
include bulk storage, metering equip- architecturally specified products.
ment to weigh and (if required) blend
pigments, a means to transport pigment Powdered pigments
to a mixer, and computerized controls
to operate and monitor the system. The Most colored concrete, by far, is pro-
equipment price tag can range from duced using pigments in their powder
$20,000 or less to over $100,000 form. The basis for the high tint
depending on the type of system, capac- strength of powder pigments also caus-
ity, number of colors and mixers to be es their biggest drawback—dirtiness.
handled, cycle speed, flexibility, accura- The extremely fine, dust-like powders
cy and reliability. Equipment can be can be spread while opening and emp-
bought or leased directly from manu- tying sacks, by blow-back from the
facturers or sometimes be obtained mechanical action in a concrete mixer,
through pigment producers as part of a and by spills. Without rigorous atten-
purchase program. tion to cleanliness and cleanup, powder
pigments can coat a concrete producer's
The labor required to manually plant and equipment with various
handle pigments must be looked at shades of iron oxide dust. Iron oxide is
carefully. Some large-volume pigment not a hazardous material, but zealous
users who have converted from manu- environmental health and safety officers
al systems to automation report that have been known to look unkindly on
they have been able to eliminate a full- any kind of nuisance dust. A clean plant
time production position. While most makes it easier to attract and retain a top
concrete "color men" are conscientious quality work force and helps to reassure
in their work, human fallibility adds to a firm's customers of its commitment to
the effective cost of manual methods. quality.
Humans can make errors reading a
work ticket or weighing pigments by Powders are packaged in a wide
hand. A brief distraction can lead to variety of sack sizes ranging from one
colors being left out of an entire batch pound bags to 2,000-pound "super-
or added so late in a mixing cycle that sacks." Many pigment producers will
they may not disperse fully to produce also prepare customized "batch-sized"
the desired concrete color. People can bags for their ready-mix customers. In
make costly errors programming auto- the past few years, disintegrating bags
matic dispensers as well. The capabili- have become the standard packaging for
ties and work practices of the plant's ready-mix producers. Disintegrating
labor force should be considered when sacks have solved most of the ready-mix
choosing a coloring method. producer's concerns about cleanliness,
but are not compatible with other types
Automation frequently allows a of concrete operations. Disintegrating
concrete producer to reduce inventory bags can be tossed into a ready-mix
costs. Instead of maintaining a separate truck without opening or pouring. The
stock of pigment for each concrete bags travel to the center of the mix where
color, many automation systems require
that only four primary colors be kept in

