The Effect of Concrete on the Environment

The Effect of Concrete on the Environment

In the modern times, concrete is a common material used in the construction of structures. It is mostly preferred due to its longevity, strength, and durability in comparison to other building materials (Alonso et al. 436). Therefore, the constructors use concrete in the construction of bridges, buildings, and roads. Nevertheless, the concrete production heavily impacts the environment because of its high demand. Environmentalists are also concerned with its carbon footprint that leads to air and water pollution.

In most literary works, the authors use the terms ‘concrete’ and ‘cement’ interchangeably. However, cement is one of the ingredients used alongside water, sand and gravel to produce concrete. Cement is a hydraulic binding material that hardens water and ties together all the aggregate production materials. The versatility and stability of concrete as a building material earns it a reputation as one of the mist widely utilized resources on the planet. However, in an era of an increased awareness of the environmental effects of the construction industry, the activists highlight concrete as one of the main contributors to climate change.

Concrete

Concrete is a mixture of cement, water, and aggregates. Tushman et al. (452) admit that the modern constructors use admixtures to modify the curing process and the physical properties. Originally when mixed, concrete assumes a plastic form that takes the shape of formwork or mold. When hardened, it becomes either a lightweight thermally insulating component or a dense load bearing material. However, much of the formation process depends on the composition of used aggregates. The builders can reinforce or pre-stress it through the incorporation of steel. Concrete is widely used in most contemporary buildings in different geographic locations.

During the Roman and Greek Empires, concrete shaped the built environment. Centuries later, the manufacturing process of this natural construction material is still the same. Over the past century alone, concrete has become the main construction component for homes, workplaces, and transport corridors. However, its durability is characterized by a devastating impact on the natural environment.

The production of concrete demands a significant amount of energy, hence leading to carbon emission through the use of coal, diesel and other forms of non-renewable energy. Regardless, the amount of carbon dioxide emitted during the manufacturing and the net effect of utilizing concrete as a construction material is relatively dismal.

The cement manufacturers heat limestone to 10000C alongside silicate feedstock materials. At this temperature, the calcium carbonate breaks down into lime, carbon dioxide, and silicon oxides. Then, the oxides combine to form tricalcium silicate ground into fine powder clinker. Eventually, they add gypsum to the clinker to prevent the cement’s flash setting. Cement plants consume 6GJ of fuel per 1 tonne of clicker produced. In China and the developing world, for example, kilns use petroleum coke and coal as primary sources of energy, thus leading to higher levels of carbon emissions.

The cement manufacture causes environmental pollution at all stages. The emission of airborne pollution occurs in the form of noise, machinery vibrations, and harmful gasses. Notably, most firms have introduced equipment to minimize dust emissions during the quarrying process and in the production of concrete.

Hazardous Cement

Specifically, environmental experts list cement as one of the most hazardous materials in the building and construction industry because it adds more carbon dioxide to the atmosphere than all the global airlines combined.  While the aviation industry carbon emission stands at 4%, concrete-based building materials account for 5-10% of the world’s greenhouse gas emission. Globally, constructors use more than 2 billion tons of cement annually. Even worse, there is a projection that the long-term effect of the concrete use on the environment will be significant. In fact, with the rise of economies such as China and India, the global demand for cement will rise by 50% by the year 2021.

Gustavsson et al. (946) argue that the amount of carbon emitted from concrete production is directly proportional to the amount of cement used in the concrete mix. Indeed, for every fabrication of 1 ton of cement, 900 kg of carbon dioxide is emitted. It accounts for more than 90% of the emissions associated with concrete mix. Thermal decomposition of calcium carbonate in the cement manufacture process contributes greenhouse gasses to the environment.

Concrete bears a negligible amount of embodied energy that is relative to the quantity used. Therefore, the materials used in the production of concrete such as pozzolans, water, and aggregates are plentiful and locally obtainable. It implies that the transportation only accounts for less than 10% of the embodied concrete energy whereas the cement production accounts for approximately 70%.

Acid Rain

The environmental effect of concrete production goes beyond carbon climate change and carbon dioxide emission. The extensive damage results from the acid rain due to emissions of nitrogen dioxide, nitric oxide, and sulfur dioxide. Additionally, a high concentration of cement kiln dust increases health risks of industrial workers besides the depletion of drinking water supply.

Concrete is a mixture of gravel, sand, chemicals, and water. There are two major sources of greenhouse gas emission during the production process. First, the manufacturer combusts fossil fuels to sustain the operation of rotary cement kiln. The second is a reactionary process through the calcining of limestone. For every ton of cement made, an estimated equal amount of carbon dioxide is emitted.

