Materials and Molecules - Behind What You See

Presentation downloadable from www.tececo.com

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Materials and Molecules - Behind What You SeeMaterials and Molecules - Behind What You See


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Materials and Moelcules – Behind What you See(Originally Concretes – Solution to Kyoto)

Materials and Moelcules – Behind What you See(Originally Concretes – Solution to Kyoto)

Our slides are deliberately verbose as most people download and view them from the net. Because of time constraints I will have to race over some slides John Harrison B.Sc. B.Ec. FCPA.

Presentation by John Harrison, managing director of TecEco and inventor of Tec and Eco-Cements and the CarbonSafe process.

TecEco are in the biggest business on the planet – that of solving global warming waste and water problems


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Techno-Processes & Earth SystemsTechno-Processes & Earth Systems

Underlying the techno-process that describes and controls the flow of matter and energy are molecular stocks and flows. If out of tune with nature these moleconomic flows have detrimental affects on earth systems.

Detrimental affects on earth systems

Earth Systems

Atmospheric composition, climate, land cover, marine ecosystems, pollution, coastal zones, freshwater and salinity.

Move 500-600 billion

tonnes

Use some 50 billion

tonnes

To reduce the impact on earth systems new technical paradigms need to be invented that result in underlying molecular flows that mimic or at least do not interfere with natural flows.

Take

Waste


4

Under Materials Flows in the Techno-Processes are Molecular FlowsUnder Materials Flows in the Techno-Processes are Molecular Flows

Take → Manipulate → Make → Use → Waste [ ←Materials→ ]

[ ← Underlying molecular flow → ]

If the underlying molecular flows are “out of tune” with nature there is damage to the environment

e.g. heavy metals, cfc’s, c=halogen compounds and CO2

MoleconomicsIs 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.


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The Carbon Cycle and EmissionsThe Carbon Cycle and Emissions

Source: David Schimel and Lisa Dilling, National Centre for Atmospheric Research 2003

Emissions from fossil fuels and cement production are a significant cause of the global warming.

Units: GtC GtC/yr


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Recycle

Re-use

Take only renewables

Waste only what is biodegradable or can be re-assimilated

Manipulate Make Use

Reduce

Changing the Techno-ProcessesChanging the Techno-Processes

ReduceRe-useRecycle

Materials

Take => manipulate => make => use => wasteDriven by fossil fuel energy with detrimental effects on earth systems.

Eco-innovate to create “industrial ecologies”

Atoms and Molecules in the global commons


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Utilizing Carbon and Wastes (Biomimicry)Utilizing Carbon and Wastes (Biomimicry) The waste from one plant or animal is the food or home for

another. During earth's geological history large tonnages of carbon

were put away as limestone and other carbonates and as coal and petroleum by the activity of plants and animals.

Sequestering carbon in magnesium binders and aggregates in the built environment mimics nature in that carbon is used in the homes or skeletal structures of most plants and animals.

We all use carbon and wastes to make our homes! “Biomimicry”

In eco-cement blocks and mortars the binder is carbonate and the aggregates are preferably wastes


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Biomimicry - Ultimate RecyclersBiomimicry - Ultimate Recyclers As peak oil looms and the price of transport is

set to rise sharply– We should not just be recycling based on chemical property

requiring sophisticated equipment and resources– We should be including wastes based on physical properties

as well as chemical composition in composites whereby they become local resources.

The Jackdaw recycles all sorts of things it finds nearby based on physical property.

The bird is not concerned about chemical composition and the nest it makes could be described as a composite material.

TecEco cements are benign binders that can incorporate all sort of wastes without reaction problems. We can do the same as the Jackdoor


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Energy from OilEnergy 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 2025. It follows that there will be economic mayhem unless the cement and concrete industry acts now to change the energy base of their products.


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Using Wastes and Non-Traditional Aggregates to Make TecEco Cement Concretes


As the price of fuel rises, theuse of local or on site lowembodied energy materialsrather than carted aggregateswill have to be considered.

Recent natural disasters such as the recent tsunami and Pakistani earthquake mean we urgently need to commercialize TecEco technologies because they provide benign environments allowing the use of many local materials and wastes without delayed reactions

No longer an option?

