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Wed 26 Mar 2008 04:00 AM

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Malleable material

Concrete is the unseen material behind Middle Eastern development.

Concrete is the unseen material behind Middle Eastern development.

From Roman columns and Byzantine vaults to the angular geometries of Brutalism and Ando's polished slabs, concrete has been the material of choice for architects for centuries.

Gropius and Mies van der Rohe found and led the Bauhaus around the concepts of rational and functional design, much of which used concrete to underscore the absence of ornamentation.

[Aircrete] is the obvious choice if you’re an enlightened, forward-thinking person. If you are a traditionalist who does it the way it’s always been done because you know it works and you don’t want to take any steps forward, then you won’t use it.

Post-Stalinist architects chose the material for its drabness; while Perret and Le Corbusier were drawn to its texture and irregularity. I.M. Pei lauds concrete for its sharp lines and simplicity; while Oscar Niemeyer uses it to create abstract, flowing, unconventional patterns.

But, within the last 60 years, concrete seems to have gone the way of the dinosaur in that while it is instrumental in certain applications, it seems to have become a bit passé. This reality is especially apparent in the glass and steel bending, twisting towers of the Middle East.

And while no building could stand without the requisite foundation, pillars or podium of concrete, within architectural circles, concrete has become a material used merely for function rather than aesthetic appeal.

Admittedly, there has been a shift toward Postmodernism across the field-which explains some of the futuristic, and often bizarre, designs being witnessed-but product innovations and concrete's inherent characteristics, could have Middle Eastern architects reconsidering their material choices.

Why concrete?

The rapid pace of development in the Middle East requires materials that are local, easily obtainable, relatively affordable and environmentally friendly. Concrete is one of few, readily available, building materials that boasts high marks in all of these categories.

While both glass and aluminium are available in abundance in the region-and are used extensively in architectural applications-glass manufacturers here combat high thermal bridging (i.e. increasing cooling costs) while aluminium begets a very high level of embodied energy.

Concrete, on the other hand, is made almost entirely of natural materials that are all very dense, which gives the product a very high thermal mass. Because of its earthen nature, concrete acts as a thermal sponge; it absorbs heat during the day and releases it at night.

"Concrete is inherently environmentally friendly. Cement, sand, aggregate and water. All the materials are very eco-friendly," says James Campbell, production manager at Mammut Technocrete.

Used in conjunction with proper insulation and well-planned site orientation, concrete structures can reduce energy consumption by up to 50%, which contributes to both comfort and cost-effectiveness for inhabitants.

On the safety front, concrete's constituent materials-cement and aggregates-are essentially inert, which means that once combined, they exhibit very poor thermal conductivity.

In fact, concrete enjoys the highest fire resistance classification under EN 13501-1, which means, essentially, it doesn't burn. Concrete's slow rate of heat transfer enables it to be used as a fire shield and if it is exposed to fire, it doesn't emit toxic fumes, smoke or molten drip.

This is a fact that must resonate with the region's architects and engineers whose projects are built under the scrutiny of evermore stringent safety regulations and within climates conducive to fire.

In terms of longevity, concrete has appeared in ruins of ancient structures that date to 7000 BCE, which suggests unparalleled durability for man-made materials.

Chemical and structural innovations in recent years have led to high-performance concrete with super-tensile load-bearing characteristics. This category of concrete is being used extensively in local infrastructure projects-Dubai Metro, 6th Crossing Bridge, Garhoud Bridge, etc.-which grants them both structural and architectural permanence.

Moreover, high-performance concrete containing admixtures that shut down water transport capillaries and incorporate fine particle cement replacements can render it waterproof and/or sulphate resistant. Concrete of this type is being used in Nakheel's Waterfront, Palm and World, as well as Dewan's Dubai Sports City.

"We're working on a massive installation for the Waterfront project where concrete will be embedded into the ground, so that concrete will have different characteristics...," says Campbell. "This cement ensures that the natural sulphates in the soil don't corrode the reinforcement in the concrete."

