presentation downloadable from 1 greening mineral binders our slides are deliberately verbose as...

1Presentation downloadable from www.tececo.com

Greening Mineral BindersGreening Mineral Binders

Our slides are deliberately verbose as most people download and view them from the net. Because of time constraints I will have to race over some slides John Harrison B.Sc. B.Ec. FCPA.

Presentation by John Harrison, managing director of TecEco and inventor of Tec and Eco-Cements and the CarbonSafe process.

The technology paradigm defines what is or is not a resource - Pillzer


Under Materials Flows in the Techno-Processes are Molecular FlowsUnder Materials Flows in the Techno-Processes are Molecular Flows

Take → Manipulate → Make → Use → Waste [ ←Materials→ ]

[ ← Underlying molecular flow → ]

If the underlying molecular flows are “out of tune” with nature there is damage to the environment

e.g. heavy metals, cfc’s, c=halogen compounds and CO2

MoleconomicsIs the study of the form of atoms in molecules, their flow, interactions, balances, stocks and positions. What we take from the environment around us, how we manipulate and make materials out of what we take and what we waste result in underlying molecular flows that affect earth systems. These flows should mimic or minimally interfere with natural flows.


Abatement and SequestrationAbatement and Sequestration To solve sustainability problems our approach

should be holistically balanced and involve– Everybody, every day– Be easy– Make money

CarbonSafe = Sequestration and waste utilisation.

Abatement = Efficiency and conversion to non fossil fuels

+

TecEco’s Contribution

New technical paradigms are required

AbatementSequestration

and


The TecEco CarbonSafe Geo-Photosynthethic ProcessThe TecEco CarbonSafe Geo-Photosynthethic Process

Greensols Process

Fossil fuels

Solar or solar derived energy

CO2Oil

MgO

CO2

Coal

CO2

MgCO3

CO2

CO2

Inputs:

Atmospheric or smokestack CO2, brines,waste acid, other wastes

Outputs:

Potable water, gypsum, sodium bicarbonate, salts, building materials, bottled concentrated CO2 (for geo-sequestration and other uses).

Carbon or carbon compoundsMagnesium oxide

1.29 gm/l Mg

The CarbonSafe Geo-Photosynthetic Process is TecEco’s evolving techno-process that delivers profitable outcomes whilst reversing underlying undesirable moleconomic flows from other less sustainable processes.

TecEco MgCO2

Cycle

TecEcoKiln


The TecEco CarbonSafe Industrial EcologyThe TecEco CarbonSafe Industrial Ecology

OutputsGypsum, Sodium bicarbonate, Salts, Building materials, Potable water

InputsBrinesWaste AcidCO2

We must design whole new technical paradigms that reverse many of our problem molecular flows


Hydroxide

Reactor

Process

CO2 as a biological or industrial input or if no other use geological sequestration

CO2 from power generation, industry or out of the air

Magnesite (MgCO3)Magnes

ia (MgO)

Other Wastes

Simplified TecEco ReactionsTec-Kiln MgCO3 → MgO + CO2 - 118 kJ/moleReactor Process MgO + CO2 → MgCO3 + 118 kJ/mole (usually more complex hydrates)

Magnesium Thermodyna

mic Cycle

Waste Acid

1.354 x 109 km3 Seawater containing 1.728 1017 tonne Mg or suitable brines from other sources

Tonnes CO2 sequestered per tonne magnesium with various cycles through the TecEco Tec-Kiln process. Assuming no leakage MgO to built environment (i.e. complete cycles).

Billion Tonnes

Tonnes CO2 sequestered by 1 billion tonnes of Mg in seawater 1.81034

Tonnes CO2 captured during calcining (same as above) 1.81034

Tonnes CO2 captured by eco-cement 1.81034

Total tonnes CO2 sequestered or abated per tonne Mg in seawater (Single calcination cycle).

3.62068

Total tonnes CO2 sequestered or abated (Five calcination cycles.) 18.1034

Total tonnes CO2 sequestered or abated (Ten calcination cycles). 36.20

Gypsum (CaSO4)

Gypsum + carbon waste (e.g. sewerage) = fertilizers

Sewerage compost

Magnesite (MgCO3)Solar Process to

Produce Magnesium Metal

Bicarbonate of Soda (NaHCO3)

Eco-CementTec-Cement

Seawater

Carbonation

ProcessOther salts Na+,K+, Ca2+,Cl-

CO2 from power generation or industry

Sequestration Table – Mg from Seawater

The CarbonSafe Geo-Photosynthetic ProcessThe CarbonSafe Geo-Photosynthetic Process

CO2


TecEco CO2 Capture Kiln TechnologyTecEco CO2 Capture Kiln Technology

Can run at low temperatures. Can be powered by various

non fossil fuels.– E.g. solar

Theoretically capable of producing much more reactive MgO– Even with ores of high Fe content.

Captures CO2 for bottling and sale to the oil industry (geological sequestration).

Grinds and calcines at the same time.– Runs 25% to 30% more efficiently as use waste heat from

grinding Will result in new markets for ultra reactive low lattice

energy MgO (e.g. cement, paper and environment industries)


Re - Engineering Materials – What we Build WithRe - Engineering Materials – What we Build With

To solve environmental problems we need to understand more about materials in relation to the environment. – the way their precursors are derived and

their degradation products re assimilated• and how we can reduce the impact of

these processes

– what energies drive the evolution, devolution and flow of materials

• and how we can reduce these energies

– how materials impact on lifetime energies With the knowledge gained re-

design materials to not only be more sustainable but more sustainable in use

Environmental problems are the result of inherently flawed materials, materials flows and energy systems


Huge Potential for Sustainable MaterialsHuge Potential for Sustainable MaterialsReducing the impact of the take and waste

phases of the techno-process.– including carbon in materials

they are potentially carbon sinks.– including wastes for

physical properties aswell as chemical compositionthey become resources.

– re – engineeringmaterials toreduce the lifetimeenergy of buildings

Many wastes can contribute to physical properties reducing lifetime energies

C

CO2

Waste

Waste

CO2

CO2

CO2


Utilizing Carbon and Wastes (Biomimicry)Utilizing Carbon and Wastes (Biomimicry)

During earth's geological history large tonnages of carbon were put away as limestone and other carbonates and as coal and petroleum by the activity of plants and animals.

Sequestering carbon in magnesium binders and aggregates in the built environment mimics nature in that carbon is used in the homes or skeletal structures of most plants and animals.

