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Keeping you informed about the TecEco Cement project. Issue 33, 27th April 2004
John Harrison will be giving a talk at 3:30 pm in room 106 on the 7th May 2004 at the Geography Department, University of Tasmania.
Interested parties are invited to attend. The abstract follows:
The techno process of take, manipulate, make, use and waste is discussed particularly in relation to reducing, reusing and recycling, earth systems, the web of life and materials including new calcium magnesium blended cements (TecEco Cements) invented by the author.
Recycling is currently initiated more for “feel good” political reasons and unfortunately still does not still make good economic sense in many instances. Some unique solutions are offered to resolve this dilemma including a unique digital electronic identification system and the use of new generation TecEco Cement composite materials as potential repositories of wastes.
Attention is drawn to the huge potential for sustainability in the built environment. Building materials include over 70% of all materials flows and over two tonnes of concrete per person per annum are produced on the planet.
We received the following unsolicited letter from an owner/builder testing our formulations for mud bricks in Victoria
"I am currently using a TecEco Eco-Cement formulation given to me by John Harrison at an addition rate of 2.5% to stabilised mud bricks.
I thought I would write to you and let you know that these are working out very well and we are getting around 1/3 extra strength over a Portland cement control block.
I was reading your reports on your Tec-Cement concretes and was wondering if there was a way to incorporate TecEco Cement in to my slab on ground pour that I hope to do in the next 8-10 weeks (I live just outside the Melbourne metro area).
Can you let me know either way, as I am very keen to give this a go.
I get a lot of interest when I explain what I am doing to other mud brick/owner builders.
Thanks for your newsletters. If I win lotto I would love to invest.
Aim: To produce a stabilised pressed earth brick that would satisfy my building inspector in order to issue a building permit for our load bearing mud brick walled dwelling. The bricks should be easy and consistent to make keeping costs reasonable (below $0.30 a brick in materials as opposed to $2-3 to purchase).
Research suggested that OPC be used as a stabiliser. Discussions with local mud brick manufacturers suggested a 2.5% by volume of OPC be mixed with local subsoil should be adequate.
Our subsoil on site contains a relatively large amount of clay, about 15-20%, which necessitated good handling and processing in order to make good pressed bricks. It is recommended that clay content be 10-15% maximum to make good pressed mud bricks.
I was about to start making bricks after purchasing a share in a hydraulic
ram operated brick press (brick size 300x220x140mm) when I read in the 13 July
2002 issue of New Scientist an article on John Harrison’s Eco-Cement. After
contacting John he suggested a make up of 2 parts MgO to I part OPC with the
possibility of adding a small amount of fly ash if needed. I purchased the MgO
from Causmag in Young NSW and made test bricks from the press (without fly ash)
and after substantial curing, over 6 months I sent 2 test batches of bricks
to the Brick and Mortar Research Laboratory (BMRL) in Hoppers Crossing Victoria
for compressive strength testing. The results were as follows:
Batch No. 6523 OPC only to 2.5% of brick by uncompressed volume Batch size:
Mean unconfined compressive strength: 0.4 MPa
Unbiased standard deviation 0.1MPa
Batch No. 6524 OPC: MgO mix 2:1 ratio to 2.5% of brick by uncompressed volume Batch size 6
Mean unconfined compressive strength: 1.0MPa
Unbiased standard deviation: 0.2Mpa
Other mixes were used (no stabiliser at all and a batch with another OPC additive)
but were not tested, as funds were limited.
The bricks having a mean strength of 1.0Mpa and therefore passed requirements
for load bearing houses according to BMRL.
Qualitative tests indicate that the bricks also have very good water erosion
resistance as the remainder of the bricks have been exposed to the elements
over a 6-month period. However mud bricks are generally recommended to be protected
by eaves and verandas, as in the case in our building.
As can be seem by the results above the replacement of OPC by MgO increases
the compressive strength by 150%. This was an unexpected result.
Traditionally stabilisers for pressed bricks have centred around additives
such as OPC, Lime, Pozzolanas, Bitumen emulsion and straw (for “puddled” mud
bricks). The ability of MgO to greatly improve strength in mud bricks for me
has a two fold effect when considering not only MgO’s effect in strength for
a small volume of stabiliser but also in sequestering CO2 which is an important
advantage for those with an interest in sustainable (alternative) building.
