Presentation on theme: "Presentation downloadable from www.tececo.com 1 Greening Mineral Binders Our slides are deliberately verbose as most people download and view them from."— Presentation transcript:
Presentation downloadable from 1 Greening 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
Presentation downloadable from 2 Under 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, cfcs, c=halogen compounds and CO 2 Moleconomics Is 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.
Presentation downloadable from 3 Abatement 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 + TecEcos Contribution New technical paradigms are required Abatement Sequestration and
Presentation downloadable from 4 The TecEco CarbonSafe Geo-Photosynthethic Process Greensols Process Fossil fuels Solar or solar derived energy CO 2 Oil MgO CO 2 Coal CO 2 MgCO 3 CO 2 Inputs: Atmospheric or smokestack CO 2, brines, waste acid, other wastes Outputs: Potable water, gypsum, sodium bicarbonate, salts, building materials, bottled concentrated CO 2 (for geo-sequestration and other uses). Carbon or carbon compounds Magnesium oxide 1.29 gm/l Mg The CarbonSafe Geo-Photosynthetic Process is TecEcos evolving techno- process that delivers profitable outcomes whilst reversing underlying undesirable moleconomic flows from other less sustainable processes. TecEco MgCO 2 Cycle TecEco Kiln
Presentation downloadable from 5 The TecEco CarbonSafe Industrial Ecology Outputs Gypsum, Sodium bicarbonate, Salts, Building materials, Potable water Inputs Brines Waste Acid CO2 We must design whole new technical paradigms that reverse many of our problem molecular flows
Presentation downloadable from 6 Hydroxid e Reactor Process CO 2 as a biological or industrial input or if no other use geological sequestration CO 2 from power generation, industry or out of the air Magnesite (MgCO 3 ) Magnesia (MgO) Other Wastes Simplified TecEco Reactions Tec-Kiln MgCO3 MgO + CO kJ/mole Reactor Process MgO + CO 2 MgCO kJ/mole (usually more complex hydrates) Magnesium Thermodynamic Cycle Waste Acid x 10 9 km3 Seawater containing 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 CO 2 sequestered by 1 billion tonnes of Mg in seawater Tonnes CO 2 captured during calcining (same as above) Tonnes CO 2 captured by eco-cement Total tonnes CO 2 sequestered or abated per tonne Mg in seawater (Single calcination cycle) Total tonnes CO 2 sequestered or abated (Five calcination cycles.) Total tonnes CO 2 sequestered or abated (Ten calcination cycles) Gypsum (CaSO 4 ) Gypsum + carbon waste (e.g. sewerage) = fertilizers Sewerage compost Magnesite (MgCO 3 ) Solar Process to Produce Magnesium Metal Bicarbonate of Soda (NaHCO 3 ) Eco-Cement Tec-Cement Seawater Carbonatio n Process Other salts Na +,K +, Ca 2+,Cl - CO 2 from power generation or industry Sequestration Table – Mg from Seawater The CarbonSafe Geo-Photosynthetic Process CO 2
Presentation downloadable from 7 TecEco CO 2 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 CO 2 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)
Presentation downloadable from 8 Re - 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
Presentation downloadable from 9 Huge Potential for Sustainable Materials Reducing 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 as well as chemical composition they become resources. –re – engineering materials to reduce the lifetime energy of buildings Many wastes can contribute to physical properties reducing lifetime energies C CO 2 Waste CO 2
Presentation downloadable from 10 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
Presentation downloadable from 11 Impact 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
Presentation downloadable from 12 Embodied Energy of Building Materials Downloaded from serv/brochures/embodied/embodied.htm (last accessed 07 March 2000) Concrete is relatively environmentally friendly and has a relatively low embodied energy
Presentation downloadable from 13 Average Embodied Energy in Buildings Downloaded from 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.
Presentation downloadable from 14 Emissions from Cement Production Chemical Release –The process of calcination involves driving off chemically bound CO 2 with heat. CaCO 3 CaO + CO 2 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 CO 2. The production of cement for concretes accounts for around 10% of global anthropogenic CO 2. –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. CO 2 CO 2
Presentation downloadable from 15 Cement Production ~= Carbon Dioxide Emissions Between Tec, Eco and Enviro-Cements TecEco can provide a viable much more sustainable alternative.
Presentation downloadable from 16 The TecEco Dream – A More Sustainable Built Environment MAGNESITE + OTHER INPUTS TECECO CONCRETES MINING SUSTAINABLE CITIES CO 2 PERMANENT SEQUESTRATION & WASTE UTILISATION (Man made carbonate rock incorporating wastes as a building material) CO 2 MgO TECECO KILN RECYCLED BUILDING MATERIALS OTHER WASTES CO 2 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
Presentation downloadable from 17 A Low Energy Post – Carbon & Waste Age? The construction industry can be uniquely responsible for helping achieve this transition Maybe then we can move confidently into a more sustainable future.