We all use carbon and wastes to make our homes! “Biomimicry”

In eco-cement blocks and mortars the binder is carbonate and the aggregates are preferably wastes


Impact of the Largest Material Flow - Cement and ConcreteImpact of the Largest Material Flow - Cement and Concrete

Concrete made with cement is the most widely used material on Earth accounting for some 30% of all materials flows on the planet and 70% of all materials flows in the built environment.– Global Portland cement production is currently in the

order of 2.2 billion tonnes per annum. – Globally over 15 billion tonnes of concrete are poured

per year.– Over 2 tonnes per person per annum– Much more concrete is used than any other building

material.

TecEco Pty. Ltd. have benchmark technologies for improvement in sustainability and properties

TecEco Pty. Ltd. have benchmark technologies for improvement in sustainability and properties


Embodied Energy of Building MaterialsEmbodied Energy of Building Materials

Downloaded from www.dbce.csiro.au/ind-serv/brochures/embodied/embodied.htm (last accessed 07 March 2000)

Concrete is relatively environmentally friendly and has a relatively low embodied energy


Average Embodied Energy in BuildingsAverage Embodied Energy in Buildings

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.


Emissions from Cement ProductionEmissions from Cement Production

Chemical Release– The process of calcination involves driving off chemically bound

CO2 with heat.

CaCO3 →CaO + ↑CO2

Process Energy– Most energy is derived from fossil fuels.

– Fuel oil, coal and natural gas are directly or indirectly burned to produce the energy required releasing CO2.

The production of cement for concretes accounts for around 10% of global anthropogenic CO2.

– Pearce, F., "The Concrete Jungle Overheats", New Scientist, 19 July, No 2097, 1997 (page 14).

Arguments that we should reduce cement production relative to other building materials are nonsense because concrete is the most sustainable building material there is. The challenge is to make it more sustainable.

CO2

CO2

CO2

CO2


Cement Production ~= Carbon Dioxide EmissionsCement Production ~= Carbon Dioxide Emissions

0

500,000,000

1,000,000,000

1,500,000,000

2,000,000,000

2,500,000,000

Metric Tonnes

Year

Between Tec, Eco and Enviro-Cements TecEco can provide a viable much more sustainable alternative.


The TecEco Dream – A More Sustainable Built EnvironmentThe TecEco Dream – A More Sustainable Built Environment

MAGNESITE + OTHER INPUTS

TECECO CONCRETES

MINING

SUSTAINABLE CITIES

CO2

PERMANENT SEQUESTRATION & WASTE UTILISATION (Man made carbonate rock incorporating wastes as a building material)

CO2

MgOTECECO KILN

RECYCLED BUILDING MATERIALS

CO2

OTHERWASTES

CO2 FOR GEOLOGICAL SEQUESTRATION

We need materials that require less energy to make them, that last much longer and that contribute properties that reduce lifetime energies

“There is a way to make our city streets as green as the Amazon rainforest”. Fred Pearce, New Scientist Magazine


A Low Energy Post – Carbon & Waste Age?A Low Energy Post – Carbon & Waste Age?

Prehistoric Classic Renaissance Industrial Revolution Contemporary Post Carbon & Waste Age

Recyclable Recyclable

CO2

Wattle & daub Stone Mud brick Etc.

Stone

Stone Brick

Concrete Eco-cements and other new technology paradigms

Waste

The construction industry can be uniquely responsible for helping achieve this transition

Maybe then we can move confidently into a more sustainable future.


Concrete Industry ObjectivesConcrete Industry Objectives

PCA (USA)– Improved energy efficiency of fuels and raw

materials. – Formulation improvements that:

• Reduce the energy of production and minimize the use of natural resources.

• Use of crushed limestone and industrial by-products such as fly ash and blast furnace slag.

WBCSD– Fuels and raw materials efficiencies– Emissions reduction during manufacture


Greening the Largest Material Flow -Concrete

Greening the Largest Material Flow -Concrete

1. Scale down Production.– Untenable nonsense, especially to developing

nations

2. Use waste for fuels– Not my area of expertise but questioned by many.

3. Reduce net emissions from manufacture– Increase manufacturing efficiency– Increase fuel efficiency– Waste stream sequestration using MgO and CaO

• E.g. Carbonating the Portlandite in waste concrete– Given the current price of carbon in Europe this

could be viable

• TecEco have a mineral sequestration process that is non fossil fuel driven using MgO and the TecEco kiln

Not discussed


Greening ConcreteGreening Concrete4. Increase the proportion of waste materials that are

pozzolanic– Using waste pozzolanic materials such as fly ash and slags has

the advantage of not only extending cement reducing the embodied energy and net emissions but also of utilizing waste. • TecEco technology will allow the use of marginal pozzolans

– Slow rate of strength development increased in first few hours and days

– Potential long term (50 year plus) durability issues overcome using tec-cement technology

– Finishing problems overcome• We could run out of fly ash as coal is phasing out. (e.g. Canada)

5. Replace Portland cement with viable alternatives– There are a number of products with similar properties to Portland

cementa) Carbonating Bindersb) Non-carbonating binders

– The research and development of these binders needs to be accelerated


Greening ConcreteGreening Concrete6. Use aggregates that extend cement

– Use air as an aggregate making cement go further• Foamed Concretes work well with TecEco cements• Use for slabs to improve insulation• Aluminium use questionable

7. Use aggregates with lower embodied energy and that result in less emissions or are themselves carbon sinks– Other materials that be used to make concrete have lower embodied energies.

• Local low impact aggregates• Waste materials• Recycled aggregates from building rubble• Glass cullet

– Materials that non fossil carbon are carbon sinks in concrete• Plastics, wood etc.

8. Improve the performance of concrete by including aggregates that improve or introduce new properties reducing lifetime energies– Wood fibre reduces weight and conductance.


4. Increasing the Proportion of Waste Materials that are Pozzolanic

4. Increasing the Proportion of Waste Materials that are Pozzolanic

Advantages– Lower costs– More durable greener concrete

Disadvantages– Rate of strength development retarded– Potential long term durability issue due to leaching of Ca from

CSH.• Resolved by presence of brucite in tec-cements

– Higher water demand due to fineness.– Finishing is not as easy

Supported by WBCSD and virtually all industry associations

Driven by legislation and sentiment


Impact of TecEco Tec-Cement Technology on the use of Pozzolans

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 in the first 3-4 days.

• Internal consumption of water by MgO as it hydrates reducing impact of fineness demand

• More pozzolanic reactions• Mg Al hydrates?

– Followed by straight line development– Improved durability as brucite is much less soluble or reactive

• Potential long term durability issue due to leaching of Ca from CSH resolved.

– Influence of kosmotopic Mg++• Concretes easier to finish with a strong shear thinning property• Gel up more quickly – so finishers can go home earlier even with

added pozzolan• Early strength development in the first few days – previously a

problem with added pozzolan• Less shrinkage and cracking


Portlandite Compared to BrucitePortlandite Compared to BruciteProperty Portlandite (Lime) Brucite

Density 2.23 2.9

Hardness 2.5 – 3 2.5 – 3

Solubility (cold) 1.85 g L-1 in H2O at 0 oC 0.009 g L-1 in H2O at 18 oC.

