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New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan.

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Title: New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan.


1
New Cements Based on the Addition of Reactive
Magnesia to Portland Cement With or Without Added
Pozzolan.
Hobart, Tasmania, Australia
All I ask is that the industry think about what I
am saying. John Harrison B.Sc. B.Ec. FCPA.
2
Sustainability Issues
  • Globally some 2 billion tonnes of cement, lime
    and magnesia are produced annually consuming
    large amounts of energy and releasing chemically
    bound CO2.
  • Around 98 of the worlds energy is derived
    from fossil fuels that when burnt to produce
    energy release vast amounts of CO2
  • Responsible between 5 and 10 of global
    emissions
  • The built environment is our footprint on earth.
  • Buildings and infrastructure account for around
    60 of the anthropogenic materials flows on
    earth. Closing loops, reducing emissions,
    lifetime and embodied energies and improving
    durability will reduce the impact on earth
    systems.

Bats Best Available Technologies
3
Materials Science Issues
  • Talked about
  • Rheology
  • Time for and method of placing and finishing
  • Shrinkage
  • Cracking, crack control
  • Durability and Performance
  • Sulphate and chloride resistance
  • Carbonation
  • Corrosion of steel and other reinforcing
  • Alkali aggregate reactions
  • Delayed ettringite formation
  • Rarely discussed
  • Sustainability
  • Emissions and embodied energies

Should the discussion be more about how we could
fix the material, overcoming rather than
tolerating and mitigating these problems?
4
Conclusion
  • Portlandite is the main problem with Portland
    cement.
  • Better to fundamentally fix the material than
    continue with what amount to band aid fixes.
  • The merits of removing and replacing Portlandite
    with another less soluble, easily manufactured
    alkali should be considered.
  • Technology improvements increase market share and
    fuel economic growth
  • Carbon trading and the BATS system will favour
    adoption of better technologies.

The TecEco technology is an opportunity to be
taken not a threat to be ignored!
5
TecEco Cement - Simple Yet Ingenious?
The consequences of removing Portlandite (lime)
with the pozzolanic reaction and filling the
voids between hydrating cement grains with
brucite, an insoluble alkaline mineral, need to
be considered.
Glue as well as Velcro?
Partially hydrated Portland cement paste
Soroos,1999 .
The important thing in science is not so much to
obtain new facts as to discover new ways of
thinking about them. -- Sir William Bragg
6
TecEco Cements A Blending System
Imagination is more important than knowledge,
knowledge is limited. Albert Einstein
TecEco cements are a system of blending reactive
magnesia, Portland cement and usually a pozzolan
7
TecEco Cement Summary
  • Two main formulation strategies so far
  • TecEco modified Portland cements.
  • Contain more Portland cement than reactive
    magnesia
  • Reactive magnesia hydrates in the same rate order
    as Portland cement forming brucite which
    densifies, maintains pH and protects due to its
    low solubility.
  • Other benefits include improvements in rheology
    and possibly less shrinkage
  • TecEco eco-cements
  • Contain more reactive magnesia than Portland
    cement
  • Brucite in porous materials eventually carbonates
  • Forming stronger fibrous minerals.
  • Resulting in huge opportunities for abatement.

8
Reactivity Overcomes Delayed Hydration.
  • Delayed hydration leads to dimensional distress.
  • Magnesium was banned in Portland cements because
    when it goes through the high temperature process
    of making Portland cement it becomes periclase.
    It is dead burned, hydrates slowly and causes
    dimensional distress.
  • Dead burned lime is much more expansive than dead
    burned magnesia1, a problem largely forgotten
    about by cement chemists.
  • The reactivity of magnesia is a function of the
    state of disorder, specific surface area and
    glass forming impurities.
  • The state of disorder is dependent on the
    temperature of calcining and probably the most
    important, followed by the level of impurities
    such as iron.
  • Make a particle small enough and it will react
    with just about anything!
  • 1 Ramachandran V. S., Concrete Science, Heydon
    Son Ltd. 1981, p 358-360.

