Presentation on theme: "Mr Tharmalingam Maheswaran"— Presentation transcript:
1 Mr Tharmalingam Maheswaran Mr Fred Andrews-PhaedonosDr Alan CarseMr Greg YorkstonMr John Harrison
2 Solving not just mitigating problems New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan.Solving not just mitigating problems
3 Plasticising our Minds "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"Imagination has brought mankind through the dark ages to its present state of civilization. Imagination led Columbus to discover America. Imagination led Franklin to discover electricity. Imagination has given us the steam engine, the telephone the talking-machine, and the automobile, for these things had to be dreamed of before they became realities.“-- L. Frank BaumImagination is more important than knowledge, knowledge is limited.-- Albert Einstein
4 Problems Remaining with Portland Type Cements Problems talked aboutShort time for placing and finishingShrinkageCracking, crack controlDurability and PerformanceSulphate and chloride resistanceCarbonationCorrosion of steel and other reinforcingAbrasion resistance of pavementMajor problem not discussedSustainabilityEmissions and embodied energiesUnder 1/3 of the papers presented at “Concrete in the Third Millennium Conference” Brisbane July 2003Maybe the discussion should be more about how we may be able to overcome - not just mitigate these problems.
5 Potential for ChangeGlobally some 2 billion tonnes of cement, lime and magnesia are produced annually.Consuming large amounts of energyAround 98% of the world’s energy is derived from fossil fuels that when burnt to produce energy they release vast amounts of CO2The production of Portland cement clinker, lime and magnesia all consume energy.The production of Portland cement, lime and reactive magnesia also result in the release of chemically bound CO2.Responsible between 5% and 10% of global emissionsThe built environment is our footprint on earth. Buildings account for 30% of the raw materials used, 42% of the energy, 25% of water, 12% of land use, 40% of atmospheric emissions, 20% of water effluents, 25% of solid waste and 13% of other releases. Include infrastructure and the numbers are more.There is a huge potential to change Portland cement to improve sustainability and properties.These days technology improvements fuel economic growth.
6 Partially hydrated Portland cement paste [Soroos,1999 ]. Imagine the consequences of getting rid of the lime and filling all these voids as Portland cement hydrates with an almost insoluble sticky alkaline paste.Partially hydrated Portland cement paste [Soroos,1999 ].
8 TecEco Cement SummaryTecEco cements are a system of blending reactive magnesia, Portland cement and usually a pozzolan.Two main formulation groups.TecEco modified Portland cements.Contain more Portland cement than reactive magnesiaThe role of magnesia as it hydrates is to densify and protect.Other benefits include improvements in rheologyTecEco eco-cementsContain more reactive magnesia than Portland cement.The brucite formed eventually carbonatesForming stronger fibrous minerals.Resulting in huge opportunities for abatement.
10 Understanding TecEco Modified Portland Cements The easiest way to understand TecEco modified Portland cements is to think of the ramifications of replacing lime in Portland cement with brucite (Mg(OH)2).TecEco achieve this by removing the lime with a pozzolan and replacing it with reactive magnesia that hydrates filling in the voids.The mean size of the reactive magnesia TecEco have been using is less than 10 micron, compared to Portland cement at around 80 micronHighly reactive magnesia and usually a pozzolan are required to prevent dimensional distress.
11 Understanding TecEco Eco-Cements The easiest way to understand eco-cements work is to think of a lime Portland mortar such as a 1:1:6-9 formulation. Replace the lime with reactive magnesia and reduce the proportion of Portland cement by around half. Add fly ash to consume the lime produced as Portland cement hydrates. The reactive magnesia will first hydrate and then carbonate as would have the lime in porous materials.Dimensional distress is not potentially so much of a problem in porous materials such as bricks, blocks, pavers and mortars and possibly even roads and footpath pavement (which should be porous.)
12 Overcoming 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 dead burned.Dead burned lime is much more expansive than dead burned magnesia.Reactivity of magnesia is a function of state of disorder, specific surface area and glass forming impurities. Make a particle small enough and it will react with just about anything!  Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p Dr Bob Solomon – a former geology lecturer of mine at the University of Tasmania
13 Ramifications of Adding Reactive Magnesia Durability: TecEco cements include highly insoluble minerals that last indefinitely. They will potentially maintain pH at ideal levels, protect steel reinforcing and reduce alkali aggregate reactions.Lower Materials Cost: With economies of scale TecEco cements could reduce costs.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!Insulating Properties / High Thermal Mass / Low Embodied Energy: Eco-cement products will be favoured for energy conserving buildings.Waste Materials: TecEco cements and Eco-cements use a high proportion of recycled materials.Recyclable: Eco-cement products can be reprocessed and reused, making them more attractive to many users.A Fire Retardant: Eco-cement products put fires out by releasing CO2Low Capital Cost: No new plant and equipment is required.Environmentally Friendly!
