Published on February 12, 2008
TecEco Eco-Cement Concretes – Abatement, Sequestration and Waste Utilization in the Built Environment : TecEco Eco-Cement Concretes – Abatement, Sequestration and Waste Utilization in the Built Environment 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. If we can make materials that take less than half as much energy, last more than twice as long (are more durable) and have a use when they are retired as well as make them net carbon sinks – Then these materials must be sustainable. TecEco Binder Systems: TecEco Binder Systems Hydration of the various components of Portland cement for strength. SUSTAINABILITY DURABILITY STRENGTH TECECO CEMENTS 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 POZZOLAN REACTIVE 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. TecEco Formulations: TecEco Formulations Tec-cements (5-15% MgO, 85-95% OPC) 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 it’s 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 (15-95% MgO, 85-5% OPC) 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 (5-15% MgO, 85-95% OPC) 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. The Magnesium Thermodynamic Cycle: The Magnesium Thermodynamic Cycle CO2 Capture Non fossil fuel energy Calcination We think this cycle is relatively independent of other constituents Strength with Blend & Porosity: Strength with Blend & Porosity High OPC High Magnesia High Porosity STRENGTH ON ARBITARY SCALE 1-100 Tec-cement concretes Eco-cement concretes Enviro-cement concretes The Carbon Cycle and Emissions: The Carbon Cycle and Emissions Source: David Schimel and Lisa Dilling, National Centre for Atmospheric Research 2003 The cause of the global warming problem Abatement and Sequestration: Abatement and Sequestration To solve the greenhouse gas problem our approach should be holistically balanced and involve Everybody, every day Be easy Make money TecEco-cements = Low Emissions Production Mineral Sequestration + Waste utilization Geological Seques-tration Emissions reduction through efficiency and conversion to non fossil fuels + + TecEco’s Contribution New technical paradigms are required Abatement Sequestration and Ramifications of TecEco Eco-Cement Technologies: Ramifications of TecEco Eco-Cement Technologies CO2 is a waste We need to think about supply and waste impacts when we design materials – not just about the utility phase in the middle. Making the built environment a repository for waste and huge carbon sink as proposed by TecEco is a politically viable and economic alternative. Concrete, a cementitous composite, is the single biggest material flow on the planet with over 2 tonnes per person produced and a good place to start. By including carbon, materials are potentially carbon sinks. By including wastes many problems at the waste end are solved. TecEco Technologies Provide a Profitable Solution: TecEco Technologies Provide a Profitable Solution Silicate → Carbonate Mineral Sequestration Using either peridotite, forsterite or serpentine as inputs to a silicate reactor process CO2 is sequestered and magnesite produced. Proven by others (NETL,MIT,TNO, Finnish govt. etc.) Tec-Kiln Technology Combined calcining and grinding in a closed system allowing the capture of CO2. Powered by waste heat, solar or solar derived energy. To be proved but simple and should work! Direct Scrubbing of CO2 using MgO Being proven by others (NETL,MIT,TNO, Finnish govt. etc.) Tec and Eco-Cement Concretes in the Built Environment. TecEco eco-cements set by absorbing CO2 and are as good as proven. TecEco More Economic under Kyoto? TecEco The TecEco Total Process: The TecEco Total Process Fe, Ni, Co. Silicate Reactor Process e.g. Mg2SiO4 +2CO2 =>2MgCO3 + SiO2 Silicic Acids or Silica Non Stored Energy Powered Tec-Kiln CO2 for Geological Sequestration Oxide Reactor Process CO2 from Power Generation, Industry or CO2 Directly From the Air Magnesite MgCO3) Crushing Grinding Screening Magnetic Sep. Heat Treatment Serpentine Mg3Si2O5(OH)4 Crushing Grinding Screening Gravity Concentration Olivine Mg2SiO4 Magnesia (MgO) MgO for TecEco Cements and Sequestration by Eco-Cements in the Built Environment Other Wastes after Processing Magnesite (MgCO3) CO2 from Power Generation or Industry Magnesium Thermodynamic Cycle Waste Sulfuric Acid or Alkali? This reaction is how most MgCO3 came to be formed anyway so why are we not using it to also sequester carbon? The TecEco Dream – A More Sustainable Built Environment: The TecEco Dream – A More Sustainable Built Environment MAGNESITE + OTHER INPUTS TECECO CONCRETES MINING SUSTAINABLE CITIES CO2 PERMANENT SEQUESTRATION & WASTE UTILISATION (Man made carbonate rock incorporating wastes as a building material) MgO TECECO KILN RECYCLED BUILDING MATERIALS OTHERWASTES CO2 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 TecEco Kiln Technology: TecEco Kiln Technology Grinds and calcines at the same time. Runs 25% to 30% more efficiency. Can be powered by variable non fossil fuel energy. Theoretically capable of producing much more reactive