Fire Resistant Buildings using TecEco Binders

The ongoing fires in Victoria, Australia give warning of a warmer drier world and the need to rethink the way we build houses to reduce the loss of life and property. At the same time as energy prices rise there are calls for materials and products that can reduce the lifetime requirement for the heating and cooling of buildings.

Research makes if very clear that flames from bush fires generally only last a few minutes during the passage of a fire front past a building [1]. Ignition from embers is however a risk factor that can last for hours depending mainly on wind strength. Burning embers may come into direct contact with combustible parts of a building or ignite litter of other debris in close proximity.

Litter is a problem of the Australian bush because leaves and debris do not decay quickly and blow up against or into buildings collecting in just about every place imaginable. We may not be able to make people clean up the litter around their houses but we can build them so they are less combustible in the first place.

The way we currently build is like constructing a slow combustion stove; we generally use bricks on the outside that will encourage and contain a fire if it starts on the inside. Our houses are not well sealed and drafts can come in through small gaps under the floor, or tin or tiles on the edges of our roofs carrying embers that ignite the insides. Much can be done about the design of buildings and the materials we use to make them with. The challenge is to improve lifetime energy performance and do something about other problems at the same time.

Consider the main risk areas

1. Ignition from under the sub - floor space.

This problem can be eliminated using slab on ground construction methods. If a timber floor is an absolute must then other options including filling under around the edges with insulating non combustibles and the management of surrounding vegetation are essential.

If a slab is specified then insulation can be improved underneath by reducing direct contact with the ground. If the insulation is vented properly the amount of cancer causing radon[2] entering a building can also be reduced. The smaller the individual voids the better the insulation and various materials can be used including gravel, kibble stones and other cheap alternatives. Builders should be careful not to create a water tank under a slab unintentionally by providing good drainage..

2. Ignition from burning embers.

When buildings warm up hot air rises and comes out through cracks and other openings. What goes out must come in somewhere and air containing embers can be sucked into a building during a bush fire that will ignite the many combustibles inside.

For bush fire resistance it is important to make sure a building can be well sealed. Air vents should be located nowhere near vegetation and doors and windows should be able to be properly closed.

Attics are very warm places during a fire and the air convection currents can be quite strong, always rising upward and generally sucking in through under the roofing surface be it tiles or tin - on the edges - right near very combustible timber. Fires often get into buildings in this way so consideration should be given to using materials that are non combustible in the detail of the design of roofs.

The challenge for TecEco is to show the world better ways of building that will not only reduce damage from bush fires but also make our houses more comfortable to live in, cheaper to heat and cool and more sustainable. The key to implementation of this dream will be cost and overcoming the dogma.

For insulation and fire reasons we have to stop building our houses like pizza ovens. If we put the insulation on the outside where current wisdom dictates it should be then the challenge becomes one of finding materials that can perform this function that are much less combustible.

Roofs especially require attention. Slopes and guttering are necessary in this country and tin and tiles are not combustible so it gets down to what we build all the supporting structure and sealing areas with and our suggestion is that non combustable composites or lightweight steel should be materials of choice.

In fires hot enough to exceed the Curie point of steel the properties change and strength reduces - think about the failure of the twin towers. That's where TecEco come into the picture as all our binders are suitable for making concretes or composites[3] and are very good fire retardants releasing water, CO2 or both as the temperature rises. We can make roof trusses and the like out of composites or if the inside and outside walling of a building are made with TecEco cements with steel trusses above then fires will never get hot enough to weaken steel. The outside walling should be insulating and the inside should have high thermal capacity and using our binders this is not hard to achieve. Furthermore TecEco cements as a result of strong polar bonding stick very well to just about anything and so a large range of composites can be made utilising wastes.

MgCO3.3H2O => MgO + CO2 + 3H2O

Mg(OH)2 => MgO + H2O

Low Temperature Decomposition Reactions of MgO Binder Components

According to Jane Blackmore[4] "A preliminary look at the BCA [5] reveals obvious problems with the non-combustibility test as a measure of performance, whatever performance is intended. Many materials which are accepted from experience and common practice to be effectively “non-combustible” fail when subjected to the test procedure. It has therefore been found necessary by the regulators to include a list of materials in the BCA that are deemed to be non-combustible, and hence allow them to be used in circumstances where they would be prohibited on the grounds of results from the combustibility test. The list includes pre-finished metal sheeting, plasterboard and some bonded laminates."

The use of plasterboard will probably continue provided the other changes I have suggested are made. Manufacturers should note that there is another product that is challenging plaster board and I will call them SIPS which is short for structural integrated panels. Most of these come from China and many are made with castable Sorel type cements as a binder and incorporate a wondrous mix of waste materials to provide tensile strength, insulation and other properties. The don't burn well but unless they are properly waterproofed with for example a coating of magnesium phosphate type cement then they will eventually break down in the weather. Fortunately most seem to be waterproofed and provide a good surface for finishing.

I have no doubt that composites will be important in the years to come and already many building materials are made from composites such as for example the abovementioned boards. Many of these new composites contain magnesium compounds because they tend to stick well to other materials used as components or fillers. The use of composites help solve another problem which is how to utilise wastes.

For walling we need to go lighter, larger and therefore faster to reduce construction times as well as manufacturing, transport and erection costs. A product that is being developed with our assistance to address this challenge is Ultrapanel from Bendigo in Victoria. So far larger has been addressed thereby reducing erection times - lighter and more insulating versions are on the drawing board. Other new composites on the drawing board with clients include foamed hemp hurd boards that have both specific heat and are good insulators. Spray on walling, foamed concretes etc. are also important. If building components were made using composites in factories to fine tolerances they can be quickly and cheaply erected. Better does not necessarily mean more expensive.

To wrap up this article I must also mention colour. Imagine a black roof in a bush fire. It would get very hot and thus easier to ignite. Light colours do not absorb heat so much and so the colour we make materials matters.

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[1] Ramsay, C. and L. Rudolph (2003). Landscape and Building Design for Bush fire Areas, CSIRO Publishing.

[2] See the BBC News Article "Radon gas linked to cancer deaths"

[3] I define a composite as a complex material in which two or more distinct, complementary substances are combine to produce structural or functional properties not present in any individual component. Concrete is just a special kind of composite.

[4] Blackmore, J. (2008). "Non-combustibility in the Building Code of Australia (BCA): Implications for a New Global Standard."

[5] The acronym "BCA" is short for the Building Code of Australia