Besides the damage inflicted on the ozone layer, concrete destroys the most fertile earth layer. Given that its removal is almost impossible, most corporations in the cement industry employ unethical means to obtain the raw material. In most cases, the workers crush river stones in some of the most serene environments on earth for mass production of cement. In the Indian sub-continent, for instance, concrete production causes significant and permanent environmental damage because the government subsidizes and reinforces the use of cement. It is arguable that the Indian leadership facilitates the extinction of traditional building techniques and architecture. In the wider Asia, there are numerous broken cement structures abandoned in pristine temple compounds and forests.

Toxicity

A research by Mehta (64) reveals that masons use concrete to create hard surfaces that result in surface runoff, flooding, water pollution and soil erosion. It mainly happens through the deflection and diversion of mudflows and flood waters. Concrete also reduces the urban heat island effect due to the high levels of albedo. The cement dangerously pollutes the air when concrete dust is released during natural disasters (such as earthquakes) and building demolition. Following the Great Hanshin earthquake, concrete dust is now ranked as one of the most dangerous sources of air pollution. The presence of unwanted and useful additives in concrete raises health concerns because of radioactivity and toxicity. Natural radioactive elements such as uranium and potassium are present in remarkable concentrations in concrete buildings. On the other hand, toxic substances are present in the mixtures, especially if the makers are unscrupulous. Moreover, wet concrete is highly alkaline. Hence, handling it without proper protective equipment is hazardous.

Light-Colored Concrete

According to Amato (300), the use of light-colored concrete proves to be effective because it reflects more than half of light in comparison to asphalt. In this way, it reduces the ambient temperature. If the value of albedo is lower, it will absorb a significant amount of solar heat, thus contributing to the excessive warming of the city environment. A problem such as this is solvable through the replacement or paving with light colored concrete.

In many US cities, pavements make up 40% of the total surface area. Therefore, the heavy use of concrete has a direct impact on the cities’ temperature demonstrated in urban heat island effect. Not only does with light-colored concrete pavements minimize the amount temperatures but also, it saves energy and increases night vision.

Limiting Carbon Emission

Many countries in the developed world are interested in minimizing greenhouse gas emissions related to the use of concrete. Therefore, scholars have suggested numerous approaches to limit carbon dioxide emission. The main reason of the high levels of carbon dioxide is the heating of cement to high temperatures for clinker to form. A major culprit of the entire process is Ca3SiO5. It is an alite mineral that cures within a few hours of pouring, hence is responsible for much of concrete’s initial strength. Still, this material has to be heated to more than 1500 degrees centigrade during the process of clinker formation. Latest researches suggest that alite is easily replaceable by minerals such as belite. The component requires 300 degrees centigrade of heat lesser than alite. Besides, it gets stronger as the concrete cures. Belite’s downside is that it takes four days to a month to set completely. In this case, the concrete will remain weaker for a prolonged period of time. Irrespective, the ongoing research focuses on determining the impurity additives such as magnesium to accelerate the curing process. Of keen to note is that belite consume more energy during the grinding process, thus contributes to environmental pollution through the excessive use of fossil fuels.

The second approach to minimize concrete’s environmental impact is the partial replacement of conventional clinker with better alternatives like bottom ash, slag, and fly ash. They are all by-products of other industries and would otherwise be disposed in landfills. Thermoelectric power plants produce bottom ash and fly ash while slag is ironwork industry’s waste. Potentially, such materials increase strength, prolong durability, and decrease the density of the concrete.

Fly Ash

Builders are yet to widely implement the use of slag and fly ash because of the technological risks and inadequate field testing. Most firms are unwilling to take chances with new concrete recipes unless the government implements the carbon tax policies. In Italy, corporations such as Italcementi have designed cement that can eradicate air pollution. According to the manufacturer, concrete made from this cement breaks down air pollutants that come into contact, thanks to the inclusion of titanium oxide to absorb ultra-violet light. Still, a section of experts is skeptical, given the extent of environmental damage and pollution. They argue that the project is not viable financially.

Further, there is a proposal to cut carbon emissions during the curing process. Admixtures like dicalcium silicate can absorb carbon dioxide as the concrete gradually cures. Even better, the use of suitable substitutes such as coal ash cuts concrete carbon emissions to 0.1 kg/m³ compared to normal levels of 300 kg/m³. An effective production of the concrete calls for the use of a power plant’s exhaust gas so that an isolated chamber can control humidity and temperature. In spite of the application of advanced additives, the occurrence of carbonation within a concrete is natural. Consequently, it absorbs carbon dioxide in a reverse process to cement production. Despite the concerns about alkalinity loss and corrosion of reinforcement, discounting this process is not easy.

Additionally, there are other concrete improvement methods that doest directly address the environmental concerns. Research facilities globally are designing prototypes of smart concretes that use mechanical and electrical signals to respond to the observable changes in loading conditions. In particular, the use of carbon fiber reinforcement ensures the provision of electrical response to monitor concrete’s structural integrity and to measure strain without the need to install sensors.

