Presentation on theme: "Presentation downloadable from www.tececo.com 1 Materials and Molecules - Behind What You See."— Presentation transcript:
Presentation downloadable from 1 Materials and Molecules - Behind What You See
Presentation downloadable from 2 Materials and Moelcules – Behind What you See (Originally Concretes – Solution to Kyoto) 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. TecEco are in the biggest business on the planet – that of solving global warming waste and water problems
Presentation downloadable from 3 Techno-Processes & Earth Systems Underlying the techno- process that describes and controls the flow of matter and energy are molecular stocks and flows. If out of tune with nature these moleconomic flows have detrimental affects on earth systems. Detrimental affects on earth systems Earth Systems Atmospheric composition, climate, land cover, marine ecosystems, pollution, coastal zones, freshwater and salinity. Move billion tonnes Use some 50 billion tonnes To reduce the impact on earth systems new technical paradigms need to be invented that result in underlying molecular flows that mimic or at least do not interfere with natural flows. Take Waste
Presentation downloadable from 4 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 5 The Carbon Cycle and Emissions Source: David Schimel and Lisa Dilling, National Centre for Atmospheric Research 2003 Emissions from fossil fuels and cement production are a significant cause of the global warming. Units: GtC GtC/yr
Presentation downloadable from 6 Changing the Techno-Processes Reduce Re-use Recycle Materials Take => manipulate => make => use => waste Driven by fossil fuel energy with detrimental effects on earth systems. Eco-innovate to create industrial ecologies Atoms and Molecules in the global commons
Presentation downloadable from 7 Utilizing Carbon and Wastes (Biomimicry) The waste from one plant or animal is the food or home for another. 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 8 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 9 Energy from Oil Peak Oil Production (Campell 2004) Most models of oil reserves, production and consumption show peak oil around 2010 (Campbell 2005) and serious undersupply and rapidly escalating prices by It follows that there will be economic mayhem unless the cement and concrete industry acts now to change the energy base of their products.
Presentation downloadable from 10 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 TecEco technologies 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 11 Huge Potential for More Sustainable Construction 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 CO 2 C Waste Many wastes including CO 2 can contribute to physical properties reducing lifetime energies CO 2
Presentation downloadable from 12 Impacts of Landfill Landfill is the technical term for filling large holes in the ground with waste. Landfills release methane, can cause ill health in the area, leads to the contamination of land, underground water, streams and coastal waters and gives rise to various nuisances including increased traffic, noise, odours, smoke, dust, litter and pests. Most damaging is the release of dangerous molecules to the global commons
Presentation downloadable from 13 Economically Driven Sustainability New, more profitable technical paradigms are required that result in more sustainable and usually more efficient moleconomic flows that mimic natural flows or better, reverse our damaging flows. $ - ECONOMICS - $
Presentation downloadable from 14 Changing the Technical Paradigm By enabling us to make productive use of particular raw materials, technology determines what constitutes a physical resource 1 1.Pilzer, Paul Zane, Unlimited Wealth, The Theory and Practice of Economic Alchemy, Crown Publishers Inc. New York.1990 By inventing new technical paradigms and re- engineering materials we can change the underlying molecular flows that are damaging this planet. It is not hard to do this and it could even be economic. All it takes is lateral thinking and imagination.
Presentation downloadable from 15 Examples of Economic Changes in Technical Paradigms that result in Greater Sustainability Robotics - A Paradigm Shift in Technology that will fundamentally affect Building and Construction Construction in the future will be largely done by robots because it will be more economic to do so. Like a color printer different materials will be required for different parts of structures, and wastes such as plastics will provide many of the properties required for the cementitious composites of the future used. A non-reactive binder such as TecEco tec-cements can supply the right rheology, and like a printer, very little will be wasted. Light Globes - A Recent Paradigm Shift in Technology Reducing Energy Consumption Light Globes in the last 10 years have evolved from consuming around 100 watts per 1700 lumens to less that 20 watts per 1700 lumens. As light globes account for around 30% of household energy this is as considerable saving. 100 watts 1700 lumens Incandescent 25 watts 1700 lumens Fluorescent <20 watts 1700 lumens Led Light
Presentation downloadable from 16 Sustainability = Culture + Technology Increase in demand/price ratio for sustainability due to educationally induced cultural drift. # $ Demand Supply Increase in supply/price ratio for more sustainable products due to innovative paradigm shifts in technology. Equilibrium shift ECONOMICS Greater Value/for impact (Sustainability) and economic growth Sustainability could be considered as where culture and technology meet. New Technical Paradigms are required that deliver sustainability.
