Presentation on theme: "Presentation downloadable from www.tececo.com 1 Tec and Eco-Cement Update I will have to race over some slides but the presentation is always downloadable."— Presentation transcript:
Presentation downloadable from www.tececo.com 1 Tec and Eco-Cement Update I will have to race over some slides but the presentation is always downloadable from the TecEco web site if you missed something. John Harrison B.Sc. B.Ec. FCPA. TecEco Masonry Products utilising Tec and TecEco eco-cements
Presentation downloadable from www.tececo.com 2 TecEco Cements SUSTAINABILITY DURABILITYSTRENGTH TECECO CEMENTS Hydration of the various components of Portland cement for strength. Reaction of alkali with pozzolans (e.g. lime with fly ash.) for sustainability, durability and strength. Hydration of magnesia => brucite for strength, workability, dimensional stability and durability. In Eco-cements carbonation of brucite => nesquehonite, lansfordite and an amorphous phase for sustainability. PORTLAND + or - POZZOLAN MAGNESIA TecEco concretes are a system of blending reactive magnesia, Portland cement and usually a pozzolan with other materials and are a key factor for sustainability.
Presentation downloadable from www.tececo.com 3 The Magnesium Thermodynamic Cycle
Presentation downloadable from www.tececo.com 4 TecEco Cement Sustainability TecEco technology will be pivotal in bringing about sustainability in the built environment. –The CO 2 released by calcined carbonates used to make binders can be captured using TecEco kiln technology. –Tec-Cements Develop Significant Early Strength even with Added Supplementary Materials. Around 25 = 30% less total binder is required for the same strength. –Eco-cements carbonate sequestering CO 2 –Both tec and eco=cements provide a benign low pH environment for hosting large quantities of waste overcoming problems of: Using acids to etch plastics so they bond with concretes. sulphates from plasterboard etc. ending up in recycled construction materials. heavy metals and other contaminants. delayed reactivity e.g. ASR with glass cullet Durability issues
Presentation downloadable from www.tececo.com 5 TecEco Formulations Tec-cements (Low MgO) –contain more Portland cement than reactive magnesia. Reactive magnesia hydrates in the same rate order as Portland cement forming Brucite which uses up water reducing the voids:paste ratio, increasing density and possibly raising the short term pH. –Reactions with pozzolans are more affective. After all the Portlandite has been consumed Brucite controls the long term pH which is lower and due to its low solubility, mobility and reactivity results in greater durability. –Other benefits include improvements in density, strength and rheology, reduced permeability and shrinkage and the use of a wider range of aggregates many of which are potentially wastes without reaction problems. Eco-cements (High MgO) –contain more reactive magnesia than in tec-cements. Brucite in porous materials carbonates forming stronger fibrous mineral carbonates and therefore presenting huge opportunities for waste utilisation and sequestration. Enviro-cements (High MgO) –contain similar ratios of MgO and OPC to eco-cements but in non porous concretes brucite does not carbonate readily. –Higher proportions of magnesia are most suited to toxic and hazardous waste immobilisation and when durability is required. Strength is not developed quickly nor to the same extent.
Presentation downloadable from www.tececo.com 6 TecEco Cement Technology 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 forming brucite which is another alkali, but much less soluble, mobile or reactive than Portlandite. In Eco-cements brucite carbonates The consequences of need to be considered
Presentation downloadable from www.tececo.com 7 Why Add Reactive Magnesia? To maintain the long term stability of CSH. –Maintains alkalinity preventing the reduction in Ca/Si ratio. To remove water. –Reactive magnesia consumes water as it hydrates to possibly hydrated forms of brucite. To reduce shrinkage. –The consequences of putting brucite through the matrix of a concrete in the first place need to be considered. To make concretes more durable Because significant quantities of carbonates are produced in porous substrates which are affective binders. Reactive MgO is a new tool to be understood with profound affects on most properties
Presentation downloadable from www.tececo.com 8 What is Reactive MgO? or 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 (Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p 358-360 )
Presentation downloadable from www.tececo.com 9 Summary of Reactions Involved Notice the low solubility of brucite compared to Portlandite and that nesquehoni te adopts a more ideal habit than calcite & aragonite We think the reactions are relatively independent.
