Presentation on theme: "Materials and Molecules - Behind What You See"— Presentation transcript:
1 Materials and Molecules - Behind What You See John Harrison Presentation CIA (WA) SeminarMaterials and Molecules - Behind What You See
2 John Harrison Presentation CIA (WA) Seminar Materials and Moelcules – Behind What you See (Originally Concretes – Solution to Kyoto)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 problemsOur 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.
3 Techno-Processes & Earth Systems John Harrison Presentation CIA (WA) SeminarTechno-Processes & Earth SystemsUnderlying 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.Bio-sphereGeo-sphereEarth SystemsAtmospheric composition, climate, land cover, marine ecosystems, pollution, coastal zones, freshwater and salinity.Detrimental affects on earth systemsWasteTakeMove billion tonnes Use some 50 billion tonnesTHE TECHNO-PROCESSMost of you will have by now come to realise that there is a process often described as the “take use waste process” that I call the techno process. Unfortunately there are affects on global systems that are detrimental.Manipulate,Make and UseTechno-sphereTo 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.
4 Under Materials Flows in the Techno-Processes are Molecular Flows John Harrison Presentation CIA (WA) SeminarUnder Materials Flows in the Techno-Processes are Molecular FlowsTake → 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, cfc’s, c=halogen compounds and CO2Moleconomics 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.MOLECONOMIC FLOWSUnderlying the flow of materials through the techno process is a moleconomic flow of molecules that is out of tune with the rest of the planet and causing damage to the environment. If you want to know more about the science of moleconomics please go to our web site and look under projects.
5 The Carbon Cycle and Emissions John Harrison Presentation CIA (WA) SeminarThe Carbon Cycle and EmissionsEmissions from fossil fuels and cement production are a significant cause of the global warming.CEMENT EMMISSIONSCement manufacture contributes significantly to global warming as I am sure Vijay Rangan has or will tell you. As members of the industry we are trying to do something about the problem. That is why we are all here todayUnits: GtC GtC/yrSource: David Schimel and Lisa Dilling, National Centre for Atmospheric Research 2003
6 Changing the Techno-Processes John Harrison Presentation CIA (WA) SeminarChanging the Techno-ProcessesTake => manipulate => make => use => waste Driven by fossil fuel energy with detrimental effects on earth systems.Eco-innovate to create “industrial ecologies”Reduce Re-use RecycleINDUSTRIAL ECOLOGY – CHANGING THE TECHNO-PROCESSI am sure you will have all heard of the three R’s. Reduce, reuse and recycle, to which some add re-make.Industrial ecology, the idea that the waste output of one kind of activity can be resource input for another, is most easily achieved in the construction industry.The materials used determine many properties including weight, embodied energies, fuel related and chemical emissions, lifetime energies, user comfort and health, use of recycled wastes, durability, recyclability and the properties of wastes returned to the bio-geo-sphere. If you cannot recycle for chemical property recycle on the basis of physical properties the material would contribute to a composite.There is huge scope for sequestration and conversion of waste to resource given the massive size of the materials flows involved in the built environment. With the right materials technology, because of its sheer size, the built environment could reduce the take from the bio-geo-sphere and utilise many different wastes including carbon dioxideMaterialsAtoms and Molecules in the global commons
7 Utilizing Carbon and Wastes (Biomimicry) John Harrison Presentation CIA (WA) SeminarUtilizing 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.BIOMIMICRYThe philosophy and chemistry of TecEco technology is backed by the greatest and longest experiment of all time – that of life on this planet.Little is wasted in nature, the waste from one living thing being the home or food for another.We must, like nature, devise ways of using carbon dioxide and other wastes.In eco-cement blocks and mortars the binder is carbonate and the aggregates are preferably wastesWe all use carbon and wastes to make our homes! “Biomimicry”
8 Biomimicry - Ultimate Recyclers John Harrison Presentation CIA (WA) SeminarBiomimicry - Ultimate RecyclersAs peak oil looms and the price of transport is set to rise sharplyWe should not just be recycling based on chemical property requiring sophisticated equipment and resourcesWe 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
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.
10 John Harrison Presentation CIA (WA) Seminar Using Wastes and Non-Traditional Aggregates to Make TecEco Cement ConcretesAs 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.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.DUE TO RISING FUEL PRICES WE WILL HAVE TO RECONSIDER USING LOCAL MATERIALSThe 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.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
11 Huge Potential for More Sustainable Construction Materials John Harrison Presentation CIA (WA) SeminarHuge Potential for More Sustainable Construction MaterialsReducing 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 buildingsMany wastes including CO2 can contribute to physical properties reducing lifetime energiesCO2CO2UTILISING WASTE IN CITIESTecEco advocate the development of materials that include waste based on physical as well as chemical properties and that reduce the lifetime energy of buildings by introducing new properties.WasteCO2CWasteCO2
12 Impacts of LandfillLandfill 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
13 Economically Driven Sustainability John Harrison Presentation CIA (WA) SeminarEconomically Driven SustainabilityNew, 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.ECONOMICALLY DRIVEN SUSTAINABILITYOur approach must not only be holistic, but also economic if we are to have any hope of success.Working for sustainability market forces will make all the difference.The challenge is to move the supply and demand of resources towards more sustainable outcomes by stimulating and harnessing human behaviours which underlay economic demand phenomena, through cultural change push by governments and other leaders, and real improvement in technical and other properties as I will explain in the next slide.Sustainable processes like the new TecEco technologies are more efficient and therefore more economic.$ - ECONOMICS - $
14 Changing the Technical Paradigm John Harrison Presentation CIA (WA) SeminarChanging the Technical Paradigm“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.1990By 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.PILZER’S RESOURCE LAWPilzer’s resource law states that “the technology paradigm defines what is or is not a resource.”By changing the technical paradigm to for example make carbon dioxide and other wastes resources we can make giant strides towards sustainability.
15 John Harrison Presentation CIA (WA) Seminar Examples of Economic Changes in Technical Paradigms that result in Greater Sustainability100 watts 1700 lumensIncandescent25 watts 1700 lumensFluorescent<20 watts 1700 lumensLed LightLight Globes - A Recent Paradigm Shift in Technology Reducing Energy ConsumptionLight 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.Robotics - A Paradigm Shift in Technology that will fundamentally affect Building and ConstructionConstruction 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.AN EXAMPLE OF A PARADIGM SHIFT IN TECHNOLOGYAn example demonstrating that technical paradigms can be achieved is of course the common light bulb which we have improved the efficiency of five times in around ten years.