Chemical jargon aside, one particularly compelling reason for using concrete in architecture is the fact this it is recyclable. In the UK for example, the use of recycled/secondary aggregates for construction increased 94% between 1989 and 2002.
In fact, in 2001 alone, 42 million tonnes of construction waste was recycled and reused for new projects. Despite similar figures in every major building market, this green technique is still not being widely considered in the UAE.

Moreover, the US LEED-on which Emirates LEED is largely based-recognizes recycled concrete when attributing LEED points to specific projects. Specifically, Credit #4 (Materials and Resources) states, "specify a minimum of 25% of building materials that contain in aggregate a minimum weighted average of 20% post-consumer recycled content material OR a minimum weighted average of 40% post-industrial recycled content material."

In terms of quality, precast slabs are better than conventional systems.

Simply put, using recycled aggregates instead of virgin extracted aggregates increases the 'green-ness' of buildings. Apart from this, the advantages of using recycled concrete for new projects are threefold: reduction of construction waste in landfills; reduction in overall cost of materials for the project; reduction in the amount of embodied energy required for extraction and manufacture of new concrete.

"Imagine a tower is going to be built. Lorries need to transport the concrete and/or do the shottering onsite; materials and labour need to be brought to and from the facility," explains Siamak Motemavelian, group marketing manager at Mammut Technocrete. "By doing everything within our production facility, we oversee the process and thus, control the pollution associated with production."

The aircrete option

While lightweight concrete is just one of a host of high-performance concrete materials on the market, it is the one being experimented with in the region and thus, has the potential to make a difference.

Aircrete is a building material that is made from several components including ground sand, pulverised fuel ash (PFA) cement, lime, aluminium powder and water. The components are blended together into a mixture which foams to create an exceptionally strong and light cement matrix with high thermal insulation.

For Martin Boardman, plant manager at German-Emarati Company Bena, the arrival of aircrete here is long overdue.

"There are so many tower blocks here that are doing dense concrete in short panels. Why?" asks Boardman. "Aircrete is ten times more energy efficient and a third of the weight. You save enormous loads on your structure and offer enormous benefit to tenants and owners."

The product is also quite versatile as it can be moulded or cut to specific project dimensions. Much like other forms of concrete, aircrete is also a great thermal insulator and fire-resistant to the highest safety class. Moreover, its durability allows for structures up to G+3 to be built without the aid of a structural frame.

Because aircrete is a third of the weight of traditional concrete and because an aircrete block is considerably larger-1.5 times larger than a dense block-productivity is 50% faster.

In Scandinavia and Europe, the use of aircrete is common practice, but the Middle East has been slower to accept the new technologies. While there are several aircrete manufacturing facilities in Saudi Arabia and two companies beside Bena building aircrete plants in the UAE, the product's slow acceptance is mainly down to economics.

"The main reason it has taken so long for aircrete to get to the Middle East is because it is a high capital investment initially," explains Boardman. "You're talking about over US $120 million to build the plant and buy the machinery."

However, Boardman is quick to point out that economics are not the only factor standing in the way of aircrete's region-wide use. All too often, says Boardman, it's a matter of knowing it exists and knowing how to effectively use it.

"Obviously you have to educate architects, engineers and consultants. You've got to show them that there's a better material out there," says Boardman. "It's also a sensitive process. It requires skill and experience and you'd need to import someone from a more established market to get everything up and running."

There is hope for aircrete in the Middle East, however. While he admits frustration about the current state of aircrete production, he's positive about the future.

"We're finding that a lot of the bigger developers are bringing in architects who do know the benefits of aircrete."

The traditional precast panel option

The longest standing concrete option-and the one with which modernist architects most closely associate-is the traditional precast panel. An age-old method of mixing, casting and forming concrete in a controlled environment, precast panels offer the benefit of being able to deliver entire sections of a wall or façade to a site.