The use of on site and local wastes will be made possible by the use of low reactivity TecEco mixes and a better understanding of particle packing. We hope with our new software to be able to demonstrate how adding specific size ranges can make an unusable waste such as a tailing or sludge suitable for making cementitious materials.

http://www.truckline.com/NR/rdonlyres/F36C2019-6DF5-4C11-BDA0-4170CE2E9783/0/dp103105.pdf


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Huge Potential for More Sustainable Construction MaterialsHuge Potential for More Sustainable Construction Materials

Reducing the impact of the take and waste phases of the techno-process.– including carbon in materials

they are potentially carbon sinks.– including wastes for

physical properties aswell as chemical compositionthey become resources.

– re engineeringmaterials toreduce the lifetimeenergy of buildings

CO2

C

CO2

Waste

Waste

Many wastes including CO2 can contribute to physical properties reducing lifetime energies

CO2

CO2


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Impacts of LandfillImpacts of Landfill

Landfill is the technical term for filling large holes in the ground with waste. Landfills release methane, can cause ill health in the area, leads to the contamination of land, underground water, streams and coastal waters and gives rise to various nuisances including increased traffic, noise, odours, smoke, dust, litter and pests.

Most damaging is the release of dangerous molecules to the global commons


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Economically Driven SustainabilityEconomically Driven Sustainability

New, more profitable technical paradigms are required that result in more sustainable and usually more efficient moleconomic flows that mimic natural flows or better, reverse our damaging flows.

$ - ECONOMICS - $


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Changing the Technical ParadigmChanging the Technical Paradigm

“By enabling us to make productive use of particular raw materials, technology determines what constitutes a physical resource1”1.Pilzer, Paul Zane, Unlimited Wealth, The Theory and Practice of Economic

Alchemy, Crown Publishers Inc. New York.1990

By inventing new technical paradigms and re-engineering materials we can change the underlying molecular flows that are damaging this planet. It is not hard to do this and it could even be economic. All it takes is lateral thinking and imagination.


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Examples of Economic Changes in Technical Paradigms that result in Greater Sustainability

Examples of Economic Changes in Technical Paradigms that result in Greater Sustainability

Robotics - A Paradigm Shift in Technology that will fundamentally affect Building and Construction

Construction in the future will be largely done by robots because it will be more economic to do so. Like a color printer different materials will be required for different parts of structures, and wastes such as plastics will provide many of the properties required for the cementitious composites of the future used. A non-reactive binder such as TecEco tec-cements can supply the right rheology, and like a printer, very little will be wasted.

Light Globes - A Recent Paradigm Shift in Technology Reducing Energy Consumption

Light Globes in the last 10 years have evolved from consuming around 100 watts per 1700 lumens to less that 20 watts per 1700 lumens. As light globes account for around 30% of household energy this is as considerable saving.

100 watts1700 lumens

Incandescent

25 watts1700 lumens

Fluorescent

<20 watts1700 lumens

Led Light


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Sustainability = Culture + TechnologySustainability = Culture + Technology

Increase in demand/price ratio for sustainability due to educationally induced cultural drift.

#

$

Demand

Supply

Increase in supply/price ratio for more sustainable products due to innovative paradigm shifts in technology.

Equilibrium shiftECONOMICS

Greater Value/for impact (Sustainability) and economic growth

Sustainability could be considered as where culture and technology meet.

New Technical Paradigms are required that deliver sustainability.


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The TecEco CarbonSafe Industrial EcologyThe TecEco CarbonSafe Industrial Ecology

Greensols Process

Fossil fuels

Solar or solar derived energy

CO2Oil

MgOCO2

Coal

CO2

MgCO3

CO2

CO2

Inputs:Atmospheric or smokestack CO2, brines,waste acid, other wastes

Outputs:Potable water, gypsum, sodium bicarbonate, salts, building materials, bottled concentrated CO2 (for geo-sequestration and other uses).

Carbon or carbon compoundsMagnesium oxide

1.29 gm/l Mg

The 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.