Road Construction

Daily, the road construction and maintenance industry in the developing world consume hundreds of tons of carbon-intensive concrete to secure urban infrastructure. Bribian et al. (1134) states that as the human population grow in urban areas, the infrastructure gets more vulnerable to vehicle damages, hence creating an ever-expanding cycle of waste and undying hunger for use of concrete in repairs. Eventually, the emissions and other forms of concrete-inspired pollution will rise uninterruptedly unless the regulatory authorities introduce and implement restrictive measures.

A major development in the building and construction industry entails the use of recycled petroleum waste to shield concrete from damage and to maintain the dynamic nature of infrastructure. In this way, Turner and Frank (125) concede that it is possible to update and maintain them without interrupting the structural foundations. A simple innovation such as this not only minimizes concrete’s environmental impact, but also preserves the foundation of buildings and structures.

Concrete Recycling

Concrete recycling is a renowned method to dispose structures. At the dawn of the millennia, corporations regularly shipped concrete debris to landfills for disposal. However, with the increase in the creation of environmental awareness, people recycle concrete debris to minimize air and land pollution. They collect concrete free of paper, wood, and trash from demolition sites to be crashed alongside rocks, asphalt, and bricks. On the other hand, reinforced concrete that has metallic reinforcements such as rebar are recycled at specialized facilities. Magnets are used to remove metals before the remaining chunks can be passed through a crusher. In the United States, many concrete recycling factories adhere to all the procedures to minimize the impact of concrete on the environment. They use smaller pieces of concrete as gravel for ongoing construction projects. Sometimes, engineers use crushed recycled materials as dry aggregate for new concrete since it is free of environmental contaminants.

According to Tayibi et al. (2379), concrete processing facilities degrades landscape. The raw materials extraction facilities are noisy and can bear a visual impact, specifically in some areas with outstanding natural beauty. Given the rapid population growth and the growing demand of limestone, a significant number of manufacturers set their facilities in close proximities to populated centers. Resultantly, this exposes the population to health complications. People lose their agricultural land too, as the acid rain decimates the farm produce.

In summary, it is clear that concrete materials wield a significant impact on the environment. Though there are positive effects of using concrete, the negative effects outweigh them, thus prompting a need to reconsider the procedures used in the manufacturing process. Already, several manufacturers have expressed interests of committing funds to research on innovative measures to limit the destructive effects. Notably, the existing knowledge in this field is limited, especially regarding the long-term impact. Therefore, scholars should bridge the knowledge gap by establishing a direct link between the carbon dioxide released by concrete and the global warming. In addition, the governments and environmental authorities should widen the scope of environmental studies to include the dangerous trends in the road construction and repairs industry. Possibly, the environmental impact of this sector surpasses the existing estimates. Researchers such as Mehta (46) fail to clarify the specific steps to be considered for environmental sustainability.

Regarding the radioactive and toxic contamination, the existing technology cannot accurately measure the amount of radioactive elements present in concrete. In essence, there is a chance that the research outcome may be compromised. Parish (289) observes that there is no outright proof that dust from broken concrete or rubble can cause serious health concerns. Not a single researcher specified the types of diseases caused by toxic concrete materials. In light of this, the future research should focus on clarifying the shallow details characteristic of the reviewed articles. Most importantly, the attention should be shifted towards the emerging trends on the concrete design improvements.

References

Alonso, C., et al. "Factors Controlling Cracking of Concrete Affected by Reinforcement Corrosion." Materials and Structures 31.7 (2012): 435-441.

Amato, Ivan. "Green Cement: Concrete Solutions." Nature ( 2013): 300-301. pdf.

Bribián, Ignacio Zabalza, Antonio Valero Capilla, and Alfonso Aranda Usón. "Life Cycle Assessment of Building Materials: Comparative Analysis of Energy and Environmental Impacts and Evaluation of the Eco-Efficiency Improvement Potential." Building and Environment 46.5 (2011): 1133-1140.

Gustavsson, Leif, and Roger Sathre. "Variability in Energy and Carbon Dioxide Balances of Wood and Concrete Building Materials." Building and Environment 41.7 (2006): 940-951.

Mehta, P. Kumar. "Global Concrete Industry Sustainability." Concrete International 31.02 (2009): 45-48.

Mehta, P. Kumar. "Reducing the Environmental Impact of Concrete." Concrete International 23.10 (2001): 61-66.

Parish, S. B. "The Effect of Cement Dust on Citrus Trees." The Plant World 13.12 (1910): 288-91. Web.

Tayibi, Hanan, et al. "Environmental Impact and Management of Phosphogypsum." Journal of Environmental Management 90.8 (2009): 2377-2386.

Turner, Louise K., and Frank G. Collins. "Carbon Dioxide Equivalent (CO 2-e) Emissions: A Comparison between Geopolymer and OPC Cement Concrete."Construction and Building Materials 43 (2013): 125-130.

Tushman, Michael L., and Philip Anderson. "Technological Discontinuities and Organizational Environments." Administrative Science Quarterly (1986): 439-465.