Presentation downloadable from 17 The TecEco CarbonSafe Industrial Ecology 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 18 The TecEco CarbonSafe Industrial Ecology Outputs Gypsum, Sodium bicarbonate, Salts, Building materials, Potable water Inputs Brines Waste Acid CO2
Presentation downloadable from 19 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 Industrial Ecology CO 2 Potable water
Presentation downloadable from 20 Reduction Global CO 2 from CarbonSafe Process
Presentation downloadable from 21 Why Magnesium Carbonates for Sequestration? Because of the low molecular weight of magnesium, magnesium oxide which hydrates to magnesium hydroxide and then carbonates, is ideal for scrubbing CO 2 out of the air and sequestering the gas into the built environment: More CO 2 is captured than in calcium systems as the calculations below show. An area 10km by 10m by 150m deep of magnesium carbonate will sequester all the excess CO2 we release to the atmosphere in a year. 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 of magnesium carbonate with CO 2 capture for geological sequestration.
Presentation downloadable from 22 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 23 Materials in the Built Environment The built environment is made of materials and is our footprint on earth. –It comprises buildings and infrastructure. Construction materials comprise –70% of materials flows (buildings, infrastructure etc.) –40-50% of waste that goes to landfill (15 % of new materials going to site are wasted.) At 1.5% of world GDP Annual Australian production of building materials likely to be in the order 300 million tonnes or over 15 tonnes per person. Over 30 billion tonnes of building materials are used annually on a world wide basis. –Mostly using virgin natural resources –Combined in such a manner they cannot easily be separated. –Include many toxic elements.
Presentation downloadable from 24 Impact of the Largest Material Flow - Cement and Concrete Some 600 billion tonnes of matter are moved around the planet a year of which some 50 billion tonnes only is used. 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 billion tonnes per annum. –Globally over 14 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 25 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 26 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 27 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 28 Cement Production ~= Carbon Dioxide Emissions Between tec, eco and enviro-cements TecEco can provide a viable much more sustainable alternative.
Presentation downloadable from 29 TecEco Binder Systems Hydration of the various components of Portland cement for strength. SUSTAINABILITY DURABILITYSTRENGTH 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.
Presentation downloadable from 30 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 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 (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.
Presentation downloadable from 31 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 32 TecEco Technology in Practice On 17th March 2005 TecEco poured the first commercial slab in the world using tec-cement concrete with the assistance of one of the larger cement and pre-mix companies. –The formulation strategy was to adjust a standard 20 MPa high fly ash (36%) mix from the company as a basis of comparison. –Strength development, and in particular early strength development was good. Interestingly some 70 days later the slab is still gaining strength at the rate of about 5 MPa a month. –Also noticeable was the fact that the concrete was not as "sticky" as it normally is with a fly ash mix and that it did not bleed quite as much. –Shrinkage was low. 7 days micro strains, 14 days micro strains, 28 days micros strains and at 56 days microstrains. => Whittlesea, Vic. Australia
Presentation downloadable from 33 TecEco Technology in Practice Allow many mega litres of good fresh water to become contaminated by the pollutants on our streets and pollute coastal waterways Capture and cleanse the water for our use? Or => Porous Pavement
Presentation downloadable from 34 TecEco Technology in Practice 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. => Whittlesea, Vic. Australia
Presentation downloadable from 35 TecEco Technology in Practice By Taus Larsen, (Architect, Low Carbon Network Ltd.) The Low Carbon Network (www.lowcarbon.co.uk) was established to raise awareness of the links between buildings, the working and living patterns they create, and global warming and aims to initiate change through the application of innovative ideas and approaches to construction. Englands first Earthship is currently under construction in southern England outside Brighton at Stanmer Park and TecEco technologies have been used for the floors and some walling. Earthships are exemplars of low-carbon design, construction and living and were invented and developed in the USA by Mike Reynolds over 20 years of practical building exploration. They are autonomous earth-sheltered buildings independent from mains electricity, water and waste systems and have little or no utility costs. For information about the Earthship Brighton and other projects please go to the TecEco web site. => Earthship Brighton, UK
