Design Life-Cycle

The Life Cycle of Green Concrete

Des 40a

Xueqing Liu, Yiyang Xiao

Section 3

Life Cycle of Green Concrete

Our human beings’ society has developed for over one hundred thousand years. From the ancient time, humans made stone tools and metal tools to survive, and constructed shelters by using the red earth and some natural materials. As the living environment of humans turned better during the long periods of evolution, the way of building shelters has changed a lot. The purpose of buildings was no longer protect humans from wild animals or other threats. Currently, the idea of buildings is to provide privacy and aestheticity for people who live in the buildings. Impressively, one of the functions of buildings, avoiding the natural disasters, has not changed much from ancient times. However, in order to better protect themselves from natural disasters such as the extreme bad weather, people consider more about choosing more long-lasting materials. For this research paper, the main idea is to talk about three parts of the one of the long-lasting materials which has been used frequently in recent days as a building material-- Green Concrete. The three parts can be distributed by materials, energy and waste. The first part is going to talk about the raw materials of the green concrete. 

Raw Materials:

To introduce the materials of green concrete, the first thing that is necessary to be thought of is the concrete. Concrete is one of the most frequently used building materials in the world. As the article “How Concrete is Made” states, concrete is a mixture of paste and aggregates, or some rocks. The components of concrete are cement, water and aggregates as the main parts. After a range of chemical reaction, which is known as “hydration”, the compounds become harder and get strength to be like rocks. That is the process of making concrete. Compared to concrete, green concrete seems to be more environmentally friendly. According to “What is Green Concrete? Its Applications and Advantages in Construction”, green concrete is a material made from concrete wastes that are eco-friendly. What’s more, “green concrete is a term given to a concrete that has had extra steps taken in the mix design and placement to insure a sustainable structure and a long life cycle with a low maintenance surface,”as the article claims.To illustrate, green concrete is more sustainable and have a longer life cycle with a low maintenance surface since it is used the waste concrete to manufacture and become a new building material. According to the data, researchers at UniversitiTeknologi MARA introduced an innovative green concrete called "green-mix concrete" that is designed and manufactured using conventional materials but partially replaced with suitable waste and recycled materials to achieve acceptable performance, economics and sustainability.

How Is the Green Concrete made? 

The green concrete is made of new raw materials which is called fly ash. Fly ash is a sort of waste product remaining from coal power plants and it is usually disposed into the ponds and brought to the landfills. What’s more, The crushed concrete received from the  waste concrete of the demolition constructions take place of the fine and coarse aggregate in various ratios. The fly ash and some other elements mix with the crush concrete in order to produce the green concrete. What they bring is the advantages of high permeability, thermal expansion and strength. Following the article “ ‘Green Mix’: An Environmentally Friendly Building Material” provided by ScienceDaily, “To produce this new concrete requires technical expertise such as new concrete mix design, new raw materials and new knowledge of green concrete properties. Not only is this newly developed green concrete environmentally friendly, it is also cost-effective as a result of optimized material proportions from our new concrete mix design. In our investigation, the new concrete can achieve an increase in strength of up to 30% compared to normal concrete.” That means the production of green concrete is definitely sustainable than that of concrete, and green concrete has lower cement footprint compared to the concrete at this time. 

Where Do We Use the Green Concrete? 

According to the ScienceDaily, in recent years, the application of green concrete has turned more and more popular in various countries such as Malaysia. As the time goes, when our human beings pay more attention to protect the environment and become more sustainable, environmentally-friendly building materials has been used more often. Green concrete is one of them. Because of the simple process of finding the raw materials and manufacturing, green concrete starts to become a material that is commonly used in Architecture. Moreover, also because it is cheap, it is easily to get this material in different places. 

About its transportation, it is pretty similar to the transportation of concrete. The mortar pan is necessary to make the green concrete stable. However, it is a little complicated since this is a labour intensive idea that requires workers working together to maintain it. Then, the wheelbarrow or hand cart is needed to take it to the truck mixer and dumper. The function of the truck mixer is to guarantee the green concrete soft, which can let it change its shapes as the building needs. The next step is putting the green concrete onto the conveyor belt and using the chute to let it go down and also skip and hoist to make it up. Finally, the green concrete is pumped and piped through Pipe-Line method. 