Presentation downloadable from www.tececo.com 10 Strength with Blend & Porosity High OPC High Magnesia High Porosity STRENGTH ON ARBITARY SCALE 1-100 Tec-cement concretes Eco-cement concretes Enviro-cement concretes
Presentation downloadable from www.tececo.com 11 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 nearly six times 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 www.tececo.com 12 Eco-Cement pH Curves
Presentation downloadable from www.tececo.com 13 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 volumentric expansion from magnesium oxide to lansfordite is for example 473 volume %.
Presentation downloadable from www.tececo.com 14 Eco-Cement Concrete 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 www.tececo.com 15 Eco-Cement Micro-Structural Strength
Presentation downloadable from www.tececo.com 16 Carbonation Because magnesium has a low molecular weight, proportionally a greater amount of CO 2 is captured. Carbonation results in significant sequestration because of the shear volumes involved. Carbonation adds strength. Carbonates are the stable phases of both calcium and magnesium. The formation of carbonates lowers the pH of concretes compromising the stability of the passive oxide coating on steel. Some steel reinforced structural concrete could be replaced with fibre reinforced porous carbonated concrete.
Presentation downloadable from www.tececo.com 17 Chemistry of Carbonation There are a number of carbonates of magnesium. The main ones appear to be an amorphous phase, lansfordite and nesquehonite. The carbonation of magnesium hydroxide does not proceed as readily as that of calcium hydroxide. – G o r Brucite to nesquehonite = - 38.73 kJ.mol-1 –Compare to G o r Portlandite to calcite = -64.62 kJ.mol-1 The dehydration of nesquehonite to form magnesite is not favoured by simple thermodynamics but may occur in the long term under the right conditions. G o r nesquehonite to magnesite = 8.56 kJ.mol-1 –But kinetically driven by desiccation during drying. Reactive magnesia can carbonate in dry conditions – so keep bags sealed! For a full discussion of the thermodynamics see our technical documents. TecEco technical documents on the web cover the important aspects of carbonation.
Presentation downloadable from www.tececo.com 18 Ramifications of Carbonation Magnesium Carbonates. –The magnesium carbonates that form at the surface of tec – cement concretes expand significantly thereby sealing off further carbonation. –Lansfordite and nesquehonite are stronger and more acid resistant than calcite or aragonite. –The curing of eco-cements in a moist - dry alternating environment seems to encourage carbonation. Portland Cement Concretes –Carbonation proceeds relatively rapidly at the surface. Vaterite followed by Aragonite and Calcite is the principal product and lowers the pH to around 8.2
Presentation downloadable from www.tececo.com 19 Proof of Carbonation - Minerals Present After 18 Months XRD showing carbonates and other minerals before removal of carbonates with HCl in a simple Mix (70 Kg PC, 70 Kg MgO, colouring oxide.5Kg, sand unwashed 1105 Kg)
Presentation downloadable from www.tececo.com 20 Proof of Carbonation - Minerals Present After 18 Months and Acid Leaching XRD Showing minerals remaining after their removal with HCl in a simple mix (70 Kg PC, 70 Kg MgO, colouring oxide.5Kg, sand unwashed 1105 Kg)
Presentation downloadable from www.tececo.com 21 TecEco Binders - Solving Waste Problems There are huge volumes of concrete produced annually ( 2 tonnes per person per year.) An important objective should be to make cementitous composites that can utilise wastes. TecEco cements provide a benign environment suitable for waste immobilisation Many wastes such as fly ash, sawdust, shredded plastics etc. can improve a property or properties of the cementitious composite. There are huge materials flows in both wastes and building and construction. TecEco technology will lead the world in the race to incorporate wastes in cementitous composites
Presentation downloadable from www.tececo.com 22 TecEco Binders - Solving Waste Problems (2) TecEco cementitious composites represent a cost affective option for both use and immobilisation of waste. –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 www.tececo.com 23 Role of Brucite in Immobilization In a Portland cement brucite matrix –PC takes up lead, some zinc and germanium –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 der waals bonding holding the layers together.
Presentation downloadable from www.tececo.com 24 Lower Solubility of Metal Hydroxides There is a 10 4 difference
Presentation downloadable from www.tececo.com 25 TecEco Materials as Fire Retardants The main phase in TecEco tec - cement concretes is Brucite. The main phases in TecEco eco-cements are Lansfordite and nesquehonite. Brucite, Lansfordite and nesquehonite are excellent fire retardants and extinguishers. At relatively low temperatures –Brucite releases water and reverts to magnesium oxide. Mg(OH) 2 MgO + H 2 O –Lansfordite and nesquehonite releases CO 2 and water and convert to magnesium oxide. MgCO 3.nH 2 O MgO + CO 2 + H 2 O Fires are therefore not nearly as aggressive resulting in less damage to structures. Damage to structures results in more human losses that direct fire hazards.