16 Sustainability = Culture + Technology John Harrison Presentation CIA (WA) SeminarSustainability = Culture + TechnologyIncrease in demand/price ratio for sustainability due to educationally induced cultural drift.$SupplyGreater Value/for impact (Sustainability) and economic growthEquilibrium shiftECONOMICSNew Technical Paradigms are required that deliver sustainability.DemandIncrease in supply/price ratio for more sustainable products due to innovative paradigm shifts in technology.#CULTURAL CHANGE AND PARADIGM SHIFTS IN TECHNOLOGYChanges in the market interaction of demand and supply reducing energy and resource usage and detrimental linkages with the planet can be achieved through cultural change and innovative changes in the technical paradigm.The nexus of supply and demand can move towards greater value for impact or sustainability which is not incompatible with economic growth.Sustainability could be considered as where culture and technology meet.
17 The TecEco CarbonSafe Industrial Ecology John Harrison Presentation CIA (WA) SeminarThe TecEco CarbonSafe Industrial EcologyThe CarbonSafe Geo-Photosynthetic Process is TecEco’s evolving techno-process that delivers profitable outcomes whilst reversing underlying undesirable moleconomic flows from other less sustainable processes.Inputs:Atmospheric or smokestack CO2, brines, waste acid, other wastesOutputs:Potable water, gypsum, sodium bicarbonate, salts, building materials, bottled concentrated CO2 (for geo-sequestration and other uses).Solar or solar derived energyCO2CO2CO2TecEco KilnTHE CARBONSAFE GEO PHOTOSYNTHETIC PROCESSTecEco’s contribution to a total industrial ecology is the CarbonSafe processCarbonSafe is an agglomeration of new technologies including TecEco’s kiln technology and cements, carbon dioxide scrubbing technology, a seawater separation technology from Greensols Pty. Ltd. and heat transfer and desalination technologies that can produce fresh water, a number of industrial commodity products including gypsum, sodium bicarbonate and various other salts as well as building materials based on magnesium carbonates that also utilize wastes. Each of these outputs uniquely provides revenue to help make the overall process economic.TecEco MgCO2 CycleCO2MgOMgCO3Greensols Process1.29 gm/l MgCoalCarbon or carbon compounds Magnesium oxideFossil fuelsOilCO2
18 The TecEco CarbonSafe Industrial Ecology John Harrison Presentation CIA (WA) SeminarThe TecEco CarbonSafe Industrial EcologyInputs Brines Waste Acid CO2CARBONSAFE VECTORSThe CarbonSafe process starts with either magnesium silicates or the Greensols process. In the case of silicates, magnesium carbonates are produced using proven mineral sequestration technology and then transferred to the MgCO3 cycle. The Greensols process on the other hand uses carbon dioxide from power stations and waste acid to extract magnesium carbonate and other salts from seawater or suitable brines and produces potable water as a by-product. The MgCO3 from either process is then calcined in the TecEco kiln which removes and captures carbon dioxide, ready for incorporation for example into cellulose or fuel made by genetically engineered blue green algae, and produces magnesium oxide. This magnesium oxide can either be used to make TecEco cements which in the case of eco-cement absorb more atmospheric CO2 as they harden or alternatively be used to sequester more CO2 in a hydroxide/carbonate slurry capture process.The MgCO3 produced by the hydroxide slurry process can be decarbonated and cycle around that process indefinitely as in this slide.OutputsGypsum, Sodium bicarbonate, Salts, Building materials, Potable water
19 The CarbonSafe Industrial Ecology John Harrison Presentation CIA (WA) SeminarThe CarbonSafe Industrial Ecology1.354 x 109 km3 Seawater containing tonne Mg or suitable brines from other sourcesSeawater Carbonation ProcessWaste AcidGypsum + carbon waste (e.g. sewerage) = fertilizersBicarbonate of Soda (NaHCO3)CO2 from power generation or industryPotable waterOther salts Na+,K+, Ca2+,Cl-Gypsum (CaSO4)Sewerage compostCO2 as a biological or industrial input or if no other use geological sequestrationMagnesite (MgCO3)Solar Process to Produce Magnesium MetalMagnesium Thermodynamic CycleSimplified TecEco Reactions Tec-Kiln MgCO3 → MgO + CO kJ/mole Reactor Process MgO + CO2 → MgCO kJ/mole (usually more complex hydrates)Magnesite (MgCO3)CO2 from power generation, industry or out of the airMagnesia (MgO)Hydroxide Reactor ProcessCARBONSAFE PROCESS DIAGRAMI do not have the time to talk a lot more about CarbonSafe, so we invite you to visit our web site.Sequestration Table – Mg from SeawaterCO2Eco-Cement Tec-CementTonnes 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 TonnesTonnes CO2 sequestered by 1 billion tonnes of Mg in seawaterTonnes CO2 captured during calcining (same as above)Tonnes CO2 captured by eco-cementTotal tonnes CO2 sequestered or abated per tonne Mg in seawater (Single calcination cycle).Total tonnes CO2 sequestered or abated (Five calcination cycles.)Total tonnes CO2 sequestered or abated (Ten calcination cycles).36.20Other Wastes
20 Reduction Global CO2 from CarbonSafe Process John Harrison Presentation CIA (WA) SeminarReduction Global CO2 from CarbonSafe ProcessCARBONSAFE CAN MAKE A REAL CONTRIBUTIONWe are even more excited about CarbonSafe now we have modelled the possible contribution it could make to reducing CO2 in the air
21 Why Magnesium Carbonates for Sequestration? John Harrison Presentation CIA (WA) SeminarWhy 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 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.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 elementMagnesium minerals are potential low cost. New kiln technology from TecEco will enable easy low cost simple non fossil fuel calcination of magnesium carbonate with CO2 capture for geological sequestration.WHY MAGNESIUM?There are a number of good reasons to use magnesium as a means of capturing carbon dioxide (as in the chlorophyll molecule).The main ones being the small mass of the atom and the fact that you can make magnesium oxide or remove the CO2 from the carbonate relatively easily.
