A chemical concrete additive causes impermeable crystals to grow inside the concrete and seal cracks, pores and capillaries, preventing liquids from penetrating the concrete. This nontoxic additive can be used to seal concrete structures in potable water systems and in more aggressive applications, such as sewage treatment and mining processing applications, says local reseller Penetron South Africa civil engineer and technical manager Gerhard Botha.

Green Building Council five-star green-rated Penetron Admix is added to concrete at the time of batching, while Penetron Slurry is applied to existing structurally sound concrete sur- faces, and increases the concrete’s compressive strength by 7% to 10%.

Penetron consists of Portland cement, fine treated silica sand and various active and proprietary chemicals.

“When applied to a concrete surface, the active silica components react with moisture and calcium hydroxide to form an insoluble silica crystalline structure. “These crystals have been proven to grow against 160 m of hydrostatic pressure into the pores, capillaries and minor shrinkage cracks in the concrete, which prevent any liquid ingress,” he says.

Penetron treated concrete will resist constant chemical environments with an acidity as low as pH 3 or an alkalinity as high as pH 11 and resist sporadic exposure to pH levels ranging from pH 2 to pH 12, Botha notes.

The company’s quality control measures include a new fourth-generation admixture containing a tracing agent, clearly visible in fresh concrete. The presence of the tracing agent can be detected, even years after construction.

“Penetron South Africa provides a free on-site supervision service and on-site technical support. We deliver construction details to our clients in computer-aided design format to help their professional teams build durable, maintenance-free and cost- effective structures for their clients.”

The additive meets US National Science Foundation 61 specifications and is certified for use in potable water applications. The additive can be used in sewage and water-treatment plants, secondary containment structures, tunnels and subway systems, underground vaults, foundations and retaining walls, as well as in precast, cast-in-place and shotcrete applications.

“Despite being waterproof, the crystalline structure enables the concrete to breathe after treatment with the additive.”

Penetron Admix has been used in more than 500 000 m3 of concrete placed in commercial roofing, mineral processing, sugar milling and water containment applications in South Africa, says Botha.

“The Penetron system is more cost effective and less time consuming than hydrolytic-membrane or clay-panel systems and cannot come apart at the seams, tear or be punctured. Concrete treated with the additive does not require any further protection or maintenance owing to the self-healing capabilities of the crystalline structures,” he concludes.