.

  • Written by Yixia (Sarah) Zhang, Associate Professor of Engineering, Western Sydney University
If the cement industry were a country, it would be the [third-largest emitter of CO₂ in the world](https://www.carbonbrief.org/qa-why-cement-emissions-matter-for-climate-change). Joe Mabel/Wikimedia, CC BY-SA

Concrete is the most widely used man-made material, commonly used in buildings, roads, bridges and industrial plants. But producing the Portland cement needed to make concrete accounts for 5-8% of all global greenhouse emissions. There is a more environmentally friendly cement known as MOC (magnesium oxychloride cement), but its poor water resistance has limited its use – until now. We have developed a water-resistant MOC, a “green” cement that could go a long way to cutting the construction industry’s emissions and making it more sustainable.

Producing a tonne of conventional cement in Australia emits about 0.82 tonnes of carbon dioxide (CO₂). Because most of the CO₂ is released as a result of the chemical reaction that produces cement, emissions aren’t easily reduced. In contrast, MOC is a different form of cement that is carbon-neutral.

Global CO₂ emissions from rising cement production over the past century (with 95% confidence interval). Source: Global CO2 emissions from cement production, Andrew R. (2018), CC BY

Read more: Buildings produce 25% of Australia's emissions. What will it take to make them 'green' – and who'll pay?


What exactly is MOC?

MOC is produced by mixing two main ingredients, magnesium oxide (MgO) powder and a concentrated solution of magnesium chloride (MgCl₂). These are byproducts from magnesium mining.

Magnesium oxide (MgO) powder (left) and a solution of magnesium chloride (MgCl₂) are mixed to produce magnesium oxychloride cement (MOC). Author provided

Many countries, including China and Australia, have plenty of magnesite resources, as well as seawater, from which both MgO and MgCl₂ could be obtained.

Furthermore, MgO can absorb CO₂ from the atmosphere. This makes MOC a truly green, carbon-neutral cement.


Read more: Greening the concrete jungle: how to make environmentally friendly cement


MOC also has many superior material properties compared to conventional cement.

Compressive strength (capacity to resist compression) is the most important material property for cementitious construction materials such as cement. MOC has a much higher compressive strength than conventional cement and this impressive strength can be achieved very fast. The fast setting of MOC and early strength gain are very advantageous for construction.

Although MOC has plenty of merits, it has until now had poor water resistance. Prolonged contact with water or moisture severely degrades its strength. This critical weakness has restricted its use to indoor applications such as floor tiles, decoration panels, sound and thermal insulation boards.

How was water-resistance developed?

A team of researchers, led by Yixia (Sarah) Zhang, has been working to develop a water-resistant MOC since 2017 (when she was at UNSW Canberra).

Adding industrial byproducts fly ash (above) and silica fume (below) improves the water resistance of MOC. Author provided

To improve water resistance, the team added industrial byproducts such as fly ash and silica fume to the MOC, as well as chemical additives.

Fly ash is a byproduct from the coal industry – there’s plenty of it in Australia. Adding fly ash significantly improved the water resistance of MOC. Flexural strength (capacity to resist bending) was fully retained after soaking in water for 28 days.

To further retain the compressive strength under water attack, the team added silica fume. Silica fume is a byproduct from producing silicon metal or ferrosilicon alloys. When fly ash and silica fume were combined with MOC paste (15% of each additive), full compressive strength was retained in water for 28 days.

Both the fly ash and silica fume have a similar effect of filling the pore structure in MOC, making the cement denser. The reactions with the MOC matrix form a gel-like phase, which contributes to water repellence. The extremely fine particles, large surface area and high reactive silica (SiO₂) content of silica fume make it an effective binding substance known as a pozzolan. This helps give the concrete high strength and durability.

Scanning electron microscope images of MOC showing the needle-like phases of the binding mechanism. Author provided

Read more: We have the blueprint for liveable, low-carbon cities. We just need to use it


Although the MOC developed so far had excellent resistance to water at room temperature, it weakened fast when soaked in warm water. The team worked to overcome this by using inorganic and organic chemical additives. Adding phosphoric acid and soluble phosphates greatly improved warm water resistance.

Examples of building products made using MOC. Author provided

Over three years, the team has made a breakthrough in developing MOC as a green cement. The strength of concrete is rated using megapascals (MPa). The MOC achieved a compressive strength of 110 MPa and flexural strength of 17 MPa. These values are a few times greater than those of conventional cement.

The MOC can fully retain these strengths after being soaked in water for 28 days at room temperatures. Even in hot water (60˚C), the MOC can retain up to 90% of its compressive and flexural strength after 28 days. The values remain as high as 100 MPa and 15 MPa respectively – still much greater than for conventional cement.