Coloring concrete

This liquid coloring system was recently the paper gets soggy and disintegrates, duced by mixing powdered pigments in
installed at A-Block, a CMU producer in releasing pigments in the center of the water to make an aqueous dispersion or
Needles, Calif. Liquid colors are drawn mixer where dispersion occurs readily slurry. Some color manufacturers refer
out of drums through a hose or pipe that without producing significant amounts to their liquid pigments as "gels" due to
set on top of the drums. Four pumps of dust. the products' thixiotropic or viscous
(center of picture) are used, one for each consistency. Chemical dispersants and
of the basic iron oxide colors. The Powders require the fewest steps to stabilizers are added to some liquid col-
cylinder in left cabinet rests on a load manufacture and are the least expensive ors to help maintain the pigments in
cell to meter the amount of liquid colors type of pigment on a per-pound basis. suspension without settling. Despite
programmed into the control panel on Yet price-per-pound may not present these additives, concrete producers
right. Colors are then transported to the the total picture. Unless one is using a must pay attention to the shelf-life of
concrete mixer. disintegrating-type of bag, some waste liquid colors as agitation or remixing
inevitably occurs due to pigment that may be required if they sit unused for a
A four-color Granumat machine is used gets left in the bottom of the bag. prolonged period.
at Pavestone, Denver to color concrete Powdered pigments offer less flexibility
pavers. Pigments in supersacks flow into for use with automated pigment meter- A typical liquid coloring system
a color metering system located below ing systems; automated equipment includes pumps to extract colors from
the production floor. There, granular designed to handle powders is generally drums, a load-cell to weigh colors or a
pigments are weighed, blended and gravity fed and must be located above volumetric metering system, pumps
pneumatically transported to the the mixer. This makes it difficult to and hoses to convey pigments to a
concrete mixer. The very low amount of retrofit automated systems into existing mixer, and a computer to control color
dust in granular pigments helps keep the concrete plants. Using pigment blends blending and equipment operation.
plant clean and efficient. instead of the basic four colors with Because liquid colors can be pumped
powder pigment dispensers makes their over some distance, color inventory and
accuracy very acceptable. This is espe- metering can be located at the most
cially important in plants that produce convenient location and away from the
small batches or lightly pigmented concrete mixer. In addition, centrally
products where even a small variation controlled systems can be configured to
in pigment can result in a color shift in serve several concrete mixers.
the concrete.
The hydraulic properties liquid col-
Liquid colors ors allow for accurate metering and fast
production cycles. A "slow fill" option is
The primary advantage of liquid colors available with most liquid coloring sys-
over dry pigments include more accu- tems to allow for extremely accurate
rate metering with base pigments, clean- metering and is especially important for
er coloring operations, and more poten- measuring small quantities of pigment.
tial flexibility in plant layout. Certain At the end of each cycle, water is flushed
situations need to be considered before through the system to clean it and avoid
using a liquid coloring system. At some color contamination of subsequent
plants or during certain times, the aggre- batches and problems that might occur
gate contains all the moisture necessary if pigments are allowed to dry in the
for the entire mix, making liquid colors lines. This water, plus the water used to
unusable. In plants where color is used manufacture the liquid colors, must be
infrequently, the pigments in liquid col- figured into the batch water required for
ors can settle or dry out. In cold cli- a concrete mix.
mates, liquids can freeze in storage or
shipment unless kept in heated areas. Liquid coloring systems are most
frequently used by concrete product
Liquids cost more to manufacture manufacturers who consume a low to
than powders and cost more than either moderate volume of color or who have
powders or granules to ship due to the screw auger type continuous mixing
water added to the pigments. equipment.
Compared to granular pigment dis-
pensers, a single liquid dispenser may On-site slurry and
not be able to keep up with cycle times
at plants with multiple mixers or form- dry-wet systems
ing machines. Liquids are available in
the primary hues and preblended cus- There are two methods for manufactur-
tom colors, and are typically shipped in ing liquid colors on-site at a concrete
drums or other bulk containers. producer's facility. In the on-site slurry
system, a concrete producer manufac-
Liquid-based pigments are pro- tures liquid colors in bulk. In the "dry-
wet" system, dry-pigments are blended

