Offering both visual appeal and functional benefits, exposed aggregate concrete finishes are used across a wide range of applications, noted for their non-slip texture and attractive natural stone appearance. The growing use of surface retarders in South Africa is driving renewed interest in the finishes, says Chryso Southern Africa’s Michelle Fick.

“Exposed aggregate is no longer just a decorative finish; it’s being adopted across a wide range of applications from pavements and driveways to architectural facades and public infrastructure,” notes Fick. “The textured non-slip surface offers a safer option for high traffic zones, while the natural stone aesthetic enhances the visual appeal of buildings and outdoor spaces.”

The finish can also be used for preparing concrete surfaces that will receive a subsequent layer. The roughened texture created by the exposed aggregate allows for improved bonding with waterproofing membrane, screed or cladding, improving the durability and lifespan of the system.

Chryso Southern Africa offers surface retarder products designed to facilitate reliable, consistent exposure of the aggregate to the required depth – up to a maximum of 3 mm, aimed at ensuring a uniform and high-quality result. This is useful for specialist applicators who rely on precision and repeatability, particularly in large-scale or architecturally-sensitive projects.

“The simplicity of the application process is another advantage,” Fick explains. “After the concrete is poured, the surface retarder must be applied evenly before the concrete begins to set. Following a predetermined curing period the surface is washed with water, removing the top layer of cement paste and revealing the aggregate below. A final sealant is then applied to enhance the surface’s durability and finish.”

Sealants can be selected to suit different environments and project needs including internal and external use, UV resistance and finishes ranging from matte to high-gloss. This flexibility allows architects and contractors to customise the final appearance while ensuring long-term durability.

Chryso asserts that it was the first manufacturer to offer a mineral solvent-free water-based retarder designed to prevent soil and groundwater pollution during the cleaning of treated concrete. The product contains no toxic substances, is 85% biodegradable, classified as harmless and complies with EEC Directives 88/379 and 93/18.

Fick notes that the company’s surface retarders offer technical consistency and ease of use, adding: “Our retarders provide reliable performance even under variable temperature and humidity conditions, which is critical for projects with tight timelines and complex environmental demands.”