Construction World

The growing range of concrete admixtures from Chryso Southern Africa is changing the face of construction by broadening the options available for both designers and contractors, according to general manager: marketing and commercial sales Hannes Engelbrecht.

“With the use of admixtures, concrete structures can be made stronger, higher and thinner,” says Engelbrecht. “An important aspect of these high strength concretes, however is their low water/binder ratios; this requires a very powerful polymer to disperse the cement and ensure mixing efficiency.”

Opening doors for concrete innovationIn South Africa, he says, about 95% of all concrete being batched is conducted in dry batch plants which rely on readymix truck drum mixers to mix the concrete. Without the correct admixture, the level of dispersion of cement in the drum could fall short of what is optimally required. This mixing efficiency is particularly important when contractors want to achieve higher strengths, as is often the case today.

“Our admixtures offer unique technology to give contractors the mixing efficiency to achieve the cement dispersion much quicker,” he says. “With high paste volumes, it is also difficult to maintain the workability of the concrete; our LSS technology therefore gives the customer the necessary open time to place the concrete.”

Included in the range are Rover technologies (incorporating both robust and versatile qualities) which are specifically aimed at ultra high density concretes, as well as fill-free technology where there is a need for high flow concrete to have superior mobility in particular applications. The latter, he says, comes without the adverse effects on the strength and setting characteristics, which characterise certain viscosity modifiers.

Becoming more complex

“It is important for customers to realise that the field of admixtures has become complex and application specific, so using these products optimally really requires users to consult with their admixture suppliers in the early stages of projects, in terms of structures being constructed and what results they require,” he says.

For instance, Chryso’s new Centre of Excellence is a laboratory facility where cements and aggregates may be evaluated, helping the customer to determine the optimal mix design to suit the customer’s purpose.

A recent showcase of what can be achieved using high strength concretes and specialised admixtures, says Engelbrecht, is the recently opened Museum of European and Mediterranean Civilisations (MuCEM) in Marseille, France. Designed by architect
Rudy Ricciotti, the concrete structure includes a 115 metre slender ‘super-concrete’ pathway linking the MuCEM to the Fort Saint-Jean. Without arches or stays, the concrete path is a testament to ever-improving concrete technology and strength.
Engelbrecht goes on to highlight various other technological advances in admixtures that give designers the opportunity to apply ideas that they could previously only imagine.

“While most contractors are familiar with traditional applications of admixtures – such as the water reduction, plasticising and acceleration or retardation of setting time – there are so many more applications that are now available to improve quality, safety and aesthetics,” says Engelbrecht. “So committed is Chryso to constant innovation that 35% of our products are less than five years old.”

Decorative and functional

One of the most recent product lines is LuminTech, an impressive new addition which facilitates decorative yet functional concretes. This remarkable range contains a variety of different luminescent particles that are applied to the surface and incorporated into the concrete skin.

“During the day, the particles imitate natural aggregates, absorbing natural and artificial ultra violet radiation,” he says. “After dark, they then release the energy to give an attractive luminous glow to concrete surfaces, illuminating selected areas of a building or home. Apart from its aesthetic value, this product provides added safety for pedestrians using walkways and paths at night.”

This offers exciting new design possibilities for architects, landscapers and homeowners, enhancing architectural lines of an urban building at night, or highlighting a domestic terrace or the edges of a swimming pool. The particles are available in four colours, and the intensity of the illumination can be adjusted by changing the volume of particles on the concrete skin.

The LuminTech range is durable and environmentally friendly, resisting both impact and friction. It is also sourced from composite recycled material and natural mineral pigments, making it suitable for projects that focus on sustainability.

Decorative concrete

In another step that has enhanced Chryso’s offering in decorative concrete, the company recently acquired French company Moderne Méthode – a global leader in stamped, polished and micro-topping concrete, millimetric coatings (with different aspects such as stabilised-sand, granite, marble and metallised effect), as well as resins and stampable overlays.

It also acquired the Béton Academy, with its highly technical modules to guide this new craft of decorative concrete applicators. The academy boasts 11 training centres and is ISO 9001 certified.

Sustainability

Sustainability and cost effectiveness remain priorities among contractors and the ready availability of pulverised fly ash (PFA) from power stations in South Africa has led to the widespread use of extended cements. Here, Chryso has played an important role in working with local contractors to facilitate the use of these extended cements without affecting the slump retention, workability and durability of the concrete.

The use of correct admixtures facilitates further extension of the concrete and Chryso has been involved in projects where more than 50% PFA has been used. Although extended cements do reach the required strengths, they react slower; the more pure cement that is replaced, the lower is the early strength of the mix. Activators are therefore introduced to trigger the early strength characteristics of the concrete.

Design mixes which include extenders must also take factors such as slump retention, setting times and strength gains into account. Typically, slump retention ensures extended workability and is considered a critical characteristic of concrete on projects today, especially given some of the complex structures that are being constructed.
The growing number of projects within the urban environment also leads to readymix trucks being subject to traffic congestion while delivering – another important reason why extending the workability of concrete through admixtures is vital.

Contact Construction World

Title: Editor
Name: Wilhelm du Plessis
Email: constr@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Erna Oosthuizen
Email: ernao@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

 
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