9
Replacing Portlandite with Brucite.
  • Portlandite is reactive, carbonates readily and
    being soluble can act as an electrolyte. TecEco
    remove Portlandite in reactions with Pozzolans.
  • TecEco replace Portlandite with brucite which is
    much less reactive or soluble, does not act as an
    electrolyte or carbonate as readily.
  • Improving the rheology
  • Using up bleed water as it hydrates
  • Filling in the pores, increasing the density
  • Sealing off the atmosphere
  • Providing long term pH control

10
The Results of Replacing Portlandite with Brucite.
  • Greater Durability.
  • TecEco cement concretes are not attacked by salts
    and do not carbonate as readily.
  • A Lower More Stable pH for much Longer? Less
    Corrosion
  • As Portlandite is removed the pH becomes governed
    by the solubility of brucite and is much lower at
    around 10.5 -11 reducing problems such as AAR and
    etching, but still high enough to keep Fe FeO and
    Fe3O4 stable (See Pourbaix diagram).
  • Increased Density
  • Brucite also densifies the matrix by filling in
    pore spaces taking up mix and bleed water as it
    hydrates reducing shrinkage. (brucite is 69
    mass water!)
  • Improved Rheology
  • Reactive magnesia being much finer acts as a
    lubricant for Portland cement
  • improving the rheology, reducing the water/cement
    ratio, improving strength and reducing shrinkage.
  • Greater Sustainability
  • Superior durability and reabsorbtion of
    chemically released CO2

11
Durability - Reduced Salt Attack and Carbonation
  • Brucite has always played a protective role
    during salt attack. Putting it in the matrix of
    concretes in the first place makes sense.
  • Brucite protects concrete from salts because of
    its low solubility (reactivity, mobility)
  • Ksp brucite 1.8 X 10-11
  • Ksp Portlandite 5.5 X 10-6
  • Carbonation of brucite is slow
  • ?Gor Brucite -19.55
  • ?Gor Portlandite -64.62
  • Carbonation of brucite is slightly expansive
  • And results in surface tightening reducing
    further carbonation - not cracking!
  • Magnesite and hydromagnesite add strength

12
A More Stable Long Term pH
Eh-pH or Pourbaix Diagram The stability fields
of iron in the presence of oxygen and carbon
dioxide. Source Krauskopf K. B., Introduction to
Geochemistry, McGraw Hill Book Company, 1967,
page 168, after Garrels Christ (1965), page 224.
As Portlandite is removed the pH becomes governed
by the solubility of brucite and is much lower at
around 10.5 -11 reducing problems such as AAR and
etching, but still high enough to keep Fe and
Fe3O4 stable. The hydroxides of most heavy metals
are also least soluble at around pH 10.5 - 11
TecEco Cement zone.
Fe2O3 is stable above around pH 8.9. Fe2O3 does
not hydrate and protects steel.
13
Reduced Steel Corrosion
  • Brucite does not react readily resulting in
    reduced carbonation rates and reactions with
    salts.
  • Brucite is less soluble resulting in less ionic
    transport to complete a circuit for electrolysis.
  • Concrete with brucite is denser (keeping water
    and CO2 out.)
  • Carbonation of brucite seals the surface
    preventing further carbonation.

Anode
Ionic transport
Cathode
14
Increased Density
  • Brucite extracts water, expanding filling pores
    and surrounding hydrated cement grains. With
    initial lower water cement ratios this results in
    greater density.
  • Greater density results in greater strength, more
    durable concrete with a higher salt resistance
    and less corrosion of steel etc.

Picture Courtesy Applied Petrographic Services
NSW Aust.
15
TecEco Cements - Improved Rheology
  • Suitable reactive magnesia is much finer than
    most other cements such as Portland cement and
    carries what we suspect is a high positive
    surface charge.
  • Finely ground reactive magnesia therefore acts as
    a plasticiser.
  • Improving rheology
  • Less water need be used resulting in greater
    strength and reduced porosity.
  • The proportion and cost of binders and
    plasticisers can be reduced.

16
TecEco Cements Improved Rheology (2)
There are also surface charge affects and water
reducing agents are not required. Reactive
Magnesia is a plasticiser as well.
17
Dimensionally Neutral TecEco Modified Portland
Cement Concretes on Hydration?
  • Portland cement shrinks around .05. Over the
    long term much more (gt.1).
  • When magnesia hydrates it expands
  • MgO (s) H2O (l) ? Mg(OH)2 (s)
  • 40.31 18.0 ? 58.3 molar
    mass
  • 11.2 liquid ? 24.3
    molar volumes1
  • lt116.96 expansion depending on whether the
    water is coming from mix water or bleed water
    from OPC.
  • So far we have not observed shrinkage in TecEco
    modified Portland cement concretes (10 subst,
    OPC) also containing flyash.
  • Could it be that the water lost by Portland
    cement as it shrinks is used by the reactive
    magnesia as it hydrates?
  • At some ratio, thought to be around 10 reactive
    magnesia and 90 OPC volume changes cancel each
    other out and setting and curing are close to
    neutral.
  • More research is required for both modified
    Portland cements and eco-cements.
  • 1 The molar volume (L.mol-1)is equal to the
    molar mass (g.mol-1) divided by the density
    (g.L-1).

