Mahboobin 10:00 R02

University of Pittsburgh, Swanson School of Engineering 1

10.4.2016

Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University

of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly

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than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University

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Green Cement: Finding an Alternative to Portland Cement

Ivan Menz (ijm10@pitt.edu)

PORTLAND CEMENT EMISSIONS: IS

THERE A GREEN SOLUTION?

The cement industry is the second largest producer of

CO2 in the world and it is growing bigger every year. After

over one hundred years of using the same high emission

cement, it is time that we replaced it with a greener

alternative. The biggest problem with finding a substitute is

that most other materials which produce similar products are

either more harmful to the environment or are not readily

available, making the product too expensive. There is one

alternative though, that is readily available and has a much

lower carbon footprint than Portland cement: Solidia cement

is heralded as a possible solution to the carbon problem

associated with cement by Lafarge, one of the world’s largest

cement manufacturers, which has partnered with Solidia to

commercialize this technology [1]. This cement has been

rigorously tested and has been proven to possess many better

characteristics than regular Portland cement. I think Solidia

cement is the best current alternative to Portland cement.

OVERVIEW OF PORTLAND CEMENT AND

ITS PROBLEMS

“Concrete is the second most used material in the world,

trailing only water” [1]. The key binding ingredient in

concrete is Portland cement (approximately 10-15% of its

volume) which makes the cement industry one of the largest

in the world [2]. In 2014 alone 92 million tons of cement were

produced in the US and 4.6 billion tons worldwide [3].

Concrete is a popular building material for several reasons: it

is extremely versatile, it is relatively inexpensive, and it is

tremendously durable and high in strength. These reasons

make it the go-to material for construction projects. In fact,

the Portland Cement Association predicts that the global use

of cement will rise by nearly “4 percent during 2017-2018”

[4]. Although the terms “cement” and “concrete” are often

used interchangeably, cement is the material that binds the

concrete and is made through a process that has two major

problems.

To produce cement, limestone (calcium carbonate) is

heated to 2,600 degrees Fahrenheit along with other feedstock

materials that contain silicates, such as clay [5][1]. At this

temperature, the two compounds break down and then

recombine to produce clinker (calcium silicate) , and carbon

dioxide (CO2). Finally, gypsum is added to the clinker (to

prevent flash setting) and ground into a fine dust to make

cement [5]. The problem with this process is that it releases

CO2 (the primary greenhouse gas contributing to global

warming) and uses a massive amount of energy [6].

For every ton of cement produced, one ton of CO2 is

released into the atmosphere [5]. The chemical reaction

during the process is responsible for 70% of the CO2 and the

fossil fuels burned, produce the other 30% [5]. This industry

alone is responsible for “5% of the world’s overall CO2

emissions,” second only to coal-powered electricity [7][5]. As

well, the fossil fuels used during the production of US cement,

account for 2.4% of US energy consumption, according to the

US Department of Energy [1]. Each ton of cement produced

“requires 4.7 million BTUs of energy, equivalent to about 400

pounds of coal” [8]. Many professionals and engineers in the

cement industry agree that both of these problems are serious

issues that need to be addressed. In fact, the National Precast

Concrete Association says that the problem is so widely

recognized that companies “from startups to the world’s

largest cement manufacturers” are working to find a solution

[1]. Given its high emissions and critical value and need in

society, cement is a very important material to reinvent and

make greener.

ALTERNATIVES TO PORTLAND CEMENT

The high-energy production of Portland cement has not

changed since it was discovered in the 1800s [8]. This says

something about the popularity and versatility of the product,

but it also cries out that even with the vast amount of

knowledge and technology invented since the 1800s, we

haven’t been able to make a greener product. Fortunately,

manufacturers across the board recognize this and are

working to reduce cement’s carbon footprint; several methods

have even already been implemented [1]. Several of these that

many large producers have already started using, are to

produce a stronger cement so that less is needed in the

concrete; to design more energy efficient kilns; or create a

way to capture the CO2 released during the chemical reaction.