Will MOC replace conventional cement?

So could MOC replace conventional cement some day? It seems very promising. More research is needed to demonstrate the practicability of uses of this green and high-performance cement in, for example, concrete.

When concrete is the main structural component, steel reinforcement has to be used. Corrosion of steel in MOC is a critical issue and a big hurdle to jump. The research team has already started to work on this issue.

If this problem can be solved, MOC can be a game-changer for the construction industry.


Read more: The problem with reinforced concrete


Yixia (Sarah) Zhang works for Western Sydney University. She receives funding from Australian Research Council under the ARC Research Hub for Nanoscience-based Construction Material Manufacturing with Monash University as the administration organization. UBIQ Pty LtD is the industrial partner and UNSW is the university partner for this project who both provided matching fund.

Khin Soe works for UBIQ Pty Ltd as a Technical and R&D Manager. She is partner investigator for this research grant that is awarded to A/Prof. Sarah Zhang. She is affiliated with Western Sydney University.

Yingying Guo does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Authors: Yixia (Sarah) Zhang, Associate Professor of Engineering, Western Sydney University

Read more http://theconversation.com/green-cement-a-step-closer-to-being-a-game-changer-for-construction-emissions-126033

Boosting Your Child’s Learning through Play

Being a parent is probably the highest responsibility one has in a lifetime. Once it happens, it becomes ongoing and keeps posing new challenges to us. Of course, it may seem easy from some perspe...

Diana Smith - avatar Diana Smith

Different ideas of Christmas Gifts to give to your beloved ones

"CHRISTMAS GIFTS – one of the best festival gifts to give to your closed ones. Find Christmas presents for everybody on your checklist. Christmas is now here, and if that you haven't got a hop on ...

News Company - avatar News Company

The Ultimate Guide to Sneakers and Sneaker Brands

When it comes to finding the perfect pair of sneakers, it can be hard to know where to start. Finding the right pair for any kind of occasion can be difficult, so brushing up on your knowledge of sn...

News Company - avatar News Company

View from The Hill: Morrison won't have a bar of public service intrusions on government's power

Scott Morrison has rejected or sidelined a number of recommendations from the long-awaited Thodey review. AAP/Paul BravenScott Morrison has rejected or sidelined a number of recommendations from the l...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

VIDEO: Michelle Grattan reflects on the year in politics

For their last video for the year, University of Canberra Vice-Chancellor Deep Saini and Michelle Grattan look backwards to the big issues which have shaped political discourse. They discuss the surpr...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

Choosing a Heavy Weighted Bathmats

Decorating your bathroom doesn’t finish with the paint choice or tile colours. You can change the whole room with the change of your towel set. There are no rules that say that you need to have a ...

News Company - avatar News Company

God as man, man as God: no wonder many Christian men today are having a masculinity crisis

How men saw God shaped how they saw themselves, and in turn, how they saw women. WikimediaThis article is part of our Gender and Christianity series. To understand contemporary Christian ideas about...

William Loader, Emeritus Professor of New Testament at Murdoch University, Murdoch University - avatar William Loader, Emeritus Professor of New Testament at Murdoch University, Murdoch University

Australia needs a national crisis plan, and not just for bushfires

Bushfires aren't the only catastrophic emergency Australia is likely to see. AAP Image/Mick TsikasCalls are growing for a national bushfire plan, including from former prime minister Malcolm Turnbull...

Andrew Gissing, General Manager, Risk Frontiers, Adjunct Fellow, Macquarie University - avatar Andrew Gissing, General Manager, Risk Frontiers, Adjunct Fellow, Macquarie University

Your Christmas shopping could harm or help the planet. Which will it be?

Many Australian consumers are concerned at the environmental impact of their shopping habits, especially at Christmas. AAPAustralian shoppers are set to spend $52.7 billion this Christmas. In the word...

Louise Grimmer, Senior Lecturer in Marketing, Tasmanian School of Business and Economics, University of Tasmania - avatar Louise Grimmer, Senior Lecturer in Marketing, Tasmanian School of Business and Economics, University of Tasmania

Right-swipes and red flags – how young people negotiate sex and safety on dating apps

For many young people, app dating is just part of regular dating life. freestocks.org/UnsplashPopular commentary on dating apps often associates their use with “risky” sex, harassment and ...

Kath Albury, Professor of Media and Communication, Faculty of Health, Arts and Design, Swinburne University of Technology - avatar Kath Albury, Professor of Media and Communication, Faculty of Health, Arts and Design, Swinburne University of Technology

Bougainville has voted to become a new country, but the journey to independence is not yet over

The Autonomous Region of Bougainville, a chain of islands that lie 959 kilometres northwest of Papua New Guinea’s capital, Port Moresby, has voted unequivocally for independence. The referendum...