18
No Volume Changes with TecEco Modified Portland
Cements on Carbonation?
  • Consider what happens when Portlandite
    carbonates
  • Ca(OH)2 CO2 ? CaCO3
  • 74.08 44.01 ? 100 molar mass
  • 33.22 gas ? 28.10 molar volumes
  • 18.22 shrinkage
  • Surface shrinkage causing cracks to appear.
  • Compared to brucite forming magnesite as it
    carbonates
  • Mg(OH)2 CO2 ? MgCO3
  • 58.31 44.01 ? 84.32 molar mass
  • 24.29 gas ? 28.10 molar volumes
  • 15.68 expansion
  • Slight expansion and densification of the surface
    preventing further ingress of CO2 and carbonation.

19
Potential for Neutral Cure Modified Portland
Cement Concretes
20
TecEco Eco-Cements - Solving Waste Problems
  • The best thing to do with wastes isif at all
    possible to use them. If theycannot directly be
    used then they haveto be immobilised.
  • TecEco cements are ideal for soil remediation and
    immobilising/utilising toxic and hazardous wastes
    such as fly and bottom ash, iron slags, red mud
    etc.
  • Brucite results in an ideal long term equilibrium
    pH of 10.5 11 at which most heavy metal
    hydroxides are relatively insoluble.
  • The OPC in TecEco cements takes up lead.
  • TecEco cements are
  • Not attacked by ground or sea water salts.
  • Thermodynamically more stable.
  • May be dimensionally more stable.

21
Summary of Ramifications of Adding Reactive
Magnesia
  • Durability TecEco cements include highly
    insoluble minerals that last indefinitely. They
    maintain pH at ideal levels, protecting steel
    reinforcing and reducing alkali aggregate
    reactions.
  • Easy to Use With improved homogeneity and
    rheology. Fine magnesia acts as a lubricant for
    Portland cement and takes up bleed water as it
    hydrates.
  • Greater Strength? Less shrinkage? A lower water
    cement ratio could mean greater strength and less
    shrinkage. Still to be examined but so far so
    good!
  • Waste Materials TecEco cements and Eco-cements
    use a high proportion of recycled materials.
  • Insulating Properties / High Thermal Mass / Low
    Embodied Energy Eco-cement products will be
    favoured for energy conserving buildings.
  • Recyclable Eco-cement products can be
    reprocessed and reused, making them more
    attractive to many users.
  • A Fire Retardant Brucite and magnesite are both
    fire retardants. TecEco cement products put fires
    out by releasing CO2 at relatively low
    temperatures
  • Low Capital Cost No new plant and equipment is
    required.
  • Lower Materials Cost With economies of scale
    TecEco cements should be cheaper.
  • Suitable for Immobilisation of Wastes and
    Environmentally Friendly!

22
Basic Chemical Reactions
Notice the low solubility of brucite compared to
Portlandite and that magnesite is stronger and
adopts a more ideal habit than calcite aragonite
23
The Magnesium Thermodynamic Cycle
24
Manufacture of Portland Cement
25
Addressing Issues in Concrete Science
  • Addressing the research objectives of concrete
    science.
  • Durability salt resistance and steel corrosion
    may become problemsof the past.
  • Lower use of materials and energyover time
    saving money and the environment.
  • Lower more stable long term alkalinity.
  • Reduced AAR and steel corrosion,.
  • Better rheology.
  • Lower water cement ratio, less shrinkage, and
    easier placement.
  • Other improved properties
  • Greater density, adjustable placing and finishing
    times. Fire retarding properties
  • Lower Costs
  • Making reactive magnesia is a benign process with
    potential for using waste energy and capture of
    CO2.
  • A wider range of aggregates including wastes will
    be availablereducing cartage costs and
    emissions.
  • Water or CO2 from the air comprise a high mass
    and volume of the magnesium minerals in TecEco
    cements. Water and CO2 are free or attract carbon
    credits

26
TecEcos Immediate Focus
  • Form strategic alliances with major companies.
  • Raise money for Research Around 4 millions
    dollars worth in the pipeline.
  • Concentrate on defined markets for low technical
    risk products that require minimal research and
    development and for which performance based
    standards apply.
  • Carbonated products such as bricks, blocks,
    stabilised earth blocks, pavers, roof tiles
    pavement and mortars that utilise large
    quantities of waste and products where
    sustainability, rheology or fire retardation are
    an issue. (Mainly eco-cement technology using fly
    ash).
  • The immobilisation of wastes including toxic
    hazardous and other wastes because of the
    superior performance of the technology and the
    rapid growth of markets. (Eco-cements and
    modified Portland cements).
  • Products where extreme durability is required.
  • Products for which weight is an issue.
  • Continue our awareness campaign regarding TecEco
    cements, the new TecEco kiln design and the Tech
    Tendon method of prestressing, partial
    prestressing and reinforcing.