Use and Reuse

The raw material of green concrete is concrete. Following what “Ways to recycle and reuse of Concrete”, concrete can be recycled and reused in many different methods. Typically (but not always) the process involves crushing or pulverizing the concrete rubble near the demolition of building site. Choosing the best method frequently depends on the size and shape of the concrete parts to be recycled. Reusing concrete can be a beneficial way to reduce construction costs while providing some benefits to the environment. Concrete is one of the main building materials, and its uses are diverse that buildings, bridges and roads are basically made with concrete. It is strong and long-lasting, so it can remain for a long time. That is also why it is harmful to the environment. If concrete is not reused, it will pollute the environment because it is hard to decompose.Therefore, green concrete is also a method to recycle concrete. Crushed recycled concrete can be used as the dry aggregate for brand new concrete if it is free of contaminants. Green concrete helps to decrease the pollution of concrete waste in some aspects. The production of concrete is with a lot of waste disposals, so it is very wise to reuse the concrete by reforming it into the green concrete, which is eco-friendly. 

Recycle

Actually the green concrete is a method to recycle the concrete, and it is being enough sustainable that recycling process is not paid much attention by people. As what the article “Recycled Materials in Concrete 

Reduced CO2 Emissions and Landfill” says, the recycling process of waste concrete, which is the process of making green concrete, contributes to the reduction of CO2 emission as high as 70%, and the range of values is between 15%-40%, and it is pretty low compared to that of concrete itself. 

Waste Management 

The issue of the waste problem of concrete is severe. There are many buildings and other constructions requiring concrete to build, but the nature cannot recycle so many concrete materials and it is because concrete is hard to deal with too. One of the methods of dealing with the waste of  concrete is to demolish it. As the article “Waste management strategies for concrete” says that “Extensive tests of structural properties such as compressive strength, flexural strength and split tensile strength of recycled concrete were carried out, in which cement and similarly fine aggregate were partially replaced by demolished waste to obtain recycled concrete and recycled aggregate concrete whose properties were compared with results for the conventional concrete.” It means that the waste concrete has values after they demolished and it has been tested several times by researchers. 

Conclusion

From the factors mentioned above, green concrete is a great substitute for concrete because it is more sustainable and it helps to recycle the waste disposals of concrete. However, nowadays people cannot abandon concrete since it is easy to make and it is really cheap. Using the green concrete should first produce concrete and then wait until it has to be abandoned, which will take at least decades. So as the time passes, maybe there will be a more effective and efficient way to deal with this cycle, but now green concrete is a great test of sustainable building material. It makes our society more environmentally friendly. 

Reference

Glavind, Mette. Green Concrete Structures. UC Davis Library. 10 March 2011.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/suco.201000022

Reed, Stanley. “Betting on a New Way to Make Concrete That Doesn't Pollute.” The New York Times, The New York Times, 2 Dec. 2018, https://www.nytimes.com/2018/12/02/climate/betting-on-a-new-way-to-make-concrete-that-doesnt-pollute.html?searchResultPosition=1. 

Barros, Joaquim. Ferrara Liberato & Martinelli, Enzo. Recent Advances on Green Concrete for Structural Purposes. Published by Springer Nature. August, 2017.

https://link.springer.com/content/pdf/10.1007%2F978-3-319-56797-6.pdf

Mishra, Gopal. “What Is Green Concrete? Its Applications and Advantages in Construction.” The Constructor, 5 June 2018, https://theconstructor.org/concrete/green-concrete/5566/. 

“Green Concrete.” Http://Www.madhavuniversity.edu.in/, Madhav University, https://madhavuniversity.edu.in/green-concrete.html. 

Life Cycle of Green Concrete (Energy)

Concrete is an essential architectural material that people consumed about six billion meters every day. The process of making cement, which is a raw material of concrete, and cost a lot of resources and requires a lot of energy input. To deal with this problem, scientists have found a new way to build a similar material of concrete, and it is called green concrete. Green concrete, as a new type of concrete, have different raw materials with traditional concrete made of cement. Also, the energy input in the whole life cycle of the green concrete is mixed with conventional concrete.  One character that is important to consider for the energy input of green cement is embodied energy.

 Embodied energy can show how architectural material has an impact on the environment. According to “embodied energy,” represented power is: “ the energy consumed by all of the processes associated with the production of a building, from the mining and processing of natural resources to manufacturing, transport, and product delivery.” This part of the essay is focused on the process of making green concrete, the embodied energy of green concrete, and compare the embodied energy of green concrete with the embodied energy of traditional concrete. 

