CATHAY Iron Oxide Pigments

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An Introduction to Coloured Concrete

Cathay Pigments Group Colouring Your World

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Coloured Concrete Products COLOURMIX

Concrete roof tiles Ready-mixed concrete Clay roof tiles & bricks Interlocking concrete pavers Architectural masonry blocks & bricks Segmented retaining walls & garden units Patio blocks Asphalt roofing shingles & granules Asphalt pavements & roads Stucco Grouts & mortars

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Product range by Cathay

FERROTINT range of powder pigments COLOURMIX range of powder pigments FLOWTINT range of free-flowing pigments CATHAYGRAN range of granular pigments

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ASTM C979 Compatible

Standards for Pigmenting Concrete Product

Synthetic & Natural Iron Oxides Chromium Oxide Cobalt Blue Titanium Dioxides Iron Oxides, Chromium Oxides, Cobalt Blue and Titanium Dioxide

are inert and possess excellent resistant to chemical or physical attacks such as sunlight, moisture, alkalis and weak acids. They are excellent UV stable and UV resistant.

Iron Oxides – Permanent Colours Cave dwellers used natural ochre and hematite for cave and cliff drawings 5,000-10,000 yearsago (Romans, Greeks and Egyptians) and Pigments are available in powder, Free Flow Powder and liquid Slurry

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Standards for Pigmenting Concrete Product

USA : ASTM C979-82 (Re-approved 1993) Standard specifications for integrally coloured concrete

Europe : EN12878 (June 1999) Pigments for the coloring of building materials based on cement and/or lime -

Specifications and methods of test (adopted by 19 European countries - supersede BS1014)

Desirable properties of pigments: Water wettable, but not soluble Alkali resistant Curing stability Light fastness Low sulfates

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Factors Affecting Concrete Colours

1. Raw Materials Pigment – the colour component Cement Aggregates Water Admixtures

2. Processing Conditions Mixing efficiency & time Water-to-cement ratio Curing conditions

3. Curing Methods4. Weathering

Getting The Right Mix

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Pigment Loadings

Typically 0.5% to 10% by weight of cement for different colour intensity Pigment saturation level generally occurs between 8-10% by weight of cement Tints and pastels require lower pigment loading Brighter colours require higher pigment loading Tints, pastels and bright colours require white cement & lighter/whiter aggregate Raw

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Pigment Loadings

Typically 0.5% to 10% by weight of cement for different color intensity Pigment saturation level generally occurs between 5-8% by weight of cement

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Colours of the Cement

Different type / colour of cements give different concrete colors “Lighter the cement colour shade, the brighter & cleaner the concrete colour results”

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Types of Aggregates

Coarse aggregates : gravel, crushed stone, pumice, or limestone

Fine aggregates : silica sand, crushed rock, blended stone sand

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Effects of Aggregate on Concrete Colours

Different type/colour of aggregate give different concrete colours

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Effect of Water-Cement Ratio

Different water-cement ratio give different concrete colors

“The higher the water-cement ratio, the lighter the concrete appears”

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Effect of Admixtures on Concrete Colours

Air-Entrainer for Durability normally makes colour slightly lighter

Accelerator to accelerate set time and strength development normally makes colour slightly darker

Interactions between admixtures Different water-cement ratio give different concrete colors

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Concrete Design Mixes

Typical Design Mix for Concrete Paving & Walling Blocks

Well graded aggregate comprising : 4-6mm Gravel or Crushed Stone 33% Sand 67% Aggregate to Cement ratio 5-6 : 1 Pigment loading on weight of cement 2-5% Water to Cement ratio 0.35 – 0.40 : 1

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Process Conditions

Mixing Time Introduction of pigments should always be at the same time in the batching sequence Pigments should be mixed at a constant specific time from batch-to-batch When using lightweight aggregates a pre-wet should be employed before introducing

pigments (and cement) “Longer mixing time, generally the brighter the colour result”

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Process Conditions

Water-to-cement Ratio Higher water/cement ratio, the lighter the colour result Lower water/cement ratio, the darker the colour result Higher water/cement ratio, the higher chance of

efflorescence due to excess water in the mix Water-to-cement ratio affects strength and colour results

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Process Conditions

Curing: A balance of time and temperature The higher the temperature, the smaller the silicate crystals, the

lighter the colour result The higher steam pressure, the lighter the colour result The shorter pre-set time, the lighter the colour result

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Effects of Weathering on Concrete Colours

Efflorescence (white deposit) Primary or Secondary Temporary Does not affect product performance Proper cleaning methods Generally disappears over time Does not affect strength or durability

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Efflorescence Control

Use low free-lime cement (BS standard on CaO content 3%, acceptable 4% max) Right design mix to produce watertight concrete Use water washed aggregates to reduce free lime content Thoroughly compacting the mix Proper curing - good circulation, consistent temperature... Store coloured concrete products under shades / covers to reduce rate of water

evaporation Add waterproofing admixture or sealant

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Effects of Weathering on Concrete Colours

CATHAY INDUSTRIES GROUP

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