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MgO Hero or Villain

Fibre Cement sheets, megaboard, Sheeting, boardsAs Magnesium Oxide Board has become more recognised as a building product with some incredible benefits, it has also revealed itself as having risks that need to be understood by builders and architects who specify it. MgO boards can be the hero based on the type of board and manufacturing process. Having worked for the last 5 years on understanding the product, I thought it may be of benefit to provide some insights into this multi-application product.

MgO Board the Villain

There have been numerous reported problems with MgO board applications over the last 10 years that has mainly related to external cladding. Whilst any failure of a building product is a disaster for the builders and the clients, the experience in Denmark is probably one of the most expensive repairs required for the use of this product ($2B DKK or AU $455M). A lengthy report was conducted by the Technical University of Denmark, Dept. of Civil Engineering, June 2017. The conclusion that they gave was that MgO boards were not suitable for exterior cladding where there was a risk of relative humidity (RH) of 84 or above. Failure of MgO used in Exterior Cladding in Denmark

Concerns about MgO Boards were also raised with TK3 sold by GlobalFibre8 TK3 a CODEMARK approved system sold to New Zealand and Cook Islands With this system, people had to have their houses knocked down and rebuilt. The common cause amongst both these examples were Magnesium OxyChloride boards. In this instance the boards cracked and like the Danish experience leaked highly corrosive chloride salts that corroded primary and secondary fixings.

Dincel have also produced a number of reports about the usage of MgO boards being used as permanent formwork Problems with Fibre Cement Sheets and MgO boards as structural formwork.

Any initial reading of this information is enough to have any architect, engineer or builder run a mile.

MgO Board the Hero

As usual there are 2 sides to a story. How is it the Taipei 101, the 8th largest building in the world, could successfully be built with MgO boards as the internal and external cladding? Why was MgO boards the building material of choice for the buildings in the Chinese Summer Olympic Games 2008? Magnesium Oxide wallboard

To some degree, MgO boards became a victim of their own marketing success, both as a manufactured product and due to their performance characteristics.

When we consider what MgO board is professed to be able to achieve it is no wonder that it was considered by many to be the building industries answer to sliced bread.

  1. non-combustible;
  2. excellent for FRL cladding;
  3. higher compression and tensile strength than its Fibre Cement Sheet (FCS) cousin;
  4. will not promote mould or mildew;
  5. will not deteriorate in contact with water;
  6. low energy embodiment (approximately 40% lower than comparative products);
  7. excellent acoustic properties;
  8. can be painted or rendered;
  9. suitable for internal or external applications;
  10. lighter than FCS;
  11. easy to work with normal carpentry tools, and
  12. excellent thermal resistance properties

MgO board was considered one of the most promising multi-application boards to be used in the lightweight construction. There are many companies in the world who not only continue to use MgO board, they have also enhanced the quality of building envelopes using this product.

So what happened?

Due to their success as a building product and rapid uptake, many companies in China started to manufacture the boards. Manufacturing MgO boards is a relatively low technology base with lower capital costs associated with the manufacturing plants. Many manufacturers went into the market not fully understanding the chemistry involved in particular the importance of quality of raw materials and the batching of the magnesia cement.

This was also the case with international buyers who looked on Alibaba and researched the pricing of MgO boards seeking cheap boards. What they did not fully understand was that not all boards were the same and not all manufacturers were the same. Many buyers purchased boards that seemed to have all the certification not realising that many of the certifications were falsified, or if testing was done, the boards they tested, were not the same as those they ended up purchasing.

During the manufacture of MgO boards, there are a number of critical factors that affect Magnesium Chloride (MgCl) boards. These factors were known to good manufacturers who had a good understanding of the chemistry involved, but were not so well known, by many of the newer manufacturers.

One of these elements related to what is known as free chloride ions. If during the manufacture the magnesia cement was not batched (mixed) properly, free chloride ions were left in the mix. The Chinese standards at that point (JG/T 414-2013) of time allowed ≤ 10% free chloride ions, this has now changed to ≤ 1.5%. The result of poorly batched boards was significant, boards were highly reactive in relative humidity or 80% or more, leading to self-cracking, leaching of highly saline water from the boards that rusted fixings. Many of the manufacturers had little knowledge on how to test for free chloride ions so boards were sent out to the international market leading to significant failures.

This is an oversimplification of many of the issues with this product and its use in the construction industry but provides some understanding of the causes.

Where is the industry now?

Since many of these problems have come to light, there has been a number of significant changes that provide a great deal of promise to this product.

  1. Changes to the Standards,

The relevant authorities in China the China Magnesite Manufacturing Association (CMMA) has taken a more proactive role in the industry leading to changes in the Chinese Standards and testing protocols.

2. The formulation of the Magnesium Oxide Cement Association (MOCA)

This is an international group that has been working on the establishment of an ASTM E06-21 sub committee has a task group working on current standards suitable for North America and Internationally.

3. The introduction of Magnesium Sulphate boards (MgS04) that have similar performance properties as Magnesium Chloride boards (MgCl), but contain very little Chloride and thus do not have the the same issues as those that have been inherent in MgCl boards.

Many manufacturers have now moved over to Magnesium Sulphate boards as there is good scientific evidence of their performance.

This product will continue to grow in the market due to many of its performance characteristics, but it will take some time for the trust to be regained.

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