One of the essential raw materials for traditional concrete is cement. The common raw materials of cement are limestone, clay, and chalk. The first stage that cement will consume energy is that people need to mine the raw materials. The earth and lime are wide distribution in the world. So they are not difficult for people to gain. To extract the limestone, people need to use a machine to peel the stone from the hill. Since these tones are too large to transport, people put them into a crusher to break them into small pieces. The clay is soft, so people will use an excavator to get them. The process of getting raw materials from the environment will consume a lot of energy since the machines require fuels and energy to be used. Also, the mines need electricity to maintain the essential services for labor to work. 

The next stage that will consume the energy of making cement if transportation. People put the raw materials on huge trucks and transport them to the factories. The vehicles need fuels to provide power. This part of embodied energy is valid depends on how far the factory is from the mines. 

The third stage is manufacturing cement. The first step of manufacturing cement is to grind the raw materials as small as possible. The goal of grinding limestone and clay is to let them become a fine powder. Then, people will mix all of the raw materials and stir them. The mix of the raw materials called a raw meal. Before the heating process, there is a preheating process to leave out the impurities. The temperature needed for this steep is around 900 degrees Celsius. The heating process is necessary for manufacturing cement. For this process, people put the raw meal into a rotary kiln, which is a huge machine that could heat the raw meal while stirring. During the heating process, the carbon dioxide will divide from the raw materials. This process of removing carbon dioxide called decarbonization. The chemical equation for decarbonisation is “CaCO3 (limestone) + heat—> CaO (lime) + CO2”. According to “Cement: Materials and Manufacture process,” the results of the heating process called “clinker,” and “A modern kiln can produce around 6000 tons of clinker a day”. The temperature needed for this process is about 1450 degrees Celsius. The next step is cooling. The clinker goes into a tube after passing out from the klin. In the tube, the clinker is cooled by the air or the wind. Since the outside temperature is lower than the clinker, the clinker will resales heat and become cooler. Then, the cooled clinker will be ground again to a fine powder. Finally, this final powder is cement. 

In the process of manufacturing cement, all the machines need electricity to work. To generate electricity, people will burn fuels. The factory itself also requires power to keep working. Thus, the embodied energy for cement is 5.6 MJ/KG. The process of making cement is very complex, and it consumes a large amount of energy and resources from the natural. 

The fourth stage is manufacturing concrete. People put cement sand and fiber into a mixing machine. At the mixing process, water will be added so the mixed materials can flow. While these materials are thoroughly mixed, the final product is concrete. During this process, the factory and the mixing machine needs energy. 

The final stage is packing and transporting. The concrete will be put into cars that can stir concrete. The vehicle will take the concrete to the construction plant. In this process, the cars need fuel to work. Finally, the embodied energy for concrete is about 1.5 MJ/KG. 

The raw material of green concrete is fly ash. According to “Fly Ash Factors for Highway Engineers,” fly ash is “the finely divided residue that results from the combustion of pulverized coal and is transported from the combustion chamber by exhaust gases.” Fly ash is made from different kinds of fuels. One of the most common fuels used to make fly ash is coal. People put coals into the burning furnace. At a temperature of about 1300-1500 degrees Celsius, the coals became coal residues and adhered to the walls of the fiery furnace. These residues gain energy from the burning process, and they chill-down and become ash after the roasting process.

Fly ash itself is one of the industrial waste which has many adverse impacts on the environment. In an industrial process, burning fuels is inescapable. Thus, the only way to solve the problem of fly ash is to reuse them. According to “Can Coal Fly Ash Waste Be Put To Good Use?”, Dodge states that the “reuse in a product that provides a functional benefit, replaces a product made from virgin raw materials, conserves natural resources, and meets product specifications and industry standards. Beneficial use of waste products can contribute to a sustainable future by reducing production costs, reducing energy consumption, and greenhouse gasses”. To make green concrete, people use fly ash to replace the most amount of cement. Although people still need a little amount of glue, about 80 percent of cement will be returned. Since fly ash is the industrial waste from other industrial processes, the embodied energy of manufacturing fly ash will not be considered in the embodied energy for green concrete. 

The first stage that considered as embodied energy for green concrete is the collecting and transporting process. People will install the fly ash collector in the factories that need to burn fuels. These collectors can collect the fly ash that is cooled on the wall of the burning furnace. After the ly ash is gathered together, they will be packed and transported to the factories that manufacturing green concrete. The cars and fly ash collectors will consume energy is this process. 

The next stage is manufacturing the green concrete. The process of making green concrete is similar to the method of manufacturing traditional concrete. People put 80 percent of fly ash, some limes, water, and a little bit of cement into a mixing machine. When the materials are well mixed, the final product is green concrete. In this process, the tools and factories will consume electricity. 

