Presentation on theme: "Hobart, Tasmania, Australia"— Presentation transcript:
1Hobart, Tasmania, Australia New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan.Hobart, Tasmania, AustraliaAll I ask is that the industry think about what I am saying.John Harrison B.Sc. B.Ec. FCPA.
2Sustainability 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 world’s energy is derived from fossil fuels that when burnt to produce energy release vast amounts of CO2Responsible between 5% and 10% of global emissionsThe 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
3Materials Science Issues Talked aboutRheologyTime for and method of placing and finishingShrinkageCracking, crack controlDurability and PerformanceSulphate and chloride resistanceCarbonationCorrosion of steel and other reinforcingAlkali aggregate reactionsDelayed ettringite formationRarely discussedSustainabilityEmissions and embodied energiesShould the discussion be more about how we could fix the material, overcoming rather than tolerating and mitigating these problems?
4Conclusion 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 growthCarbon 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!
5TecEco 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
6TecEco Cements – A Blending System Imagination is more important than knowledge, knowledge is limited.Albert EinsteinTecEco cements are a system of blending reactive magnesia, Portland cement and usually a pozzolan
7TecEco Cement Summary Two main formulation strategies so far: TecEco modified Portland cements.Contain more Portland cement than reactive magnesiaReactive magnesia hydrates in the same rate order as Portland cement forming brucite which densifies, maintains pH and protects due to it’s low solubility.Other benefits include improvements in rheology and possibly less shrinkageTecEco eco-cementsContain more reactive magnesia than Portland cementBrucite in porous materials eventually carbonatesForming stronger fibrous minerals.Resulting in huge opportunities for abatement.
8Reactivity 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 magnesia, 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! Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p
9Replacing 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 rheologyUsing up bleed water as it hydratesFilling in the pores, increasing the densitySealing off the atmosphereProviding long term pH control
10The 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 CorrosionAs Portlandite is removed the pH becomes governed by the solubility of brucite and is much lower at around reducing problems such as AAR and etching, but still high enough to keep Fe FeO and Fe3O4 stable (See Pourbaix diagram).Increased DensityBrucite 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 RheologyReactive 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 SustainabilitySuperior durability and reabsorbtion of chemically released CO2
11Durability - 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 it’s low solubility (reactivity, mobility)Ksp brucite = 1.8 X 10-11Ksp Portlandite = 5.5 X 10-6Carbonation of brucite is slowGor Brucite =Gor Portlandite =Carbonation of brucite is slightly expansiveAnd results in surface tightening reducing further carbonation - not cracking!Magnesite and hydromagnesite add strength5 orders of magnitude3 orders of magnitude
12A More Stable Long Term pH Eh-pH or Pourbaix DiagramThe 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 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 pHTecEco Cement zone.Fe2O3 is stable above around pH 8.9. Fe2O3 does not hydrate and protects steel.
13Reduced 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.AnodeIonic transportCathode
14Picture Courtesy Applied Petrographic Services NSW Aust. Increased DensityBrucite 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.
15TecEco 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 rheologyLess water need be used resulting in greater strength and reduced porosity.The proportion and cost of binders and plasticisers can be reduced.
16TecEco Cements – Improved Rheology (2) There are also surface charge affects and water reducing agents are not required. Reactive Magnesia is a plasticiser as well.
17Dimensionally Neutral TecEco Modified Portland Cement Concretes on Hydration? Portland cement shrinks around .05%. Over the long term much more (>.1%).When magnesia hydrates it expands:MgO (s) + H2O (l) ↔ Mg(OH)2 (s)↔ molar massliquid ↔ molar volumes<= % 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. The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1).
18No Volume Changes with TecEco Modified Portland Cements on Carbonation? Consider what happens when Portlandite carbonates:Ca(OH)2 + CO2 CaCO3↔ 100 molar massgas ↔ molar volumes18.22% shrinkageSurface shrinkage causing cracks to appear.Compared to brucite forming magnesite as it carbonates:Mg(OH)2 + CO2 MgCO3↔ molar massgas ↔ molar volumes15.68% expansionSlight expansion and densification of the surface preventing further ingress of CO2 and carbonation.