Presentation downloadable from 36 TecEco Technology in Practice The Clifton Surf Life Saving Club was built by first pouring footings, On the footings block walls were erected and then at a later date concrete was laid in between. As the ground underneath the footings was sandy, wet most of the time and full of salts it was a recipe for disaster. Predictably the salty water rose up through the footings and then through the blocks and where the water evaporated there was strong efflorescence, pitting, loss of material and damage. The TecEco solution was to make up a formulation of eco-cement mortar which we doctored with some special chemicals to prevent the rise of any more moisture and salt. The solution worked well and appears to have stopped the problem. => Clifton Surf Life Saving Club
Presentation downloadable from 37 TecEco Technology in Practice Mike Burdon, Builder and Plumber. I work for a council interested in sutainability and have been involved with TecEco since around 2001 in a private capacity helping with large scale testing of TecEco tec-cements at our shack. I am interested in the potentially superior strength development and sustainability aspects. To date we have poured two slabs, footings, part of a launching ramp and some tilt up panels using formulations and materials supplied by John Harrison of TecEco. I believe that research into the new TecEco cements essential as overall I have found: 1.The rheological performance even without plasticizer was excellent. As testimony to this the contractors on the site commented on how easy the concrete was to place and finish. 2.We tested the TecEco formulations with a hired concrete pump and found it extremely easy to pump and place. Once in position it appeared to gel up quickly allowing stepping for a foundation to a brick wall. 3.Strength gain was more rapid than with Portland cement controls from the same premix plant and continued for longer. 4.The surfaces of the concrete appeared to be particularly hard and I put this down to the fact that much less bleeding was observed than would be expected with a Portland cement only formulation => Mike Burdons Murdunna Works
Presentation downloadable from 38 TecEco Technology in Practice Tec-Cement concretes exhibit little or no shrinkage. At 10% substitution of MgO for PC the shrinkage is less than half normal. At 18% substitution with no added pozzolan there was no measurable shrinkage or expansion. The above photo shows a tec-cement concrete topping coat (with no flyash) 20mm thick away from the door and 80 mm thick near the door. Note that there has been no tendency to push the tiles or shrink away from the borders as would normally be the case. => DJ Motors, Hobart
Presentation downloadable from 39 TecEco Technology in Practice 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. => Island Block and Paver,Tasmania
Presentation downloadable from 40 TecEco Technology in Practice BUILD LITE CELLULAR CONCRETE 4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169 PH FX Foamed TecEco cement concretes can be produced to about 30% weight reduction in concrete trucks using cellflow additive or to about 70% weight reduction using a foaming machine with mearlcrete additive (or equivalents) => Foamed Concretes
Presentation downloadable from 41 Tec & Eco Cement Foamed Concrete Slabs BUILD LITE CELLULAR CONCRETE 4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169 PH FX => Foamed Concrete Slabs
Presentation downloadable from 42 TecEco Technology in Practice Solutions in Steel ABN TEL: FAX: Mica Street Carole Park 4300 Queensland Australia Imagine a conventional steel frame section with a foamed concrete panel built in adding to structural strength, providing insulation as well as the external cladding of a structure. Rigid Steel Framing have developed just such a panel and have chosen to use TecEco cement technology for the strength, ease of use and finish. Patents applied for by Rigid Steel Framing Please direct commercial enquiries to Rigid Steel Framing at rigidsteel.com.au => Foamed Concretes Panels
Presentation downloadable from 43 Rear view of test panels showing tongue and groove and void for services. Interior plasterboard is fixed conventionally over gap for services. TecEco Technology in Practice => Foamed Concretes Panels
Presentation downloadable from 44 TecEco Technologies Take Concrete into the Future More rapid early strength gain even with added pozzolans –More supplementary materials can be used reducing costs and take and waste impacts. Higher strength/binder ratio, provided greater plasticity contributed by magnesia used to reduce water. Less shrinkage and cracking More durable concretes –Reducing costs and take and waste impacts. Use of wastes including 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