22 The TecEco Dream – A More Sustainable Built Environment John Harrison Presentation CIA (WA) SeminarThe TecEco Dream – A More Sustainable Built EnvironmentCO2OTHERWASTESCO2 FOR GEOLOGICAL SEQUESTRATIONCO2PERMANENT SEQUESTRATION & WASTE UTILISATION (Man made carbonate rock incorporating wastes as a building material)MININGMgOTECECO KILNMAGNESITE + OTHER INPUTSTECECO CONCRETESRECYCLED BUILDING MATERIALSWe 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 MagazineTECECO’S DREAMOur dream is to create cities that mimic nature in that have a balance of carbon, other wastes and energy.SUSTAINABLE CITIES
23 Materials in the Built Environment John Harrison Presentation CIA (WA) SeminarMaterials in the Built EnvironmentThe built environment is made of materials and is our footprint on earth.It comprises buildings and infrastructure.Construction materials comprise70% 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 resourcesCombined in such a manner they cannot easily be separated.Include many toxic elements.THE IMPORTANCE OF MATERIALSMaterials are our footprint on the planet and of first consideration in our quest to devise ways of using carbon dioxide and other wastes.Building 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.)
24 Impact of the Largest Material Flow - Cement and Concrete John Harrison Presentation CIA (WA) SeminarImpact of the Largest Material Flow - Cement and ConcreteSome 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 annumMuch more concrete is used than any other building material.CONCRETESome 600 billion tonnes of matter are moved around the planet a year of which some 50 billion tonnes only is used. By far the greatest single material flow is that of concrete at over 14 billion tonnes, that’s more than two tonnes per man woman and child on the planet.TecEco Pty. Ltd. have benchmark technologies for improvement in sustainability and properties
25 Embodied Energy of Building Materials John Harrison Presentation CIA (WA) SeminarEmbodied Energy of Building MaterialsConcrete is relatively environmentally friendly and has a relatively low embodied energyCONCRETE IS AN ENVIRONMENTALLY FRIENDLY MATERIALConcrete is an environmentally friendly material with a relatively low embodied energy and high specific heat.Downloaded from (last accessed 07 March 2000)
26 Average Embodied Energy in Buildings John Harrison Presentation CIA (WA) SeminarAverage Embodied Energy in BuildingsMost of the embodied energy in the built environment is in concrete.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.CONCRETE MAKES A BIG CONTRIBUTION TO EMBODIED ENERGY AND EMISSIONSThe huge volume of concrete used means that it makes a significant overall contribution to embodied energies and emissions.Downloaded from (last accessed 07 March 2000)
27 Emissions from Cement Production John Harrison Presentation CIA (WA) SeminarEmissions from Cement ProductionChemical ReleaseThe process of calcination involves driving off chemically bound CO2 with heat.CaCO3 →CaO + ↑CO2Process EnergyMost energy is derived from fossil fuels.Fuel oil, coal and natural gas are directly or indirectly burned to produce the energy required releasing CO2.The production of cement for concretes accounts for around 10% of global anthropogenic CO2.Pearce, F., "The Concrete Jungle Overheats", New Scientist, 19 July, No 2097, 1997 (page 14).CO2 CO2EMISSIONS FROM CONCRETEEmissions from concrete are from the chemical release during pyroprocessing and of course the energy required for processing.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.
28 Cement Production ~= Carbon Dioxide Emissions John Harrison Presentation CIA (WA) SeminarCement Production ~= Carbon Dioxide EmissionsCEMENT GLOBAL PRODUCTION AND EMISSIONSAt roughly 1 tonne to the tonne emissions can approximately be equated to productionWith the manufacture of concrete and placement contributing further emissions this figure is likely to be conservative.Between tec, eco and enviro-cements TecEco can provide a viable much more sustainable alternative.
29 John Harrison Presentation CIA (WA) Seminar TecEco Binder SystemsSUSTAINABILITYPORTLANDPOZZOLANHydration 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.TECECO CEMENTSDURABILITYSTRENGTHTECECO BINDER SYSTEMSI am now going to talk just a little about are binder systems which are basically a blending system between Portland and other hydraulic cement, reactive magnesia and, as required, a pozzolanTecEco concretes are a system of blending reactive magnesia, Portland cement and usually a pozzolan with other materials and are a key factor for sustainability.REACTIVE MAGNESIAHydration of magnesia => brucite for strength, workability, dimensional stability and durability. In Eco-cements carbonation of brucite => nesquehonite, lansfordite and an amorphous phase for sustainability.
30 John Harrison Presentation CIA (WA) Seminar TecEco FormulationsTec-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.TECECO FORMULATIONSWe have three main formulations to date, Tec-Cements which are really pre-mix concretes, Eco-Cements which have much more magnesia in them and set by carbonation in porous substrates and Enviro-Cements which are relatively weak as they do not carbonate, they are however potentially suitable for toxic and hazardous wastes.
31 John Harrison Presentation CIA (WA) Seminar TecEco Cement LCATecEco Concretes will have a big role post Kyoto as they offer potential sequestration as well as waste utilisationTECECO LCA MODELFor more information on the contribution our Tec and Eco-Cements can make to the global carbon balance please consult our LCA model under tools on the web site.The TecEco LCA model is available for download under “tools” on the web site
32 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Whittlesea, Vic. AustraliaOn 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.TECECO TECHNOLOGY IN PRACTICEI will now flick through a number of slides just to let you know that we are trying to get as much experience as possible as quickly as possible in all sorts of applications.
33 TecEco Technology in Practice => Porous PavementAllow many mega litres of good fresh water to become contaminated by the pollutants on our streets and pollute coastal waterwaysOrCapture and cleanse the water for our use?
34 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Whittlesea, Vic. AustraliaFirst Eco-cement mud bricks and mortars in AustraliaTested up twice as strong as the PC controlsMud 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.WHITTLESEAAt Whittlesea, shown on this and the previous slide, we have been responsible for all cementitious materials including the slab, mortars, mud bricks, renders etc.
35 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Earthship Brighton, UKBy 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. England’s 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.EARTHSHIP BRIGHTONThis slide shows the interior and exterior of Earthship Brighton in the UK which was the first building we were ever involved in.At Brighton we mainly used Eco-CementsEarthships 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.
36 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Clifton Surf Life Saving ClubThe 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 CLUBThe 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.We are able to remedy the problem with 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.