Solubility (hot) .77 g L-1 in H2O at 100 oC .004 g L-1 H2O at 100 oC

Solubility (moles, cold) 0.000154321 M L-1 0.024969632 M L-1

Solubility (moles, hot) 0.000685871 M L-1 0.010392766 M L-1

Solubility Product (Ksp) 5.5 X 10-6 1.8 X 10-11

Reactivity High Low

Form Massive, sometime fibrous

Usually fibrous

Free Energy of Formation of Carbonate Gof

- 64.62 kJ.mol-1 -19.55 kJ.mol-1

-119.55 kJ.mol-1(via hydrate)

Cement chemists in the industry should be getting their heads around the differences


Tec-Cement Concrete Strength Gain CurveTec-Cement Concrete Strength Gain Curve

The possibility of high early strength gain with added pozzolans is of great economic and environmental importance.

Tec – Cement Concrete with 10% reactive magnesia

OPC Concrete

HYPOTHETICAL STRENGTH GAIN CURVE OVER TIME (Pozzolans added)

MPa

Log Days Plastic Stage

7 14 28 3

We have observed this kind of curve with over 300 cubic meters of concrete


5.a Replacement of PC by Carbonating Binders5.a Replacement of PC by Carbonating Binders

Lime– The most used material next to Portland cement in

binders.– Generally used on a 1:3 paste basis since Roman

times– Non-hydraulic limes set by carbonation and are

therefore close to carbon neutral once set.CaO + H2O => Ca(OH)2

Ca(OH)2 + CO2 => CaCO3

33.22 + gas ↔ 36.93 molar volumes– Very slight expansion, but shrinkage from loss of

water.


5.a Replacement of PC Carbonating Binders5.a Replacement of PC Carbonating Binders

Eco-Cement (TecEco)– Have high proportions of reactive magnesium oxide– Carbonate like lime– Generally used in a 1:5-1:12 paste basis because much more carbonate

“binder” is produced than with lime

MgO + H2O <=> Mg(OH)2

Mg(OH)2 + CO2 + H2O <=> MgCO3.3H2O

58.31 + 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)

– Carbonates tend to be fibrous adding significant micro structural strength compared to lime

Mostly CO2 and water


5.b Replacement with Non Carbonating Binders5.b Replacement with Non Carbonating Binders

There are a number of other novel cements with intrinsically lower energy requirements and CO2 emissions than conventional Portland cements that have been developed – High belite cements

• Being research by Aberdeen and other universities– Calcium sulfoaluminate cements

• Used by the Chinese for some time– Magnesium phosphate cements

• Proponents argue that a lot stronger than Portland cement therefore much less is required.

• Main disadvantage is that phosphate is a limited resource– Geopolymers


GeopolymersGeopolymers

“Geopolymers” consists of SiO4 and AlO4 tetrahedra linked alternately by sharing all the oxygens.– Positive ions (Na+, K+, Li+, Ca++, Ba++, NH4

+, H3O+) must be present in the framework cavities to balance the negative charge of Al3+ in IV fold coordination.

Theoretically very sustainable Unlikely to be used for pre-mix concrete or waste in

the near future because of.– process problems

• Requiring a degree of skill for implementation

– nano porosity• Causing problems with aggregates in aggressive environments

– no pH control strategy for heavy metals in waste streams


TecEco CementsTecEco CementsSUSTAINABILITY

DURABILITY STRENGTHTECECO CEMENTS

Hydration of the various components of Portland cement for strength.

Reaction of alkali with pozzolans (e.g. lime with fly ash.) for sustainability, durability and strength.

Hydration of magnesia => brucite for strength, workability, dimensional stability and durability. In Eco-cements carbonation of brucite => nesquehonite, lansfordite and an amorphous phase for sustainability.

PORTLAND

+ or - POZZOLAN

MAGNESIA

TecEco concretes are a system of blending reactive magnesia, Portland cement and usually a pozzolan with other materials and are a key factor for sustainability.


The Magnesium Thermodynamic CycleThe Magnesium Thermodynamic Cycle

An alkaline environment in which silicates form

Thermal decomposition MgCO3 MgO + CO2 ΔH = 118.28 kJ.mol-1 ΔG = 65.92 kJ.mol-1

Carbonation Mg(OH)2 + CO2 + 2H2O MgCO3.3 H2O ΔH = -175.59 kJ.mol-1 ΔG = -38.73 kJ.mol-1

Hydration MgO + H2O Mg(OH)2 ΔH = -81.24 kJ.mol-1 ΔG = -35.74 kJ.mol-1

Reactive phase

TOTAL CALCINING ENERGY (Relative to MgCO3) Theoretical = 1480 kJ.Kg-1 With inefficiencies = 1948 kJ.Kg-1 Nesquehonite

? Representative of other hydrated mineral carbonates including an amorphous phase and lansfordite Magnesite*

Magnesia

Dehydration

CO2

Brucite*

Eco - Cements

Tec - Cements

CO2

CO2 CaptureNon fossil fuel energy

Calcination

We think this cycle is relatively independent of other constituents


TecEco Cement Technology Theory TecEco Cement Technology Theory Portlandite (Ca(OH)2) is too soluble, mobile and

reactive.– It carbonates, reacts with Cl- and SO4

- and being soluble can act as an electrolyte.

TecEco generally (but not always) remove Portlandite using the pozzolanic reaction and

TecEco add reactive magnesia– which hydrates, consuming water and concentrating alkalis

forming brucite which is another alkali, but much less soluble, mobile or reactive than Portlandite.

In Eco-cements brucite carbonates


TecEco FormulationsTecEco Formulations 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.

– Reactions with pozzolans are more affective. 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.

Eco-cements (High MgO)– contain more reactive magnesia than in tec-cements. Brucite in porous

materials carbonates forming stronger fibrous mineral carbonates and therefore presenting huge opportunities for waste utilisation and sequestration.

Enviro-cements (High MgO)– contain similar ratios of MgO and OPC to eco-cements but in non porous

concretes brucite does not carbonate readily.– Higher proportions of magnesia are most suited to toxic and hazardous waste

immobilisation and when durability is required. Strength is not developed quickly nor to the same extent.


TecEco Cements – Impact on SustainabilityTecEco Cements – Impact on Sustainability

The CO2 released by calcined carbonates used to make binders can be captured using TecEco kiln technology.