Presentation downloadable from 45 Tec & Eco-Cement Theory Many Engineering Issues are Actually Mineralogical Issues –Problems with Portland cement concretes are usually resolved by the band aid engineering fixes. e.g. Use of calcium nitrite, silanes, cathodic protection or stainless steel to prevent corrosion. Use of coatings to prevent carbonation. Crack control joins to mitigate the affects of shrinkage cracking. Plasticisers to improve workability. –Portlandite and water are the weakness of concrete TecEco remove Portlandite it and replacing it with magnesia which hydrates to Brucite. The hydration of magnesia consumes significant water
Presentation downloadable from 46 Tec & Eco-Cement 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 significant water and concentrating alkalis forming B rucite which is another alkali, but much less soluble, mobile or reactive than Portlandite. In Eco-Cements brucite carbonates forming hydrated compounds with greater volume
Presentation downloadable from 47 Why Add Reactive Magnesia? Reactive magnesia is added to maintain the long term stability of CSH. –Preventing a reduction in the Ca/Si ratio in CSH. To remove water. –Reactive magnesia consumes water as it hydrates to possibly hydrated forms of Brucite. To control long term Ph. –Reducing reactivity To reduce shrinkage. To make concretes more durable Because significant quantities of carbonates are produced in porous substrates which are affective binders. The consequences of putting brucite through the matrix of a concrete in the first place need to be considered Reactive MgO is a new tool to be understood with profound affects on most properties
Presentation downloadable from 48 Strength with Blend & Porosity High OPC High Magnesia High Porosity STRENGTH ON ARBITARY SCALE Tec-cement concretes Eco-cement concretes Enviro-cement concretes
Presentation downloadable from 49 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 50 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 51 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 52 Eco-Cement Reactions
Presentation downloadable from 53 Eco-Cement Micro-Structural Strength
Presentation downloadable from 54 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 55 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 56 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!
Presentation downloadable from 57 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.
Presentation downloadable from 58 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
Presentation downloadable from 59 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 60 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 61 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 62 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 63 Tec-Cement Concretes - The Form of MgO Matters - 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 64 Tec-Cement Reactions MgO + H 2 O => Mg(OH) 2.nH 2 O - water consumption resulting in greater density and higher alkalinity. Higher alkalinity => more reactions involving silica & alumina. Mg(OH) 2.nH 2 O => Mg(OH) 2 + H 2 O – slow release water for more complete hydration of PC MgO + Al + H 2 O => 3MgO.Al.6H 2 O ??? – equivalent to flash set?? MgO + SO 4 -- => various Mg oxy sulfates ?? – yes but more likely ettringite reaction consumes SO 4 -- first. MgO + SiO 2 => MSH ?? Yes but high alkalinity required. Strength?? We think the reactions are relatively independent of PC reactions
Presentation downloadable from 65 More Rapid and Greater Strength Development Higher Strength Binder Ratio 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 –15-30% more strength or less binder for the same strength. –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 66 Tec-Cement Strength Development Graphs above by Oxford Uni Student are for standard 1PC:3 aggregate mixes, w/c =.5 WHITTLESEA SLAB (A modified 20 mpa mix) PC = 180 Kg / m3 MgO = 15 Kg / m3 Flyash = 65 Kg / m3 Rate of strength development is of great interest to engineers and constructors
Presentation downloadable from 67 Reasons for Compressive Strength Development in Tec-Cements. Reactive magnesia increases plasticity and therefore should allow skilled operators to use less water. –We admit however that we have done little work with plasticisers yet. 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? 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 68 Reasons for Compressive Strength Development in Tec-Cements. Micro-structural strength due to particle packing Cement grains are around 2.5 times the size of magnesia in Australia at around 20 micron. (Magnesia particles at 5-9 micron roughly 2.5 times smaller, which Francois Larrard (1) maintains is a requirement for good packing.) Formation of MgAl hydrates? Similar to flash set in concrete but slower?? Formation of MSH?? We do not think relevant. 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? (1) de Larrard, F. (1999). Concrete Mixture Proportioning: A Scientific Approach, E & FN Spon.