Coloring concrete

Liquid colors, also called slurries, are in water on a batch-by-batch basis. Both ing, very low in dust, and disperse read-
manufactured by mixing powdered of these methods combine some of the ily upon being added to a concrete mix
pigment and dispersing agents in water features typically associated with both to develop full tint strength. These pig-
using high-shear blenders. dry powder and liquid coloring systems. ments have been successfully used in
On the plus side, they both allow the use over 300 concrete plants, including
The control panel for the Granumat of low-cost powder pigments plus the block, paver and retaining wall produc-
automated coloring system at Unilock flexibility of being able to locate coloring tion facilities around the world.
Chicago (background) is linked to the operations away from the concrete
plant’s control system. mixer. On the minus side, they still have The organic binder used in
most of the dusting concerns that come Brockhues-type granules dissolves in
The choice between manual and from handling dry pigments. water and disperses readily in any type
automated coloring systems depends, in of concrete mixer. A newer type of
part, on the concrete producer’s product In the on-site slurry process, a con- granular pigment uses an inorganic
line. Here, red and black batches of crete producer formulates liquid colors binder that does not dissolve in water. It
concrete mix together in the hopper in the same way a pigment manufactur- depends instead upon the shearing
above a paver machine to produce multi- er would. Large mixing and storage action of the aggregate to break down
colored concrete paver units. tanks and a scale are required, plus all the granules and may not achieve full
the equipment required to dispense liq- color development with certain con-
uid colors. The concrete producer takes crete mixes, types of mixers and batch-
full responsibility for quality control of ing sequences. Under optimum condi-
the liquid color and requires properly tions, inorganically bound granules will
trained personnel to blend colors and develop only 80 to 90 percent of the
assure consistency from batch to batch. tinting strength of an organically bound
Despite these limitations, on-site slurry granule or good powdered pigment.
can be a viable system for concrete pro-
ducers who use a large volume of color Granular pigments offer all the ben-
and prefer a liquid coloring system. efits of automation without many of the
limitations of other forms of automa-
In the dry-wet system, powdered tion. The pneumatic dispensing sys-
pigments are fed as required into a small tems offer very accurate metering and
mixing tank. The mixer is covered to fast production cycles, can serve multi-
limit dust problems and is equipped ple concrete mixers, and can be located
with a load cell to weigh the pigments as up to 180 feet from the concrete mixers.
they are added. Computer controlled They are the most compact form of pig-
meters dispense the required amounts ments available, saving about half the
of the primary colors and water. The volume of powders. Similarly, they can-
ingredients are then mixed, and upon a not freeze, are not limited by shelf life or
signal from the system, transported settlement problems, will not dry out in
with compressed air or pumped into the hoses, and can be used in mixes which
concrete mixer. A water spray washes can not accept additional water.
out the mixer bowl and is then forced
into the concrete batch to clean the In a typical installation, supersacks
hose. Due to the time required for these of granules are hung in a rack above a
operations, some dry-wet systems may color metering system. The computer-
not be able to cycle quickly enough to controlled metering system weighs out
use in plants with multiple concrete the required amount of each of the pri-
mixers. mary colors and drops the blended col-
ors into a pressure vessel. From there
Granular colors they are pneumatically transported to a
hopper above the concrete mixer. Upon
Granular pigments are the fastest grow- a signal from the concrete mixer, the
ing type of concrete coloring. The first pigments cascade into the mix and dis-
successful granular system was intro- perse throughout the concrete.
duced in 1989 by Brockhues Corp. and
is now marketed by Davis Colors. The Granules offer savings when com-
patented method uses an automated pared to liquid colors; since they con-
metering system and color granules tain no water, they cost less to ship and
made with an organic binding ingredi- have greater tint-strength on a pound-
ent which holds the pigment together for-pound basis. Granules are also used
during transport and then dissolves to in manual coloring operations where
enhance color development when they are selected over powders for their
mixed into concrete. The small, ease of use and cleanliness. They are
microbeads of pigment are free-flow- packaged in supersacks and 50 pound
bags.

