Use of Color Pigments in Precast Buildings

Introduction

The use of color pigments in precast buildings has been gaining popularity in recent years. This trend is driven by the desire for more aesthetically pleasing and distinctive architectural designs. Colored concrete, achieved through the addition of pigments, offers a durable and cost-effective solution for enhancing the visual appeal of precast structures.

Pigments, which can be natural or synthetic, organic or inorganic, are added to the concrete during the batching process. This results in a color that becomes an integral part of the concrete, offering hues more stable than paint. The use of pigments in concrete has been prevalent for about a century and is popular for use in architectural building panels, infrastructure projects, bridges, paving, and street furniture.

However, it’s important to note that pigments should always be at most 10% of the weight of cement. Higher doses of pigments usually do not improve color but may reduce strength.

This article will delve into the use of color pigments in precast buildings, exploring various case studies, advantages and disadvantages, costs, and future trends in this innovative field.

Colored Pigments Used in Concrete

Pigments are fine dry powder slurry or aqueous suspensions that are added to the concrete ingredients to produce colors other than the normal grey color. They can be natural or synthetic, organic or inorganic. Synthetic pigments are more stable and colorfast. Here are some examples of pigments:

1. Iron Oxide: These pigments come in black, brown, red, and yellow colors of varying particle size and shape. They are widely utilized but can be costly.
2. Chromix Oxide: This pigment is used to attain a green color.
3. Titanium Dioxide: This pigment is used for a white color.
4. Phthalocyanine: These pigments come in blue and green colors.

Fig 1: Cement Color Pigments

Courtesy: Gardeners Dream

Pigments are added during batching as a liquid or finely divided colored inert powder. The maximum pigment dosage is equal to or less than 10% of the mass of cement. However, the normal range is between 3% and 6%. When two types of pigments are blended to achieve a certain color, the same maximum dosage of single pigments applies to the total amount of both pigments used.

The color of the pigment becomes an integral part of the concrete. Pigments decrease concrete strength, but the maximum allowable dosage rate shall not cause a strength decline of less than 90% of unpigmented concrete strength at 28 days. When a maximum of 10% of pigment dosage is used, it should neither accelerate the initial or final set by more than 1 hour nor retard the initial or final set by more than 1.5 hours, compared with an unpigmented concrete control mixture. Pigments influence concrete air content, but they shall not change the air content by more than 1.0%, as compared to the unpigmented concrete mixture, when a maximum of 10% pigment is added.

Explore Leading Brands for Colored Concrete Pigments

Here are some brands that sell pigments for colored concrete:

Indian Brands:

1. Kings International: They offer a variety of cement and concrete colors.
2. Tanishka Enterprises: They provide Iron Oxide Red Concrete Color T-445.
3. Lotus Traders: They offer Microcame Powder Iron Oxide color for construction.
4. Golden Hydraulic Industries: They offer Iron Oxide Colors for Paver Block Making and Tile Making.
5. SMS Industries: They offer Powder Type Cement Concrete Colors for Paver block making.

Global Brands:

1. LANXESS: They offer Bayferrox iron oxide pigments, which have been used for decades in the coloration of cementitious and bituminous construction, such as cast in-situ concrete, pre-cast concrete components, concrete roofing tiles, or pavers.
2. Cheng, Surecrete, Interstar, and CX brands: These brands offer a variety of concrete color pigments, including stains and dry pigments.
3. Cement Colors: This brand offers multiple colors of raw pigment for concrete.

Colored Concrete Innovation & Long-Term Durability

Innovative ways to color concrete include:

1. Using Integral Dye: Integral dye is combined in concrete in the mixer so it’s one consistent color when poured. The dye is transferred to a plain paper bag and then tossed into the mixer because the paper will dissolve in the cement. The consistency of the concrete is checked before adding the dye, as it can cause the concrete to thicken. The dye bag is inserted into the concrete mixer and mixed for about 15 minutes at max mixing speed.
2. Staining Concrete: Concrete stains are brushed on the surface of concrete to change its color. The surface of the concrete is cleaned thoroughly before applying the stain.
3. Thermochromatic Pigment and Wire Heating Technology: By incorporating thermochromatic pigment and wire heating technology into a standard concrete mix, the color of concrete can be changed.

With increasing the specific surface area of pigment, the flow of fresh concrete decreases, which affects workability. However, this characteristic feature causes a slightly higher density of concrete matrix, which results in better durability.

Case Study Of Projects Which Have Used Colored Concrete

Sure, here are brief descriptions of each case:

1. Centro Cultural Comunitario Teotitlán del Valle by PRODUCTORA: This cultural center in Mexico used black pigmented concrete to create a contrast between the dark exterior and the white interior. The center exhibits the archeological and textile wealth of Teotitlán del Valle.