Presentation downloadable from www.tececo.com 26 Tec-Cement Concrete Strength Gain Curve strength gain with less cement and added pozzolans is of great economic and environmental importance. Concretes are more often than not made to strength. The use of tec-cement results in –20-30% greater 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
Presentation downloadable from www.tececo.com 27 Reasons for Strength Development in Tec-Cements. Reactive magnesia requires considerable water to hydrate resulting in: –Denser, less permeable concrete. –A significantly lower voids/paste ratio. Higher early pH initiating more effective silicification reactions? –The Ca(OH) 2 normally lost in bleed water is used internally for reaction with pozzolans. –Super saturation of alkalis caused by the removal of water? Micro-structural strength due to particle packing (Magnesia particles at 4-5 micron are a little over ½ the size of cement grains.) 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? Formation of MgAl hydrates? Similar to flash set in concrete but slower??
Presentation downloadable from www.tececo.com 28 Water Reduction During the Plastic Phase Water is required to plasticise concrete for placement, however once placed, the less water over the amount required for hydration the better. Magnesia consumes water as it hydrates producing solid material. Less water results in less shrinkage and cracking and improved strength and durability. Concentration of alkalis and increased density result in greater strength.
Presentation downloadable from www.tececo.com 29 Tec-Cement Compressive Strength Graphs by Oxford Uni Student
Presentation downloadable from www.tececo.com 30 Tec-Cement Tensile Strength Graphs by Oxford Uni Student Tensile strength is thought to be caused by change in surface charge on MgO particles from +ve to –ve at Ph 12 and electrostatic attractive forces
Presentation downloadable from www.tececo.com 31 Other Strength Testing to Date BRE (United Kingdom) 2.85PC/0.15MgO/3pfa(1 part) : 3 parts sand - Compressive strength of 69MPa at 90 days. Note that there was as much pfa as Portland cement plus magnesia. Strength development was consistently greater than the OPC control TecEcoLarge Cement Company Modified 20 MPa mix
Presentation downloadable from www.tececo.com 32 Concretes have a high percentage (around 18% - 25%) of voids. On hydration magnesia expands 116.9 % filling voids and surrounding hydrating cement grains and compensates for the shrinkage of Portland cement. Brucite is 44.65 mass% water. Lower voids:paste ratios than water:binder ratios result in little or no bleed water less permeability and greater density. –Compare the affect to that of vacuum dewatering. Increased Density – Reduced Permeability
Presentation downloadable from www.tececo.com 33 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. Consequences: –Tec - cement concretes tend to dry from within, are denser and less permeable and therefore stronger more durable and more waterproof. Cement powder is not lost near the surfaces. –Tec-cements have a higher salt resistance and less corrosion of steel etc.
Presentation downloadable from www.tececo.com 34 Tec-Cement pH Curves
Presentation downloadable from www.tececo.com 35 Lower More Stable Long Term pH with Less Corrosion Eh-pH or Pourbaix Diagram The stability fields of hematite, magnetite and siderite in aqueous solution; total dissolved carbonate = 10 -2 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 10.5 -11, 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
Presentation downloadable from www.tececo.com 36 Reduced Steel Corrosion Steel remains protected with a passive oxide coating of Fe 3 O 4 above pH 8.9. –A pH of over 8.9 is maintained by the equilibrium Mg(OH) 2 Mg ++ + 2OH - for much longer than the pH maintained by Ca(OH) 2 because: –Brucite does not react as readily as Portlandite resulting in reduced carbonation rates and reactions with salts. Concrete with brucite in it is denser and carbonation is expansive, sealing the surface preventing further access by moisture, CO 2 and salts. 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.)
Presentation downloadable from www.tececo.com 37 Corrosion in Portland Cement Concretes Passive Coating Fe 3 O 4 intact Both carbonation, which renders the passive iron oxide coating unstable or chloride attack (various theories) result in the formation of reaction products with a higher electrode potential resulting in anodes with the remaining passivated steel acting as a cathode. Corrosion Anode: Fe Fe ++ + 2e- Cathode: ½ O 2 + H 2 O +2e - 2(OH) - Fe ++ + 2(OH) - Fe(OH) 2 + O 2 Fe 2 O 3 and Fe 2 O 3.H 2 O (iron oxide and hydrated iron oxide or rust) The role of chloride in Corrosion Anode: Fe Fe ++ + 2e- Cathode: ½ O 2 + H 2 O +2e - 2(OH) - Fe ++ +2Cl - FeCl 2 FeCl 2 + H 2 O + OH - Fe(OH) 2 + H + + 2Cl - Fe(OH) 2 + O 2 Fe 2 O 3 and Fe 2 O 3.H 2 O Iron hydroxides react with oxygen to form rust. Note that the chloride is recycled in the reaction and not used up.