The final stage of green concrete is the same as the final stage of traditional concrete. That is to say, in this transportation and packing process, the energy input is the same for both conventional concrete and green concrete. Thus, replacing fly ash with cement can require less energy. According to “Can Fly Ash Waste Be Put to Good Use?”, the research shows that using fly ash to manufacture green concrete can save 85 percent of energy. 

To conclude, concrete and green concrete have similar characteristics, but concrete has a complex manufacture process. In the manufacturing process of concrete, a lot of energy is consumed. The method of making the raw material — cement contributes most of the embodied energy of traditional concrete. During the burning step of making cement, many carbon dioxides is released to the atmosphere, which will damage the environment. Nowadays, a massive amount of concrete is used in the world. Although the embodied energy for concrete is not too much, but a large amount of concrete consumption will cause many problems. The embodied energy of green concrete is 80 percent less than the embodied energy of traditional concrete since it uses fly ash to replace cement for the raw material of concrete. This replacement will help people to save a lot of energy input to make concrete. Making products with similar characteristics with more environmental friendly raw materials is a necessary way for people to protect the environment and be sustainable. Thus, to due with both greenhouse gases and energy input problem, replacing traditional concrete with green concrete can be really helpful. 

References

“Fly Ash Facts for Highway Engineers.” U.S. Department of Transportation/Federal Highway Administration, https://www.fhwa.dot.gov/pavement/recycling/fach01.cfm. 

Dodge, Ed. “Can Coal Fly Ash Waste Be Put To Good Use?” Breaking Energy, https://breakingenergy.com/2014/02/18/can-coal-fly-ash-waste-be-put-to-good-use/. 

admin_yourhome. “Embodied Energy.” YourHome, 29 July 2013, http://www.yourhome.gov.au/materials/embodied-energy. 

“Cement: Materials and Manufacturing Process.” Greenspec, http://www.greenspec.co.uk/building-design/cement-materials-and-manufacturing-process/. 

Des 40 

Research project 

Xueqing Liu

Section 3

The Life Cycle of Green Concrete (waste and emission)

Concrete is one of the most common architecture materials in our daily life. Since concrete has many advantages, such as cheap and excellent durability, concrete is a wide application by people nowadays. On the opposite side, the huge amount of concrete used has caused a lot of problems for the environment. The process of making concrete has a lot of waste and emissions. To deal with this problem, scientists have designed a new material called green concrete. Green concrete has similar characteristics with traditional concrete and has less waste and emission. This paper will focus on comparing the waste and emissions for traditional concrete and green concrete to show how green concrete is environmentally friendly. 

The raw materials of concrete are cement, sand, and water. Since the cement is not the primary resource that people can get direct ally from the natural, people need to manufacture it. The process of manufacturing cement will have waste and emission. The raw materials for cement are limestone and clay. Before making cement, people need to get the raw materials for it. Thus, in the concrete production lines, the first stage that will waste and emission is getting lime and clay. 

Limestone is widely distributed in the world, so it is easy for people to find. The factories of mining limestone are always set up on the hills. Since limestone is a kind of tone, people will use a large machine to peel the limestone from the. To make the limestone easy to pack and transport, people need to put the large pieces of limestone into a crusher. The crusher will grind the limestone to small pieces or powder. In the process of peeling and crushing, many particles and powders will release into the atmosphere. These particles called particulate matter (PM). The particulate matter will have a negative impact on both people’s health and the environment. According to “Health and Environmental Effects of Particulate Matter(PM)”, the negative impacts of particulate matter has on human’s health are: “premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function, and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.” The particulate matter in the atmosphere will cause the acidic rain. These particles can also be considered as waste in the process of mining limestone. 

The next stage that the industrial process of cement will cause waste and emissions in mining clay. While silicate mineral morals and manners, they formed. Although clay is soft, it still looks like the stone. To gain clay, people will use excavators. The emission for clay is the same as the emission for limestone. Mining clay use causes the release of particulate matter to the atmosphere. 