37 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Mike Burdon’s Murdunna WorksMike 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: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.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.Strength gain was more rapid than with Portland cement controls from the same premix plant and continued for longer.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 formulationMIKE BURDON’S MURDUNNA WORKSMike is a plumber and a friend of mine.We have built footings, two slabs and some tilt ups at his shack. All were significantly better than controls on the same site.
38 TecEco Technology in Practice John Harrison Presentation CIA (WA) Seminar=> DJ Motors, HobartTec-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.SHRINK AND CRACKPROOF CONCRETEAt the new DJ motors in Hobart we poured some very difficult topping coats that were low or zero shrinkage.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.
39 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Island Block and Paver,TasmaniaTecEco 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.BLOCK MAKINGIsland Block and Paver Pty. Ltd. are a shareholder in TecEco and have made both Tec and Eco-Cement blocks successfully for us.
40 TecEco Technology in Practice John Harrison Presentation CIA (WA) Seminar=> Foamed ConcretesFoamed 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 CONCRETESWe are working with Buildlite cellular concrete making foamed concretes where the huge mass and volume increase of magnesia as it hydrates become of value.BUILD LITE CELLULAR CONCRETE 4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169 PH FX
41 Tec & Eco Cement Foamed Concrete Slabs John Harrison Presentation CIA (WA) SeminarTec & Eco Cement Foamed Concrete Slabs=> Foamed Concrete SlabsFOAMED CONCRETE SLABSFoamed concrete slabs, useful for insulation, are made stronger with TecEco technologyBUILD LITE CELLULAR CONCRETE 4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169 PH FX
42 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Foamed Concretes PanelsImagine 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 FramingSolutions in SteelABNTEL: FAX: Mica Street Carole Park 4300 Queensland AustraliaFOAMED CONCRETES IN ACTIONRigid steel are using our Tec-Cement foam formulations to make a rather interesting panel.Please direct commercial enquiries to Rigid Steel Framing at rigidsteel.com.au
43 TecEco Technology in Practice John Harrison Presentation CIA (WA) SeminarTecEco Technology in Practice=> Foamed Concretes PanelsRIGID STEEL FRAMINGThe panels fit together forming the outside cladding of a building as you put together the frame.Rear view of test panels showing tongue and groove and void for services. Interior plasterboard is fixed conventionally over gap for services.
44 TecEco Technologies Take Concrete into the Future John Harrison Presentation CIA (WA) SeminarTecEco Technologies Take Concrete into the FutureMore rapid early strength gain even with added pozzolansMore 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 crackingMore durable concretesReducing costs and take and waste impacts.Use of wastes including carbon dioxideMagnesia component can be made using non fossil fuel energy and CO2 captured during production.Tec -CementsTec & Eco-CementsTECECO TECHNOLOGIES TAKE CONCRETE INTO THE FUTUREMagnesia is a new tool which if used properly in accordance with our directions can improve properties.Eco-Cements
45 Tec & Eco-Cement Theory John Harrison Presentation CIA (WA) SeminarTec & Eco-Cement TheoryMany Engineering Issues are Actually Mineralogical IssuesProblems 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 concreteTecEco remove Portlandite it and replacing it with magnesia which hydrates to Brucite.The hydration of magnesia consumes significant waterENGINEERING ISSUES ARE MINERALOGICAL ISSUESEngineering issues are usually mineralogical issues and TecEco believe that it is better to fix the fundamental chemistry of Portland cement.
46 Tec & Eco-Cement Theory John Harrison Presentation CIA (WA) SeminarTec & Eco-Cement TheoryPortlandite (Ca(OH)2) is too soluble, mobile and reactive.It carbonates, reacts with Cl- and SO4- and being soluble can act as an electrolyte.TecEco generally (but not always) remove Portlandite using the pozzolanic reaction andTecEco add reactive magnesiawhich hydrates, consuming significant water and concentrating alkalis forming Brucite which is another alkali, but much less soluble, mobile or reactive than Portlandite.In Eco-Cements brucite carbonates forming hydrated compounds with greater volumeMOST PROBLEMS OF PORTLAND CEMENT CONCRETE RELATE TO LIMELime is the weakness of Portland cement concrete, it is too soluble, mobile and reactive. At TecEco we usually remove lime with the pozzolanic reaction
47 Why Add Reactive Magnesia? John Harrison Presentation CIA (WA) SeminarWhy 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 reactivityTo reduce shrinkage.To make concretes more durableBecause significant quantities of carbonates are produced in porous substrates which are affective binders.WHY ADD REACTIVE MAGNESIA?Reactive magnesia is added to maintain the long term stability of CSH.Preventing a reduction in the Ca/Si ratioTo remove water.Reactive magnesia consumes water as it hydrates to possibly hydrated forms of Brucite.To control long term Ph.Reducing reactivityTo reduce shrinkage.To make concretes more durableBecause significant quantities of carbonates are produced in porous substrates resulting in effective binders.The consequences of putting brucite through the matrix of a concrete in the first place need to be consideredThe consequences of putting brucite through the matrix of a concrete in the first place need to be consideredReactive MgO is a new tool to be understood with profound affects on most properties
48 Strength with Blend & Porosity John Harrison Presentation CIA (WA) SeminarStrength with Blend & PorosityTec-cement concretesEco-cement concretesHigh PorosityEnviro-cement concretesHigh OPCHigh MagnesiaSTRENGTH IN RELATION TO THE PROPORTION OF MAGNESIA AND POROSITYThe strength of TecEco Cements depends on the porosity and magnesia added.There are of course other contributing reasons for strength including particle packing and water (=> voids) and unless the increased workability introduced by magnesia is taken advantage off increased strength of Tec-Cements will not result because Brucite is the weaker mineral.With higher proportions of magnesia carbonation is the main contributor to strength. However please note that strength is not the major issue!!!STRENGTH ON ARBITARY SCALE 1-100
49 John Harrison Presentation CIA (WA) Seminar Eco-CementsEco-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-CEMENTSEco-Cements are best understood by comparison with lime mortars. The underlying chemistry is very similar however eco-cements are potentially superior because:More water is included in magnesium carbonates than calcium carbonates with the result that less binder need be addedMagnesium minerals are generally more fibrous and acicular than calcium minerals and thus also provide micro structural strength.Because magnesium has a low molecular weight, proportionally a much greater amount of CO2 is captured in its carbonates.