There is a great interest in this topic by owner builders and suppliers in the
alternative building and sustainable building product market. OPC use is seen
as problematic because of its high-embodied energy and CO2 created, but necessary
due to its strength characteristics. I think there would also be many commercial
mud brick suppliers that would be interested in replacing OPC product.
Perhaps similar results could have been achieved by increasing the percentage
of OPC in OPC only stabilised bricks the added advantage of less CO2 involved
in production and its ability to sequester CO2 is still an advantage over the
higher cost of MgO over OPC.
While a lot more testing on different batches could build a better picture including soil tests it is clear that MgO combined with OPC can produce stabilised earth bricks that can be used to build load bearing walls by meeting compression strength and erosion requirements. Which was my goal in the beginning. However I would now like to know how I could incorporate Eco-Cements and concrete into the rest of our building project including the floor slab, concrete blocks and mortar etc.
I would like to thank John Harrison for the time he gave to help kick start
my interest and subsequent use of eco-type cement for our house building project
and subsequent projects. I am happy to provide further information such as test
result if interested.
References: Building with Earth, a handbook. John Norton, IT Publications, 1986.
A senior member of the British cement association (BCA) recently remarked about the similarities of TecEco Tec-Cement concretes and ground vitrified blast furnace slag (GBFS) concretes.
TecEco Tec-Cement cements contain around 5-15 % additionally added pure reactive magnesia and concretes made with them share many of the excellent qualities of concretes made with the addition of GBFS as a supplementary material such as better rheology, less bleeding, more strength and greater density.
The question needs to be raised as to whether any of the similarities between TecEco Cement concretes and Portland cement concretes with added GBFS are due to the high magnesia content of GBFS.
The composition of North American ground blast furnace slags varies as in the table below.
|TYPICAL COMPOSITION OF NORTH AMERICAN BLAST FURNACE SLAG|
|Calcium Oxide (CaO)||41||34-48||41||31-47||39||32-44||39||34-43|
|Silicon Dioxide (SiO2)||36||31-45||36||31-44||36||32-40||36||27-38|
|Aluminum Oxide (Al2O3)||13||10t-17||13||8-18||12||8-20||10||7-12|
|Magnesium Oxide (MgO)||7||1-15||7||2-16||11||2-19||12||7-15|
|(FeO or Fe2O3)|
|Data source is the National Slag Association data: 1949 (22 sources); 1957 (29 sources); 1968 (30 sources) and 1985 (18 sources).|
Recently I had an analysis given to me of some Japanese GBFS and it was running at about 6-7% with a maximum in the spec of 8%. I understand Australian slags are slightly lower at 4-5% although I don't think anybody has been interested enough to gather the evidence.
Indian GBFS typically contains about 30-35% CaO, 35-38% SiO2, 10-18% Al2O3, 7-10% MgO. (Indorma Cement Ltd at http://www.indorama.co.in/faq.htm)
Russian GBFS seems to run closer to 10% MgO (http://alexeyev.boom.ru/index.htm)
For Europe Cembureau give a variable content of magnesia from 0 to 11% (http://www.cembureau.be/Documents/Publications/CEMBUREAU_BAT_Reference_Document_2000-03.pdf) which is not surprising considering Europe is a large place.
I suspect the English figures for MgO in GBFS would be all over the place as are the summaries from Cembureau.
There is a high MgO content in GBFS partly because of the MgO naturally occurring in the limestones used and partly because companies like Qmag (debatably the worlds largest MgO producer) sell iron and steel smelters MgO to add to limestone as it fluxes better.
The chemical composition and glassy (noncrystalline) nature of vitrified slags is such that when water is added they react to form highly polymerized cementitious hydration products. The nature of these reactions depends on the glass content, fineness of the slag and chemical composition. The chemical reaction between GBFS and water is slow, but it is greatly enhanced by the presence of calcium hydroxide, alkalis and sulfates such as gypsum (CaSO4).
GBFS is one of the best supplementary cementing materials available and is generally used up to a 50-50 blend. The permeability of concretes made with GBFS is reduced and the workability improved. Workability is related to the fineness of the grind but the magnesia present should consume water increasing density and thereby reducing permeability and bleeding as it does in Tec-Cement concretes.
Although Portland cement has been inter ground with blast furnace slag for more than 60 years, the use of separately ground blast furnace slag (GBFS) as a supplementary material did not start until the late 1970s (1). In the United States, 13 million metric tons of slag are produced from iron production each year, but only 1.5 million metric tons are used directly in concrete. Most slag is air cooled, rendering it non-Cementitious and of little value
The setting times of concretes containing GBFS increases as the GBFS content increases. The direct addition of a low percentage of reactive magnesia in Tec-Cement concretes appears to increase the Bingham plastic nature of the concrete and may reduce the setting time as measured with the vicat needle and this is one of the reasons combinations of Tec-Cements with pozzolans and GBFS are being studied.