Using these methods, manufactures claim that by 2020 the

process will produce 20% less CO2 than it did in 1990 [1].

Although history proves that this is not so easy, a better

Ivan Menz

2

solution is to totally redesign the process and final product.

Several companies have managed to come up with alternative

products, some of which claim to even be carbon neutral. The

problem with most of these products is that they tend to be

more expensive than Portland cement and therefore haven’t

got off the ground.

A few of these products use fly ash, a waste product

from coal power plants, as a partial substitute for cement.

When mixed with lime and water, fly ash “forms a compound

similar to Portland cement that is extremely strong and

durable” [1]. These high-volume fly ash concretes can reduce

the cement needed in concrete by up to 25%, which greatly

reduces its carbon footprint [1]. Another alternative, Ferrock,

is produced from the waste products of the steel and glass

industries. Not only does it use waste products, but it absorbs

CO2 during its curing process, making it carbon negative. One

big problem, though, is that if it were to become an in-demand

product, steel dust and glass would no longer be waste

products but valuable items, and its price would sky rocket

[9]. Thus, it isn’t considered a good solution. Solidia cement,

on the other hand, is a green cement that I think is a great

solution. Although it still releases CO2 during its

manufacturing phase, when it cures it uses CO2 as its catalyst,

significantly reducing its net CO2 emissions. Solidia cement

is being recognized by many professionals as the “sustainable

solution” to this major problem, most recently by the Federal

Highway Administration, which is seriously considering

using it as a green pavement alternative to tarmac [11].

SOLIDIA TECHNOLOGIES

Solidia cement has many unique properties that make it

the best replacement for Portland cement. Solidia “offers a

low-lime containing calcium silicate cement that emits 30%

less CO2 during the production process compared to ordinary

Portland cement” [10]. The reasons for this is that the

chemical reaction releases less CO2 and can be done at a lower

temperature [11]. As well, the curing process can consume

“up to 300 kg of CO2 per ton of cement…resulting in up to a

70% reduction in CO2 emissions” [12] This is because “the

reaction products of the cement are CaCO3 and SiO2 and do

not contain any hydrating phase” [12]. Dr. Sahu, the master-

mind behind Solidia, explained that during the curing process,

“Solidia uses carbonation instead on hydration, so we are also

able to recycle and save water used in the process. If the

worldwide cement and concrete industry were to adopt

Solidia’s technologies, it would save two trillion liters of

water per year” [11]. This is because cement must be made

with “natural water that is drinkable” [2]. Anything that has

excessive impurities in it will create a weaker cement that has

potential to decay sooner or corrode reinforcements [2].

Not only does Solidia have a smaller environmental

impact than Portland cement, it has several properties that are

more desirable. One of these is the speed that it cures. Typical

concrete requires up to 28 days to reach maximum strength

because of the long hydrate reaction that takes place, whereas

Solidia can do the same in 24 hours due to the carbonate

reaction. This is a massive benefit to the construction industry

because of the time saved. As well, “the Tuner-Fairbank

research and other independent tests show that Solidia

concrete is stronger, more durable, more flexible and costs

less than traditional concrete products, all while using the

same raw materials and equipment, but less water, energy,

and time throughout the entire supply chain” [12]. These

characteristics make Solidia cement a much better cement

than Portland which is why Lafarge has partnered with them.

The fact that Lafarge, a leader in the cement industry, would

decide to commercialize Solidia cement is a statement about

the potential Solidia has to transform this industry.