TecEco MgCO2

Cycle

TecEcoKiln


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The TecEco CarbonSafe Industrial EcologyThe TecEco CarbonSafe Industrial Ecology

Outputs

Gypsum, Sodium bicarbonate, Salts, Building materials, Potable water

Inputs

BrinesWaste AcidCO2


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Hydroxide

Reactor

Process

CO2 as a biological or industrial input or if no other use geological sequestration

CO2 from power generation, industry or out of the air

Magnesite (MgCO3)Magnes

ia (MgO)

Other Wastes

Simplified TecEco ReactionsTec-Kiln MgCO3 → MgO + CO2 - 118 kJ/moleReactor Process MgO + CO2 → MgCO3 + 118 kJ/mole (usually more complex hydrates)

Magnesium Thermodyna

mic Cycle

Waste Acid

1.354 x 109 km3 Seawater containing 1.728 1017 tonne Mg or suitable brines from other sources

Tonnes CO2 sequestered per tonne magnesium with various cycles through the TecEco Tec-Kiln process. Assuming no leakage MgO to built environment (i.e. complete cycles).

Billion Tonnes

Tonnes CO2 sequestered by 1 billion tonnes of Mg in seawater 1.81034

Tonnes CO2 captured during calcining (same as above) 1.81034

Tonnes CO2 captured by eco-cement 1.81034

Total tonnes CO2 sequestered or abated per tonne Mg in seawater (Single calcination cycle).

3.62068

Total tonnes CO2 sequestered or abated (Five calcination cycles.) 18.1034

Total tonnes CO2 sequestered or abated (Ten calcination cycles). 36.20

Gypsum (CaSO4)

Gypsum + carbon waste (e.g. sewerage) = fertilizers

Sewerage compost

Magnesite (MgCO3)Solar Process to

Produce Magnesium Metal

Bicarbonate of Soda (NaHCO3)

Eco-CementTec-Cement

Seawater

Carbonation

Process

Other salts Na+,K+, Ca2+,Cl-

CO2 from power generation or industry

Sequestration Table – Mg from Seawater

The CarbonSafe Industrial EcologyThe CarbonSafe Industrial Ecology

CO2

Potable water

http://www.harrisongypsum.com/ACGImages/ACGCyril%20(7-10-02)%20027%20-%20FormingRockPile.jpg

http://www.nubergindia.com/gifs/nuberg-plant-3.jpg


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Reduction Global CO2 from CarbonSafe ProcessReduction Global CO2 from CarbonSafe Process

Global CO2 in the Atmosphere

2,900

3,100

3,300

3,500

2005 2010 2015 2020 2025

Mas

s o

f C

O2

(Gt)

Mass CO2 in the atmosphere without "CarbonSafe"sequestration (Gt)Mass CO2 in the atmosphere with "CarbonSafe"sequestration (Gt)Upper CO2 limit (Gt)


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Why Magnesium Carbonates for Sequestration? Why Magnesium Carbonates for Sequestration?

Because of the low molecular weight of magnesium, magnesium oxide which hydrates to magnesium hydroxide and then carbonates, is ideal for scrubbing 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 element

Magnesium minerals are potential low cost. New kiln technology from TecEco will enable easy low cost simple non fossil fuel calcination of magnesium carbonate with CO2 capture for geological sequestration.

%5284

44

3

2

MgCO

CO%43

101

44

3

2

CaCO

CO


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The TecEco Dream – A More Sustainable Built EnvironmentThe TecEco Dream – A More Sustainable Built Environment

MAGNESITE + OTHER INPUTS

TECECO CONCRETES

MINING

SUSTAINABLE CITIES

CO2

PERMANENT SEQUESTRATION & WASTE UTILISATION (Man made carbonate rock incorporating wastes as a building material)

CO2

MgOTECECO KILN

RECYCLED BUILDING MATERIALS

CO2

OTHERWASTES

CO2 FOR GEOLOGICAL SEQUESTRATION

We need materials that require less energy to make them, that last much longer and that contribute properties that reduce lifetime energies

“There is a way to make our city streets as green as the Amazon rainforest”. Fred Pearce, New Scientist Magazine


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Materials in the Built EnvironmentMaterials in the Built Environment

The built environment is made of materials and is our footprint on earth.– It comprises buildings and infrastructure.

Construction materials comprise– 70% of materials flows (buildings, infrastructure etc.)– 40-50% of waste that goes to landfill (15 % of new materials

going to site are wasted.) At 1.5% of world GDP Annual Australian

production of building materials likely to be in the order 300 million tonnes or over 15 tonnes per person.

Over 30 billion tonnes of building materials are used annually on a world wide basis.– Mostly using virgin natural resources– Combined in such a manner they cannot easily be separated.– Include many toxic elements.