MgO can be made using non fossil fuel energy Tec-Cements Develop Significant Early Strength

even with Added Supplementary Materials. Eco-Cements carbonate sequestering CO2

requiring 25-75% less binder in some mixes


Benefits to the Concrete Industry of Adopting TecEco Technology

Benefits to the Concrete Industry of Adopting TecEco Technology

Both Tec and Eco-Cements provide a benign low pH environment for hosting large quantities of waste overcoming problems of delayed reactions:

– Using acids to etch plastics so they bond with concretes.– sulphates from plasterboard etc. ending up in recycled construction materials.– heavy metals and other contaminants.– delayed reactivity e.g. ASR with glass cullet– Resolving durability issues– Indian and Chinese quality control issues

Concretes containing MgO– shrink less

– are demonstrably more durable.

– can incorporate wastes that contribute to physical properties reducing lifetime energies

The biggest business on the planet is going to be the sustainability business


6. Using Aggregates that Extend Cement6. Using Aggregates that Extend 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 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


7. Use Aggregates with Lower Embodied Energy and that Result in less Emissions or

that are Themselves Carbon Sinks

7. Use Aggregates with Lower Embodied Energy and that Result in less Emissions or

that are Themselves Carbon Sinks

Use of aggregates that lower embodied energies– wastes such as recycled building rubble Tec and Eco-

Cements do not have problems associated with high gypsum content

Use of other aggregates that include non fossil carbon– sawdust and other carbon based aggregates can make eco-

cement concretes a net carbon sink. Reduce transport embodied energies by using local

materials such as earth– mud bricks and adobe.– our research in the UK and with mud bricks in Australia

indicate that Eco-Cement formulations seem to work better than PC for this


Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes


As the price of fuel rises, theuse of local or on site lowembodied energy materialsrather than carted aggregateswill have to be considered.

Recent natural disasters such as the recent tsunami and Pakistani earthquake mean we urgently need to commercialize technologies like TecEco’s because they provide benign environments allowing the use of many local materials and wastes without delayed reactions

No longer an option?

The use of on site and local wastes will be made possible by the use of low reactivity TecEco mixes and a better understanding of particle packing. We hope with our new software to be able to demonstrate how adding specific size ranges can make an unusable waste such as a tailing or sludge suitable for making cementitious materials.


8. Improve the Performance of Concrete by Including Aggregates that

Improve or Introduce New Properties Reducing Lifetime Energies

8. Improve the Performance of Concrete by Including Aggregates that

Improve or Introduce New Properties Reducing Lifetime Energies

Rather than be taken to landfill many wastes can be used to improve properties of concrete that reduce lifetime energies.– For example paper and plastic have in common reasonable

tensile strength, low mass and low conductance and can be used to make cementitious composites that assume these properties


Biomimicry - Ultimate RecyclersBiomimicry - Ultimate Recyclers As peak oil looms and the price of transport is set to rise sharply

– We should not just be recycling based on chemical property requiring sophisticated equipment and resources

– We should be including wastes based on physical properties as well as chemical composition in composites whereby they become local resources.

The Jackdaw recycles all sorts of things it finds nearby based on physical property.

The bird is not concerned about chemical composition and the nest it makes could be described as a composite material.

TecEco cements are benign binders that can incorporate all sort of wastes without reaction problems. We can do the same as the Jackdoor


TecEco Technologies Take Concrete into the FutureTecEco Technologies Take Concrete into the Future

More rapid strength gain even with added pozzolans– More supplementary materials can be used reducing

costs and take and waste impacts. Easier to finish even with added pozzolans

– The stickiness concretes with added fly ash is retarding use

Higher strength/binder ratio Less cement can be used reducing costs and

take and waste impacts More durable concretes

– Reducing costs and take and waste impacts. Use of wastes Utilizing carbon dioxide Magnesia component can be made using non

fossil fuel energy and CO2 captured during production.

Eco-Cements

Tec -Cements

Tec & Eco-Cements

Contact:

John Harrison, TecEco Pty. Ltd. www.tececo.com


Eco-CementsEco-Cements Eco-cements are similar but potentially superior to lime

mortars because:– The calcination phase of the magnesium thermodynamic cycle takes

place at a much lower temperature and is therefore more efficient.

– Magnesium minerals are generally more fibrous and acicular than calcium minerals and hence add microstructural strength.

Water forms part of the binder minerals that forming making the cement component go further. In terms of binder produced for starting material in cement, eco-cements are much more efficient.

Magnesium hydroxide in particular and to some extent the carbonates are less reactive and mobile and thus much more durable.


Eco-Cement Strength DevelopmentEco-Cement Strength Development

Eco-cements gain early strength from the hydration of PC.

Later strength comes from the carbonation of brucite forming an amorphous phase, lansfordite and nesquehonite.

Strength gain in eco-cements is mainly microstructural because of– More ideal particle packing (Brucite particles at 4-5 micron are

under half the size of cement grains.)– The natural fibrous and acicular shape of magnesium carbonate

minerals which tend to lock together. More binder is formed than with calcium

– Total volumetric expansion from magnesium oxide to lansfordite is for example volume 811%.

Mg(OH)2 + CO2 MgCO3.5H2O

From air and water


Eco-Cement Strength Gain CurveEco-Cement Strength Gain Curve

Eco – Cement Concrete with 50% reactive magnesia

OPC Concrete


MPa


?

?

?

?

7 14 28 3

Eco-cement bricks, blocks, pavers and mortars etc. take a while to come to the same or greater strength than OPC formulations but are stronger than lime based formulations.


Chemistry of Eco-CementsChemistry of Eco-Cements

There are a number of carbonates of magnesium. The main ones appear to be an amorphous phase, lansfordite and nesquehonite.

The carbonation of magnesium hydroxide does not proceed as readily as that of calcium hydroxide. Gor Brucite to nesquehonite = - 38.73 kJ.mol-1 – Compare to Gor Portlandite to calcite = -64.62 kJ.mol-1

The dehydration of nesquehonite to form magnesite is not favoured by simple thermodynamics but may occur in the long term under the right conditions.

Gor nesquehonite to magnesite = 8.56 kJ.mol-1 – But kinetically driven by desiccation during drying.

Reactive magnesia can carbonate in dry conditions – so keep bags sealed!

For a full discussion of the thermodynamics see our technical documents.

TecEco technical documents on the web cover the important aspects of carbonation.


Eco-Cement ReactionsEco-Cement Reactions

Hardness: 2.5 - 3.0 2.5

Form: Massive-Sometimes Fibrous Often Fibrous Acicular - Needle-like crystals

Solubility (mol.L-1): .00015 .01 .013 (but less in acids)

Magnesia Brucite Amorphous Lansfordite

MgO + nH2O Mg(OH)2.nH2O + CO2 MgCO3.nH2O + MgCO3.5H2O + MgCO3.3H2O

In Eco - Cements

Hardness: 2.5 3.5

Form: Massive Massive or crystalline More acicular

Solubility (mol.L-1): .024 .00014

Portlandite Calcite

Ca(OH)2 + CO2 CaCO3

Compare to the Carbonation of Portlandite

Aragonite

Nesquehonite


Eco-Cement Micro-Structural StrengthEco-Cement Micro-Structural Strength

Elongated growths of nesquehonite near the surface, growing inwards over time and providing microstructural strength.