After getting the raw materials, the cement can be manufactured. The manufacturing process of cement causes the most significant amount of waste and emission. First, the worker will put all the raw materials together and mixed them. The missing product is the raw meal. Next, people will put the raw meal into a kiln. The raw meals are heated in a kiln at a temperature of 1450 degree Celsius. The chemical reaction that happened in the kiln is “CaCO3 (limestone) + heat—> CaO (lime) + CO2”. The chemical reaction can show that while heating the Kiln, the carbon dioxide will divide from the raw materials. This process of removing carbon from limestone  dioxide called decarbonization. According to the operation of decarbonization, carbon dioxide is the dominant emission for the production of cement. According to “Emissions from the Cement Industry,” the carbon dioxide emission for the heating process “accounts for ~50 percent of all emissions for the cement industry”. To heat the kiln, people need to burn fuels. Coals are the most common ones to provide heat. Burning coal or other fuels will cause the emission of carbon dioxide and particulate matter. According to “Climate Change: the Massive CO2 Emitter You May Not Know About”, research shows that “in 2016, world cement production generated around 2.2 billion tonnes of CO2 - equivalent to 8% of the global total. More than half of that came from the decarbonization process”. 

The last stage is manufacturing concrete.  To get concrete, workers put cement sand and fiber into a mixing machine. In the mixing process, people will add water and let the mixed materials become flow. During this process, the emission of concrete should be calculated matters. Also, this process will not cause a large number of emissions. 

The raw material of green concrete is fly ash. Since fly ash is an industrial waste, people did not need to manufacture it. The reason why fly ash has occurred during the industrial process is that people always burned fuels to provide heat and electricity. Fly ash be made by many kinds of fuels. While people put fuel into the burning furnace at a temperature of about 1300-1500 degrees Celsius, the coals will turn into coal residues and adhered to the walls of the burning furnace. After the residual fuel cooling down, it will become to fly ash. 

Since the fly ash is the industrial waste, and all the burning process produces it, the emission of producing fly ash will not be considered as the emission of green concrete. Also, using industrial waste to make new materials is the right way for human beings to solve the problem of industrial waste. 

Fly ash is very tiny and light. The collection of fly ash is a little bit difficult. Although there are many fly ash collectors, they can not collect fly ash in one hundred percent. The process of collecting fly ash will have both waste and emission. The fly ash that could not be collected is the waste of product green concrete. When the fly ash release to the atmosphere, it will become the particulate matter. 

The manufacturing process of green concrete is similar to the process of making traditional concrete. One significant difference is that to make green concrete; people will use fly ash to replace a part of cement for the raw material of concrete. The previous part of this paper shows that making cement contributes to most of the emission of concrete. Since making fly ash will not cause emission, replacing cement with fly ash can reduce the amount of emission. To mix the raw materials, the machine needs electricity to work. Burning fuels can provide power. This burning process will lead to carbon dioxide emissions. The mixing process will also cause waste of raw materials and release particulate matter. Compared with the process of making cement, the emission of making green concrete is not significant. According to “Can Coal Fly Ash Waste Be Put to Good Use”, the research states that replacing cement with fly ash “requires 81% less energy to manufacture, incorporate 37% recycled fly ash and emit 84% less CO2 during production”. Using fly ash to make green concrete is not only a way to deal with industrial waste but also a way to protect the environment. 

To sum up, Green concrete is the concrete that has the same characteristics as traditional concrete but has less emission and waste. With the development of technology, human beings consume more and more energy and resources. The resources on Earth are limited. The consumption of resources also leads to many environmental problems such as greenhouse gases and acid rain. Using environmentally-friendly materials can help people protect the environment. Using green concrete can help human beings reduce industrial waste, save resources, and reduce emissions. According to “Environmental Impact of Green Concrete in Particle,” research shows that: “replacing 30% of  Portland cement with fly ash causes 17% reduction in CO2 emissions and 4% reduction in mineral extraction. If a country can decrease cement production by 50% through replacement of cement by fly ash, slag or other supplementary cementing materials, the country would reduce its CO2 emissions for the production of cement by about 50%”. Although using green concrete still causes some problems, but less means better. 

References

“Health and Environmental Effects of Particulate Matter (PM).” EPA, Environmental Protection Agency, 20 June 2018, https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm. 

Rubenstein, Madeleine, et al., “Emissions from the Cement Industry.” State of the Planet, 18 June 2018, https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry/. 

Rodgers, Lucy. “Climate Change: The Massive CO2 Emitter You May Not Know About.” BBC News, BBC, 17 Dec. 2018, https://www.bbc.com/news/science-environment-46455844. 

Zasiah, Tafheem, and Khusru Shovona. Environmental Impact of Green Concrete in Particle. 2011. 

Dodge, Ed. “Can Coal Fly Ash Waste Be Put To Good Use?” Breaking Energy, https://breakingenergy.com/2014/02/18/can-coal-fly-ash-waste-be-put-to-good-use/.