The rate and quantity of bleeding in concrete containing slag or slag cements is usually less than that in concrete containing no slag because of the relatively higher fineness of slag and possibly, as is thought to be the case with Tec-Cement concretes, the water demand of magnesia as it hydrates.
According to Malhotra 1987(2) the strength development profile of GBFS concrete depends primarily upon the type, fineness, activity index, and the proportions of GBFS used in concrete mixtures. Strength development is slower in the first 1-5 days. Between 7 and 28 days, the strength approaches that of concretes without slag and thereafter the strength of the GBFS concrete usually exceeds the strength of normal concrete. Flexural strength is also improved by the use of slag cement, making it suitable for concrete paving applications where flexural strengths are important. Stronger bonds in the cement-slag-aggregate system are generally thought to cause the higher flexural strength and this is considered to be related to the shape and surface texture of the slag particles. Tec-Cements are probably stronger because of more affective silicification reactions caused by a higher pH as a result of the super saturation of lime as magnesia hydrates removing water as well as densification for the same reason. As slag -OPC blends are also rich in magnesia the same mechanism should be considered.
The incorporation of GBFS reduces the average pore size and this may be partly due to a mechanism thought to exist in Tec-Cement concretes whereby the hydration of amorphous magnesia consumes unbound water producing hydration products such as brucite and small air voids resulting in reduced permeability of the matrix.
The freeze-thaw durability of slag concrete has been studied by many researchers and is comparable to ordinary Portland cement concretes. With TecEco Tec, Eco and Enviro-Cements resistance may be due to the consumption of unbound water creating solid and minute air voids and the compressibility of brucite which would take up internal strains. It is possible the same mechanism is active in GBFS-OPC blended cement concretes.
The effectiveness of slag in preventing damage due to ASR is attributed to the reduction of total alkalis in the cement-slag blend, the lower permeability of the system, and the tying up of the alkalis in the hydration process. In TecEco Cement concretes mobile cations such as Na+ and K+ are thought to be bound in brucite and this may also occur in slag cement concretes.
Many of the desirable properties of concretes made with additions of GBFS can be explained in relation to the high magnesium oxide content of the glass and it would be interesting to re-examine them in this context and compare low and high magnesia slags as well as the affect of added reactive MgO.
TecEco have demonstrated in preliminary work that additions of reactive MgO improve properties and challenge universities and research centers to take up this work.
1. Lewis, D. W. 1981. History of slag cements. Paper presented at University of Alabama Slag Cement Seminar, American Slag Association MF 186-6, April.
2. Malhotra, V. M. 1987. Properties of fresh and hardened concrete incorporating ground granulated blast furnace slag. In Supplementary cementing materials for concrete, ed. V. M. Malhotra, 291-331. Ottawa: Canadian Government Publishing Center.
Recently in Melbourne I was shown a small wax 3D model of a building built by a robot by Professor Mike Xie of RMIT university. A week later, whilst in USA I interviewed Professor Behrokh Khoshnevis, an engineering professor at the University of Southern California, Marina del Rey campus who has actually started building walls with concrete using a robot. He was using the same principle of contour crafting that Mike Xie was using except he had progressed from wax and clay to concrete.
There is no doubt that the application of robots to construction is the way of the future. A little like a colour inkjet printer prints different colours, but only in two dimensions, building robots will squeeze out different building materials with the various properties required in three dimensions tirelessly around the clock. The outcome will not only be much lower costs but a whole new range of design options shapes and textures. According to Khoshnevis, "architects love the technology" because all sorts of organic shapes are possible.
Xie and Khoshnevis may have the robotics under control except for some development cost issues. The remaining hurdles will be in the materials science area. Structures are made of a huge variety of materials. Some are void filling and insulative, others decorative, some let light in. A broad distinction would also be between structural and non-structural. All these materials would have in common the need to be able to be squeezed out a little like toothpaste out of a tube and retain their shape once ejected until hardened. They would have to have a Bingham plastic shear thinning property.