Portland clinker minerals (black). Hydration providing structural framework.

Micro spaces filled with hydrating magnesia (? brucite) – acting as a “waterproof filler”

Flyash grains (red) reacting with lime resulting in the formation of pozzolanic CSH. Also acting as micro aggregates.


CarbonationCarbonation

Eco-cement is based on blending reactive magnesium oxide with other hydraulic cements and then allowing the Brucite and Portlandite components to carbonate in porous materials such as concretes blocks and mortars.

– Magnesium is a small lightweight atom and the carbonates that form contain proportionally a lot of CO2 and water and are stronger because of superior microstructure.

The use of eco-cements for block manufacture, particularly in conjunction with the kiln also invented by TecEco (The Tec-Kiln) would result in sequestration on a massive scale.

As Fred Pearce reported in New Scientist Magazine (Pearce, F., 2002), “There is a way to make our city streets as green as the Amazon rainforest”.

Ancient and modern carbonating lime mortars are based on this principle


Aggregate Requirements for CarbonationAggregate Requirements for Carbonation

The requirements for totally hydraulic limes and all hydraulic concretes is to minimise the amount of water for hydraulic strength and maximise compaction and for this purpose aggregates that require grading and relatively fine rounded sands to minimise voids are required

For carbonating eco-cements and lime mortars on the on the hand the matrix must “breathe” i.e. they must be porous– Requiring relative mono grading so that particle packing is imperfect

causing physical air voids and some vapour permeability.


CO2 Abatement in Eco-CementsCO2 Abatement in Eco-Cements

Eco-cements in porous products absorb carbon dioxide from the atmosphere. Brucite carbonates forming lansfordite, nesquehonite and an amorphous phase, completing the thermodynamic cycle.

No Capture11.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.37 tonnes to the tonne. After carbonation. approximately .241 tonne to the tonne.

Portland Cements15 mass% Portland cement, 85 mass% aggregate

Emissions.32 tonnes to the tonne. After carbonation. Approximately .299 tonne to the tonne.

.299 > .241 >.140 >.113Bricks, blocks, pavers, mortars and pavement made using eco-cement, fly and bottom ash (with capture of CO2 during manufacture of reactive magnesia) have 2.65 times less emissions than if they were made with Portland cement.

Capture CO211.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.25 tonnes to the tonne. After carbonation. approximately .140 tonne to the tonne.

Capture CO2. Fly and Bottom Ash11.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.126 tonnes to the tonne. After carbonation. Approximately .113 tonne to the tonne.

For 85 wt% Aggregates

15 wt% Cement

Greater Sustainability


TecEco Cement LCATecEco Cement LCA

TecEco Concretes will have a big role post Kyoto as they offer potential sequestration as well as waste utilisation

The TecEco LCA model is available for download under “tools” on the web site


Tec-Cement Concretes - Lattice Energy Destroys a MythTec-Cement Concretes - Lattice Energy Destroys a Myth

Magnesia, provided it is reactive rather than “dead burned” (or high density, crystalline periclase type), can be beneficially added to cements in excess of the amount of 5 mass% generally considered as the maximum allowable by standards prevalent in concrete dogma.– Reactive magnesia is essentially amorphous magnesia with low lattice

energy.– It is produced at low temperatures and finely ground, and– will completely hydrate in the same time order as the minerals contained

in most hydraulic cements. Dead burned magnesia and lime have high lattice energies

– Crystalline magnesium oxide or periclase has a calculated lattice energy of 3795 Kj mol-1 which must be overcome for it to go into solution or for reaction to occur.

– Dead burned magnesia is much less expansive than dead burned lime in a hydraulic binder (Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p 358-360 )


More Rapid Early Strength DevelopmentMore Rapid Early Strength Development

Early strength gain with less cement and added pozzolans is of great economic and environmental importance as it will allow the use of more pozzolans.

Concretes are more often than not made to strength. The use of tec-cement results in

– more rapid early strength development even with added pozzolans.

– Straight line strength development for a long time

We have observed this sort of curve in over 500 cubic meters of concrete now

Tec – Cement Concrete with 10% reactive magnesia

OPC Concrete


MPa


7 14 28 3


Reasons for Compressive Strength Development in Tec-Cements.Reasons for Compressive Strength Development in Tec-Cements.

Kosmotropic nature of Mg++

Reactive magnesia requires considerable water to hydrate resulting in:– Denser, less permeable concrete. Self compaction?– A significantly lower voids/paste ratio.

Higher early pH initiating more effective silicification reactions?– The Ca(OH)2 normally lost in bleed water is used internally for reaction with pozzolans.

– Super saturation of alkalis caused by the removal of water?

Micro-structural strength due to particle packing (Magnesia particles at 4-5 micron are a little over ½ the size of cement grains.)

Formation of MgAl hydrates? Similar to flash set in concrete but slower??

Formation of MSH?? Slow release of water from hydrated Mg(OH)2.nH2O supplying H2O for

more complete hydration of C2S and C3S?

Brucite gains weight in excess of the theoretical increase due to MgO conversion to Mg(OH)2 in samples cured at 98% RH.

Dr Luc Vandepierre, Cambridge University, 20 September, 2005.


Greater Tensile StrengthGreater Tensile Strength

MgO Changes Surface Charge as the Ph Rises. This could be one of the reasons for rapid gelling and greater tensile strength displayed during the early plastic phase of tec-cement concretes. The affect of additives is not yet known

0

1

2

3

4

5

6

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

CURING TIME (days)

STR

EN

GTH

(MP

a)

OPC(100%)

OPC(90%)+ MgO(10%)

+

+

+

+

++

+

+

+

+

+++

++

+

+

+

+

+Mutual Repulsion

=>

+

+

+

+++

+

+

+

+

+

++

+-

-

-

-

--

-

Ph 12 ?

Cement

Cement

MgO Sand

Sand

MgO

Mutual Repulsion

Mutual Attraction


Non Newtonian Rheology – Rapid GellingNon Newtonian Rheology – Rapid Gelling

O

O

O

O Mg++

+

- +

+

+

+

+

+

+

+

+

O +

+

+

+

+

+

O

O O

- -

- -

-

-

The strongly positively charged small kosmotropic Mg++ atoms attract water (which is polar) in deep layers introduce a shear thinning property affecting the rheological properties and making concretes less “sticky” with added pozzolan

It is not known how deep these layers get

Etc.