Presentation downloadable from 69 Greater Tensile Strength MgO Changes Surface Charge as the Ph Rises. This could be one of the reasons for the 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 70 Improved Durability Reasons for Improved Durability: –Reduced shrinkage and Cracking –Greater Density = Lower Permeability Physical Weaknesses => Chemical Attack Chemical weaknesses –Removal of Portlandite with the Pozzolanic Reaction. Removal of reactive components –Substitution by Brucite => Long Term pH control Reducing corrosion DURABILITY Durability is a very important property that is significantly improved with TecEco cements. As Paul Hawkins says in his book, The Ecology of Commerce something that is made with half as much energy and last twice as long is 80% more sustainable (1) The main contributions or our technology are the removal of Portlandite and replacement with a much more stable alkali and reduced shrinkage and cracking. (1) Hawken, P. (1993). The Ecology of Commerce. New York, HarperCollins
Presentation downloadable from 71 Durability. Shrinkage and Cracking Concretes are said to be less durable when they are physically or chemically compromised. Physical factors can result in access to water and chemicals resulting in reactions reducing durability e.g. –Porosity and –Cracking due to shrinkage can allow reactive gases and liquids to enter concrete. Chemical factors can result in physical outcomes reducing durability e.g. –Reactivity of lime with aggressive agents such as chloride or sulphate –Alkali silica reaction opening up cracks allowing other agents such as sulfate and chloride in seawater to enter. –Other reactions can also occur as a result of the pH being too high. This presentation will describe benchmark improvements in durability as a result of using the new TecEco magnesia cement technologies
Presentation downloadable from 72 Cracking 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 73 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 74 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 75 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 76 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 fill voids preventing shrinkage or 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. MgO (s) + H 2 O (l) Mg(OH) 2.nH 2 O (s)
Presentation downloadable from 77 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 possible expansive stoichiometry of MgO reactions (depending on where the water is coming from 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 78 With TecEco Tec-Cements it is important to take advantage of the increased plasticity to add less water so the water for hydration of magnesia is substantially coming from the excess water added to concretes to fluidise them. 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 79 Other Benefits of Preventing Shrinkage through Loss of Water Internal water consumption 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 80 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 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 81 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 82 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 83 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. –Other delayed reactions with aggregates Delayed reactions cause dimensional distress, cracking and possibly even failure.
Presentation downloadable from 84 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 85 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 equilibria Mg(OH) 2 Mg OH - (equilbirium pH is 10.48) CSH Ca OH - + SiO 2 (equilibriam pH is around 11.2) – for much longer than the pH maintained by Ca(OH) 2 Ca(OH) 2 Ca OH - (equilbirium pH is 12.5) 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 86 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 87 Long Term pH control 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 at a lower level in Tec- Cement concretes, but still sufficiently high to prevent corrosion of steel reinforcing. A pH in the range 10.5 (the equilibrium pH of brucite and 11.2 (the equilibrium pH of CSH) is ideal in a concrete
Presentation downloadable from 88 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 89 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 90 Reducing Cracking Related to Autogenous Shrinkage The main cause of autogenous shrinkage 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 91 Reducing Cracking Related to Autogenous Shrinkage Autogenous shrinkage should 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) –Note that as brucite is a relatively weak mineral is can be compressed densifying 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 (provided no additional water is added and plasticity is taken advantage of). 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 92 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. The magnesia component of TecEco cements will always carbonate near the surface of concretes and because of the high mass of hydrated carbonates that forms, expansion will seal that surface. –On carbonation to nesquehonite brucite expands 307% sealing the surface.
Presentation downloadable from 93 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. 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 94 Densification During the Plastic Phase Water Observable Characteristic Relevant Fundamental Binder + supplementary cementitious materials High water for ease of placement Less water for strength and durability Variables such as % hydration of mineral, density, compaction, % mineral H 2 0 etc. Consumption of water during plastic stage Voids Hydrated Binder Materials Unhydrated Binder Less water results in increased density and concentration and early reaction of alkalis - less shrinkage and cracking and improved strength and durability. 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.
Presentation downloadable from 95 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 has a lower pH and 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 96 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 97 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 98 Easier to Finish Concretes Easier to pump and finish concretes are likely to have less water added to them resulting in less cracking
Presentation downloadable from 99 Shear Thinning Rheology The strongly positively charged small Mg++ ions 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 100 Understanding Water - Bingham Plastic Rheology TecEco concretes and mortars are: –Very homogenous and do not segregate easily. –Exhibit good adhesion and have a shear thinning property. –Exhibit Bingham plastic qualities and –React well to energy input displaying good workability TecEco concretes with the same water/binder ratio have a lower slump but greater plasticity and workability. TecEco tec-cements are potentially suitable for mortars, renders, patch cements, colour coatings, pumpable and self compacting concretes. A range of pumpable composites with Bingham plastic properties will be required in the future as buildings will be printed.