For the structural elements of a building some sort of concrete is an obvious choice, but for other requirements the materials are yet to be developed. Waste materials with various properties added to a benign TecEco Cement binder will result in a wide range of materials with the properties required for the differing purposes required within a structure
The TecEco materials technology has the potential for exactly the right shear thinning property to enable the materials required to be self hardening and squeezable out of a tube. The TecEco technology therefore offers huge rheological advantages, as well as sustainability, durability, strength and adjustable setting times.
John has recently returned from a trip to USA, Canada, the UK and Taiwan. Here is his report
My first stop was a Professor Behrokh Khoshnevis at the university of Southern
California, Marina del Rey Campus. Khoshnevis has designed a robot to "print"
buildings. See http://www.newscientist.com/news/news.jsp?id=ns99994764. and
the preceding article.
I then met a couple of people from the University of San Hose who are keen to initiate some research projects.
After that I attended the ACBM - RILEM conference at North-western University in Evanston, Chicago. It was very cold. One night the heating went off in my cheap hotel room and I felt like an icicle when I woke up in the middle of the night. Outside it was 20 or 30 below with wind chill factor! I am told in the middle of winter it can get much colder!
To cut a long story short, my talk went well, and I am hopeful that something will come of my efforts. Prof Shah, the head of school was interested in the freeze-thaw characteristics of our cements and as this is a big issue in North America.
I was also able to catch up with Dr Neil Milestone from Sheffield who will be involved in the BRE project.
The main reason for my going to Canada was to meet up with Professor Jean Marc Lalancette from Sherbrooke university (French speaking). Prof Lalancette has developed a process for concentrating and extracting the cobalt and nickel from old asbestos tailings all over Canada and this is exciting for us because the bi-product will be MgO. They are very interested and I am confident something to our benefit will come out of Canada.
In London the highlight was a meeting with Dr Mark Tyrer and Chris Cheesman
from Imperial College. These guys were really switched on and I am sure will
be of great value in the future as they initiate research projects and for their
contribution to the Minerals Industry Research Organisation (MIRO) team.
The meeting at the British research Establishment (BRE) went OK and they have so far been able to confirm greater strength with Tec-Cements. They were having some trouble with carbonation of Eco-Cements and I have since figured out that this may be because they were using the wrong sands. Because of the thermodynamics a wet dry environment and permeable substrate is required.
We also have another young man who wants to represent us in the UK and I had meetings with him. We have a team of four or five professionals now working with us.
I met up with a few of the people from CIRIA, the UK's premier research organisation for construction with over 700 members for industry. I believe they are now enthused to apply for grants to get on with the development of our technologies.
I also had a meeting with the chief scientist of Greenpeace, a Dr Parr and believe we have their full support. Watch for this
Our greatest ally in the UK and for that matter the world is the Minerals Industry Research Organisation (MIRO). They have already applied for a 4 million euro grant and are talking about applying for more in relation to the kiln. The companies behind MIRO include the likes of BHP - Billiton and Conzinc Rio Tinto.
I look forward to working more with MIRO.
We also look like we may have won another research grant in the UK but until it is official that is all I can say about that.
Taiwan, like the UK
is a small island with a lot of people. The Taiwanese produce about 100,000
tonnes of waste a day and have enormous problems finding places to dispose of
The challenge in both the UK and Taiwan is to produce materials that utilise wastes and for this reason I believe we can still broker and agreement with some of the leaders in the area that I spoke to. It goes beyond patents to what amounts to technology transfer. Fortunately a lot of the problems that need to be addressed in Taiwan are being studied in the UK and we will therefore be in a position to assist the Taiwanese. If we keep it reasonable and provide value for money then whether or not we have a patent in the country hopefully pails into irrelevance.
Warren Kalinko, a team member of the company and solicitor, introduced me to Simeon Michaels, vice president of the ethical investors association and even though I was exhausted from lack of sleep on airplanes I think I managed to enthuse him.
I have been going as hard as I physically can and trust me I am exhausted
and long for a break. I cannot really do this until we have shoved the giant
snowball we are building over the top of the hill and it gathers a momentum
all of it's own. I now have the distinct feeling that we are getting up to critical
mass around the world and perhaps within a year or so the fact that I need to
stay alive and well will not be so important.
Changing the world is not quite as easy I thought it would be, but we are winning. We do however have enormous economy of scale and credibility mountains to climb.
Because of recent legislation regarding spamming I cannot just add people to the newsletter. If you have any associates who may be interested in being kept in touch please encourage them to go to the web site and subscribe themselves.
John Harrison B.Sc. B.Ec. FCPA