Presentation on theme: "Www.tececo.com 1 New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan. All I ask is that the industry."— Presentation transcript:
1 New Cements Based on the Addition of Reactive Magnesia to Portland Cement With or Without Added Pozzolan. All I ask is that the industry think about what I am saying. John Harrison B.Sc. B.Ec. FCPA. Hobart, Tasmania, Australia
2 Sustainability Issues Globally some 2 billion tonnes of cement, lime and magnesia are produced annually c onsuming large amounts of energy* and releasing chemically bound CO 2. *Around 98% of the worlds energy is derived from fossil fuels that when burnt to produce energy release vast amounts of CO 2 –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 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? Materials Science Issues
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 Partially hydrated Portland cement paste [Soroos,1999 ]. 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. 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 TecEco Cement - Simple Yet Ingenious? Glue as well as Velcro?
6 TecEco Cements – A Blending System TecEco cements are a system of blending reactive magnesia, Portland cement and usually a pozzolan Imagination is more important than knowledge, knowledge is limited. Albert Einstein
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 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
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 reducing problems such as AAR and etching, but still high enough to keep Fe FeO and Fe 3 O 4 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 CO 2
11 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 –Ksp Portlandite = 5.5 X Carbonation of brucite is slow – G o r Brucite = – G o r Portlandite = Carbonation of brucite is slightly expansive –And results in surface tightening reducing further carbonation - not cracking! Magnesite and hydromagnesite add strength Durability - Reduced Salt Attack and Carbonation 5 orders of magnitude 3 orders of magnitude
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. Fe 2 O 3 is stable above around pH 8.9. Fe 2 O 3 does not hydrate and protects steel. TecEco Cement zone. 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 pH
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 CO 2 out.) Carbonation of brucite seals the surface preventing further carbonation. Anode Cathode Ionic transport
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 (>.1%). When magnesia hydrates it expands: MgO (s) + H 2 O (l) Mg(OH) 2 (s) molar mass liquid 24.3 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).
18 No Volume Changes with TecEco Modified Portland Cements on Carbonation? Consider what happens when Portlandite carbonates: Ca(OH) 2 + CO 2 CaCO molar mass gas molar volumes –18.22% shrinkage –Surface shrinkage causing cracks to appear. Compared to brucite forming magnesite as it carbonates: Mg(OH) 2 + CO 2 MgCO molar mass gas molar volumes –15.68% expansion –Slight expansion and densification of the surface preventing further ingress of CO 2 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 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.
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 CO 2 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 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 properties –Lower Costs Making reactive magnesia is a benign process with potential for using waste energy and capture of CO 2. A wider range of aggregates including wastes will be available reducing cartage costs and emissions. Water or CO 2 from the air comprise a high mass % and volume % of the magnesium minerals in TecEco cements. Water and CO 2 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 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
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 Manufactur ing Process Energy Release 100% Efficient (Mj.tonne -1 ) From Manufacturin g Process Energy Release with Inefficiencie s (Mj.tonne -1 ) Relative Product Used in Cement From Manufacturi ng Process Energy Release 100% Efficient (Mj.tonne -1 ) From Manufacturin g Process Energy Release with Inefficiencies (Mj.tonne -1 ) Relative to Mineral Resulting in Cement From Manufacturi ng Process Energy Release 100% Efficient (Mj.tonne -1 ) From Manufacturi ng Process Energy Release with Inefficienci es (Mj.tonne -1 ) CaCO 3 + Clay Portlan d Cement Hydrated OPC CaCO Ca(OH) MgCO MgO Mg(OH)
31 Energy – On a Volume Basis Relative to Raw Material Used to make Cement From Manufacturi ng Process Energy Release 100% Efficient (Mj.metre -3 ) From Manufacturin g Process Energy Release with Inefficiencies (Mj.metre -3 ) Relative Product Used in Cement From Manufactur ing Process Energy Release 100% Efficient (Mj.metre -3 ) From Manufacturin g Process Energy Release with Inefficiencies (Mj.metre -3 ) Relative to Mineral Resulting in Cement From Manufactur ing Process Energy Release 100% Efficient (Mj.metre -3 ) From Manufacturing Process Energy Release with Inefficiencies (Mj.metre -3 ) CaCO 3 + Clay Portland Cement Hydrated OPC CaCO Ca(OH) MgCO MgO Mg(OH)
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 CO 2 The production of Portland cement, lime and reactive magnesia also results in the release of chemically bound CO 2 See newsletter 28 for more detail at
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 CO 2. 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 Global mass of Concrete (assuming a proportion of 15 mass% cement) Global CO 2 Emissions from Portland Cement 3.60 Mass of Eco-Cement assuming an 80% Substitution in global concrete use 9.60 Resulting Abatement of Portland Cement CO 2 Emissions 2.88 CO 2 Emissions released by Eco-Cement Resulting Abatement of CO 2 emissions by Substituting Eco-Cement
37 Abatement from Substitution Figures are in millions of Tonnes Building Material to be substituted Realisti c % Subst- itution by TecEco technol ogy Size of World Market (millio n tonnes Substit uted Mass (million tonnes) CO2 Fact ors (1) Emission From Material Before Substituti on Emission/Sequestrati on from Substituted Eco-Cement (Tonne for Tonne Substitution Assumed) Net Abatement Emission s - No Capture Emission s - CO2 Capture Abatem ent - No Capture Abatem ent CO2 Capture Bricks85% Steel25% Aluminium20% TOTAL Concretes already have low lifetime energies. If embodied energies are improved could substitution mean greater market share?
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. –CO 2 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