| 497 Main Road
Tasmania 7010 Australia
Phone: 61 3 62497868 (am)
Phone: 61 3 62713000 (pm)
Fax: 61 3 62730010
Printed in cyberspace on recycled electrons
Keeping you informed about the TecEco Cement project. Issue 29 17th August 2003
John will be in Melbourne on the 25th of August 2003 at various meetings.
After that he will be in Singapore speaking at the 28th Conference on OUR
WORLD IN CONCRETE and STRUCTURES Hotel New Otani, on the 28 - 29 August
2003. John leaves Singapore and arrives at Heathrow on the 30th and will stay
at least the first night or so with his relatives. John will probably then
travel by train to Dundee, Scotland where on the 3- 4 September 2003 he is
speaking at the INTERNATIONAL SYMPOSIA celebrating concrete: people and practice,
in honour of Professor Fred Glasser, University of Aberdeen, UK.
After that John will be hiring a car and traveling south through England and hopefully calling on relatives in York and Cambridge, Cambridge university, the BRE at Watford and possibly the Centre for Alternative Technology in Wales and maybe as far down south as earthship Brighton.
John will be leaving from London on the 13th September on his way home via Delhi, India, where he will be between the 14th and 17th September.
TecEco apologise for the whirlwind tour but is the way it is these days. Should anybody wish to catch up with John during his travels please go to the contact page on the tececo web site.
John Harrison was a speaker at the 21st Biennial Conference of the Concrete Institute of Australia "Concrete in the Next Millennium" 17-19 July 2003, Brisbane, Australia. The reception was warm, scientists present were genuinely interested and John left with many new contacts.
The web site has been improved just a little. We have split the Corporate Documentation page into Corporate Documentation and Technical Documentation and loaded a number of new technical documents including two papers and a new presentation well worth viewing. If anyone is is doubt about the chemistry including how the problems with Portland cement can be fixed and the massive abatement that could occur with the widespread use of Eco-Cements, they should read these papers and view the chemistry presentation.
These newsletters are electronic and dynamic. As it is important that we tell the right story, when we ourselves have become confused and later find out we have either deleted or amended articles. We are human and have made mistakes!
Newsletter 28 has been rewritten and re loaded.
In years gone by forests and grassland covered most of our planet. When it rained much of the water naturally percolated though soils that performed vital functions of slowing down the rate of transport to rivers and streams, purifying the water and replenishing natural aquifers.
Our legacy has been to pave this natural bio filter, redirecting the water that fell as rain as quickly as possible to the sea. Given global water shortages, problems with salinity, pollution, volume and rate of flow of runoff we need to change our practices so as to mimic the way it was for so many millions of years before we started making so many changes.
Porous pavements are now seriously being considered by enlightened engineers around the world as a way of reducing run-off and improving safety. TecEco believe they are essential for our long term survival on this planet.
Proponents claim that pervious pavements reduce the overloading of our present drainage system, cleanse water before it enters aquifers or streams and rivers, improve safety, reduce maintenance on buildings due to seasonal ground movement and reduce the costs of watering street trees.
Ideally a pervious pavement should be made with stone aggregates and a cementitious binder and be similar to concrete to handle and install. In cold areas it is important that the pavement should not trap water otherwise in winter the water would freeze and cause cracking. It is also important to detail a permeable structural base and sub base for the pavement that has a high void ratio as this acts as a reservoir, and provide underground drainage as required.
TecEco are interested in pervious pavements because they would allow access by CO2 curing Eco-Cement formulations with all the associated improvements in sustainability including massive waste utilization and large scale sequestration.
The experience of many engineers is that with relatively minor control and maintenance clogging will not reduce the infiltration rate below a design rate within the lifecycle of the pavement. Like any other kind of surface, pervious pavements have to be swept periodically to remove debris and water under pressure can be used.
Porous pavement would allow the replenishment of aquifers and reduced the cost of infrastructure to carry water out to sea as the volume and rate of flow would be less. Not as many pollutants, rubbish and debris would be transported reducing waterway pollution.