50 Eco-Cement Strength Development John Harrison Presentation CIA (WA) SeminarEco-Cement Strength DevelopmentEco-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 ofMore 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 calciumTotal volumetric expansion from magnesium oxide to lansfordite is for example volume 811%.ECO-CEMENT STRENGTH DEVELOPMENTEco-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 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 + CO2 MgCO3.5H2OFrom air and water
51 Eco-Cement Strength Gain Curve John Harrison Presentation CIA (WA) SeminarEco-Cement Strength Gain CurveSTRENGTH GAIN CURVEEco-Cements do not gain strength as quickly as ordinary PC concretes or Tec-Cement concretes. It takes time and porosity for carbonation to occur.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.
52 John Harrison Presentation CIA (WA) Seminar Eco-Cement ReactionsCHEMISTRYThis slide shows some of the reactions that go on in eco-cements. If you need more time to think about them, download the presentation later from our web site
53 Eco-Cement Micro-Structural Strength John Harrison Presentation CIA (WA) SeminarEco-Cement Micro-Structural StrengthMICROSTRUCTURAL STRENGTH IN ECO-CEMENTSOne advantage of magnesium carbonates over calcium carbonates is that they form fibrous and acicular minerals a bit like the needles in Superman’s fort if you ever watched the movie. These of course add strength.
54 John Harrison Presentation CIA (WA) Seminar CarbonationEco-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”.CARBONATIONCarbonation is the main reason to use an eco-cement.Ancient and modern carbonating lime mortars are based on this principle
55 CO2 Abatement in Eco-Cements John Harrison Presentation CIA (WA) SeminarCO2 Abatement in Eco-CementsFor 85 wt% Aggregates15 wt% CementPortland Cements 15 mass% Portland cement, 85 mass% aggregateEmissions .32 tonnes to the tonne. After carbonation. Approximately .299 tonne to the tonne.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.Capture CO % mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.Emissions .25 tonnes to the tonne. After carbonation. approximately 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.Eco-cements in porous products absorb carbon dioxide from the atmosphere. Brucite carbonates forming lansfordite, nesquehonite and an amorphous phase, completing the thermodynamic cycle.Greater SustainabilityCO2 ABATEMENT IN AN ECO-CEMENT BLOCKThis slide shows that for an eco-cement concrete in a block which is 15% eco-cement if the eco-cement contains 75% reactive magnesia and with capture of CO2 during the manufacturing process net emissions are less than a third as much..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.
56 Aggregate Requirements for Carbonation John Harrison Presentation CIA (WA) SeminarAggregate Requirements for CarbonationThe 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 requiredFor carbonating eco-cements and lime mortars on the on the hand the matrix must “breathe” i.e. they must be porousrequiring a coarse fraction to cause physical air voids and some vapour permeability.Coarse fractions are required in the aggregates used!REQUIREMENTS OF AGGREGATES FOR PROPER CARBONATIONSome people (such as the scientists at the BRE) have not understood that for carbonation to occur it is essential to allow all parts of a material to have contact with carbon dioxide contained in low concentrations in air. Carbonating materials therefore have to be air porous.
57 John Harrison Presentation CIA (WA) Seminar Roman SpecificationsThe 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 centuryused 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.CARBONATIONEven the Romans understood the difference between the requirements for aggregates for carbonating mortars and hydraulic concretes.There should be imperfect particle packing caused by an absence of fines and somewhat mono-grading in other sizes.
58 Eco-Cement Porous Pavement – A Solution for Water Quality? John Harrison Presentation CIA (WA) SeminarEco-Cement Porous Pavement – A Solution for Water Quality?Porous Pavements are a Technology Paradigm Change Worth InvestigatingBefore 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 PAVEMENTOur roads are our drainage network and should be being used to capture as well as cleanse water for uses such as flushing toilets and irrigationMade of Eco-Cement Concretes, porous pavements would of course also sequester CO2.
59 John Harrison Presentation CIA (WA) Seminar Using Wastes and Non-Traditional Aggregates to Make TecEco Cement ConcretesMany 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 wastesTec, enviro and eco-cements can utilize wastes including carbon to increase sequestration preventing their conversion to methaneThere are huge volumes of concrete produced annually (>2 tonnes per person per year)CONVERTING WASTES TO RESOURCEMany wastes and local materials can contribute physical property values.Tec, Eco and Enviro-Cements will allow a wide range of wastes and non-traditional aggregates such as local materials to be used.
60 Solving Waste & Logistics Problems John Harrison Presentation CIA (WA) SeminarSolving Waste & Logistics ProblemsTecEco cementitious composites represent a cost affective option forusing non traditional aggregates from on site reducing transports costs and emissionsuse and immobilisation of waste.Because they haveLower reactivityless waterlower pHReduced solubility of heavy metalsless mobile saltsGreater durability.denser.impermeable (tec-cements).dimensionally more stable with less shrinkage and cracking.Homogenous.No bleed water.WASTE UTILISATIONThere are a number of reasons why our formulations are ideal for using wastes:Lower reactivityless waterlower pHReduced solubility of heavy metalsless mobile saltsGreater durability.denser.impermeable (tec-cements).dimensionally more stable with less shrinkage and cracking.Homogenous.No bleed water.TecEco Technology - Converting Waste to Resource
61 Role of Brucite in Immobilization John Harrison Presentation CIA (WA) SeminarRole of Brucite in ImmobilizationIn a Portland cement Brucite matrixPC derive CSH takes up lead, some zinc and germaniumPozzolanic CSH can take up mobile cationsBrucite 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.STRUCTURE OF BRUCITEThe brucite structure can be likened to wet newspaper, the layers between which it is possible to hold many different molecules.
62 Lower Solubility of Metal Hydroxides John Harrison Presentation CIA (WA) SeminarLower Solubility of Metal HydroxidesThere is a 104 differenceLOWER SOLUBILITY OF METAL HYDROXIDESThe most important strategy for dealing with toxic wastes is long term pH regulation which in the case of Tec-Cement concretes is around the minimum solubility of most heavy metals.All waste streams will contain heavy metals and a strategy for long term pH control is therefore essential
63 John Harrison Presentation CIA (WA) Seminar Tec-Cement Concretes - The Form of MgO Matters - Lattice Energy Destroys a MythMagnesia, 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, andwill completely hydrate in the same time order as the minerals contained in most hydraulic cements.Dead burned magnesia and lime have high lattice energiesCrystalline 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 )TEC-CEMENT CONCRETESMagnesia, 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 and are dangerous in concretes as they hydrate later and cause dimensional distress.