Presentation downloadable from 18 Concrete 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
Presentation downloadable from 19 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
Presentation downloadable from 20 Greening Concrete 4.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 cement a)Carbonating Binders b)Non-carbonating binders –The research and development of these binders needs to be accelerated
Presentation downloadable from 21 Greening Concrete 6.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.
Presentation downloadable from 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
Presentation downloadable from 23 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
Presentation downloadable from 24 Portlandite Compared to Brucite PropertyPortlandite (Lime)Brucite Density Hardness2.5 – 3 Solubility (cold)1.85 g L -1 in H 2 O at 0 o C0.009 g L -1 in H 2 O at 18 o C. Solubility (hot).77 g L -1 in H 2 O at 100 o C.004 g L -1 H 2 O at 100 o C Solubility (moles, cold) M L M L -1 Solubility (moles, hot) M L M L -1 Solubility Product (K sp )5.5 X X ReactivityHighLow FormMassive, sometime fibrous Usually fibrous Free Energy of Formation of Carbonate G o f kJ.mol kJ.mol kJ.mol -1 (via hydrate) Cement chemists in the industry should be getting their heads around the differences
Presentation downloadable from 25 Tec-Cement Concrete Strength Gain Curve The possibility of high early strength gain with added pozzolans is of great economic and environmental importance. We have observed this kind of curve with over 300 cubic meters of concrete
Presentation downloadable from 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 + H 2 O => Ca(OH) 2 Ca(OH) 2 + CO 2 => CaCO gas molar volumes –Very slight expansion, but shrinkage from loss of water.
Presentation downloadable from 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 + H 2 O Mg(OH) 2 Mg(OH) 2 + CO 2 + H 2 O MgCO 3. 3H 2 O molar mass (at least!) gas 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 CO 2 and water
Presentation downloadable from b Replacement with Non Carbonating Binders There are a number of other novel cements with intrinsically lower energy requirements and CO 2 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
Presentation downloadable from 29 Geopolymers Geopolymers consists of SiO 4 and AlO 4 tetrahedra linked alternately by sharing all the oxygens. –Positive ions (Na +, K +, Li +, Ca ++, Ba ++, NH 4 +, H 3 O + ) must be present in the framework cavities to balance the negative charge of Al 3+ 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
Presentation downloadable from 30 TecEco Cements SUSTAINABILITY DURABILITYSTRENGTH TECECO 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.
Presentation downloadable from 31 The Magnesium Thermodynamic Cycle CO 2 Capture Non fossil fuel energy Calcination We think this cycle is relatively independent of other constituents
Presentation downloadable from 32 TecEco Cement Technology Theory Portlandite (Ca(OH) 2 ) is too soluble, mobile and reactive. –It carbonates, reacts with Cl - and SO 4 - 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
Presentation downloadable from 33 TecEco 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 its 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.
Presentation downloadable from 34 TecEco Cements – Impact on Sustainability The CO 2 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 CO 2 requiring 25-75% less binder in some mixes
Presentation downloadable from 35 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
Presentation downloadable from 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/m 3 –Concretes of over 10 mp as light as 1000 Kg/m 3 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
Presentation downloadable from 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
Presentation downloadable from 38 Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes As the price of fuel rises, the use of local or on site low embodied energy materials rather than carted aggregates will have to be considered. Recent natural disasters such as the recent tsunami and Pakistani earthquake mean we urgently need to commercialize technologies like TecEcos 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.
Presentation downloadable from 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
Presentation downloadable from 40 Biomimicry - 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
Presentation downloadable from 41 TecEco 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 CO 2 captured during production. Eco-Cements Tec - Cements Tec & Eco- Cements Contact: John Harrison, TecEco Pty. Ltd.
Presentation downloadable from 42 Eco-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.
Presentation downloadable from 43 Eco-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 + CO 2 MgCO 3.5H 2 O From air and water
Presentation downloadable from 44 Eco-Cement Strength Gain Curve 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.
Presentation downloadable from 45 Chemistry 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. – G o r Brucite to nesquehonite = kJ.mol-1 –Compare to G o r Portlandite to calcite = 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. G o r 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.
Presentation downloadable from 46 Eco-Cement Reactions
Presentation downloadable from 47 Eco-Cement Micro-Structural Strength
Presentation downloadable from 48 Carbonation 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 CO 2 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
Presentation downloadable from 49 Aggregate 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.
Presentation downloadable from 50 CO 2 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 Capture 11.25% 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 Cements 15 mass% Portland cement, 85 mass% aggregate Emissions.32 tonnes to the tonne. After carbonation. Approximately.299 tonne to the tonne..299 >.241 >.140 >.113 Bricks, blocks, pavers, mortars and pavement made using eco-cement, fly and bottom ash (with capture of CO 2 during manufacture of reactive magnesia) have 2.65 times less emissions than if they were made with Portland cement. Capture CO % 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 CO 2. Fly and Bottom Ash 11.25% 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
Presentation downloadable from 51 TecEco 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
Presentation downloadable from 52 Tec-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 )
Presentation downloadable from 53 More 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
Presentation downloadable from 54 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.nH 2 O supplying H 2 O for more complete hydration of C 2 S and C 3 S? 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.