Etc.

Ca++ = 114, Mg++ = 86 picometres


DurabilityDurability

Concretes are said to be less durable when they are physically or chemically compromised.

Physical factors can result in chemical reactions reducing durability– E.g. Cracking due to shrinkage can allow reactive gases and liquids to enter

the concrete

Chemical factors can result in physical outcomes reducing durability– E.g. Alkali silica reaction opening up cracks allowing other agents such as

sulfate and chloride in seawater to enter.

This presentation will describe benchmark improvements in durability as a result of using the new TecEco magnesia cement technologies


Crack CollageCrack Collage

TecEco technology can reduce if not solve problems of cracking:– Related to (shrinkage) through open system loss of water.

– As a result of volume change caused by delayed reactions

– As a result of corrosion.

– Related to autogenous shrinkage

Thermal

PlasticShrinkage

DryingShrinkage

Corrosion Related

Freeze Thaw D Cracks

StructuralSettlement Shrinkage

Photos from PCA and US Dept. Ag Websites

Autogenous or self-desiccation shrinkage(usually related to stoichiometric or chemical shrinkage)

Alkali aggregateReaction

EvaporativeCrazingShrinkage


Causes of Cracking in ConcreteCauses of Cracking in Concrete Cracking commonly occurs when the induced stress exceeds

the maximum tensile stress capacity of concrete and can be caused by many factors including restraint, extrinsic loads, lack of support, poor design, volume changes over time, temperature dependent volume change, corrosion or delayed reactions.

Causes of induced stresses include:– Restrained thermal, plastic, drying and stoichiometric shrinkage, corrosion

and delayed reaction strains.– Slab curling.– Loading on concrete structures.

Cracking is undesirable for many reasons– Visible cracking is unsightly– Cracking compromises durability because it allows entry of gases and ions

that react with Portlandite.– Cracking can compromise structural integrity, particularly if it accelerates

corrosion.


Graphic Illustration of CrackingGraphic Illustration of Cracking

Combined Effect of Concrete Volume Change (Example Only)

-50

0

50

100

150

200

250

0 12 24 36 48 60 72 84 96 108

120

Time since Cast (Hrs)

Sh

rin

kag

e/(E

xpan

sio

n)

Mic

rost

rain

Max Tensile Strain

Temperature effect

Drying Shrinkage

Autogenous Shrinkage

Total Srain Induced

Total Strain Less Creep

After Tony Thomas (Boral Ltd.) (Thomas 2005)

Autogenous shrinkage has been used to refer to hydration shrinkage and is thus stoichiometric


Cracking due to Loss of WaterCracking due to Loss of Water

DryingShrinkage

PlasticShrinkage

Picture from: http://www.pavement.com/techserv/ACI-GlobalWarming.PDF

EvaporativeCrazingShrinkage

Settlement Shrinkage

We may not be able to prevent too much water being added to concrete by fools.TecEco approach the problem in a different way by providing for the internal removal/storage of water that can provide for more complete hydration of PC.

Brucite gains weight in excess of the theoretical increase due to MgO conversion to Mg(OH)2 in samples cured at 98% RH.

Dr Luc Vandepierre, Cambridge University, 20 September, 2005.

Bucket of Water

Fool


Solving Cracking due to Shrinkage from Loss of WaterSolving Cracking due to Shrinkage from Loss of Water

In the system water plus Portland cement powder plus aggregates shrinkage is in the order of .05 – 1.5 %.

Shrinkage causes cracking There are two main causes of Portland cements

shrinking over time.– Stoichiometric (chemical) shrinkage and– Shrinkage through loss of water.

The solution is to:– Add minerals that compensate by stoichiometrically expanding

and/or to– Use less water, internally hold water or prevent water loss.

TecEco tec-cements internally hold water and prevent water loss.

The kosmotropic nature of Mg++ makes water more viscous without shear.

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)


When magnesia hydrates it consumes 18 litres of water per mole of magnesia probably more depending on the value of n in the reaction below:

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s) The dimensional change in the system MgO + PC depends on:

– The ratio of MgO to PC– Whether water required for hydration of PC and MgO is coming from stoichiometric mix water

(i.e. the amount calculated as required), excess water (bleed or evaporative) or from outside the system.

– In practice tec-cement systems are more closed and thus dimensional change is more a function of the ratio of MgO to PC

As a result of preventing the loss of water by closing the system together with expansive stoichiometry of MgO reactions (see below).

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)40.31 + 18.0 ↔ 58.3 molar mass (at least!)

11.2 + liquid ↔ 24.3 molar volumes (at least!) It is possible to significantly reduce if not prevent (drying, plastic,

evaporative and some settlement) shrinkage as a result of water losses from the system.

The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1).

Preventing Shrinkage through Loss of WaterPreventing Shrinkage through Loss of Water


Portland cements stoichiometrically require around 23 -27% water for hydration yet we add approximately 45 to 60% at cement batching plants to fluidise the mix sufficiently for placement.

If it were not for the enormous consumption of water by tri calcium aluminate as it hydrates forming ettringite in the presence of gypsum, concrete would remain as a weak mush and probably never set.

– 26 moles of water are consumed per mole of tri calcium aluminate to from a mole of solid ettringite. When the ettringite later reacts with remaining tri calcium aluminate to form monosulfoaluminate hydrate a further 4 moles of water are consumed.

The addition of reactive MgO achieves water removal internally in a closed system in a similar way.

Preventing Shrinkage through Loss of WaterPreventing Shrinkage through Loss of Water



Other Benefits of Preventing Shrinkage through Loss of Water

Other Benefits of Preventing Shrinkage through Loss of Water

Internal water consumption and prevention of loss also results in:– Greater strength

• More complete hydration of PC .

• Reduced in situ voids:paste ratio

– Greater density• Increased durability

• Higher short term alkalinity

• More effective pozzolanic reactions.

More complete hydration of PC .– Small substitutions of PC by MgO result in water being trapped

inside concrete as Brucite and Brucite hydrates which can later self desiccate delivering water to hydration reactions of calcium silicates (Preventing so called “Autogenous” shrinkage).


Bleeding is a Bad ThingBleeding is a Bad Thing

Bleeding is caused by:– Lack of fines– Too much water

Bleeding can be fixed by:– Reducing water or adding fines– Air entrainment or grading adjustments– Adding kosmotropic ions like Mg++

Bleeding causes:– Reduced pumpability– Loss of cement near the surface of concretes– Delays in finishing– Poor bond between layers of concrete– Interconnected pore structures that allow aggressive agents to enter later– Slump and plastic cracking due to loss of volume from the system– Loss of alkali that should remain in the system for better pozzolanic reactions– Loss of pollutants such as heavy metals if wastes are being incorporated.