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Impact of the Largest Material Flow - Cement and ConcreteImpact of the Largest Material Flow - Cement and Concrete

Some 600 billion tonnes of matter are moved around the planet a year of which some 50 billion tonnes only is used.

Concrete made with cement is the most widely used material on Earth accounting for some 30% of all materials flows on the planet and 70% of all materials flows in the built environment.– Global Portland cement production is currently in the order of 2

billion tonnes per annum. – Globally over 14 billion tonnes of concrete are poured per year.– Over 2 tonnes per person per annum– Much more concrete is used than any other building material.

TecEco Pty. Ltd. have benchmark technologies for improvement in sustainability and properties

TecEco Pty. Ltd. have benchmark technologies for improvement in sustainability and properties


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Embodied Energy of Building MaterialsEmbodied Energy of Building Materials

Downloaded from www.dbce.csiro.au/ind-serv/brochures/embodied/embodied.htm (last accessed 07 March 2000)

Concrete is relatively environmentally friendly and has a relatively low embodied energy


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Average Embodied Energy in BuildingsAverage Embodied Energy in Buildings

Downloaded from www.dbce.csiro.au/ind-serv/brochures/embodied/embodied.htm (last accessed 07 March 2000)

Because so much concrete is used there is a huge opportunity for sustainability by reducing the embodied energy, reducing the carbon debt (net emissions) and improving properties that reduce lifetime energies.

Most of the embodied energy in the built environment is in concrete.


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Emissions from Cement ProductionEmissions from Cement Production

Chemical Release– The process of calcination involves driving off chemically bound CO2

with heat.

CaCO3 →CaO + ↑CO2 Process Energy

– Most energy is derived from fossil fuels.– Fuel oil, coal and natural gas are directly or indirectly burned to produce the

energy required releasing 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).

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.

CO2

CO2

CO2

CO2


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Cement Production ~= Carbon Dioxide EmissionsCement Production ~= Carbon Dioxide Emissions

0

500,000,000

1,000,000,000

1,500,000,000

2,000,000,000

2,500,000,000

Metric Tonnes

Year

Between tec, eco and enviro-cements TecEco can provide a viable much more sustainable alternative.


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TecEco Binder SystemsTecEco Binder Systems

Hydration of the various components of Portland cement for strength.

SUSTAINABILITY

DURABILITY STRENGTHTECECO CEMENTS

Reaction of alkali with pozzolans (e.g. lime with fly ash.) for sustainability, durability and strength.

Hydration of magnesia => brucite for strength, workability, dimensional stability and durability. In Eco-cements carbonation of brucite => nesquehonite, lansfordite and an amorphous phase for sustainability.

PORTLAND POZZOLAN

REACTIVE MAGNESIA

TecEco concretes are a system of blending reactive magnesia, Portland cement and usually a pozzolan with other materials and are a key factor for sustainability.


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TecEco FormulationsTecEco Formulations Tec-cements (5-15% MgO, 85-95% OPC)

– contain more Portland cement than reactive magnesia. Reactive magnesia hydrates in the same rate order as Portland cement forming Brucite which uses up water reducing the voids:paste ratio, increasing density and possibly raising the short term pH.

– Reactions with pozzolans are more affective. After all the Portlandite has been consumed Brucite controls the long term pH which is lower and due to it’s low solubility, mobility and reactivity results in greater durability.

– Other benefits include improvements in density, strength and rheology, reduced permeability and shrinkage and the use of a wider range of aggregates many of which are potentially wastes without reaction problems.

Eco-cements (15-95% MgO, 85-5% OPC)– contain more reactive magnesia than in tec-cements. Brucite in porous

materials carbonates forming stronger fibrous mineral carbonates and therefore presenting huge opportunities for waste utilisation and sequestration.

Enviro-cements (5-15% MgO, 85-95% OPC)– contain similar ratios of MgO and OPC to eco-cements but in non porous

concretes brucite does not carbonate readily.– Higher proportions of magnesia are most suited to toxic and hazardous waste

immobilisation and when durability is required. Strength is not developed quickly nor to the same extent.


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TecEco Cement LCATecEco Cement LCA

TecEco Concretes will have a big role post Kyoto as they offer potential sequestration as well as waste utilisation

The TecEco LCA model is available for download under “tools” on the web site


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TecEco Technology in PracticeTecEco Technology in Practice

On 17th March 2005 TecEco poured the first commercial slab in the world using tec-cement concrete with the assistance of one of the larger cement and pre-mix companies.