Coloring concrete

Selecting the best system Nick Paris is Vice President of Coloring Basics
Marketing for Davis Colors, a leading
As we have seen, selecting a color- producer of powder concentrates, Regardless of the coloring process, additives com-
ing system for a concrete plant Hydrotint liquids and Granufin plying with ASTM C979–STANDARD SPECIFICATION
requires management to consider micro-granulated colors for concrete. FOR PIGMENTS should be used. This document
many factors. Before making a He can be reached at 323/269-7311 or establishes criteria for the alkali resistance, light
selection, concrete producers via email at [email protected]. resistance, water wettability, and other factors affect-
should visit the plants of other pro- ing the compatibility of pigments with other concrete
ducers who are using the coloring Michael Chusid is a Los Angeles- mix components. Pigment content in concrete is limit-
systems under consideration. based technical and marketing con- ed to 10 percent of the weight of the portland
Pigment and equipment manufac- sultant to building product manufac- cement, fly ash, and other cementitious material in
turers are also good sources of turers. the mix. Color saturation, the dosage level beyond
information, especially those who which additional pigment has no effect on the con-
offer a range of solutions and are References crete color, is nearly achieved at about six percent
not limited to just a single pigment dosage rate depending upon the type and color of
type or coloring system. "Manufacturing Colored Concrete pigment used. Many popular and economical subtle
Masonry," Beckett, Livesay and shades can be produced at dosage rates as low as
To select a pigment or equip- Rainey, Concrete Products, October one percent, To assure optimum tinting strength, pig-
ment supplier, look for a manufac- 1995 ments are milled to microscopic particle size, some-
turer that can provide a proven times only one-hundredth the diameter of a grain of
product and technical support. "Coloring Concrete - A Pleasure?" portland cement. These fine particles mix into and
Equipment suppliers should be able Jungk and Wölfert, Betonwerk + BFT bond with the cement paste which then coats the
to provide turn-key installation and Fertigteil-Technik, 1989. sand and coarse aggregate in the concrete.
rapid response when service or
spare parts are required. Pigment Powder, liquid and granular Iron oxides are the most widely used type of
suppliers should be willing to pigments provide concrete pigment; they are economical, durable, pose no sig-
develop color blends or formulas to producers with a wide range of nificant environmental or health hazard and are read-
match the producer's standard concrete coloring systems. ily available. In addition to naturally occurring iron
product line and special color oxide ores, synthetic iron oxides are also used.
matches. Pigment availability and Synthetic iron oxides provide greater tinting strength
delivery time must also be consid- and color or uniformity. Synthetic iron oxides come in
ered along with pricing. Use a pig- four "primary” colors: yellow, black and two different
ment manufacturer with rigorous reds (yellow and blue shade reds). Chromium oxide
quality control to assure uniformity produces green and cobalt is used for blue.
from batch to batch and year to Titanium dioxide can lighten a concrete color, but is
year. With the range of pigments seldom used because white portland cement
available today, there is a coloring obtains the same effect at a lower cost. The basic
system available to fit every con- pigment hues are blended to produce a wide spec-
crete producer's needs. trum of concrete colors.

In addition to pigment, concrete color is affected
by the color of cement, sand and aggregate, water-
cement ratio, surface texture, curing conditions, and
consistency of manufacturing and finishing opera-
tions. While integral colors are as durable as the con-
crete itself, the appearance of colored concrete can
shift over time due to staining, erosion of cement
paste from the concrete surface, or the natural yel-
lowing of concrete as it ages. With proper quality
control, modern concrete producers can reliably
achieve a high degree of color consistency from
batch to batch. However, it is important that end
users understand that, as with any natural material,
the appearance of concrete can vary whether col-
ored or not.

While two pigment shipments may look the same
to the untrained observer, differences from batch to
batch, such as variations in tinting strength, can
affect the color of a concrete product. Since few
concrete producers have the fully equipped color
laboratory necessary to measure the differences,
they are well advised to consider the color manufac-
turer's reputation and quality control program.

REPRINTED FROM CONCRETE PRODUCTS, JANUARY 1998

CONCRETE COLORS

Colors for block & pavers. It’s what we do.

Color is an integral part of your business.
At Davis Colors it’s our only business.

Above: Our powder concentrates, Granufin® What does this mean to you? First, you can
low dust granules and Hydrotint ® liquids expect powder, liquid or granulated pigments
with unmatched color, purity and intensity.
are manufactured to exceed the most stringent Second, you’ll find Davis Colors leading the way
quality standards in our industry. in the development of efficient and innovative
pigment metering systems. And third, you’ll
We also offer state of the art, turn-key dispensing benefit from a level of dedicated and responsive
systems and a variety of customer service not found anywhere else.
efficient product
packaging Since 1952 Davis Colors has concentrated on
options. colors for block, pavers and a variety of concrete
products. This singular focus has enabled us to
provide our customers with the best products
and service available. After all, it’s all we do.

Above: To meet Tel 800-800-6856 Fax 323-269-1053
the growing demand for www.daviscolors.com
Granufin® granulated colors, we have just
completed a new, seven story ©1997 Davis Colors all rights reserved

manufacturing facility.
Located in Maryland, Granufin®
production in the U.S. will begin January 1998.