EF Technology ® is a process that uses alternative cementitious materials that results in the reduction of greenhouse gasses. This resource saving process not only produces greener and more sustainable concrete mixes, but also stronger and more durable concrete products. EF Technology family of concrete mixes can contribute to LEED and lower the carbon footprint for your next project
Our core business strategy is centered around providing green concrete products that conserve energy resources, reduce pollutants, and bring green foundations to all type of concrete constructions. Through EF Technology, we are at the forefront of the market transformation towards green building, paving the way for a greener future.
Cement and CO2 emissions
Portland cement, an essential component of concrete, is the glue that
binds concrete together. In recent decades however, the production of
cement has been designated as a major greenhouse gas pollutant. Worldwide,
the production of Portland cement alone accounts for some 5% of human-generated
carbon dioxide (CO2), the greenhouse gas most attributed as the source
of global warming.
The CO2 associated with Portland cement manufacturing falls into 3 categories:
CO2 derived from de-carbonation of limestone.
CO2 from kiln fuel combustion.
CO2 produced by vehicles in cement plants and distribution.
This does not account for the CO2 associated with electric power consumption,
since this varies according to the local generation type and efficiency.
Typical electrical energy consumption is of the order of 40-45 kWh per
ton of cement produced.
As a result of these measures, the general rule is that the creation of one ton of cement releases one ton of carbon dioxide into the atmosphere.
EF Technology solutions
To combat this problem, there are a number of methods and technologies
now available from U.S. Concrete across the United States that provide
a multitude of environmentally friendly solutions (called EF Technologies).
Among these is the use of alternate or supplementary cementitious materials
(SCMs) such as fly ash and slag.
Fly Ash
Fly ash (also known as a coal combustion product or CCP) is the mineral residue
resulting from the combustion of powdered coal in power generating plants.
Fly ash consists mostly of silicon dioxide, aluminum oxide and iron oxide. It
is pozzolanic in nature, meaning it reacts with calcium hydroxide and alkali
to form cementitious compounds.
Most power plants are required by law to reduce their fly ash emissions
to less than 1 percent. The remaining 99% is collected using electrostatic
precipitators or filter bags. Initially, this collected ash was disposed of
in ash ponds or landfills. Once its pozzolanic properties were discovered,
however, it became useful as a replacement for Portland cement in concrete.
Fly ash can replace up to 50% of the Portland cement required to manufacture concrete. Fly ash can be used to improve workability and
pumpability of concrete. Due to its generally slower rate of hydration, fly ash also
lowers the heat of hydration and is important in mass concrete structures,
such as large foundations, bridges, and piers. High fly ash concrete shows
less bleeding and shrinkage than straight cement mixes. Fly ash is also used
as a component in the production of flowable fill, which is used as self-leveling,
self-compacting backfill material in lieu of compacted earth or granular fill.
More and more fly ash is being used beneficially as a recycled material, although
it is still far from fully utilized as more than 65% of fly ash produced from coal
power stations is disposed in landfills. This amounts to approximately 40 million
tons of fly ash in the United States.
Slag Cement
Slag is the by-product of smelting ore to purify metals. In nature, the ores of metals
are found in impure states, often oxidized and mixed in with silicates or other metals.
During smelting, when the ore is exposed to high temperatures, these impurities are
separated from the molten metal and can be removed as slag.
Through determining its many uses, it was found that ground granulated slag reacts with
water to produce cementitious properties. It could therefore be used in concrete, in
combination with Portland cement, as part of blended cement. Concrete containing ground
granulated slag develops strength over a longer period, leading to reduced permeability
and better durability properties. Since the unit volume of Portland cement will also be
reduced, concrete is less vulnerable to alkali-silica and sulfate attack.
As with fly ash, processing blast furnace slag into slag cement or slag aggregate eases
the burden on our environment in a number of ways. It reduces the air emissions at the
blast furnace as well as the material in landfills. Most significantly, slag decreases
Portland cement usage by as much as 50 percent, thereby diminishing CO2 emissions.
Typical mix designs for structural or paving concrete normally use substitution rates
between 25 and 50 percent; high-performance and mass concrete applications can use
substitution rates up to 80 percent. As stated earlier, approximately one ton of CO2 is
released for every ton of Portland cement produced. Figure 2 illustrates the benefits of
substituting 50 percent slag cement in various concrete mixtures. Between 165 and 374
pounds of CO2 are saved per cubic yard of concrete by using a 50 percent slag cement
substitution, a 42 to 46 percent reduction in greenhouse gas emissions.
Energy Savings
Slag cement requires nearly 90 percent less energy to produce than an equivalent amount
of Portland cement. Reducing the use of Portland cement in concrete by substituting a
portion of it with slag reduces the embodied energy in a cubic yard of concrete by 30
to 48 percent.
Reduced Material Extraction
Raw materials for Portland cement are gathered through mining operations. A ton of
Portland cement actually requires about 1.6 tons of raw materials. Substituting 50
percent slag cement can save between 281 and 640 pounds of virgin material per cubic
yard of concrete.