– The formulation strategy was to adjust a standard 20 MPa high fly ash (36%) mix from the company as a basis of comparison.

– Strength development, and in particular early strength development was good. Interestingly some 70 days later the slab is still gaining strength at the rate of about 5 MPa a month.

– Also noticeable was the fact that the concrete was not as "sticky" as it normally is with a fly ash mix and that it did not bleed quite as much.

– Shrinkage was low. 7 days - 133 micro strains, 14 days - 240 micro strains, 28 days - 316 micros strains and at 56 days - 470 microstrains.

Strength Development of Tec-Cement Concrete

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Days w ater cured

Str

en

gth

, M

Pa

CompressiveStrength

=> Whittlesea, Vic. Australia


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Allow many mega litres of good fresh water to become contaminated by the pollutants on our streets and pollute coastal waterways

Capture and cleanse the water for our use?

Or

=> Porous Pavement


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First Eco-cement mud bricks and mortars in Australia

– Tested up twice as strong as the PC controls

– Mud brick addition rate 2.5%– Addition rate for mortars 1:8

not 1:3 because of molar ratio volume increase with MgO compared to lime.

=> Whittlesea, Vic. Australia


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TecEco Technology in PracticeTecEco Technology in PracticeBy 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.

Earthships are exemplars of low-carbon design, construction and living and were invented and developed in the USA by Mike Reynolds over 20 years of practical building exploration. They are autonomous earth-sheltered buildings independent from mains electricity, water and waste systems and have little or no utility costs.

For information about the Earthship Brighton and other projects please go to the TecEco web site.

=> Earthship Brighton, UK


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The Clifton Surf Life Saving Club was built by first pouring footings, On the footings block walls were erected and then at a later date concrete was laid in between.

As the ground underneath the footings was sandy, wet most of the time and full of salts it was a recipe for disaster.

Predictably the salty water rose up through the footings and then through the blocks and where the water evaporated there was strong efflorescence, pitting, loss of material and damage.

The TecEco solution was to make up a formulation of eco-cement mortar which we doctored with some special chemicals to prevent the rise of any more moisture and salt.

The solution worked well and appears to have stopped the problem.

=> Clifton Surf Life Saving Club


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Mike Burdon, Builder and Plumber.I work for a council interested in sutainability and have been involved with TecEco since around 2001 in a private capacity helping with large scale testing of TecEco tec-cements at our shack.

I am interested in the potentially superior strength development and sustainability aspects.

To date we have poured two slabs, footings, part of a launching ramp and some tilt up panels using formulations and materials supplied by John Harrison of TecEco. I believe that research into the new TecEco cements essential as overall I have found:

1. The rheological performance even without plasticizer was excellent. As testimony to this the contractors on the site commented on how easy the concrete was to place and finish.

2. We tested the TecEco formulations with a hired concrete pump and found it extremely easy to pump and place. Once in position it appeared to “gel up” quickly allowing stepping for a foundation to a brick wall.

3. Strength gain was more rapid than with Portland cement controls from the same premix plant and continued for longer.

4. The surfaces of the concrete appeared to be particularly hard and I put this down to the fact that much less bleeding was observed than would be expected with a Portland cement only formulation

=> Mike Burdon’s Murdunna Works


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Tec-Cement concretes exhibit little or no shrinkage. At 10% substitution of MgO for PC the shrinkage is less than half normal. At 18% substitution with no added pozzolan there was no measurable shrinkage or expansion.

The above photo shows a tec-cement concrete topping coat (with no flyash) 20mm thick away from the door and 80 mm thick near the door. Note that there has been no tendency to push the tiles or shrink away from the borders as would normally be the case.

=> DJ Motors, Hobart


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TecEco Tec and Eco-Cement blocks are now being made commercially in Tasmania and with freight equalization may be viable to ship to Victoria for your “green” project. Hopefully soon we will have a premix mortar available that uses eco-cement.

