Sulf8CEM – for low-maintenance concrete in aggressive environments

Frequently encountered problems when constructing concrete infrastructure in the water sector are the heat of hydration in mass pours (dams) and building in an aggressive environment (sewage plants) with exposure to sulfate and/ or chloride attack. One of Lafarge South Africa’s recent cement innovations, Sulf8CEM, offers a solution for both challenges.

Sulfates are a challenge for concrete civil works in aggressive environments such as sewage plants, areas exposed to mining activity, and coastal areas where the soil is high in sulfate.

As a general guideline, if ground concentrations of sulfate are above 1 000 ppm, sulfateresistant cement (such as Sulf8CEM) should be used to build concrete structures.

In these typical locations, sulfates are said to ‘attack’ concrete because they can permeate the surface layers in solution with water and react with calcium hydroxide and tricalcium aluminate in the cement paste. A variety of compounds are formed, which are far more voluminous than the original chemicals – as much as 600% more.

The results are:

• Surface layers of the concrete begin to burst open allowing for a bigger surface area to react further.

• Aggregate ceases to be bound together by the cement paste. • Reinforcing becomes exposed to corrosion.

• The concrete structure progressively disintegrates.

Sulf8CEM

“Faced with the demands of rapid urbanisation, South Africa has to build a longer service life in its concrete structures. We simply cannot afford to reconstruct or repair our raw, potable or wastewater infrastructure every few years,” explains Roelof Jacobs, manager: Integrated Solutions & Innovation, Lafarge South Africa. “We set out to offer the water industry a solution for creating durable concrete structures suitable for use in aggressive environments. Lafarge South Africa is extremely proud to have developed this all-round high-performance product – Sulf8CEM.”

Sulf8CEM is a low-heat (LH), sulfateresistant (SR) cement that is formulated from Portland clinker that meets the C3A requirement and over 36% selected quality siliceous fly ash, as well as performanceenhancing additives. It has been certified to conform to the latest applicable South

African and European standards (SANS 50197-1 and EN 197-1) for a CEM IV/B-V 42,5 N LH SR. As a classified low heat of hydration product, Sulf8CEM also offers a significant benefit for constructing concrete civils infrastructure for the water industry.

The cement hydration reaction that rapidly raises the temperature of freshly placed concrete is a problem in large structures as the heat cannot dissipate, causing high temperatures and the expansion of the concrete while it is hardening.

The resulting cracking not only weakens the structure but also creates entrance points for harmful substances to penetrate the concrete. As a result of the high siliceous fly ash content in its formulation, Sulf8CEM is an exceptionally good lowheat common cement.