Presentation downloadable from www.tececo.com 38 Reduced Delayed Reactions A wide range of delayed reactions can occur in Portland cement based concretes –Delayed alkali silica and alkali carbonate reactions –The delayed formation of ettringite and thaumasite –Delayed hydration of minerals such as dead burned lime and magnesia. Delayed reactions cause dimensional distress and possible failure.
Presentation downloadable from www.tececo.com 39 Reduced Delayed Reactions (2) 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, probably holding it for slow release to extended hydration reactions of Ca silicates. –Magnesia dries concrete out from the inside. Reactions do not occur without water.
Presentation downloadable from www.tececo.com 40 Brucite has always played a protective role during salt attack. Putting it in the matrix of concretes in introduces considerable durability. Brucite does not react with salts because it is a least 5 orders of magnitude less soluble, mobile or reactive. –Ksp brucite = 1.8 X 10 -11 –Ksp Portlandite = 5.5 X 10 -6 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 www.tececo.com 41 Bingham Plastic Rheology Finely ground reactive magnesia consumes water but also acts as a plasticiser There are also surface charge affects
Presentation downloadable from www.tececo.com 42 Bingham Plastic Rheology The strongly positively charged small Mg++ atoms attract water (which is polar) in deep layers 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 www.tececo.com 43 Rheology TecEco concretes and mortars are: –Very homogenous and do not segregate easily. They exhibit good adhesion and have a shear thinning property. –Exhibit Bingham plastic qualities and react well to energy input. –Have good workability. TecEco concretes with the same water/binder ratio have a lower slump but greater plasticity and workability. A range of pumpable composites with Bingham plastic properties will be required in the future as buildings will be printed.
Presentation downloadable from www.tececo.com 44 Reduced Shrinkage Dimensional change such as shrinkage results in cracking and reduced durability Net shrinkage is reduced due to stoichiometric expansion of Magnesium minerals, and reduced water loss.
Presentation downloadable from www.tececo.com 45 Reduced Shrinkage – Less Cracking Cracking, the symptomatic result of shrinkage, is undesirable for many reasons, but mainly because it allows entry of gases and ions reducing durability. Cracking can be avoided only if the stress induced by the free shrinkage strain, reduced by creep, is at all times less than the tensile strength of the concrete. Tec-cements also have greater tensile strength. Test Age (days)Microstrain 7133 14240 28316 56470 Large Cement Company Tec-cements exhibit higher tensile strength and less shrinkage and therefore less cracking
Presentation downloadable from www.tececo.com 46 When magnesia hydrates it expands: MgO (s) + H 2 O (l) Mg(OH) 2.nH 2 O (s) 40.31 + 18.0 58.3 (minimum) molar mass 11.2 + liquid 24.3 (minimum) molar volumes Up to 116.96% solidus expansion depending on whether the water is coming from stoichiometric mix water, bleed water or from outside the system. In practice less as the water comes from mix and bleed water. The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1). Volume Changes on Hydration
Presentation downloadable from www.tececo.com 47 Volume Changes on Carbonation Consider what happens when Portlandite carbonates: Ca(OH) 2 + CO 2 CaCO 3 74.08 + 44.01 100 molar mass 33.22 + gas 36.93 molar volumes –Slight expansion. But shrinkage from surface water loss Compared to brucite forming nesquehonite as it carbonates: Mg(OH) 2 + CO 2 MgCO 3.3H 2 O 58.31 + 44.01 138.32 molar mass 24.29 + gas 74.77 molar volumes –307 % expansion (less water volume reduction) and densification of the surface preventing further ingress of CO 2 and carbonation. Self sealing? The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1).
Presentation downloadable from www.tececo.com 48 Dimensionally Control Over Concretes During Curing? Portland cement concretes shrink around.05%. Over the long term much more (>.1%). –Mainly due to plastic and drying shrinkage. The use of some wastes as aggregates causes shrinkage e.g. wood waste in masonry units, thin panels etc. By varying the amount and form of magnesia added dimensional control can be achieved.