14 Durability of TecEco Cement Concretes Reducing Corrosion.Portlandite is removed in reactions with Pozzolans.Replacement of Portlandite which carbonates readily and being soluble can act as an electrolyte by brucite which is much less soluble, does not act as an electrolyte or carbonate as readily.Portlandite - Free Energy of Formation of Carbonate Gor kJ.mol-1, Ksp = 5.5 X 10-6Brucite - Free Energy of Formation of Carbonate Gor kJ.mol-1, Ksp = 1.8 X 10-11Lower More Stable pH for much Longer?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 (See Pourbaix diagram)Increased DensityAs reactive magnesia is much finer than Portland cement it tends to act as a lubricant improving rheology even without plasticiser and lowering the water cement ratio.Brucite also densifies the matrix by filling in pore spaces taking up mix and bleed water as it hydrates.
15 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.
16 TecEco Modified Portland Cements Improving the triple bottom line (society, the economy and the environment )Durability and corrosion may become problems of the past.Lower use of materials and energy over time saving money and the environment.Concretes may become easier to use with less problems.AAR, shrinkage, steel corrosion, fire resistance, placement and finish time are all problems that may be solved to varying extents.Lower CostsMaking reactive magnesia is a benign process with potential for using waste energy.A wider range of aggregates including wastes will be available reducing cartage costs and emissions.Higher Standard of LivingMore with less cost to the environment.
18 TecEco 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 immobilisedTecEco eco-cements are ideal for utilising hazardous wastes such as fly and bottom ash, iron slags, red mud etc.TecEco Modified Portland cements are excellent for toxic and hazardous waste immobilisation as they are not corroded by ground or sea water.TecEco Cements are a formidable solution to toxic and hazardous waste fixation problems
21 Abatement 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 CO2Some of TecEco’s early publications on emissions were not very clear as to how they were abated and this has been compounded by the press. How CO2 releases are abated in TecEco modified Portland cements and eco-cements is discussed in detail in newsletter 28 freely available on the web.
22 Emissions Total CO2 Released (tonnes/tonne) Relative to Product Calcination Energy 100% EfficientCalcination Energy With InefficienciesChemicalTotal 100% EfficientTotal with InefficienciesMgO0.1880.2351.0921.2801.327Ca(OH)20.1540.2320.7850.9391.016Portland Cement0.1160.2120.5140.6300.726
24 Global Abatement No Capture CO2 Capture CO2 Units Total Portland cement produced globally1.800billion tonnesConcrete with same proportion OPC (15 mass%)12.000Emissions Portland Cement3.59380% substitution by eco-cements9.600Abatement Portland Cement Emissions2.875Emissions/Sequestration Substituted Eco-Cement2.5851.343Abatement/Sequestration Substituted Eco-Cement0.2891.532
25 Substitution (Millions of Tonnes) MaterialSubstitutionWorld MarketSubstituted TonnesCO2 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 CaptureBricks85.00%250212.50.2859.557.2329.732.2729.77Steel25.00%8402102.38499.856.5629.38443.24470.42Aluminium20.00%20.54.118126.96.36.19972.7073.23TOTAL426.620.66633.1114.8959.68518.21573.42Concretes already have low lifetime energies.If embodied energies are improved could substitution mean greater market share?Figures are in millons of Tonnes
26 TecEco Kiln Technology Calcining and grinding occur at the same time.Clastic conditions lower the state of disorder. Heat is literally squashed into a material.CO2 can be captured at source.The heat lost through grinding is used for calcining.Approx 25% greater efficiency.Much more reactive magnesia should result.
27 TecEco’s Immediate Focus Raise money for Research – Around 4 millions dollars worth in the pipeline.Focus is 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 and mortars for the masonry industry 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.Considerable interest is also being shown in the new TecEco kiln design and the Tech Tendon method of prestressing, partial prestressing and reinforcing.
28 TecEco 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 students at universities around the world doing researchTecEco have 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.TecEco have received huge global publicity – not all of which is correct!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
30 TecEco Technology Summary Simple, Smart and SustainableTecEco cement technology has resulted in potential solutions to the problem of the rusting of steel in concrete, 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