MgO Even with ores of high Fe content. Captures CO2 for bottling and sale to the oil industry (geological sequestration). Runs at low temperatures. Can be run cyclicly as part of a major process to solve global CO2 problems. Will result in new markets for ultra reactive low lattice energy MgO (e.g. paper and environment industries) TecEco need your backing to develop the kiln Advantages of Adopting TecEco Eco-Cement Technology: Advantages of Adopting TecEco Eco-Cement Technology Utilizing wastes to make materials like concretes. Tec-cements have more rapid strength development with fly ash, bottom ash, industrial slags etc. (Tec-Cements.) Reducing energy and emissions during the production of cements using the TecEco kiln. MgO can be made using non fossil fuel energy Concretes containing MgO are demonstrably more durable. It makes sense to sequester carbon by allowing MgO to re-carbonate and thereby gain strength. The biggest business on the planet is going to be the sustainability business 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. 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 CO2 captured during production. Eco-Cements Tec -Cements Tec & Eco-Cements TecEco Technologies Take Concrete into the Future Carbonation: 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 CO2 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 Eco-Cement Biomimicry: Eco-Cement 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 A Post – Carbon Age: A Post – Carbon Age We cannot get there without new technical paradigms. The construction industry can be uniquely responsible for helping achieve this transition “By enabling us to make productive use of particular raw materials, technology determines what constitutes a physical resource1” Pilzer, Paul Zane, Unlimited Wealth, The Theory and Practice of Economic Alchemy, Crown Publishers Inc. New York.1990 Why Magnesium Carbonates?: Why Magnesium Carbonates? Because of the low molecular weight of magnesium, magnesium oxide which hydrates to magnesium hydroxide and then carbonates, is ideal for scrubbing CO2 out of the air and sequestering the gas into the built environment: More CO2 is captured than in calcium systems as the calculations below show. At 2.09% of the crust magnesium is the 8th most abundant element Magnesium minerals are potential low cost. New kiln technology from TecEco will enable easy low cost simple non fossil fuel calcination with CO2 capture of magnesium carbonate. Why Magnesium Carbonates?: Why Magnesium Carbonates? Reactive, low lattice energy forms of magnesium oxide are most suitable as they are Easier to get into solution Efficiently absorb CO2 A high proportion of CO2 and water means that a little MgO goes a long way. In terms of sequestration or binder produced for starting material in cement, eco-cements are much more efficient. Capture of CO2 during manufacture and use for sequestration directly in the built environment makes a lot of sense. Drivers for TecEco Cement and Kiln Technology: Drivers for TecEco Cement and Kiln Technology Producer Push The opportunity cost of compliant waste disposal Profitability and cost recovery Technical merit Resource issues Robotics Research objectives Consumer Pull Environmental sentiment Fear of climate change Cost and technical advantages Competition, robotics Government Influence Carbon Taxes Provision of Research Funds Environmental education Huge Markets Cement 2 billion tonnes. Bricks 130,000 million tonnes TecEco cements are the only binders capable of utilizing very large quantities of wastes based on physical property rather than chemical composition overcoming significant global disposal problems, and reducing the impact of landfill taxes. TecEco eco-cements can sequester CO2 on a large scale and will therefore provide carbon accounting advantages. TecEco kiln technology could be the first non fossil fuel powered industrial process Eco-Cements: 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. Eco-Cement Strength Development: 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%. Eco-Cement Strength Gain Curve: 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. Chemistry of Eco-Cements: 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. Gor Brucite to nesquehonite = - 38.73 kJ.mol-1 Compare to Gor Portlandite to calcite = -64.62 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. Gor 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. Eco-Cement Reactions: Eco-Cement Reactions Eco-Cement Micro-Structural Strength: Eco-Cement Micro-Structural Strength Proof of Carbonation - Minerals Present After 18 Months: Proof of Carbonation - Minerals Present After 18 Months XRD showing carbonates and other minerals before removal of carbonates with HCl in a simple Mix (70 Kg PC, 70 Kg MgO, colouring oxide .5Kg, sand unwashed 1105 Kg) Proof of Carbonation - Minerals Present After 18 Months and Acid Leaching: Proof of Carbonation - Minerals Present After 18 Months and Acid Leaching XRD Showing minerals remaining after their removal with HCl in a simple mix (70 Kg PC, 70 Kg MgO, colouring oxide .5Kg, sand unwashed 1105 Kg) CO2 Abatement in Eco-Cements: CO2 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 CO2 during manufacture of reactive magnesia) have 2.65 times less emissions than if they were made with Portland cement. Capture CO2 11.25% 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 CO2. 