Anna Powles, Senior Lecturer in Security Studies, Massey University - avatar Anna Powles, Senior Lecturer in Security Studies, Massey University

Comfortable Footwear That'll Get You Through From Day To Night In Style

When you are choosing your footwear, you need to make sure that you are choosing something that is going to be comfortable. This is especially important if you are going to be wearing your shoes a...

Rosana Beechum - avatar Rosana Beechum

How to Have a Peaceful Retirement

Retirement is the time to treat yourself after a lifetime of working, to complete your bucket list and to spend time with the people that you care for. However, having a peaceful retirement can be d...

News Company - avatar News Company

Friday essay: eco-disaster films in the 21st century - helpful or harmful?

A scene from the 2017 film Geostorm: many societies have historically attempted to deal with collective trauma by replaying and restaging it in art. Warner Bros., Electric Entertainment, Rat Pac-Dune ...

Ari Mattes, Lecturer in Communications and Media, University of Notre Dame Australia - avatar Ari Mattes, Lecturer in Communications and Media, University of Notre Dame Australia

A new study shows an animal's lifespan is written in the DNA. For humans, it's 38 years

A genetic "clock" lets scientists estimate how long extinct creatures lived. Wooly mammoths could expect around 60 years. Australian MuseumHumans have a “natural” lifespan of around 38 yea...

Benjamin Mayne, Molecular biologist and bioinformatician, CSIRO - avatar Benjamin Mayne, Molecular biologist and bioinformatician, CSIRO

Vital Signs: Australia's wafer-thin surplus rests on a mine disaster in Brazil

On Monday the Australian government will release the Mid-Year Economic and Fiscal Outlook (MYEFO). This will – as required by the Charter of Budget Honesty – provide an update on the key a...

Richard Holden, Professor of Economics, UNSW - avatar Richard Holden, Professor of Economics, UNSW

Don't believe the stereotype: these 5 charts show our democracy is safe in the hands of future voters

Almost 900 school kids, aged 12 to 17, were surveyed. ShutterstockA new, ongoing survey on how young Australians understand and imagine their democracy is already challenging long-held stereotypes. ...

Mark Evans, Professor of Governance and Director of Democracy 2025 - bridging the trust divide at Old Parliament House, University of Canberra - avatar Mark Evans, Professor of Governance and Director of Democracy 2025 - bridging the trust divide at Old Parliament House, University of Canberra

Private health insurance premiums should be based on age and health status

Policy changes have failed to stop young people dropping their private health insurance. ShutterstockPrivate health insurance has come under intense scrutiny in recent months, as it becomes clear heal...

Francesco Paolucci, Associate Professor; Head of Health Policy Program, Sir Walter Murdoch School of Public Policy and International Affairs, University of Newcastle - avatar Francesco Paolucci, Associate Professor; Head of Health Policy Program, Sir Walter Murdoch School of Public Policy and International Affairs, University of Newcastle

Knowledge is a process of discovery: how constructivism changed education

According to constructivists, we truly understand something when we filter it through our senses and interactions. from shutterstock.comThis is the second of two essays exploring key theories – ...

Luke Zaphir, Researcher for the University of Queensland Critical Thinking Project; and Online Teacher at Education Queensland's IMPACT Centre, The University of Queensland - avatar Luke Zaphir, Researcher for the University of Queensland Critical Thinking Project; and Online Teacher at Education Queensland's IMPACT Centre, The University of Queensland

Sick and Tired of Your Dead End Job? Try Teaching!

Tired of the same old grind at the office? Want an opportunity to impact lives both in your community and around the world? Do you love to travel and have new experiences? Teaching English is the perfect job for you! All you need is a willingness to ...

News Company - avatar News Company

The Impact of an Aging Population in Australia

There’s an issue on the horizon that Australia needs to prepare for. The portion of elderly citizens that make up the country’s overall population is increasing, and we might not have the infrastructure in place to support this. Australians h...

News Company - avatar News Company

LifeStyle

Boosting Your Child’s Learning through Play

Being a parent is probably the highest responsibility one has in a lifetime. Once it happens, it...

Different ideas of Christmas Gifts to give to your beloved ones

"CHRISTMAS GIFTS – one of the best festival gifts to give to your closed ones. Find Christmas pr...

How to Have a Peaceful Retirement

Retirement is the time to treat yourself after a lifetime of working, to complete your bucket list...

Latest Wednesday Lotto Results

Wednesday Lotto draw 3917 Lucky numbers for this draw were 43 followed by 25. The rest of the...