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Sustainable Concrete: Environmental Impact And Methods

Concrete is a common building material worldwide because of its durability. However, sustainability topics aren't discussed very much. Thankfully, green or sustainable concrete has been studied and developed in recent years.

Attention is often devoted to intensive animal farming, fossil fuels, and plastic waste as big problems. In the coming decades, we need all sectors of society to decarbonize. That should include infrastructure development, and thus concrete.

This article explores the definitions of green concrete and the environmental impacts of traditional concrete. We will also discuss how to reduce concrete industry emissions dramatically.

What is green concrete?  

concrete block
Photo by Ablazejo on Wikimedia Commons licensed under CC BY-SA 3.0 (Cropped from original).

Green concrete is a building material with a minimal environmental impact when used in the construction industry. The traditional concrete we use for construction is harmful to the environment. It releases high levels of carbon emissions, leading to the acceleration of climate change. 

Manufacturing sustainable concrete makes use of waste material from other industries. Its production also uses less energy than traditional concrete. Traditional concrete is made from cement, water, and sand. 

The cement sector is a harmful part of concrete production. Cement, made from substances found in limestone and slag, is a binding element in concrete. Eco-friendly concrete production replaces cement with supplemental cementitious materials (SCMs), recycled aggregates, and admixtures.  

Environmental Impacts of Cement in Concrete Production 

Cement is the crucial building material used in the production of concrete structures. There are various types of cement and production methods used in concrete manufacturing. The methods used to make Portland cement are dry, wet, and semi-dry, although the dry method is the most common production method.

To manufacture cement for concrete structures, manufacturers need a chemical combination of calcium, silicon, iron, aluminum, and other ingredients. The raw materials used to create Portland cement, one of the most used cement in construction, are limestone, slates, chalk, and clay.  

They grind and blend these raw materials up to a certain proportion. Then, they burn the mix at about 2700 Fahrenheit in an enormous cylindrical steel rotary kiln to form a rock-like substance. The kilns are as long as a 40-story building.

The product from feeding the materials into the kiln is known as the clinker— a grey ball resembling small rocks. Manufacturers let the clinker cool down before cement plants grind it with 5% gypsum to control the set time of the cement. 

As you can see, cement production requires lots of energy and resources. Using it to produce concrete structures has severe consequences for the world. The environmental impacts are:    

  1. High Energy Consumption 
  2. Traditional concrete structures release huge amounts of carbon dioxide and other greenhouse gas emissions.  
  3. It causes air pollution. 
  4. Water pollution

Related Read: Environmental Impact Of Construction.

High Energy Consumption   

concrete plant
Photo by Checkteam on Wikimedia Commons licensed under CC BY-SA 3.0 (Cropped from original).

The concrete sector is energy-intensive because of the production of cement. The cement industry uses the most energy out of all industrial manufacturing industries. It starts from the mining process and the transportation of raw materials to the factory. Statistics show that a ton of cement produced for construction uses about 1,758 kWh of energy.

The concrete industry's energy source is from fossil fuels like pet coke, fuel oil, coal, and gas, with coal as the main energy source. Research shows the energy distribution between the production process4– 92% for burning, 5.4% for finishing grinding, and 1.9% for raw grinding.

These stats show that burning materials uses the most energy, even though the dry process kilns are more energy-efficient than the wet process kilns. Dry-process kilns use 50% less energy than wet-process kilns because there is no need to remove moisture. 

The concrete industry would require less power without cement because of the other materials (crushed stone, water, and sand) used. 

Traditional concrete structures release huge amounts of carbon dioxide and other greenhouse gas emissions.  

The concrete industry releases carbon dioxide through fuel combustion and chemical process combustion. Most of the concrete’s carbon footprint comes from burning and clinker production. Burning releases about 81% of  CO2 emissions, fuel combustion releases 36.8%, while the reaction from burning fuel produces about 46.3% of CO2.

Research shows that the carbon footprint from producing cement increased by 17% from 1994 to 2001. Using waste fuels also releases other greenhouse gases like methane and nitrous oxide. These gases are more potent than carbon dioxide. The amount of carbon released during production varies according to the cement produced5.

Mason cement doesn't produce as much carbon emissions as Portland cement. However, adding limestone to the kiln releases tons of carbon emissions. These greenhouse gas emissions are harmful because they damage the ozone layer, accelerating climate change. 

The occurrence of climate change means there will be more natural disasters. Wildlife species will lose their habitats, and those that can't adapt to the new, fluctuating climate are at risk of extinction. 

Concrete is a durable construction material, but it is responsible for the depletion of the environment. As a society advocating for the safety of wildlife and its environment, we should find safe alternatives that release less greenhouse gas emissions. 

It causes air pollution.

air pollution
Photo from PickPik.

The concrete industry also contributes to air pollution in the world. Producing concrete releases particulate pollutants into the atmosphere. Air pollution starts from the mining and transporting of natural resources to grinding clinker and packaging finished cement. 

One of the most visible pollutants is dust from manufacturing cement. Research shows that every ton of cement releases 360 pounds of dust. China released 3.58 million tons of particulate matter and 0.67 million in 2009 and 2012, respectively.

The particulate pollutants reduce the air quality. They often contain mineral matter, organic matter, elemental carbon, heavy metals, secondary inorganic aerosols, and some unknown compounds.

Inhaling high concentrations of these materials is harmful to human health2. It can cause respiratory problems like reduced lung function, inflammation of the lung lining, and increased risk of cardiovascular diseases.

People living close to cement and concrete factories and those working there are prone to diseases such as endocrine disruption, silicosis, cancer, and infertility. You’ll often find a thick cloud of dust around these areas.