=> Island Block and Paver,Tasmania


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BUILD LITE CELLULAR CONCRETE4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169PH 61 3 9547 0255 FX 61 3 9547 0266

Foamed TecEco cement concretes can be produced to about 30% weight reduction in concrete trucks using cellflow additive or to about 70% weight reduction using a foaming machine with mearlcrete additive (or equivalents)

=> Foamed Concretes


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Tec & Eco Cement Foamed Concrete SlabsTec & Eco Cement Foamed Concrete Slabs

BUILD LITE CELLULAR CONCRETE4 Rosebank Ave Clayton Sth MELBOURNE AUSTRALIA 3169PH 61 3 9547 0255 FX 61 3 9547 0266

=> Foamed Concrete Slabs


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Solutions in Steel

ABN 48 103 573 039

TEL: 61 7 3271 3900FAX: 61 7 3271 2701

80 Mica StreetCarole Park 4300

QueenslandAustralia

Imagine a conventional steel frame section with a foamed concrete panel built in adding to structural strength, providing insulation as well as the external cladding of a structure.

Rigid Steel Framing have developed just such a panel and have chosen to use TecEco cement technology for the strength, ease of use and finish.

Patents applied for by Rigid Steel Framing

Please direct commercial enquiries to Rigid Steel Framing at rigidsteel.com.au

=> Foamed Concretes Panels


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Rear view of test panels showing tongue and groove and void for services.Interior plasterboard is fixed conventionally over gap for services.


=> Foamed Concretes Panels


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TecEco Technologies Take Concrete into the FutureTecEco Technologies Take Concrete into the Future

More rapid early strength gain even with added pozzolans– More supplementary materials can be used reducing

costs and take and waste impacts. Higher strength/binder ratio, provided

greater plasticity contributed by magnesia used to reduce water.

Less shrinkage and cracking More durable concretes

– Reducing costs and take and waste impacts. Use of wastes including carbon dioxide

– Magnesia component can be made using non fossil fuel energy and CO2 captured during production. Eco-

Cements

Tec -Cements

Tec & Eco-Cements


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Tec & Eco-Cement TheoryTec & Eco-Cement Theory

Many Engineering Issues are Actually Mineralogical Issues– Problems with Portland cement concretes are usually resolved

by the “band aid” engineering fixes. e.g.• Use of calcium nitrite, silanes, cathodic protection or stainless steel

to prevent corrosion.• Use of coatings to prevent carbonation.• Crack control joins to mitigate the affects of shrinkage cracking.• Plasticisers to improve workability.

– Portlandite and water are the weakness of concrete• TecEco remove Portlandite it and replacing it with magnesia which

hydrates to Brucite.• The hydration of magnesia consumes significant water


46

Tec & Eco-Cement TheoryTec & Eco-Cement Theory Portlandite (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 and TecEco add reactive magnesia

– which 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 volume


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Why Add Reactive Magnesia?Why Add Reactive Magnesia?

Reactive magnesia is added to maintain the long term stability of CSH.– Preventing a reduction in the Ca/Si ratio in CSH.

To remove water.– Reactive magnesia consumes water as it hydrates to possibly

hydrated forms of Brucite. To control long term Ph.

– Reducing reactivity To reduce shrinkage. To make concretes more durable Because significant quantities of carbonates are

produced in porous substrates which are affective binders.

The consequences of putting brucite through the matrix of a concrete in the first place need to be considered

Reactive MgO is a new tool to be understood with profound affects on most properties


48

Strength with Blend & PorosityStrength with Blend & Porosity

0

50

100

150

100-150

50-100

0-50

High OPC High Magnesia

High Porosity

STRENGTH ON ARBITARY SCALE 1-100

Tec-cement concretes

Eco-cement concretes

Enviro-cement concretes


49

Eco-CementsEco-Cements Eco-cements are similar but potentially superior to lime

mortars because:– The calcination phase of the magnesium thermodynamic cycle takes

place at a much lower temperature and is therefore more efficient.– Magnesium minerals are generally more fibrous and acicular than calcium

minerals and hence add microstructural strength. Water forms part of the binder minerals that forming making

the cement component go further. In terms of binder produced for starting material in cement, eco-cements are much more efficient.

Magnesium hydroxide in particular and to some extent the carbonates are less reactive and mobile and thus much more durable.


50

Eco-Cement Strength DevelopmentEco-Cement Strength Development

Eco-cements gain early strength from the hydration of PC.

Later strength comes from the carbonation of brucite forming an amorphous phase, lansfordite and nesquehonite.