27
TecEco Minding the Future
  • TecEco are aware of the enormous weight
    ofopinion necessary before standards can
    bechanged globally for TecEco modified
    cementconcretes for general use.
  • TecEco already have a number of institutions and
    universities around the world doing research.
  • TecEco have received huge global publicity not
    all of which is correct and have therefore
    publicly released the technology.
  • TecEco research documents are available from
    TecEco by request. Soon they will be able to be
    purchased from the web site.
  • Other documents by other researchers will be made
    available in a similar manner as they become
    available.

Technology standing on its own is not inherently
good. It still matters whether it is operating
from the right value system and whether it is
properly available to all people. -- William
Jefferson Clinton
28
TecEco Cements - Sustainability
  • In the take-make-waste linear system, which
    underpins the majority of the worlds economies.
  • Utility is added until final point of sale and
    from then on utility generally declines until
    wastage it complete.
  • If utility can be maintained by greater
    durability or reuse then the system must produce
    less waste, slow down and consume less
  • New materials are required that are more durable
    and that do not exit the linear system forming
    return loops eliminating wastes, reducing output
    and thus our take from natural ecosystems.
  • TecEco cements have been designed with these
    desirable characteristics
  • Energy costs money and is the largest cost factor
    in the production of mineral binders.
  • Whether more or less energy is required for the
    manufacture of reactive magnesia compared to
    Portland cement or lime depends on the stage in
    the utility adding process.
  • Volume of built material has greater utility and
    is more validly compared.

29
TecEco Eco - Cements for Sustainable Cities
30
Energy On a Mass Basis
Relative to Raw Material Used to make Cement From Manufacturing Process Energy Release 100 Efficient (Mj.tonne-1) From Manufacturing Process Energy Release with Inefficiencies (Mj.tonne-1) Relative Product Used in Cement From Manufacturing Process Energy Release 100 Efficient (Mj.tonne-1) From Manufacturing Process Energy Release with Inefficiencies (Mj.tonne-1) Relative to Mineral Resulting in Cement From Manufacturing Process Energy Release 100 Efficient (Mj.tonne-1) From Manufacturing Process Energy Release with Inefficiencies (Mj.tonne-1)
CaCO3 Clay 1545.73 2828.69 Portland Cement 1807 3306.81 Hydrated OPC 1264.90 2314.77
CaCO3 1786.09 2679.14 Ca(OH)2 2413.20 3619.80
MgCO3 1402.75 1753.44 MgO 2934.26 3667.82 Mg(OH)2 2028.47 2535.59
31
Energy On a Volume Basis
Relative to Raw Material Used to make Cement From Manufacturing Process Energy Release 100 Efficient (Mj.metre-3) From Manufacturing Process Energy Release with Inefficiencies (Mj.metre-3) Relative Product Used in Cement From Manufacturing Process Energy Release 100 Efficient (Mj.metre-3) From Manufacturing Process Energy Release with Inefficiencies (Mj.metre-3) Relative to Mineral Resulting in Cement From Manufacturing Process Energy Release 100 Efficient (Mj.metre-3) From Manufacturing Process Energy Release with Inefficiencies (Mj.metre-3)
CaCO3 Clay 4188.93 7665.75 Portland Cement 5692.05 10416.45 Hydrated OPC 3389.93 6203.58
CaCO3 6286.62 8429.93 Ca(OH)2 5381.44 8072.16
MgCO3 4278.39 5347.99 MgO 9389.63 11734.04 Mg(OH)2 4838.32 6085.41
32
Abatement of Emissions
  • The production of Portland cement clinker, lime
    and magnesia all consume energy
  • Around 98 of the worlds energy is derived from
    fossil fuels that when burnt to produce energy
    release vast amounts of CO2
  • The production of Portland cement, lime and
    reactive magnesia also results in the release of
    chemically bound CO2
  • See newsletter 28 for more detail at
    www.tececo.com

33
But Maybe Less Energy!
  • There are reasons however why given volume
    production less energy should be required.
  • The manufacture of magnesia is a benign process
    occurring at relatively low temperatures and for
    which waste energy should be able to effectively
    be used.
  • The manufacture of more durable building
    materials will mean that less energy is required
    per unit of time because structures require
    replacing less often.
  • The manufacture of reactive magnesia is suited to
    new TecEco kiln technology in which 25 greater
    efficiencies should result due to the capture of
    waste heat from grinding.