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 Aggregate Requirements for Carbonation: 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 a coarse fraction to cause physical air voids and some vapour permeability. Coarse fractions are required in the aggregates used! Roman Specifications: Roman Specifications The oldest record: Book II, chapter IV of the Ten Books of Architecture by Vitruvius Pollio. According to Vitruvius “the best (sand) will be found to be that which crackles when rubbed in the hand, while that which has much dirt in it will not be sharp enough. Again: throw some sand upon a white garment and then shake it out; if the garment is not soiled and no dirt adheres to it, the sand is suitable” Vitruvious was talking about gritty sand with no fines. The 16th century architect Andrea Palladio is renowned for "The Four Books of Architecture“ translated into English in the early 18th century used as a principal reference for building for almost two centuries (Palladio, Isaac Ware translation, 1738). In the first book Palladio says, "the best river sand is that which is found in rapid streams, and under water-falls, because it is most purged". In other words, it is coarse. Compare this with most sand for use in mortar today. The conclusion form history is that a coarse gritty sand that is not graded for minimum paste is required. Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes: Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes As the price of fuel rises, the use of 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 TecEco technologies because they provide benign environments allowing the use of many local materials and wastes without delayed reactions No longer an option? Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes: 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) Solving Waste & Logistics Problems: 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 Recycling Materials = Reduced Embodied Energies and Emissions: Recycling Materials = Reduced Embodied Energies and Emissions The above relationships hold true on a macro scale, provided we can change the technology paradigm to make the process of recycling much more efficient = economic. TecEco Technology in Practice - Whittlesea, Vic. Australia: TecEco Technology in Practice - Whittlesea, Vic. Australia First Eco-cement mud bricks and mortars in Australia Tested up twice as strong as the PC controls Mud brick addition rate 2.5% Addition rate for mortars 1:8 not 1:3 because of molar ratio volume increase with MgO compared to lime. TecEco Technology in Practice - Whittlesea, Vic. Australia: TecEco Technology in Practice - Whittlesea, Vic. Australia On 17th March 2005 TecEco poured the first commercial slab in the world using tec-cement concrete. The formulation strategy was to adjust a standard 20 MPa high fly ash (36%) mix from the supplier as a basis of comparison. Strength development, and in particular early strength development was good. Shrinkage was low. First Eco-cement mud bricks and mortars Tested up twice as strong as the PC controls Mud brick addition rate 2.5% Rate for mortars 1:8 not 1:3 because of molar ratio increase. Blocks also available: Blocks also available TecEco tec and eco-cement blocks are now being made commercially in Tasmania and with freight equalization may be viable to ship to Victoria for your “green” project. Hopefully soon we will have a premix mortar available that uses eco-cement. Eco-Cement Porous Pavement – A Solution for Water Quality? : Eco-Cement Porous Pavement – A Solution for Water Quality? Before three were cites forests and grassland covered most of our planet. When it rained much of the water naturally percolated though soils that performed vital functions of slowing down the rate of transport to rivers and streams, purifying the water and replenishing natural aquifers. Our legacy has been to pave this natural bio filter, redirecting the water that fell as rain as quickly as possible to the sea. Given global water shortages, problems with salinity, pollution, volume and rate of flow of runoff we need to change our practices so as to mimic the way it was for so many millions of years before we started making so many changes. Porous Pavements are a Technology Paradigm Change Worth Investigating Earthship Brighton – First Building to Use Eco-Cements Throughout: Earthship Brighton – First Building to Use Eco-Cements Throughout Conclusion As materials scientists we must do all we can to change the technology paradigms so that carbon and wastes become resources. TecEco are mimicking nature where the principle building materials for trees, animals and fish has been for millennia carbon Aubrey John Weston Harrison B.Sc. B.Ec. FCPA.