64 John Harrison Presentation CIA (WA) Seminar Tec-Cement ReactionsMgO + H2O => Mg(OH)2.nH2O - water consumption resulting in greater density and higher alkalinity.Higher alkalinity => more reactions involving silica & alumina.Mg(OH)2.nH2O => Mg(OH)2 + H2O – slow release water for more complete hydration of PCMgO + Al + H2O => 3MgO.Al.6H2O ??? – equivalent to flash set??MgO + SO4-- => various Mg oxy sulfates ?? – yes but more likely ettringite reaction consumes SO4-- first.MgO + SiO2 => MSH ?? Yes but high alkalinity required. Strength??TEC-CEMENT REACTIONSTec-Cement reactions are included here for completeness.The most important reaction is that of the consumption of water so that it approaches the ideal stoichiometric amount for the hydration of PC.The slow release of that water for later more complete hydration of PC adds strength.We think the reactions are relatively independent of PC reactions
65 John Harrison Presentation CIA (WA) Seminar More Rapid and Greater Strength Development Higher Strength Binder RatioConcretes are more often than not made to strength.The use of tec-cement results in15-30% 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 timeEarly strength gain with less cement and added pozzolans is of great economic and environmental importance as it will allow the use of more pozzolans.We have observed this sort of curve in over 500 cubic meters of concrete nowTEC-CEMENT STRENGTHSo far our strength development curves show early strength even with added pozzolan as well as significant later strength development. Around 28 days strength is similar to that of a normal PC concrete.
66 Tec-Cement Strength Development John Harrison Presentation CIA (WA) SeminarTec-Cement Strength DevelopmentGraphs above by Oxford Uni Student are for standard 1PC:3 aggregate mixes, w/c = .5WHITTLESEA SLAB (A modified 20 mpa mix)PC = 180 Kg / m3 MgO = 15 Kg / m3 Flyash = 65 Kg / m3TEC-CEMENT STRENGTHProbably of greater importance than the strength issue is the rate of strength development. Our curve is quite different to that of PC and importantly rises rapidly in the first few hours and days.Rate of strength development is of great interest to engineers and constructors
67 Reasons for Compressive Strength Development in Tec-Cements. John Harrison Presentation CIA (WA) SeminarReasons 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?STRENGTH GAINProvided users take advantage of the additional plasticity introduced by magnesia to use less water then they will observe better and particularly early strength development.As concretes containing magnesia are thixotropic users will not observe more strength by working to slump or a fixed amount of water. In fact brucite is weaker than CSH so some have observed less strength.To those (such as the PC industry through the BRE in the UK) who are trying to discredit us on the strength issue. Please try and understand these very basic facts!!!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.
68 Reasons for Compressive Strength Development in Tec-Cements. John Harrison Presentation CIA (WA) SeminarReasons 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.nH2O supplying H2O for more complete hydration of C2S and C3S?STRENGTH ISSUESGood particle packing provides micro structural strength and is very important.Cement grains are around 20 micron in size.Magnesia particles at 5-9 micron are roughly 2.5 times smaller, which Francois Larrard maintains is a requirement for good packing.(1) de Larrard, F. (1999). Concrete Mixture Proportioning: A Scientific Approach, E & FN Spon.
69 Greater Tensile Strength John Harrison Presentation CIA (WA) SeminarGreater Tensile Strength++++++++Cement++MgO+Sand+++++++++Mutual RepulsionPh 12 ?=>Mutual Repulsion++-++-+++Cement-+-MgOSand+-+++--++Mutual AttractionTENSILE STRENGTHWe have also observed greater tensile strength and think this is probably due to an electrostatic affect as magnesia changes surface charge at around pH 12 just as lime is starting to be formed by reaction of C2S and C3S with water.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
70 John Harrison Presentation CIA (WA) Seminar Improved DurabilityDURABILITYDurability 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, HarperCollinsReasons for Improved Durability:Reduced shrinkage and CrackingGreater Density = Lower PermeabilityPhysical Weaknesses => Chemical AttackChemical weaknessesRemoval of Portlandite with the Pozzolanic Reaction.Removal of reactive componentsSubstitution by Brucite => Long Term pH controlReducing corrosionIMPROVED DURABILITYDurability is a very important property in relation to sustainability 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 that lasts twice as long is 80% more sustainable.
71 Durability. Shrinkage and Cracking John Harrison Presentation CIA (WA) SeminarDurability. Shrinkage and CrackingConcretes 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 andCracking 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 sulphateAlkali 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 technologiesDURABILITYPhysical factors can result in entry of 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 reactions can also result in physical outcomes reducing durability e.g.The reactivity of lime with aggressive agents such as chloride or sulphateAlkali silica reaction which opens 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.
72 John Harrison Presentation CIA (WA) Seminar CrackingAlkali aggregate ReactionEvaporative Crazing ShrinkageDrying ShrinkageThermalSettlement ShrinkageFreeze Thaw D CracksStructuralPlastic ShrinkagePhotos from PCA and US Dept. Ag WebsitesCorrosion RelatedAutogenous or self-desiccation shrinkage (usually related to stoichiometric or chemical shrinkage)CRACKINGCracking is the result of dimensional distress and there are many causes as the collage in this slide illustrates.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 reactionsAs a result of corrosion.Related to autogenous shrinkage
73 Causes of Cracking in Concrete John Harrison Presentation CIA (WA) SeminarCauses of Cracking in ConcreteCracking 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 reasonsVisible cracking is unsightlyCracking compromises durability because it allows entry of gases and ions that react with Portlandite.Cracking can compromise structural integrity, particularly if it accelerates corrosion.CRACKINGWe think the concrete industry will seriously examine our Tec-Cement concretes for the reduced cracking and shrinkage and greater durability they exhibit.
74 Graphic Illustration of Cracking John Harrison Presentation CIA (WA) SeminarGraphic Illustration of CrackingAutogenous shrinkage has been used to refer to hydration shrinkage and is thus stoichiometricCRACKINGCracking commonly occurs when the induced stress exceeds the maximum tensile stress capacity of concrete as shown in these graphs by Tony Thomas from Boral.After Tony Thomas (Boral Ltd.) (Thomas 2005)
75 Cracking due to Loss of Water John Harrison Presentation CIA (WA) SeminarCracking due to Loss of WaterBrucite 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.Drying ShrinkageFoolPlastic ShrinkageEvaporative Crazing ShrinkageBucket of WaterSettlement ShrinkageCRACKING DUE TO LOSS OF WATERCracking due to loss of water includes drying shrinkage, plastic shrinkage, evaporative shrinkage and settlement shrinkagePicture from: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.
