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Reinventing Concrete

HySSIL.jpgConcrete is one of the lesser-known players in the world of greenhouse gas emission. As Jeremy noted last November, the manufacturing of concrete is responsible for up to 7-10% of all CO2 emissions worldwide, a combination of the sheer volume of concrete produced and the very high temperatures required to create the core "Portland cement" material used in the standard process. But the industry is starting to wake up to the need to become more energy efficient, and two recent developments give some hope that a much greener (and potentially more sustainable) model for concrete manufacturing will soon emerge. One is a new form of concrete; the other is a new set of guidelines for the industry.

Jeremy's piece listed some of the alternatives to traditional concrete, including some which take less energy to make, have better thermal properties, or make use of materials which otherwise would have gone into landfills. Each has its drawbacks, as well, typically in cost -- one reason why traditional concrete remains so popular is that it's very cheap to make. In May of this year, however, CSIRO -- the Australian science and industrial research office -- announced the development of a form of concrete called HySSIL:

Dr Swee Liang Mak, who leads the HySSIL development team at CSIRO says, 'HySSIL is a revolutionary aerated cementitious (cement-based) product that is as strong as normal concrete but is only half as heavy. It provides up to five times the thermal insulation of concrete and is also impact and fire resistant'.

'HySSIL wall panels are also expected to offer significant cost advantages over existing products', says Dr Mak.

'Significant savings are achieved because CSIRO HySSIL technology uses readily available raw materials in smaller quantities and the-low cost and low-energy technology developed by CSIRO.

'Unlike certain processes used to manufacture aerated products, HySSIL production does not require expensive autoclaves (curing equipment)'.

Dr Mak says, 'This means there are significant savings on the cost of start-up manufacturing plant for HySSIL'.

HySSIL also offers the extra bonus of being easily recyclable.

Dr Mak adds, 'The use of lightweight building materials such as HySSIL will contribute to a reduction in greenhouse gas emissions, by increasing the energy efficiency of buildings and reducing the energy used during transportation and construction'.

The data on the material (PDF) look impressive. The light weight and high thermal insulation have been noted, but HySSIL is also easier to recycle than traditional concrete, more resistant to earthquakes (because of lower density and lighter "dead weight"), and is made of non-toxic material, so that no toxic fumes result during fires. The lower cost compared to regular concrete comes from a combination of lower energy use for manufacturing and lower transport expenses because of its light weight; the light weight also greatly reduces the cost of use in construction.

It would be interesting to see how HySSIL manufacturing measures up under the updated Cement CO2 Protocol released this month as a joint project of the World Business Council for Sustainable Development and the World Resources Institute. The protocol combines a set of CO2 accounting and reporting guidelines (PDF) and a step-by-step worksheet (Excel).

This protocol is intended as a tool for cement companies worldwide. It provides a harmonized methodology for calculating CO2 emissions, with a view to reporting these emissions for various purposes. It addresses all direct and the main indirect sources of CO2 emissions related to the cement manufacturing process in absolute as well as specific or unit-based terms. The protocol comprises two main elements: this guidance document, and an Excel spreadsheet. The spreadsheet is designed as a practical tool to help cement companies prepare their CO2 inventories.

For those of us outside of the concrete industry, the guidelines provide insights into the aspects of concrete production which have the greatest amount of greenhouse gas emission -- that is, those aspects most in need of attention. It also is a demonstration of the complexity of measuring CO2 emissions from industrial production. Figuring out CO2 output from cars and power use is relatively straightforward; determining the quantity of greenhouse gases -- both direct and indirect -- arising from multi-step industrial processes is far more difficult. It's entirely possible that, for some concrete manufacturers, use of these guidelines and worksheet will be the very first attempt to determine greenhouse emissions.

In combination, the development of HySSIL and the promulgation of the revised Concrete CO2 Protocol demonstrate that the potential is there for a significant transformation of the construction materials industry. What's needed now is a clear demonstration of the desire on the part of the industry to embrace these developments and make the necessary changes.

(Thank you, Suzanne Clifford)

Comments (6)


Problem with new building materials is that they have to be approved by the international building councils, then in Europe, then usually the USA follows, and finally the locales (cities and counties) where building actually occurs can sign on. The process takes years even for non-revolutionary products, never mind totally new materials.

A new variation of an already-approved building material is not as difficult. This product might be considered a variation on a structural concrete, provided it meets certain performance specifications. This also looks very similar to autoclaved aerated concrete (AAC), which is already approved. It looks like a stronger, cheaper variation. Either case could make approval much easier.


On a side note this Tasmanian company claims to produce a carbon-sequestering alternative to Portland cement. http//:www.tececo.com/sustainability.tececo_sequestration.php


And ... hey, with enough public pressure ... things do move slightly quicker. :)

These sort of developments show another side of a green world, the refinement of existing product production methods, I'm waiting patiently with a rather large interest in the result.


PS: Can this technolgy in any way lower the cost of those concrete refugee tents that featured on worldchanging a while back?

It will be VERY interesting to see this product evaluated by the new CO2 accounting guidelines. It may get its strength-to-weight ratio by using more Portland cement, the production of which contributes most of the CO2 emissions of concrete. It would take a lot of savings in transport and HVAC energy to offset that. Folks interested in this issue may want to investigate "fly ash concrete" as well as take a look at this product (I have no connection to the company):


Marlow Johnson:

a small correction to the post. the majority of CO2 emissions from cement production are process-related -during the production of lime, which is then used to make clinker. Combustion-related emissions account for less than half of total CO2 emissions, and are even less from a lifecycle-Kyoto perspective because, often times waste products are used as fuel (e.g. tires). None of this, however, is meant to suggest that cement production isn't CO2 intensive -- it is.


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