Fig 2: Centro Cultural Comunitario Teotitlán del Valle

Courtesy: ArchDaily

1. Textilmacher by Tillicharchitektur: Located in an industrial zone in Munich, this building hosts production and office spaces for a textile company. The anthracite-pigmented concrete used changes its character depending on various factors like season, time of day, and light incidence.

Fig 3: Textilmacher

Courtesy: ArchDaily

1. Victorian home in Hackney: This Victorian home was given a rose-hued extension with a colored concrete wall (tinted with a powered dye). The colored concrete wall creates a seamless transition between the interior and the exterior.

Fig 4: Victorian home

Courtesy: Hamptons

1. Lebanon County Conservation District: The conservation district designed a unique two-color pervious picnic pad using colored concrete. The pad functions as a decorative area for staff lunches while demonstrating that pervious concrete can be aesthetically pleasing.

Advantages and Disadvantages of Use of Pigments in Concrete

Pigments are added to the concrete ingredients during batching as a liquid or finely divided colored inert powder to produce colors other than the normal grey color. The color of pigment becomes an integral part of the concrete.

Advantages:

1. Aesthetic Appeal: Pigments can be used to create a wide range of colors, enhancing the aesthetic appeal of the concrete.
2. Durability: The color from pigments is integral to the concrete, meaning it won’t fade or peel off over time.
3. UV Resistance: Most pigments are UV resistant so that they won’t fade in sunlight.

Disadvantages:

1. Strength Reduction: Pigments can decrease the strength of concrete, but this is usually insignificant if the maximum allowable dosage rate is not exceeded. According to ASTM C 979-10, the maximum pigment dosage is equal to or less than 10% mass of cement. However, the normal range is between 3% and 6%. When two types of pigments are blended to achieve a certain color, the same maximum dosage of single pigments applies to the total amount of both pigments used.
2. Limited Use: Pigments can only be used when installing new concrete.
3. Cost: The use of pigments can increase the cost of concrete.

Cost Breakdown: Concrete Pigment Pricing

The cost of pigments for concrete can vary widely depending on the type, brand, and quantity. Here are some approximate costs based on the information available:

1. Cement & Concrete Colors: These are priced at approximately ₹100 per Kg.
2. Iron Oxide Red Concrete Color T-445: This product by Tata Pigment is priced at approximately ₹125 per Kg.
3. Microcame Powder Iron Oxide color: This product by Lotus Traders is used for construction and is priced at approximately ₹6,250 per Bag.
4. Powder Type Cement Concrete Colors: These are used for making paver blocks and are priced at approximately ₹125 per Kg.

Please note that these prices are in Indian Rupees (INR). As per the exchange rate on October 19, 2023, 1 USD is equivalent to 83.25 INR, so you can convert these prices to USD accordingly. These are approximate costs, and the actual cost can vary based on various factors, such as the supplier, location, and quantity purchased. It’s always a good idea to get quotes from multiple suppliers before making a purchase.

Can We Avoid Painting Of Concrete If We Use Pigmented Concrete?

Yes, using pigmented concrete can help avoid the need for painting. Pigments are added to the concrete during the batching process, resulting in a color that becomes an integral part of the concrete. This means the color won’t fade or peel off over time like paint can. However, it’s important to note that while pigmented concrete can provide a wide range of colors, it may not be able to provide the same variety of finishes and textures that paint can. Also, once the color is mixed into the concrete, it cannot be changed like paint can. So, if you’re sure about the color and don’t plan on changing it, pigmented concrete could be a good option.

Conclusion

The use of color pigments in precast buildings offers a versatile and durable solution for achieving a wide range of aesthetic effects in concrete. Pigments, whether natural or synthetic, can be seamlessly integrated into the concrete mixture, resulting in colors that won’t fade or peel over time. While they may slightly reduce concrete strength, this effect is typically negligible within the recommended dosage range. Additionally, the cost of pigments can vary, but they provide a cost-effective alternative to post-application painting.

Innovative approaches like integral dye and concrete staining offer even more design possibilities and the inclusion of thermochromatic pigments and wire-heating technology can create dynamic color changes. These techniques are valuable for architectural and design projects seeking to make a visual impact.

Case studies demonstrate the successful application of colored concrete in various architectural contexts, enhancing the aesthetic appeal and character of the buildings. Overall, the advantages of using pigments in concrete, including durability and UV resistance, outweigh the minor strength reduction they may cause. For those looking to avoid the need for future painting and ensure long-lasting color, pigmented concrete presents a compelling solution. However, it’s important to carefully consider the specific needs and design goals of each project to determine the most suitable approach to achieving colored concrete results.