34
The Sustainability of TecEco Cements
  • TecEco cements generally
  • A high proportion of brucite compared to
    Portlandite is water and of magnesite compared to
    calcite is CO2.
  • Every mass unit of cement powder therefore
    produces a greater volume of built environment
    than Portland other calcium based cements. Less
    need therefore be used.
  • Improved durability and other properties.
  • Brucite is less soluble, mobile or reactive than
    Portlandite and not attacked by salts.
  • The Ph is lower but more stable resulting in less
    AAR, etching and other problems but still high
    enough for longer, maintaining the passivity of
    steel for longer.
  • Improved durability will result in a lower use of
    materials and energy over time saving money and
    the environment.
  • A high proportion of pozzolanic or non reactive
    wastes can be included.
  • TecEco eco-cements
  • Carbon dioxide is also reabsorbed by brucite from
    the atmosphere.

35
Abatement TecEco Eco-Cements
36
Global Abatement
Without CO2 Capture during manufacture (billion tonnes) With CO2 Capture during manufacture (billion tonnes)
Total Portland Cement Produced Globally 1.80 1.80
Global mass of Concrete (assuming a proportion of 15 mass cement) 12.00 12.00
Global CO2 Emissions from Portland Cement 3.60 3.60
Mass of Eco-Cement assuming an 80 Substitution in global concrete use 9.60 9.60
Resulting Abatement of Portland Cement CO2 Emissions 2.88 2.88
CO2 Emissions released by Eco-Cement 2.59 1.34
Resulting Abatement of CO2 emissions by Substituting Eco-Cement 0.29 1.53
37
Abatement from Substitution
Building Material to be substituted Realistic Subst-itution by TecEco technology Size of World Market (million tonnes Substituted Mass (million tonnes) CO2 Factors (1) Emission From Material Before Substitution Emission/Sequestration from Substituted Eco-Cement (Tonne for Tonne Substitution Assumed) Emission/Sequestration from Substituted Eco-Cement (Tonne for Tonne Substitution Assumed) Net Abatement Net Abatement
            Emissions - No Capture Emissions - CO2 Capture Abatement - No Capture Abatement CO2 Capture
Bricks 85 250 212.5 0.28 59.5 57.2 29.7 2.3 29.8
Steel 25 840 210 2.38 499.8 56.6 29.4 443.2 470.4
Aluminium 20 20.5 4.1 18.0 73.8 1.1 0.6 72.7 73.2
TOTAL 426.6 20.7 633.1 114.9 59.7 518.2 573.4
Concretes already have low lifetime energies. If
embodied energies are improved could
substitution mean greater market share?
Figures are in millions of Tonnes
38
Manufacture of Eco-Cement Products
39
TecEco Kiln Technology
  • Remember
  • The reactivity of most calcined materials
    including magnesia is a function of the state of
    disorder, specific surface area and glass forming
    impurities.
  • What if calcining and grinding occurred at the
    same time?
  • Heat would literally be squashed into the
    material to be calcined, reducing the risk of
    overburning.
  • The clastic conditions should increase the state
    of disorder and reduce the formation of glasses
    resulting in greater reactivity.
  • CO2 could be captured at source.
  • The heat lost through grinding could be used for
    calcining resulting in around 25 greater
    efficiency.

40
TecEco Technology Summary
  • Simple, Smart and Sustainable?
  • TecEco cement technology has resulted in
    potential solutions to a number of problems with
    Portland and other cements including durability
    and corrosion, the alkali aggregate reaction
    problem and the immobilisation of many problem
    wastes and will provides a range of more
    sustainable building materials.
  • The Right Technology at the Right Time?
  • TecEco cement technology addresses important
    triple bottom line issues solving major global
    problems with positive economic and social
    outcomes.

Climate Change Pollution
Durability Corrosion
ASR Rheology
Shrinkage Placement , Finishing
41
TecEco Movie Theatre
Discovery Channel Movie on Eco-Cements
Shown courtesy Discovery Channel Canada
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