A pervious pavement with integral bacteria would improve water quality entering aquifers, streams and rivers. The critical "first flush" of pollutants would be sent rapidly into the cross-section where constantly available sources of bacteria and microbes exist and have sufficient air exchange capability to maintain themselves and perform their cleaning functions. Porous pavements could act as both pavements and bio-filters at the same time.
Water penetrates through pervious pavements quickly leaving drier and safer surfaces with no standing water.
Drier pavements have the obvious effect of increasing friction between shoes or tyres and the foot, cycle path or road surface in wet weather and at the same time reducing road noise and spray, improving visibility.
Pavements are safer because they are not lubricated with a film of water flowing across the upper surface to the edge drains. As water does not tend to collect, sheet ice problems should be less in colder climates.
Aquifers would be more regularly replenished resulting in less variable ground moisture content, reduced ground movement with wet dry cycles and less maintenance on buildings and infrastructure.
A permeable surface will allow water to penetrate to street trees reducing the need for watering during dry periods and saving money.
Porous pavements made with TecEco Eco-Cements would not be attacked by salts and would last considerably longer that conventional binders such as bitumen ( in some countries referred to as asphalt) and Portland cement.
Porous pavements made with TecEco Eco-Cements would utilise a considerable proportion of wastes such as fly ash and as they would carbonate, provide substantial abatement. Water entering aquifers, streams and rivers would be of higher quality and carry less macro pollutants. Fresh water replenishment of aquifers would reduce salinity and reverse falling water tables.
TecEco are looking for governements/research institutions around the world interested in laying down experimental roads using Eco-Cement pervious pavements and then monitoring run-off, water quality etc.
The Cement Sustainability Initiative (CSI) was formed to help the cement industry to address the challenges of sustainable development. The business leaders of a group of major cement companies lead the initiative under the auspices of the World Business Council.
The results and recommendations of a number of detailed studies over a 3-year period were published during 2002 and are accessible at www.wbcsdcement.org
The cement industry emits approximately 5%-10% of global man made CO2 emissions. Current proposals (i.e. The Kyoto Treaty) to curb CO2 emissions will profoundly affect the activities and finances of the industry. The cement industry as a whole is not yet contributing toward sustainability and little has been achieved over the past decade.
The cement companies participating in this study were: CEMEX (Mexico), Cimpor (Portugal), Heidelberg Cement (Germany), Holcim (Switzerland), Italcementi (Italy), Lafarge (France), RMC (UK), Siam Cement (Thailand), Taiheiyo Cement (Japan), Votorantim (Brazil).
The study notes that use of by-products such as blast furnace slag and fly ash will cut CO2 emissions dramatically. These technically proven materials are compatible with TecEco Cements which were unfortunately discovered too late to be included.
World Meteorological Organisation (WMO), Geneva, 2 July 2003
Record extremes in weather and climate events continue to occur around the world. Recent scientific assessments by the WMO indicate that, as the global temperatures continue to warm due to climate change, the number and intensity of extreme events will most likely increase.
Many parts of Europe have been experiencing record hot weather. In the United States, there were 562 tornados during May, which resulted in 41 deaths. This established a record for the number of tornados in any month. The previous monthly record was 399 tornados in June 1992. In the eastern and southeastern part of the US, wet and cold conditions prevailed for well over a month. Weekly negative temperature anomalies of –2°C to –6°C were experienced in May while precipitation excesses, ranging from 50 mm to 350 mm over a period of more than 12 weeks starting in March 2003, have been recorded.
In India, this year’s pre-monsoon heat wave brought peak temperatures of between 45°C and 49°C which correspond to weekly temperature departures from the normal of +2 to +5°C. At least 1400 people died in India due to the hot weather. In Sri Lanka, heavy rainfalls from Tropical Cyclone 01B exacerbated already wet conditions, resulting in flooding and landslides and killing at least 300 people. The infrastructure and economy of southwestern Sri Lanka was heavily damaged. A reduction of 20-30% is expected for the output of low-grown tea in the next three months.
It is time to start seriously considering the ramifications of utilising Eco-Cements on a wide scale!