19Potential for Neutral Cure Modified Portland Cement Concretes
20TecEco Eco-Cements - Solving Waste Problems The best thing to do with wastes is if at all possible to use them. If they cannot directly be used then they have to 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.
21Summary 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 temperaturesLow 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!
22Basic 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
25Addressing Issues in Concrete Science Addressing the research objectives of concrete science.Durability salt resistance and steel corrosion may become problems of the past.Lower use of materials and energy over 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 propertiesLower CostsMaking 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 available reducing 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
26TecEco’s 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.
27TecEco Minding the Future TecEco are aware of the enormous weight of opinion necessary before standards can be changed globally for TecEco modified cement concretes 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
28TecEco Cements - Sustainability In the take-make-waste linear system, which underpins the majority of the world’s 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 lessNew 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 characteristicsEnergy 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.
30Energy – On a Mass Basis CaCO3 + Clay 1545.73 2828.69 Portland Cement Relative to Raw Material Used to make CementFrom Manufacturing Process Energy Release 100% Efficient (Mj.tonne-1)From Manufacturing Process Energy Release with Inefficiencies (Mj.tonne-1)Relative Product Used in CementRelative to Mineral Resulting in CementCaCO3 + ClayPortland Cement1807Hydrated OPCCaCO3Ca(OH)2MgCO3MgOMg(OH)2
31Energy – On a Volume Basis Relative to Raw Material Used to make CementFrom Manufacturing Process Energy Release 100% Efficient (Mj.metre-3)From Manufacturing Process Energy Release with Inefficiencies (Mj.metre-3)Relative Product Used in CementRelative to Mineral Resulting in CementCaCO3 + ClayPortland CementHydrated OPCCaCO3Ca(OH)2MgCO3MgOMg(OH)2
32Abatement of Emissions The production of Portland cement clinker, lime and magnesia all consume energyAround 98% of the world’s energy is derived from fossil fuels that when burnt to produce energy release vast amounts of CO2The production of Portland cement, lime and reactive magnesia also results in the release of chemically bound CO2See newsletter 28 for more detail at
33But 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.
34The Sustainability of TecEco Cements TecEco cements generallyA 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-cementsCarbon dioxide is also reabsorbed by brucite from the atmosphere.
36Global AbatementWithout CO2 Capture during manufacture (billion tonnes)With CO2 Capture during manufacture (billion tonnes)Total Portland Cement Produced Globally1.80Global mass of Concrete (assuming a proportion of 15 mass% cement)12.00Global CO2 Emissions from Portland Cement3.60Mass of Eco-Cement assuming an 80% Substitution in global concrete use9.60Resulting Abatement of Portland Cement CO2 Emissions2.88CO2 Emissions released by Eco-Cement2.591.34Resulting Abatement of CO2 emissions by Substituting Eco-Cement0.291.53
37Abatement from Substitution Building Material to be substitutedRealistic % Subst-itution by TecEco technologySize of World Market (million tonnesSubstituted Mass (million tonnes)CO2 Factors (1)Emission From Material Before SubstitutionEmission/Sequestration from Substituted Eco-Cement (Tonne for Tonne Substitution Assumed)Net AbatementEmissions - No CaptureEmissions - CO2 CaptureAbatement - No CaptureAbatement CO2 CaptureBricks85%250212.50.2859.522.214.171.1249.8Steel25%8402102.38499.856.629.4443.2470.4Aluminium20%20.54.118.073.81.10.672.773.2TOTAL426.620.7633.1114.959.7518.2573.4Concretes already have low lifetime energies.If embodied energies are improved could substitution mean greater market share?Figures are in millions of Tonnes
39TecEco 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.
40TecEco 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 ChangePollutionDurabilityCorrosionASRRheologyShrinkagePlacement , Finishing
41TecEco Movie Theatre Discovery Channel Movie on Eco-Cements Shown courtesy Discovery Channel Canada