Concrete is better as a closed system

Better to keep concretes as closed systems


Dimensional Control in Tec-Cement Concretes over TimeDimensional Control in Tec-Cement Concretes over Time

By adding MgO volume changes are minimised to close to neutral.– So far we have observed significantly less shrinkage in

TecEco Tec - Cement concretes with about (8-10% substitution OPC) with or without fly ash.

– At some ratio, thought to be around 15-18% reactive magnesia there is no shrinkage.

– The water lost by concrete as it shrinks is used by the reactive magnesia as it hydrates eliminating shrinkage.

Note that brucite is > 44.65 mass% water and it makes sense to make binders out of water!

More research is required to accurately establish volume relationships and causes for reduced shrinkage.


Reducing Cracking as a Result of Volume Change caused by Delayed Reactions

Reducing Cracking as a Result of Volume Change caused by Delayed Reactions

Photo Courtesy Ahmad Shayan ARRBAn Alkali Aggregate Reaction Cracked Bridge Element


Types of Delayed ReactionsTypes of Delayed Reactions

There are several types of delayed reactions that cause volume changes (generally expansion) and cracking.– Alkali silica reactions– Alkali carbonate reactions– Delayed ettringite formation– Delayed thaumasite formation– Delayed hydration or dead burned lime or periclase.

Delayed reactions cause dimensional distress, cracking and possibly even failure.


Reducing Delayed ReactionsReducing Delayed Reactions

Delayed reactions do not appear to occur to the same extent in TecEco cements.– A lower long term pH results in reduced reactivity after the

plastic stage.– Potentially reactive ions are trapped in the structure of

brucite.– Ordinary Portland cement concretes can take years to dry

out however the reactive magnesia in Tec-cement concretes consumes unbound water from the pores inside concrete.

– Magnesia dries concrete out from the inside. Reactions do not occur without water.


Reduced Steel Corrosion Related CrackingReduced Steel Corrosion Related Cracking

Steel remains protected with a passive oxide coating of Fe3O4 above pH 8.9.

A pH of over 8.9 is maintained by the equilibrium Mg(OH)2 ↔ Mg++ + 2OH- for much longer than the pH maintained by Ca(OH)2 because:– Brucite does not react as readily as Portlandite resulting in

reduced carbonation rates and reactions with salts.

Concrete with brucite in it is denser and carbonation is expansive, sealing the surface preventing further access by moisture, CO2 and salts.

Rusting Causes Dimensional Distress


Reduced Steel CorrosionReduced Steel Corrosion

Brucite is less soluble and traps salts as it forms resulting in less ionic transport to complete a circuit for electrolysis and less corrosion.

Free chlorides and sulfates originally in cement and aggregates are bound by magnesium– Magnesium oxychlorides or oxysulfates are formed.

( Compatible phases in hydraulic binders that are stable provided the concrete is dense and water kept out.)

As a result of the above the rusting of reinforcement does not proceed to the same extent.

Cracking or spalling due to rust does not occur


Long Term pH controlLong Term pH control Important if you wish to also add wastes TecEco add reactive magnesia which hydrates forming

brucite which is another alkali, but much less soluble, mobile or reactive than Portlandite.

Brucite provides long term pH control.

13.7

pH

Log Time

10.5

Tec – Cement Concrete with 10% reactive magnesia (red). Ph maintained by brucite

OPC Concrete

HYPOTHETICAL pH CURVES OVER TIME (with fly ash)

Plastic Stage

? ?

?

Tec-Cement (red) - more affective pozzolanic reactions

11.2

OPC Concrete – Lower long term pH due to consumption of lime and carbonation

Surface hydrolysis and more polymeric species? A pH in the range 10.5 – 11.2 is ideal in a concrete


Steel Corrosion is Influenced by Long Term pHSteel Corrosion is Influenced by Long Term pH

Eh-pH or Pourbaix Diagram The stability fields of hematite, magnetite and sideritein aqueous solution; total dissolved carbonate = 10-2M.

In TecEco cements the long term pH is governed by the low solubility and carbonation rate of brucite and is much lower at around 10.5 -11, allowing a wider range of aggregates to be used, reducing problems such as AAR and etching. The pH is still high enough to keep Fe3O4 stable in reducing conditions.

Steel corrodes below 8.9

Equilibrium pH of Brucite and of lime


Reducing Cracking Related to Autogenous ShrinkageReducing Cracking Related to Autogenous Shrinkage

Autogenous shrinkage tends to occur in high performance concretes in which dense microstructures develop quickly preventing the entry of additional water required to complete hydration.– First defined by Lynam in 1934 (Lynam CG. Growth and movement in

Portland cement concrete. London: Oxford University Press; 1934. p. 26-7.)

The autogenous deformation of concrete is defined as the unrestrained, bulk deformation that occurs when concrete is kept sealed and at a constant temperature.



Main cause is stoichiometric or chemical shrinkage as observed by Le Chatelier.– whereby the reaction products formed during the hydration of

cement occupy less space than the corresponding reactants.

A dense cement paste hydrating under sealed conditions will therefore self-desiccate creating empty pores within developing structure. If external water is not available to fill these “empty” pores, considerable shrinkage can result.

Le Chatelier H. Sur les changements de volume qui accompagnent Ie durcissement des ciments. Bulletin de la Societe d'Encouragement pour I'Industrie Nationale 1900:54-7.



Autogenous shrinkage does not occur in high strength Tec-Cement concretes because:– The brucite hydrates that form desiccate back to brucite delivering water in

situ for more complete hydration of Portland cement.

Mg(OH)2.nH2O (s) ↔ MgO (s) + H2O (l)• As brucite is a relatively weak mineral compressed and densifies the

microstructure.

– The stoichiometric shrinkage of Portland cement (first observed by Le Chatelier) is compensated for by the stoichiometric expansion of magnesium oxide on hydration.


40.31 + 18.0 ↔ 58.3 molar mass (at least!)

11.2 + liquid ↔ 24.3 molar volumes (at least 116% expansion, probably more initially before desiccation as above!)


Improved DurabilityImproved Durability

Materials that last longer need replacing less often saving on energy and resources. Reasons for Improved Durability:

– Greater Density? = Lower Permeability• Physical Weaknesses => Chemical Attack

– Removal of Portlandite with the Pozzolanic Reaction.• Removal or reactive components

– Substitution by Brucite => Long Term pH control• Reducing corrosion


Reduced PermeabilityReduced Permeability

As bleed water exits ordinary Portland cement concretes it creates an interconnected pore structure that remains in concrete allowing the entry of aggressive agents such as SO4

--, Cl- and CO2

TecEco tec - cement concretes are a closed system. They do not bleed as excess water is consumed by the hydration of magnesia.