There are two basic methods of foaming, mechanical and chemical. Chemicals are either foaming agents (i.e they do not produce a gas but facilitate the formation of a stable film around mechanically entrained bubbles ) or produce a gas. Often one or more methods are combined.
Mechanical foaming may be carried out in two principal ways by strong air entraining agitation:
(i) Pre foaming a suitable agent with water and then combining the foam with the paste or mortar or with the dry constituents;
(ii) Adding a quantity of foaming agent to the slurry, paste or mortar and whisking or agitating the whole into a stable mass.
The first method is more suitable than the second for making very low density concrete.
In conjunction with agitation a foaming agent is usually used.
Suitable agents for either method of mechanical foaming are:
(a) Saponified wood resin stabilised with animal glue.
(b) Saponified resin (in 20 percent concentration)
(c) Sodium compounds of certain aliphatic and aromatic sulphates - e.g. sodium lauryl, cetyl and oleyl sulphates; sodium napthalene isopropyl sulphate. (These compounds should be as free as possible from salt contamination.)
(d) Certain sulphates of petroleum derivatives.
(e) Certain complex organic compounds - e.g. keratin compound; saponin.
(f) Proprietary foaming agents.
TecEco are also aware of the use of dried animal blood proteins that hydrolyse (e.g. neopur from Neopur GmbH), soy protein foaming agents and glues, pectins and aqueous concentrate of a surface-active polypeptide-alkylene polyol condensates.
To improve the stability of foams other ingredients may be added. Resinate foams may be stabilised after preparation by aluminium sulphate added to the mixing water of the paste or mortar, or incorporated in the foam, in the proportion of .25 to .5 % weight of the cement. Sulphates of aliphatic and aromatic compounds as well as sulphates of petroleum derivatives may be stabilised by animal glue (soaked in water for some hours ) ammonium caseinate or sodium carboxymethyl cellulose.
Comparatively few surface active agents appear to be suitable for the manufacture of foamed concrete products. Agents-having only moderate foaming propensities often give satisfactory results provided that they are used in sufficient quantity to form stable foams. TecEco are looking for cheap foaming agents preferably of natural origin and biodigestable and/or degradable.
The addition of a small quantity (of the order of 0.05 mass % of the cement) of a wetting or dispersing agent, such as sulphated methyl and ethyl oleates, sodium napthalene dibutyl sulphonate or partly polymerised lignin sulphonates, assists aeration and increases the fluidity of the mix and uniformity of the set product.
Portland cement and lime slurries and mortars are foamed chemically by adding material which causes the evolution of bubbles of gas throughout the mix which may swell to several times its original volume, the expansion occurring after casting. A common method is to add 0.05 - 0.15 mm flake aluminium powder, depending on the pore size required in the proportion of 0.1-to 0.7 percent by weight of Portland cement and lime used in the mix, the expansion within limits, varying directly as to the amount of aluminium. (The use of too much aluminium causes rupture and subsidence of the expanded mass.)
The aluminium reacts with the alkaline mix and evolves hydrogen which is entrapped as innumerable small bubbles in the setting mass. Powdered zinc may be used similarly, but it is less effective than aluminium in producing small and evenly distributed bubbles. The rate of reaction, which depends on the alkalinity of the mix, is increased, in the case of Portland cement mixes, by the addition of hydrated lime or, more effectively, by a relatively small amount of sodium hydroxide solution. The optimum proportion of metallic admixture depends on the crater/cement-ratio, the temperature of the mixing water, the fineness and quality of the aluminium powder, the method of incorporation, the alkalinity and uniformity of the cement and the composition and desired density of the mix. The aluminium powder is intimately mixed or ground with the dry constituents before adding the water, or else is incorporated in the mix with a portion of the dry constituents as a final ingredient. The problem with using aluminium powder is that it has a high embodied energy, i.e. is consumed considerable energy during manufacture and is therefore less sustainable.
Mechanical and chemical methods may be combined to obtain low density products having small closed cavities evenly distributed through the mass and good physical properties.