WHY SOLIDIA CEMENT IS THE ANSWER

The cement industry produces 5% of global CO2

emissions every year. This problem needs to be addressed by

engineers today because if we continue like this, we will never

be able to stop global warming repair. I think that Solidia

cement is the best alternative to Portland cement currently

available. Environmentally, it reduces the carbon footprint of

cement by 70%. As well, if the whole cement industry would

adopt Solidia cement, two trillion liters of fresh water would

be saved annually. This would be huge considering the

current global water crisis. Solidia cement also has many

advantages over traditional cement including drastically

reduced curing time, higher strength and lower costs. These

attributes are important because less cement will be needed to

produce regular strength concrete, which will save valuable

natural resources. This is very important for every citizen of

the world, because we all breath the same air and feel the

effects of global warming, and it is our responsibility to

protect our environment for future generations.

SOURCES

[1] “Green Cement.” National Precast Concrete Association.

11.17.2015. Accessed 10.29.2016

http://precast.org/2015/11/green-cement/

[2] “How Concrete is Made?” Portland Cement Association.

10.29.2016 http://www.cement.org/cement-concrete-

basics/how-concrete-is-made

[3] “United States and World Cement Production in 2010 and

2015.” Statista. Accessed 10.29.2016

https://www.statista.com/statistics/219343/cement-

production-worldwide/

[4] “Global Cement Consumption on the Rise.” Portland

Cement Association. 6.03.2015. Accessed 10.29.2016

http://www.cement.org/news/2015/06/03/global-cement-

consumption-on-the-rise

[5] “Is Concrete Bad for the Environment?” TheGreenAge.

6.18.2014. Accessed 10.28.2016

http://www.thegreenage.co.uk/article/concrete-is-bad-for-

the-environment/

Ivan Menz

3

[6] “Can Concrete be Eco Friendly?” Green Living Ideas.

2008. Accessed 10.29.2016

http://greenlivingideas.com/2008/12/21/can-concrete-be-

eco-friendly/

[7] “Ferrock: A Stronger, More Flexible and Greener

Alternative to Concrete?” Build Abroad. 9.27.2016. Accessed

10.29.2016

https://www.buildabroad.org/2016/09/27/ferrock/

[8] “Emissions from the Cement Industry.” State of the

Planet. 5.09.2012. Accessed 10.28.2016

http://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-

cement-industry/

[9] “An In-Depth Look at Ferrock and how it Compares to

Concrete.” HRL Tech. 12.02.2014. Accessed 10.29.2016

http://hrltech.com/2014/12/02/an-in-depth-look-at-ferrock-

and-how-it-compares-to-concrete/

[10] “Solidia Technologies Joins USDOT Effort to Develop

Sustainable Alternative Cementitious Materials for

Infrastructure.” Business Wire. 9.12.2016. Accessed

10.29.2016

http://www.businesswire.com/news/home/20160912006266/

en/Solidia-Technologies-Joins-USDOT-Effort-Develop-

Sustainable

[11] “Sustainable Solution to Infrastructure Decline Exhibited

at Federal Highway Administration.” CSR News. 10.18.2016.

Accessed 10.29.2016

http://www.csrwire.com/press_releases/39368-Sustainable-

Solution-to-Infrastructure-Decline-Exhibited-at-Federal-

Highway-Administration

[12] “Performance of Carbonated Concrete.” Solidia

Technologies. 9.07.2016. Accessed 10.28.2016

http://solidiatech.com/wp-

content/uploads/2016/09/Performance-of-Carbonated-

Concrete-Sada-Sahu-Abstract-Formatted-for-Website.pdf

[13] “Lafarge and Solidia Commercialize a New Low-carbon

Solution for the Construction Sector” Lafarge. 4.28.2015

Accessed 10.30.2016 http://www.lafarge.com/en/04282015-

Lafarge-Solidia-commercialize-new-low-carbon-solution-

for-construction-sector

ACKNOWLEDGEMENTS

Thank you to my roommate, Nate, for all the

encouragement while I spent many late nights working on this

essay. And thank you also to my house parents, Jonty and

Shula, for keeping me sustained while I toiled away on this

paper.

I would also like to thank my two Engineering Analysis

teammates, Ayem and Duncan, for providing me with advice

on the most difficult parts of this assignment.