Schedule placing and finishing work to minimize exposure to hot sun before curing materials can be applied. Postpone colour concreting until windy conditions pass. Don't place concrete if rain, snow or frost is in the forecast.
Take note of surrounding. Areas that are shaded will cure differently than areas in the sun.
Dark or black-coloured concrete will absorb additional heat during sunny, dry conditions. Provide extra curing protection to prevent thermal cracking.
Do not pour when temperature is below 10°C
Concrete from one supplier can cure to different colours if pouring or curing takes place under different climates. Concrete temperature should be maintained between 15° to 25° C in most applications for proper hardening to occur during the crucial first days.
Temperature also affects the amount of water required to make the mix workable. In cool temperatures, it takes less water to get a workable mix. Variations in water-cement ratio have a significant effect on concrete colour. Plasticizer is required to change slump after design water slump is achieved.
Colours shown on the colour palettes are approximate. Concrete colours are altered by many factors, including cement colour, slump, finishing practices, and curing method. Using the contemplated materials and construction techniques representative samples should be cast for approval, especially when colour matching is important.
Allow concrete to dry completely before applying sealer ( approx 30 days)
Concrete colour will continue to lighten until it is completely cured.
The optimal dose of pigment ranges from 2% to 7% based on the weight of the cementitious materials. The colour saturation point is 10%. Higher doses may significantly degrade the durability of the finished product and will not enhance the colour further.
Sub-grade must be uniformly graded, compacted, and dampened. Do not place concrete on sub-grade with standing water, ice, frost or muddy areas.
Add a 50-75mm layer of sand, gravel, or crushed stone and compact uniformly with vibrating equipment.
Grading should be sloped so that water drains away from slab.
If a vapour barrier is used, a layer of uniformly damp sand should be placed over the barrier to minimize risk of cracking. Overlap sheets and tape any holes.
Forms and reinforcement: For slabs, formwork should be positioned to achieve slab thickness. American Concrete Institute (ACI) standards for reinforcement and joint placement should be followed to control cracking.
Prevent segregation of mix ingredients. Place concrete nears its final location and move it with shovels. Don't move by vibrating.
Water added at job-site to mixer or pumps will cause colour to change. Change slump with plasticizer only. Don't use wet finishing tools or brooms. Avoid sprinkling ("blessing") water on the surface. A colour change will be visible after curing.
Concrete minimum thickness must be consistent and appropriate for end use
If vapor barrier is used, overlap sheets and tape over holes in barrier. Place a 3" (75mm) layer of granular self-draining compactable fill over the barrier to minimize shrinkage cracking.
Avoid several small pours and pouring on different days
Avoid wet coverings, plastic sheeting, water-proof paper or liquid membrane curing compounds
Protect adjacent slabs and structures from splatters with plastic sheets.
Consistency in finishing is mandatory for quality coloured concrete.
Bull float after striking off the slab. Skip jitterbugging unless slump is <25mm. To reduce discolouration use wood bull floats and darbies, not magnesium when possible.
Wait for bleed water "sheen" to disappear before troweling. Do not trowel bleed water into the surface.
Do not over trowel or start troweling late. This leads to burns and dark spots.
Do not sprinkle the surface with cement or grey hardeners.
Don't fog the coloured concrete with water or add water to tools or brooms. Adding water causes the surface to pale or discolour.
A broom, rotary or textured finish will produce optimum colour uniformity. A super-hard, dark, slippery-smooth finish is made by extended troweling. Trowel with care!! The potential for discolouration (darkening) rises as troweling time increases.
Late or hard troweling and edging causes "burns" or dark spots
Spacing and timing of joints/saw cuts is critical
Rotary, dry-broom, pattern stamped or rough finishes usually cure more even-coloured than smooth-troweled finishes
Curing is one of the most important and often neglected aspects of quality concrete construction. Uneven curing = uneven drying = uneven colour. Poor curing contributes to shrinkage cracks, dusting and surface deterioration.
Apply a curing compound as soon as the surface will not be damaged by the application. (Salt finish is an exception.) Note: Using sodium silicate curing compounds can cause discolouration.
If saw cutting is used for control joints, it should take place before application of curing materials. Thoroughly rinse all cutting residues off the surface to prevent stains.
Apply a curing compound formulated for coloured concrete. Ask your local supplier.
Curing with water sprinkling, membranes, paper, sodium silicate-hardeners, and non-approved compounds can cause discolouration. If water is used to cure, a lighter colour is likely; the water must be clean, free of salts.
We always recommend the use of a powered airless sprayer to apply cure, which will produce a uniform and consistent application of the material.
Wood and other objects left on curing concrete cause discolouration.
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