76 Solving Cracking due to Shrinkage from Loss of Water John Harrison Presentation CIA (WA) SeminarSolving Cracking due to Shrinkage from Loss of WaterIn the system water plus Portland cement powder plus aggregates shrinkage is in the order of .05 – 1.5 %.Shrinkage causes crackingThere are two main causes of Portland cements shrinking over time.Stoichiometric (chemical) shrinkage andShrinkage through loss of water.The solution is to:Add minerals that fill voids preventing shrinkage or compensate by stoichiometrically expanding and/or toUse less water, internally hold water or prevent water loss.TecEco tec-cements internally hold water and prevent water loss.CRACKING DUE TO LOSS OF WATERCracking is reduced in our concretes due to internal consumption of water by brucite hydrates as they form.MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
77 Preventing Shrinkage through Loss of Water John Harrison Presentation CIA (WA) SeminarPreventing Shrinkage through Loss of WaterWhen 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) + H2O (l) ↔ Mg(OH)2.nH2O (s)The dimensional change in the system MgO + PC depends on:The ratio of MgO to PCWhether 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 PCAs 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).↔ molar mass (at least!)liquid ↔ 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.CRACKING DUE TO LOSS OF WATEROf course it also depends on where the water is coming from as this slide shows!The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1).
78 Preventing Shrinkage through Loss of Water John Harrison Presentation CIA (WA) SeminarPreventing Shrinkage through Loss of WaterWith 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 SHRINKAGEWith 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.MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
79 Other Benefits of Preventing Shrinkage through Loss of Water John Harrison Presentation CIA (WA) SeminarOther Benefits of Preventing Shrinkage through Loss of WaterInternal water consumption also results in:Greater strengthMore complete hydration of PC .Reduced in situ voids:paste ratioGreater densityIncreased durabilityHigher short term alkalinityMore effective pozzolanic reactions.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).INTERNAL WATER CONSUMPTION HAS OTHER BENEFITSThere are other good reasons for internal water consumption adding strength.Fortunately some of the water is held as brucite hydrates which can add to later strength particularly in high PC mixes by allowing more complete hydration
80 John Harrison Presentation CIA (WA) Seminar Bleeding is a Bad ThingBleeding is caused by:Lack of finesToo much waterBleeding can be fixed by:Reducing water or adding finesAir entrainment or grading adjustmentsBleeding causes:Reduced pumpabilityLoss of cement near the surface of concretesDelays in finishingPoor bond between layers of concreteInterconnected pore structures that allow aggressive agents to enter laterSlump and plastic cracking due to loss of volume from the systemLoss of alkali that should remain in the system for better pozzolanic reactionsLoss of pollutants such as heavy metals if wastes are being incorporated.Concrete is better as a closed systemBetter to keep concretes as closed systemsCONTRARY TO SOME OPINIONS BLEEDING IS NOT A GOOD THINGBleeding is only good to the extent that it indicates that drying (the rate of water loss) is not so high that a film of water cannot remain on the surface of concrete.
81 Dimensional Control in Tec-Cement Concretes over Time John Harrison Presentation CIA (WA) SeminarDimensional Control in Tec-Cement Concretes over TimeBy 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.MgO for DIMENSIONAL CONTROL OF CONCRETESMgO is a useful tool to control time and water related dimensional change in concretes
82 John Harrison Presentation CIA (WA) Seminar Reducing Cracking as a Result of Volume Change caused by Delayed ReactionsDELAYED REACTIONS CAUSE VOLUME CHANGEDelayed reactions cause volume changes and thus dimensional distress.Most notable is the alkali silica reaction so well documented by Ahmad Shayan of the ARRBAn Alkali Aggregate Reaction Cracked Bridge ElementPhoto Courtesy Ahmad Shayan ARRB
83 Types of Delayed Reactions John Harrison Presentation CIA (WA) SeminarTypes of Delayed ReactionsThere are several types of delayed reactions that cause volume changes (generally expansion) and cracking.Alkali silica reactionsAlkali carbonate reactionsDelayed ettringite formationDelayed thaumasite formationDelayed hydration or dead burned lime or periclase.Other delayed reactions with aggregatesDelayed reactions cause dimensional distress, cracking and possibly even failure.DELAYED REACTIONSThere are several types of delayed reactions that cause volume changes (generally expansion) and cracking.Alkali silica reactionsAlkali carbonate reactionsDelayed ettringite formationDelayed thaumasite formationDelayed hydration or dead burned lime or periclase.Other delayed reactions with aggregates
84 Reducing Delayed Reactions John Harrison Presentation CIA (WA) SeminarReducing Delayed ReactionsDelayed 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.TECECO CONCRETES HAVE REDUCED DELAYED REACTIONSDelayed 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.
85 Reduced Steel Corrosion Related Cracking John Harrison Presentation CIA (WA) SeminarReduced Steel Corrosion Related CrackingRusting Causes Dimensional DistressSteel remains protected with a passive oxide coating of Fe3O4 above pH 8.9.A pH of over 8.9 is maintained by the equilibriaMg(OH)2 ↔ Mg++ + 2OH- (equilbirium pH is 10.48)CSH ↔ Ca++ + 2OH- + SiO2 (equilibriam pH is around 11.2)for much longer than the pH maintained by Ca(OH)2Ca(OH)2 ↔ Ca++ + 2OH- (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, CO2 and salts.REDUCED STEEL CORROSIONThe pH maintained by brucite and CSH acting together in equilibrium with water is at a much more suitable level than that maintained by CSH and lime.The presence of OH-- because of brucite should be sufficient to keep CSH stable in the long run when pozzolans have removed most of the lime.
86 Reduced Steel Corrosion John Harrison Presentation CIA (WA) SeminarReduced Steel CorrosionBrucite 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 magnesiumMagnesium 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 occurREDUCED STEEL CORROSIONBrucite also removes mobile ions by trapping them in its lattice
87 John Harrison Presentation CIA (WA) Seminar Long Term pH controlTecEco 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 concretepH CONTROL IN CONCRETESThe pH and eH of concretes is very important as it governs their reactivityBrucite and CSH end up through their own equilibria with water controlling pH in Tec-Cement concretes at a much more suitable level.