Presentation downloadable from 55 Greater 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 Mutual Repulsion => Ph 12 ? Cement MgO Sand MgO Mutual Repulsion Mutual Attraction
Presentation downloadable from 56 Non Newtonian Rheology – Rapid Gelling 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. Ca++ = 114, Mg++ = 86 picometres
Presentation downloadable from 57 Durability 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
Presentation downloadable from 58 Crack 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 Plastic Shrinkage Drying Shrinkage Corrosion Related Freeze Thaw D Cracks Structural Settlement Shrinkage Photos from PCA and US Dept. Ag Websites Autogenous or self-desiccation shrinkage (usually related to stoichiometric or chemical shrinkage) Alkali aggregate Reaction Evaporative Crazing Shrinkage
Presentation downloadable from 59 Causes 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.
Presentation downloadable from 60 Graphic Illustration of Cracking After Tony Thomas (Boral Ltd.) (Thomas 2005) Autogenous shrinkage has been used to refer to hydration shrinkage and is thus stoichiometric
Presentation downloadable from 61 Cracking due to Loss of Water Drying Shrinkage Plastic Shrinkage Picture from: Evaporative Crazing Shrinkage 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, Bucket of Water Fool
Presentation downloadable from 62 Solving 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) + H 2 O (l) Mg(OH) 2.nH 2 O (s)
Presentation downloadable from 63 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) + H 2 O (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) + H 2 O (l) Mg(OH) 2. nH2O (s) molar mass (at least!) 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 Water
Presentation downloadable from 64 Portland cements stoichiometrically require around % 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 Water MgO (s) + H 2 O (l) Mg(OH) 2.nH 2 O (s)
Presentation downloadable from 65 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).
Presentation downloadable from 66 Bleeding 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
Presentation downloadable from 67 Dimensional 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 > 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.
Presentation downloadable from 68 Reducing Cracking as a Result of Volume Change caused by Delayed Reactions Photo Courtesy Ahmad Shayan ARRB An Alkali Aggregate Reaction Cracked Bridge Element
Presentation downloadable from 69 Types 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.
Presentation downloadable from 70 Reducing 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.
Presentation downloadable from 71 Reduced Steel Corrosion Related Cracking Steel remains protected with a passive oxide coating of Fe 3 O 4 above pH 8.9. A pH of over 8.9 is maintained by the equilibrium Mg(OH) 2 Mg OH - 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, CO 2 and salts. Rusting Causes Dimensional Distress
Presentation downloadable from 72 Reduced 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
Presentation downloadable from 73 Long 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. A pH in the range 10.5 – 11.2 is ideal in a concrete
Presentation downloadable from 74 Steel Corrosion is Influenced by Long Term pH Eh-pH or Pourbaix Diagram The stability fields of hematite, magnetite and siderite in aqueous solution; total dissolved carbonate = M. In TecEco cements the long term pH is governed by the low solubility and carbonation rate of brucite and is much lower at around , allowing a wider range of aggregates to be used, reducing problems such as AAR and etching. The pH is still high enough to keep Fe 3 O 4 stable in reducing conditions. Steel corrodes below 8.9 Equilibrium pH of Brucite and of lime
Presentation downloadable from 75 Reducing 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; p ) The autogenous deformation of concrete is defined as the unrestrained, bulk deformation that occurs when concrete is kept sealed and at a constant temperature.
Presentation downloadable from 76 Reducing Cracking Related to Autogenous Shrinkage 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.
Presentation downloadable from 77 Reducing Cracking Related to Autogenous Shrinkage 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.nH 2 O (s) MgO (s) + H 2 O (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. MgO (s) + H 2 O (l) Mg(OH) 2. nH 2 O (s) molar mass (at least!) liquid 24.3 molar volumes (at least 116% expansion, probably more initially before desiccation as above!)
Presentation downloadable from 78 Improved 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
Presentation downloadable from 79 Reduced 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 SO 4 --, Cl - and CO 2 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.
Presentation downloadable from 80 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 Permeability
Presentation downloadable from 81 Densification 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.
Presentation downloadable from 82 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 –Ksp Portlandite = 5.5 X 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 Attack
Presentation downloadable from 83 Less 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) + H 2 O (l) Mg(OH) 2 (s) molar mass molar volumes molar volumes At 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
Presentation downloadable from 84 Rosendale 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
Presentation downloadable from 85 Solving 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
Presentation downloadable from 86 Role 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.
Presentation downloadable from 87 Lower Solubility of Metal Hydroxides There is a 10 4 difference All waste streams will contain heavy metals and a strategy for long term pH control is therefore essential
Presentation downloadable from 88 Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes 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)
Presentation downloadable from 89 Sustainable Materials in the Built Environment Technical Focus This 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 Websites ASSMIC Website: Materials Australia Website: Sustainable Materials in the Built Environment 2007 Innovation - Process – Design Announcement and Call for Papers 18th to 20th February 2007 Melbourne, Australia