"Most people use precast concrete to remove the hassle from the contractor...it's the convenience factor," says Campbell.
Like other concrete products, precast concrete panels offer complete fire and weather resistance, UV integrity and durability, but proponents cite efficiency as the predominant advantage.

"Rather than causing problems on the construction site, we can switch out any panels right there," says Motemavelian.

Lacking unknown variables like erratic temperature, humidity, material integrity and onsite craftsmanship, precast panels generally exhibit very high quality.

"We also have our own dedicated quality-control department. If requested by the client, we use third-party testing to verify our own in-house results," adds Campbell.

Moreover, the strength of precast panels increases over time as their load-bearing capacity is derived from their own structural qualities rather than those of surrounding backfill material. This is particularly relevant when considering issues of timelessness and preservation.

If the concrete industry is shifting toward lightweight high-performance concrete for building applications, Motemavelian and Campbell are unconcerned.

"There are several people in Dubai experimenting with lightweight systems but the Dubai Municipality are notoriously reluctant to accept new things. It's not impossible but it takes time and a lot of convincing," says Campbell.

Mammut's reluctance to move into lightweight concrete is motivated not only by politics but by statistics. "We've done trials with lightweight concrete here but have had very poor results in terms of strength and durability," adds Campbell.

The hollow core wall panel option

Little is known about a new product from Abu Dhabi-based Hi Tech Concrete-a division of ANP Group-that purports to be the only company in the Gulf manufacturing large-span hollow core wall panels.

According to Sujit Pasad, executive director of Hi Tech Concrete, hollow core wall panels were developed specifically to be load-bearing precast panels that are able to span massive distances.

"We can span beyond 200 metres but the rules and regulations in this country won't allow us to transport anything larger than that," says Pasad. "Our panels are also 2.4 metres wide, which allows them to cover a larger area."

An American technology that is not even being used extensively in Europe yet, hollow core wall panels are load-bearing and pre-stressed, which removes the requirement for additional columns and beams within G+5 structures.

While the Hi Tech product is designed to be lightweight, environmentally friendly and durable, its biggest advantage is the speed with which projects can completed.

Hi Tech hollow core panels require 60% less manpower than regular precast, which means one high-span panel can be assembled by two people in 15 minutes.

"Basically they're like Legos. We cast the walls in the factory and assemble them onsite," says Pasad. "A wall that would take a mason 14 days to build, we can do in a matter of hours."

Deeply involved in the Hydra Village projects located in and around Abu Dhabi, Hi Tech plans to specialise in large-scale turnkey projects. The 2,000-5,000-villa Hydra projects or larger universities and/or townships are their target projects.

Falling victim to the same philosophical shift as postmodern, neomodern and deonstructivist architects, Pasad understands that, to some, his product has design limitations. "At the end of the day, it's a slab of concrete. For most architects, let's face it, concrete is not the most interesting subject," he says.

However, he's quick to mention that the hollow core panels can be designed to include various mouldings and artistic variations that add aesthetic value and architectural style.

"If an architect develops a complex design, the idea is to allow that vision to be realised using these materials. Making architects aware of such products allows them to incorporate these products in other designs."

Final word

While a shift back to the minimalism and clean lines of modernist architecture isn't likely, concrete technology is evolving to the point where it may, once again, be architecturally relevant.

Especially in the Middle East, where a harsh climate and lack of natural resources make material selection paramount, concrete could be the way toward cleaner landfills and greener buildings.

Facts about concreteConcrete derives from the Latin concretus, which means 'to harden'.

Roman engineers discovered that adding horse hair to concrete decreased its likelihood of cracking while adding blood made it frost resistant.

Egyptian engineers discovered that adding volcanic ash to concrete allowed it to set underwater.

Concrete is the most used man-made material on the planet.

In April 2007, a team from the University of Tehran used an aggregate of steel fibres and quartz to produce blocks with four times the compression strength (50,000-60,000 psi) of regular blocks.

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