88 Steel Corrosion is Influenced by Long Term pH John Harrison Presentation CIA (WA) SeminarSteel Corrosion is Influenced by Long Term pHIn 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 Fe3O4 stable in reducing conditions.LONG TERM PH CONTROLThe long term pH of Tec-Cement concretes is at an ideal level as indicated in this Pourbaix diagramEh-pH or Pourbaix Diagram The stability fields of hematite, magnetite and sideritein aqueous solution; total dissolved carbonate = 10-2M.Steel corrodes below 8.9Equilibrium pH of Brucite and of lime
89 Reducing Cracking Related to Autogenous Shrinkage John Harrison Presentation CIA (WA) SeminarReducing Cracking Related to Autogenous ShrinkageAutogenous 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.AUTOGENOUS SHRINKAGE AND INDUCED CRACKINGAutogenous shrinkage tends to occur in high performance concretes in which dense microstructures develop quickly preventing the entry of additional water required to complete hydration
90 Reducing Cracking Related to Autogenous Shrinkage John Harrison Presentation CIA (WA) SeminarReducing Cracking Related to Autogenous ShrinkageThe 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.AUTOGENOUS SHRINKAGEThe main cause of autogenous shrinkage is stoichiometric or chemical shrinkage as observed by Le Chatelier.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.
91 Reducing Cracking Related to Autogenous Shrinkage John Harrison Presentation CIA (WA) SeminarReducing Cracking Related to Autogenous ShrinkageAutogenous 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.nH2O (s) ↔ MgO (s) + H2O (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) + H2O (l) ↔ Mg(OH)2.nH2O (s)↔ molar mass (at least!)liquid ↔ molar volumes (at least 116% expansion, probably more initially before desiccation as above!)REDUCING AUTOGENOUS SHRINKAGEAutogenous 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.Note that as brucite is a relatively weak mineral is can be compressed densifying the microstructure.
92 John Harrison Presentation CIA (WA) Seminar Reduced PermeabilityAs 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 SO4--, Cl- and CO2TecEco 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.PERMEABILITYWe have observed that Tec-Cement concretes do not bleed and there should therefore be less interconnecting pore structures.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
93 Greater Density – Lower Permeability John Harrison Presentation CIA (WA) SeminarGreater Density – Lower PermeabilityConcretes 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.REDUCING VOIDSConcretes have around 18 – 22 % of voids and we think that magnesia as it hydrates to Brucite fills these voids.
94 Densification During the Plastic Phase John Harrison Presentation CIA (WA) SeminarDensification During the Plastic PhaseConsumption of water during plastic stageObservable CharacteristicWater 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.Relevant FundamentalWaterVoidsVariables such as % hydration of mineral, density, compaction, % mineral H20 etc.Hydrated Binder MaterialsBinder + supplementary cementitious materialsUnhydrated BinderLess water for strength and durabilityHigh water for ease of placementDENSIFICATION DURING THE PLASTIC PHASEWater 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 strength, less shrinkage and cracking and the concentration of alkalis during the plastic stage with improved non hydraulic reactions.Less water results in increased density and concentration and early reaction of alkalis - less shrinkage and cracking and improved strength and durability.
95 Durability - Reduced Salt & Acid Attack John Harrison Presentation CIA (WA) SeminarDurability - Reduced Salt & Acid AttackBrucite 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 10-11Ksp Portlandite = 5.5 X 10-6TecEco cements are more acid resistant than Portland cementThis is because of the relatively high acid resistance (?) of Lansfordite and nesquehonite compared to calcite or aragoniteREDUCED SALT AND ACID ATTACKBrucite has always played a protective role during salt attack.. It does not react with salts because it has a lower pH and is a least 5 orders of magnitude less soluble, mobile or reactive.Putting it in the matrix of concretes in the first place makes sense.
96 Less Freeze - Thaw Problems John Harrison Presentation CIA (WA) SeminarLess Freeze - Thaw ProblemsDenser concretes do not let water in.Brucite will to a certain extent take up internal stressesWhen magnesia hydrates it expands into the pores left around hydrating cement grains:MgO (s) + H2O (l) ↔ Mg(OH)2 (s)↔ molar mass↔ molar volumes↔ molar volumesAt least 38% air voids are created in space that was occupied by magnesia and water!Air entrainment can also be used as in conventional concretesTecEco concretes are not attacked by the salts used on roadsLESS FREEZE THAW PROBLEMSTo the extent that magnesia consumes internal water and reduce larger voids that can fill with water and expand, freeze thaw will be reduced.
97 Rosendale Concretes – Proof of Durability John Harrison Presentation CIA (WA) SeminarRosendale Concretes – Proof of DurabilityRosendale cements contained 14 – 30% MgOA 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.ROSENDALE CONCRETESRosendale concretes are proof that high levels of magnesium can be tolerated in concretes and contribute significantly to durabilityMore information from
98 Easier to Finish Concretes John Harrison Presentation CIA (WA) SeminarEasier to Finish ConcretesEasier to pump and finish concretes are likely to have less water added to them resulting in less crackingEASIER TO FINISH CONCRETESTecEco concretes are easier to finish because of the strong shear thinning property that the Mg++ ion imparts to them.Easier to pump and finish Concretes are likely to have less water added to them resulting in less cracking
99 Shear Thinning Rheology John Harrison Presentation CIA (WA) SeminarShear Thinning RheologyThe 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 pozzolanIt is not known how deep these layers getEtc.SHEAR THINNING RHEOLOGYThe 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 pozzolanEtc.Ca++ = 114, Mg++ = 86 picometres
100 Understanding Water - Bingham Plastic Rheology John Harrison Presentation CIA (WA) SeminarUnderstanding Water - Bingham Plastic RheologyTecEco concretes and mortars are:Very homogenous and do not segregate easily.Exhibit good adhesion and have a shear thinning property.Exhibit Bingham plastic qualities andReact well to energy input displaying good workabilityTecEco 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.”UNDERSTANDING WATERWe have had more trouble understanding the role of water in our Tec-Cement concretes than any other aspect of the technology.So far we have concluded that Tec-Cement concretes:Are very homogenous and do not segregate easily.They exhibit good adhesion and have a shear thinning property.They exhibit Bingham plastic qualities andReact well to energy input displaying good workability