Iron-oxide and other inorganic pigments give concrete colour that lasts for decades, provided the mix, dosing and curing are controlled.
Dose on cement weight
Pigment dosage is expressed as a percentage of cement weight, not of the whole mix. Colour strength rises quickly up to about 5 percent and then flattens; beyond the saturation point extra pigment adds cost without adding colour. Pigments for concrete are specified to EN 12878 and ASTM C979.
Consistency is about the mix, not only the pigment
Cement colour, sand colour, water-to-cement ratio and curing all change the final shade. Keep raw materials from the same sources, control water closely and cure products the same way every day. Granules and liquid slurries dose more accurately than powders and remove dust at the mixer.
Efflorescence
White deposits on coloured concrete come from calcium hydroxide reaching the surface and carbonating. They are more visible on dark colours. Lower water-to-cement ratios, good compaction, proper curing and, where needed, efflorescence-control admixtures reduce the effect.
Quick checks for a new colour
- Make test pieces with your own cement and aggregates
- Compare after full curing and drying, not when wet
- Keep a reference sample from each production day