Presentation downloadable from www.tececo.com 49 TecEco Cement Concretes –Dimensional Control Combined – Hydration and Carbonation can be manipulated to be close to neutral. –So far we have not observed significant shrinkage in TecEco tec - cement concretes (5% -10% substitution OPC) also containing fly ash. –At some ratio, thought to be around 10% reactive magnesia and 90% PC volume changes are optimised as higher additions of MgO reduce strength. –The water lost by Portland cement as it shrinks is used by reactive magnesia as it hydrates also reducing shrinkage.
Presentation downloadable from www.tececo.com 50 Tec - Cement Concretes – Less or no Dimensional Change It may be possible to engineer a particle with slightly delayed expansion to counterbalance the expansion and then shrinkage concretes containing gbfs.
Presentation downloadable from www.tececo.com 51 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) 40.31 + 18.0 58.3 molar mass 11.2 + 18.0 24.3 molar volumes 39.20 24.3 molar volumes 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 www.tececo.com 52 TecEco Cement Implementation Summary
Presentation downloadable from www.tececo.com 53 High Performance-Lower Construction Costs Less binders (OPC + magnesia) for the same strength. Faster strength gain even with added pozzolans. Elimination of shrinkage reducing associated costs. Tolerance and consumption of water. Reduction in bleed water enables finishing of lower floors whilst upper floors still being poured and increases pumpability. Cheaper binders as less energy required Increased durability will result in lower costs/energies/emissions due to less frequent replacement. Because reactive magnesia is also an excellent plasticiser, other costly additives are not required for this purpose. A wider range of aggregates can be utilised without problems reducing transport and other costs/energies/emissions. Foolproof Concrete?
Presentation downloadable from www.tececo.com 54 TecEco Concretes - Lower Construction Costs (2) Homogenous, do not segregate with pumping or work. Easier placement and better finishing. Reduced or eliminated carbon taxes. Eco-cements can to a certain extent be recycled. TecEco cements utilise wastes many of which improve properties. Improvements in insulating capacity and other properties will result in greater utility. Products utilising TecEco cements such as masonry and precast products can in most cases utilise conventional equipment and have superior properties. A high proportion of brucite compared to Portlandite is water and of Lansfordite and nesquehonite compared to calcite is CO 2. –Every mass unit of TecEco cements therefore produces a greater volume of built environment than Portland and other calcium based cements. Less need therefore be used reducing costs/energy/emissions.
Presentation downloadable from www.tececo.com 55 Relevance to the Masonry Industry The Canadian masonry industry is ideally placed to take advantage of the Kyoto protocol to solve the worlds global warming problem as the country: –Making bricks, blocks, pavers and mortars using tec or eco-cements in Canada would help the country meet its Kyoto objectives and together with the raw materials required provide a new export. Canada: Canada: –Is close by countries that are big emitters (Europe, the US) –Has abundant Mg minerals suitable for a silicate reactor process to sequester CO2 from concentrated sources such as power stations etc. –Has abundant non fossil fuel energy (hydro, wind) to power TecEco kilns –Is close to markets that could use Mg carbonate products with associated carbon credits
Presentation downloadable from www.tececo.com 56 Summary Simple, smart and sustainable? –TecEco cement technology has resulted in potential solutions to a number of problems with Portland and other cements including shrinkage, durability and corrosion and the immobilisation of many problem wastes and will provides a range of more sustainable building materials. The right technology at the right time? –TecEco cement technology addresses important triple bottom line issues solving major global problems with positive economic and social outcomes. Climate Change Pollution Durability Corrosion Strength Delayed Reactions Placement, Finishing Rheology Shrinkage Carbon Taxes There is a way to make our city streets as green as the Amazon rainforest Fred Pearce New Scientist Magazine
Presentation downloadable from www.tececo.com 57 TecEco Doing Things
Presentation downloadable from www.tececo.com 58 The Use of Eco-Cements for Building Earthship Brighton 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.
Presentation downloadable from www.tececo.com 59 Repair of Concrete Blocks. Clifton Surf Club 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.
Presentation downloadable from www.tececo.com 60 Mike Burdons Murdunna Works 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
Presentation downloadable from www.tececo.com 61 Tec-Cement Slab Whittlesea, Vic. Australia 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 - 133 micro strains, 14 days - 240 micro strains, 28 days - 316 micros strains and at 56 days - 470 microstrains.