While concrete is a sustainable material in terms of its life cycle, according to industry experts, reducing the cement
content in concrete with other alternatives such as fly ash is a good solution. Besides, the production of Portland cement
leads to the release of significant amount of carbon and this is a concern that is being addressed globally and in the GCC.
"Concrete is a sustainable building material, which ensures durable and long-lasting structures that will not rust and burn.
It also ensures longevity - an integral part of reducing cost and use of resources in a project," Dr. Huiqing He, corporate
sustainability manager at Al Fara'a Group and deputy operations director (SME) at Unibeton, told Zawya.
"Besides, the thermal mass of a concrete building means reduced requirements for heating and cooling systems, which in turn
means an energy-efficient building. In addition, concrete is manufactured using many post-industrial by-products and it can
also be recycled and reused to save material resources," she said.
Concrete is one of the most widely used construction materials globally due to its sustainability properties, agreed Rabih
Fakih, managing director of Grey Matters. "However, the production of Portland cement leads to the release of significant
amount of carbon emissions. One ton of Portland cement clinker production creates approximately one ton of carbon emissions
and other greenhouse gases (GHGs). Hence, environmental issues will play a leading role in the sustainable development of the
cement and concrete industry in this century."
Still, concrete, as an end product, is a sustainable material. "It is produced with very little waste, made from some of the
most plentiful resources on earth (limestone), and minimizes the effects that produce urban heat islands, among other
benefits," Fakih said.
"At the process level, re-use of post-consumer waste and industrial by-products in concrete produces 'greener' concrete. Use
of coal ash, rice-husk ash, wood ash, natural pozzolans, GGBFs, silica fume, and other similar pozzolanic materials can
reduce the use of manufactured Portland cement clinker and simultaneously produce a more durable concrete."
Local and international design and construction are governed by codes and certifications such as the NRMCA Sustainable
Concrete Plant Certification (US), GreenStar, Estidama (UAE), LEED (US), GSAS (Qatar), Breeam Gulf, ASTM published technical
standards and ASTM sustainability committee (E60), and ACI 318 building code requirement for structural concrete.
Green concrete can contribute to earning points for the certification of the structure. "Regionally, two major bodies making
a tremendous impact in this area are Estidama in the UAE and GSAS in Qatar," Fakih said.
According to Estidama's Pearl rating system in Abu Dhabi, concrete is covered within credits SM-9 (regional materials) and
SM-10 (recycled materials). "In June 2010, all new development applications for communities are mandated to satisfy all
required credits to achieve a minimum 1 Pearl level of compliance," Fakih said.
However, Maher Tadros, managing partner of the US-based e.construct and professor emeritus at the University of Nebraska,
said: "Currently, initial costs are driving the implementation of most standards."
Carbon Emissions
So, will replacing Portland cement with fly ash (by-product of electric power generation) or other materials solve the carbon
emissions problem in the long run? Dr. He agrees that using fly ash reduces embedded carbon emission in the long run and
ensures a higher resistance to chemical attack, which also extends the life span of the product.
"Slag cement (ground granulated blast-furnace slag or GGBS) is another common supplementary cementitious material (SCM) used
in manufacturing concrete. A by-product of a controlled process from iron production, it results in a very uniform
composition, increases concrete durability and enables a higher volume replacement of Portland cement (by up to 70%)."
Tadros agreed that reducing the cement content in a concrete mix results in significant sustainability. "Modern mixes are
using cement replacement materials such as fly ash and rice ash in a proportion of above 70%. New varieties of cement are
also in the development stages. Again, when a structure runs its life cycle, the reinforced concrete used in the building can
be recycled as aggregates and recycled reinforcing bars. But since reinforced concrete is a structural material, one has to
be careful about what is put into the concrete mix. It has to be carefully specified and regulated to avoid potential long
term durability problems," he noted.
Researchers at Missouri University of Science and Technology said recently that increasing the amount of fly ash in concrete
up to 70% can also prevent millions of tons of the waste product from ending up in landfills.
Fakih added that replacing Portland cement with fly ash also improves the plastic behavior of the concrete. "Other SCMs have
been widely and intensively used in the GCC for more than a decade. Recycled aggregates from demolished buildings and
returned concrete can also be used to replace the natural aggregates," he said.
In order to ensure that concrete production also ensures energy efficiency and reduction of valuable water resources in the
GCC, Dr. He suggested that companies implement the NRMCA comprehensive program called "Concrete Sustainable Plant
Guidelines", which addresses a sustainable operation and practice through life cycle perspectives.
It covers process control and evaluation from material purchasing, production and delivery, product use, to waste reduce,
recycle and reuse. Dr. He added that currently, only Unibeton Ready Mix has achieved this certification in the region.
"Following our management requirement, waste water and waste concrete are recycled and reused through in-house developed
water treatment plant and concrete recycling plant to enhance sustainable development and practice, and further reduce CO2
emission, waste disposal and resources usage. All recycled water is reused to reduce water consumption," she said.
Water Demand
Additionally, chemical liquids (admixtures) are used to reduce the water demand needed for mixing while improving the fresh
and hardened properties of the concrete, added Fakih. "Also, recycling process water is a common phenomenon in most GCC
countries, where water is recycled/treated to be used in the concrete process," he said.
Tadros noted a new trend emerging in North America as an alternate to reduce the usage of concrete - using precast concrete
insulated panels (sometimes called sandwich panels). "The insulation layer not only reduces the volume of concrete used but
also adds considerable insulation value to the building envelope. Using fiberglass connectors across the insulation ensures
that the two outside wythes of concrete work together in composite action.
"Thus a 75-100-75 mm sandwich wall acts like a solid 250 mm wall while using only 150 mm concrete. It also provides an R
rating of 20 (US units). In addition to these features, one could use a concrete mix with very little cement and a lot of fly
ash, and still get the required capacity," he said.
Though the concrete sector experienced the full brunt of the recession, the GCC markets have performed quite positively in
the last one year, said B. Tolga Candan, operations manager (strategic business development) at Unibeton.
"Backed by the vast reserves of oil and gas, the GCC countries have a great vision for major developments across many
sectors," he said. "We feel that 2013 will be a more positive year. Today, the key to overcome the challenges lies in
technical strength and diversification."
The biggest challenge that faces the concrete sustainability business is the cost attribution, said Fakih. "The relatively
high cost of producing green concrete (as the SCM are imported with high cost of freight) has not yet been justified by the
client. Moreover, authorities have not yet set strict specifications to obey the minimum sustainability requirements," he
said.
Agreed Tadros: "The conventional cement industry is not anxious to opt for products that use less cement. Private corporates
will only do what gives them the most and immediate profit. There is inertia in changing ready mix concrete plants, mixes and
storage of fly ash and additional materials. Also, structural engineers will not use products that put their design at risk,"
he said.
"But the changes are coming. Government agencies must lead the way. The countries that are best prepared to accept the
changes will be ahead of the game," he said.
Looking forward in terms of business confidence for the next year, Candan said that numerous large infrastructure projects in
the social and transport infrastructure sectors will boost industry growth. "Such high end projects in a competitive market
will have challenges and requirements where only the technically strongest can satisfy and sustain the business," he said.
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