1 Presentation downloadable from www.tececo.com Greening Concrete Why Green Concrete? – Huge impact on sustainability – Most widely used material on Earth • 30% of all materials flows on the planet – 70% of all materials flows in the built environment. • > 2.1 billion tonnes per annum. • >15 billion tonnes poured each year. • Over 2 tonnes per person per annum The fine print which is there for people to read if they download the presentation from the web site
Greening Concrete. Why Green Concrete? Huge impact on sustainability Most widely used material on Earth 30% of all materials flows on the planet 70% of all materials flows in the built environment . > 2.1 billion tonnes per annum. >15 billion tonnes poured each year. - PowerPoint PPT Presentation
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1Presentation downloadable from www.tececo.com
Greening Concrete Why Green Concrete?
– Huge impact on sustainability
– Most widely used material on Earth
• 30% of all materials flows on the planet
– 70% of all materials flows in the built environment.
• > 2.1 billion tonnes per annum. • >15 billion tonnes poured each
year.• Over 2 tonnes per person per
annum
The fine print which is there for people to read if they download the presentation from the web site
Greening Concrete7. Innovative New Concrete Products
– Including aggregates that improve or introduce new properties reducing lifetime energies• E.g. Including wood fibre or Hemp hurd reduces weight and conductance• Phase change minerals to improve specific heat capacity
– Use aggregates with lower embodied energy and that result in less emissions or are themselves carbon sinks• materials that be used to make concrete have lower embodied energies.
– Local low impact waste aggregates– Local “dirt”– Recycled aggregates from building rubble– Glass cullet
• Materials that are non fossil carbon are carbon sinks in concrete– Plastics, wood etc.
– Using aggregates that extend concrete• Aluminium use questionable• Foamed Concretes
– Use for slabs to improve insulation– Innovative products the reduce emissions and other impacts
Downloaded from www.dbce.csiro.au/ind-serv/brochures/embodied/embodied.htm (last accessed 07 March 2000)
Because so much concrete is used there is a huge opportunity for sustainability by reducing the embodied energy, reducing the carbon debt (net emissions) and improving properties that reduce lifetime energies.
Most of the embodied energy in the built environment is in concrete.
ACC Emissions to Fuel Project ACC, formerly Associated Cement Companies and now part of
the Holcim group have initiated a project to– Sequester CO2 generated by cement kilns– Produce high energy algal biomass
• Reused as fuel in its cement kilns.• Cellulose contents could be converted to alcohols• Protein residue could be use for animal feed
The project involves– The screening of appropriate high yielding algae cultures– The development of a bioreactor on a lab bench scale– Scaling up the technology to a pilot plant and then– Demonstrating the commercial viability.
This will require– A multi disciplinary approach and– Involve microbiologists, algae experts, bio-technologists, engineers and
other professionals– Cost around $ 3m over a period of 3 years.
Impact of TecEco Tec-Cement Technology on the use of Pozzolans
In TecEco tec-cements Portlandite is generally consumed by the pozzolanic reaction and replaced with brucite– Increase in rate of strength development particularly in the first
3-4 days.• concrete gells more quickly and finishers can go home!
– Kosmotrophic property of the magnesium ion– Change in surface charge on MgO
– Improved durability as brucite is much less soluble or reactive• Potential long term durability issue due to leaching of Ca from CSH
resolved.– Easier to finish fly ash concretes - Mg++ contributes a strong
6. Improve Particle Packing for Binder Minimisation and Carbonation
In the past, concrete proportioning was based on experience and estimates only.
TecSoft Pty. Ltd. are developing batching software, using theory from the world’s best experts (F. de Larrard and Ken Day), to optimize mix design and particularly particle packing.
Satterfield, S. G. (2001). Visualization aggregate in high performance concrete, National institute of standard and technology.(NIST)
Scientific knowledge of the concrete behaviour coupled with the use of optimization software will allow concrete technologists to:
- Design more sustainable concrete- Less cement of same strength- More durable- Use secondary aggregate and mining
wastes (poor size distribution)- Dramatically reduce the number of
experiment needed to design a concrete for a special application
Scientific Approach to Concrete Design Optimization of particle packing will improve
– The strength/cost ratio and– Concrete sustainability
• Less cement for the same strength Improving packing (other parameters being equal) leads
to an increase of:– The compressive and tensile strength– The workability – The durabilityAnd a decrease of:– The porosity– The risk of segregation– The yield stresses (easier to compact)
Could help improve the skill level in the industry– An expert in the box
Extending Cement Air used in foamed concrete is a cheap low
embodied energy aggregate and has the advantage of reducing the conductance of concrete.– Concrete, depending on aggregates weighs in the order of
2350 Kg/m3 – Concretes of over 10 mp as light as 1000 Kg/m3 can be
achieved.– At 1500 Kg/m3 25 mpa easily achieved.
From our experiments so far with Build-lite Cellular Concrete PL Tec-Cement formulations increase strength performance by around 5-10% for the same mass.
Claimed use of aluminium and autoclaving to make more sustainable blocks questionable?
Replacement of PC with Magnesium Based Carbonating Binders
Eco-Cement (TecEco)– Have high proportions of reactive magnesium oxide– Carbonate like lime– Generally used in a 1:2:18 (PC:MgO:Sand) paste basis because much more
carbonate “binder” is produced than with lime.– Like lime are carbon neutral but take up more weight of CO2 due to low weight of
MgMgO + H2O <=> Mg(OH)2
Mg(OH)2 + CO2 + H2O <=> MgCO3.3H2O58.31 + 44.01 <=> 138.32 molar mass (at least!)24.29 + gas <=> 74.77 molar volumes (at least!)
– 307 % expansion (less water volume reduction) producing much more binder per mole of MgO than lime (around 8 times) and les shrinkage
– Carbonates tend to be fibrous adding significant micro structural strength compared to lime
– Can include a wider range of wastes• Stick well due to hydrogen bonding• Low long term pH = low reactivity
Tec-Cements (Low MgO)– contain more Portland cement than reactive magnesia.
Reactive magnesia hydrates in the same rate order as Portland cement forming Brucite which uses up water reducing the voids:paste ratio, increasing density and possibly raising the short term pH.
– More pozzolans can be used. After all the Portlandite has been consumed Brucite controls the long term pH which is lower and due to it’s low solubility, mobility and reactivity results in greater durability.
– Other benefits include improvements in density, strength and rheology, reduced permeability and shrinkage and the use of a wider range of aggregates many of which are potentially wastes without reaction problems.