– As a result TecEco tec - cement concretes dry from within, are denser and less permeable and therefore stronger more durable and less permeable. Cement powder is not lost near the surfaces. Tec-cements have a higher salt resistance and less corrosion of steel etc.


Concretes have a high percentage (around 18% – 22%) of voids.

On hydration magnesia expands >=116.9 % filling voids and surrounding hydrating cement grains => denser concrete.

On carbonation to nesquehonite brucite expands 307% sealing the surface.

Lower voids:paste ratios than water:binder ratios result in little or no bleed water, lower permeability and greater density.

Greater Density – Lower PermeabilityGreater Density – Lower Permeability


Densification During the Plastic PhaseDensification During the Plastic Phase

Water is required to plasticise concrete for placement, however once placed, the less water over the amount required for hydration the better. Magnesia consumes water as it hydrates producing solid material.

Less water results in increased density and concentration of

alkalis - less shrinkage and cracking and improved strength and durability.

Water

Log time

Observable Characteristic

Relevant Fundamental

Voids

Binder + supplementary cementitious materials

Hydrated Binder Materials

High water for ease of placement

Less water for strength and durability

Variables such as % hydration of mineral, density, compaction, % mineral H20 etc.

Consumption of water during plastic stage

Unhydrated Binder


Brucite has always played a protective role during salt attack. Putting it in the matrix of concretes in the first place makes sense.

Brucite does not react with salts because it is a least 5 orders of magnitude less soluble, mobile or reactive. – Ksp brucite = 1.8 X 10-11

– Ksp Portlandite = 5.5 X 10-6

TecEco cements are more acid resistant than Portland cement– This is because of the relatively high acid resistance (?) of

Lansfordite and nesquehonite compared to calcite or aragonite

Durability - Reduced Salt & Acid AttackDurability - Reduced Salt & Acid Attack


Less Freeze - Thaw ProblemsLess Freeze - Thaw Problems

Denser concretes do not let water in. Brucite will to a certain extent take up internal stresses When magnesia hydrates it expands into the pores left around hydrating

cement grains: MgO (s) + H2O (l) ↔ Mg(OH)2 (s)

40.31 + 18.0 ↔ 58.3 molar mass 11.2 + 18.0 ↔ 24.3 molar volumes

39.20 ↔ 24.3 molar volumesAt least 38% air voids are created in space that was occupied by magnesia

and water! Air entrainment can also be used as in conventional concretes TecEco concretes are not attacked by the salts used on roads


Rosendale Concretes – Proof of DurabilityRosendale Concretes – Proof of Durability

Rosendale cements contained 14 – 30% MgO A major structure built with Rosendale cements commenced in 1846 was Fort Jefferson

near key west in Florida. Rosendale cements were recognized for their exceptional durability, even under severe

exposure. At Fort Jefferson much of the 150 year-old Rosendale cement mortar remains in excellent condition, in spite of the severe ocean exposure and over 100 years of neglect. Fort Jefferson is nearly a half mile in circumference and has a total lack of expansion joints, yet shows no signs of cracking or stress. The first phase of a major restoration is currently in progress.

More information from http://www.rosendalecement.net/rosendale_natural_cement_.html


Solving Waste & Logistics ProblemsSolving Waste & Logistics Problems TecEco cementitious composites represent a cost affective

option for– using non traditional aggregates from on site reducing transports costs and

emissions– use and immobilisation of waste.

Because they have– lower reactivity

• less water• lower pH

– Reduced solubility of heavy metals• less mobile salts

– greater durability.• denser.• impermeable (tec-cements).• dimensionally more stable with less shrinkage and cracking.

– homogenous.– no bleed water.

TecEco Technology - Converting Waste to Resource


Role of Brucite in ImmobilizationRole of Brucite in Immobilization

In a Portland cement Brucite matrix– PC derive CSH takes up lead, some zinc and germanium– Pozzolanic CSH can take up mobile cations– Brucite and hydrotalcite are both excellent hosts for toxic and

hazardous wastes. – Heavy metals not taken up in the structure of Portland cement

minerals or trapped within the brucite layers end up as hydroxides with minimal solubility.

The Brucite in TecEco cements has a structure comprising electronically neutral layers and is able to accommodate a wide variety of extraneous substances between the layers and cations of similar size substituting for magnesium within the layers and is known to be very suitable for toxic and hazardous waste immobilisation.

Layers of electronically neutral brucite suitable for trapping balanced cations and anions as well as other substances.

Salts and other substances trapped between the layers.

Van de waals bonding holding the layers together.


Lower Solubility of Metal HydroxidesLower Solubility of Metal Hydroxides

Pb(OH) Cr(OH) 3

Zn(OH) 2

Ag(OH) Cu(OH) 2 Ni(OH) 2 Cd(OH) 2

10 -6

10 -4

10 -2

10 0

10 2

Co

nce

ntr

atio

n o

f D

isso

lved

Met

al, (

mg

/L)

14 6 7 8 9 10 11 12 13

Equilibrium pH of brucite is 10.52 (more ideal)*

Equilibrium pH of Portlandite is 12.35

*Equilibrium pH’s in pure water, no other ions present. The solubility of toxic metal hydroxides is generally less in the range pH 10.52 -11.2 than at higher pH’s.

Equilibrium pH of PC CSH is 11.2

There is a 104 difference

All waste streams will contain heavy metals and a strategy for long term pH control is therefore essential




Many wastes and local materials can contribute physical property values.– Plastics for example are collectively light in weight, have tensile

strength and low conductance. Tec, eco and enviro-cements will allow a wide range of

wastes and non-traditional aggregates such as local materials to be used.

Tec, enviro and eco-cements are benign binders that are:– low alkali reducing reaction problems with organic materials.– stick well to most included wastes

Tec, enviro and eco-cements can utilize wastes including carbon to increase sequestration preventing their conversion to methane

There are huge volumes of concrete produced annually (>2 tonnes per person per year)


Sustainable Materials in the Built Environment - 2007Sustainable Materials in the Built Environment - 2007

Technical FocusThis Conference will focus on: The impacts and connectivity

of different parts of the supply chain.

Fabrication, performance, recycling and waste

New developments in materials and processes

Reviewing existing materials assessment tools

Future directions in regulation

Opportunities/barriers to introduction of sustainable materials and technologies in the building industry.

New materials and more sustainable built environments: the evidence?

Joint Venture WebsitesASSMIC Website: www.aasmic.orgMaterials Australia Website: www.materialsaustralia.com.au

Sustainable Materials in the Built

Environment

2007

Innovation - Process – Design

Announcement and Call for Papers18th to 20th February 2007

Melbourne, Australiawww.materialsaustralia.com.au/SMB2007

presentation downloadable from 1 greening mineral binders our slides are deliberately verbose as...

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