Water pollution  

Manufacturing concrete also contributes to water pollution around cement plants. These factories release untreated wastewater into water bodies in the environment. The heavy metals and other pollutants in the wastewater can harm aquatic ecosystems and their living organisms. 

Releasing wastewater into rivers and streams introduces high concentrations of metals like chromium, lead, copper, and cadmium. Particles like this in water bodies make it unsafe for agricultural and personal use. Concrete wastewater can also increase the water temperature, hurting biological life and processes.

For example, the particles in the wastewater can clog fish gills and introduce toxic matter into their immune system. Research conducted on river Athi, near a cement plant in Kenya, shows it reduces water quality. Concrete and cement factories release waste materials that affect water temperature, turbidity, pH, and conductivity.

It also changes the water’s pH, making it taste bitter and harming aquatic plants and animals. Releasing concrete wastewater surface water sources also increases their nitrogen content, leading to the growth of algae blooms. The polluted water is also very harmful to human health. 

For example, drinking contaminated water can damage the lungs, brain, and liver. In babies,   

It can react with the blood hemoglobin, leading to blue baby syndrome. Blue baby syndrome is the inability of the blood to hold oxygen.

Ways to make concrete sustainable? 

concrete blocks and plant
Photo from PxHere.

There are several ways to make traditional concrete sustainable without compromising its durability. One of these ways is by replacing the cement content in concrete because cement is responsible for the carbon emissions from producing concrete. 

Factories can improve concrete sustainability by using Supplementary Cementitious Materials (SCMs) and  recycled aggregates like: 

  • Fly ash
  • Blast furnace slag
  • Micro silica
  • Recycled concrete waste 
  • Hempcrete  

Fly ash 

Fly ash is the by-product of burnt pulverized coal from coal power plants. Fly ash is a harmless substance that coal plants release into the atmosphere until the government set up control regulations. 

They forced coal plants to store fly ash in coal power plants or send it to a landfill because it reduced the air quality. The construction sector soon discovered they could use it to make concrete. 

Fly ash has aluminous and siliceous components that mimic cement reactions when mixed with water. It has two classifications, Class F and Class C. Class C has a higher calcium content, which makes it an excellent substance to improve the structural integrity of concrete. 

Class F fly ash has particles covered in glass. It helps reduce the risk of concrete expansion while increasing concrete's resistance to sulfate and alkali-aggregate reactions. The construction sector uses fly ash to make building materials like Portland cement3, concrete bricks, concrete pipes, hot mix asphalt, and ceramic tiles.

Blast furnace slag 

granulated slag
Photo by Blast furnace chip worker on Wikimedia Commons licensed under CC BY-SA 3.0 (Cropped from original).

Blast furnace blast is a waste product from the developing iron, iron ore, and iron scrap. It contains silicates, aluminosilicates, and calcium-alumina-silicates. There are four types of furnace slag; 

  • air-cooled furnace slag,
  • expanded or foamed furnace slag,
  • pelletized furnace slag,
  • granulated furnace slag.

We can use this recycled non-metallic waste to create concrete for buildings and infrastructures. Construction uses it as cement and sandblasting shot materials1.

Micro silica 

Micro silica, also known as silica fume, is a waste product from the manufacturing process of silicon metal and ferrosilicon alloys. Silicon metal and ferrosilicon alloys are used to develop computer chip fabrication, aluminum, and steel products. 

Silica fumes look similar to fly ash. It has grey particles that are 100 times smaller than traditional cement particles. Using microsilica to make concrete is excellent because it is highly durable. 

It reduces transportation, manufacturing, and transportation costs. It also reduces heat and permeability. Constructors can use it to make bridges, marine infrastructure, and a parking structure.

Recycled concrete waste  

concrete waste
Photo from Needpix.

We can also recycle concrete waste to reduce emissions and waste sent to the landfill.  De Maio and Strukton developed a machine called Advanced Dry Recovery to separate concrete waste into two groups. 

It separates waste from demolished concrete buildings into gravel, sand, and cement. It separates gravel easily, which can be used immediately. However, the second group has to enter a Heating Air System classification system to separate sand and cement. 

We can reuse these recovered materials to construct new concrete buildings without damaging the earth.

Conclusion: Sustainable Concrete

We use concrete for most buildings because it is durable. However, concrete has a high carbon uptake and harmful impact on the world because cement is a binding material. 

Green concrete is highly efficient because it uses alternative fuels and materials. The construction company should use carbon-neutral concrete to build a strong foundation for pavements, bridges, and structures.

1

U.S. Department of Transportation Federal Highway Administration. (2016). Blast Furnace Slag - Material Description - User Guidelines for Waste and Byproduct Materials in Pavement Construction. FHWA-RD-97-148.

2

Hasanbeigi, A., Bhadbhade, N., Ghosh, A. (2022). Air Pollution from Global Cement Industry - An International Benchmarking of Criteria Air Pollutants Intensities. Global Efficiency Intelligence. Florida, United States.

3

U.S. Department of Transportation Federal Highway Administration. (2017). Chapter 1 - Fly Ash - An Engineering material.

4

Fadayini, O. M., Madu, C., Oshin, T. T., Obisanya, A. A., Ajiboye, G. O., Ipaye, T. O., Rabiu, T. O., Akintola, J. T., Ajayi, S. J., & Kingsley, N. A. (2021). Energy and Economic Comparison of Different Fuels in Cement Production. IntechOpen eBooks.

5

Hanle, L. J., Jayaraman, K. R., & Smith, J. S. (2004). CO2 emissions profile of the US cement industry. Washington DC: Environmental Protection Agency, 10.

By Jennifer Okafor, BSc.

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Fact Checked By:
Isabela Sedano, BEng.

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