A plasticiser is added to mortar or concrete to make the mix more workable without increasing the water content. It introduces tiny air pockets that help the mix spread and apply more smoothly. Reducing water content also means less shrinkage as the mix cures, which lowers the risk of cracking. Plasticisers are widely used in bricklaying, rendering and pointing.
Cement Additives and Dyes for Mortar, Concrete and Render
Additives change what a cement or mortar mix can do. MacBlair stocks a range of cement and mortar additives covering the most common site needs: plasticisers to improve workability, waterproofers to reduce water penetration in renders and screeds, frost proofers for cold-weather work, and accelerators or retarders to adjust setting times. Each product targets a specific problem, so the right choice depends on the conditions and the application.
Cement dyes are added directly to the mix to give mortar, concrete, render or pointing a consistent, lasting colour. Available in powder and liquid forms, they suit a wide range of applications including:
- Patio and driveway concrete, where a coloured finish adds visual interest
- Pointing and brickwork mortar, to match or contrast with existing stonework
- Render and screeds, for a consistent tone across larger surfaces
- Garden features and decorative concrete work
Getting colour consistency across multiple batches comes down to measuring accurately. Weigh both the dye and cement rather than gauging by volume, and keep the ratio identical each time. For a mortar project such as tile grout or jointing work, dye powder should be blended thoroughly into the dry mix before water is added. Liquid dyes are often easier to measure consistently and disperse cleanly through the mix.
These additives sit within the broader chemicals range at MacBlair, which also covers damp-proofing and waterproofing treatments for walls and floors. For bonding and priming applications before laying, PVA adhesive is a useful companion product. Order online for delivery across Northern Ireland or collect from a local MacBlair branch.
Additive and Dye's FAQ's
For powder dyes, blend the dye thoroughly into the dry sand and cement before adding any water. This gives an even distribution of colour throughout the mix. Measure by weight rather than volume, and use the same ratio for every batch to keep the colour consistent across the job. Liquid dyes are added with the gauging water and are often easier to measure accurately.
No. Cement dyes are pigment-based colourants and, when used at the correct dosage, they do not affect the structural properties of the mix. The colour goes through the full depth of the material rather than sitting on the surface, so it will not flake or peel over time. Always follow the manufacturer's recommended dosage to avoid using too much.
Frost proofers are useful when working in cold conditions, typically below 5°C, as they help protect the mix during the early curing stages before it has gained sufficient strength. Accelerators speed up the setting and hardening process, which can be helpful in cooler weather or when a faster turnaround is needed. If you are laying brickwork, rendering or pointing in autumn or winter in Northern Ireland, a frost proofer or combined frost proofer and hardener is worth having on site.
This is a common shortcut but it is not recommended. Washing-up liquid can introduce too many air voids into the mix, which weakens the concrete or mortar once it has hardened. It can also affect long-term durability. A proper mortar plasticiser is inexpensive and gives far more predictable results, so it is worth using the correct product rather than a substitute.