Strength gain in eco-cements is mainly microstructural because of– More ideal particle packing (Brucite particles at 4-5 micron are

under half the size of cement grains.)– The natural fibrous and acicular shape of magnesium carbonate

minerals which tend to lock together. More binder is formed than with calcium

– Total volumetric expansion from magnesium oxide to lansfordite is for example volume 811%.

Mg(OH)2 + CO2 MgCO3.5H2O

From air and water


51

Eco-Cement Strength Gain CurveEco-Cement Strength Gain Curve

Eco – Cement Concrete with 50% reactive magnesia

OPC Concrete

HYPOTHETICAL STRENGTH GAIN CURVE OVER TIME (Pozzolans added)

MPa

Log Days Plastic Stage

?

?

?

?

7 14 28 3

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

Eco-Cement ReactionsEco-Cement Reactions

Hardness: 2.5 - 3.0 2.5

Form: Massive-Sometimes Fibrous Often Fibrous Acicular - Needle-like crystals

Solubility (mol.L-1): .00015 .01 .013 (but less in acids)

Magnesia Brucite Amorphous Lansfordite

MgO + nH2O Mg(OH)2.nH2O + CO2 MgCO3.nH2O + MgCO3.5H2O + MgCO3.3H2O

In Eco - Cements

Hardness: 2.5 3.5

Form: Massive Massive or crystalline More acicular

Solubility (mol.L-1): .024 .00014

Portlandite Calcite

Ca(OH)2 + CO2 CaCO3

Compare to the Carbonation of Portlandite

Aragonite

Nesquehonite


53

Eco-Cement Micro-Structural StrengthEco-Cement Micro-Structural Strength

Elongated growths of lansfordite and nesquehonite near the surface, growing inwards over time and providing microstructural strength.

Portland clinker minerals (black). Hydration providing Imperfect structural framework.

Micro spaces filled with hydrating magnesia (→brucite) – acting as a “waterproof glue”

Flyash grains (red) reacting with lime producing more CSH and if alkaline enough conditions bonding through surface hydrolysis. Also acting as micro aggregates.

Mysterious amorphous phase?


54

CarbonationCarbonation

Eco-cement is based on blending reactive magnesium oxide with other hydraulic cements and then allowing the Brucite and Portlandite components to carbonate in porous materials such as concretes blocks and mortars.– Magnesium is a small lightweight atom and the carbonates that form contain

proportionally a lot of CO2 and water and are stronger because of superior microstructure.

The use of eco-cements for block manufacture, particularly in conjunction with the kiln also invented by TecEco (The Tec-Kiln) would result in sequestration on a massive scale.

As Fred Pearce reported in New Scientist Magazine (Pearce, F., 2002), “There is a way to make our city streets as green as the Amazon rainforest”.

Ancient and modern carbonating lime mortars are based on this principle


55

CO2 Abatement in Eco-CementsCO2 Abatement in Eco-Cements

Eco-cements in porous products absorb carbon dioxide from the atmosphere. Brucite carbonates forming lansfordite, nesquehonite and an amorphous phase, completing the thermodynamic cycle.

No Capture11.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.37 tonnes to the tonne. After carbonation. approximately .241 tonne to the tonne.

Portland Cements15 mass% Portland cement, 85 mass% aggregate

Emissions.32 tonnes to the tonne. After carbonation. Approximately .299 tonne to the tonne.

.299 > .241 >.140 >.113Bricks, blocks, pavers, mortars and pavement made using eco-cement, fly and bottom ash (with capture of CO2 during manufacture of reactive magnesia) have 2.65 times less emissions than if they were made with Portland cement.

Capture CO211.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.25 tonnes to the tonne. After carbonation. approximately .140 tonne to the tonne.

Capture CO2. Fly and Bottom Ash11.25% mass% reactive magnesia, 3.75 mass% Portland cement, 85 mass% aggregate.

Emissions.126 tonnes to the tonne. After carbonation. Approximately .113 tonne to the tonne.

For 85 wt% Aggregates

15 wt% Cement

Greater Sustainability


56

Aggregate Requirements for CarbonationAggregate Requirements for Carbonation

The requirements for totally hydraulic limes and all hydraulic concretes is to minimise the amount of water for hydraulic strength and maximise compaction and for this purpose aggregates that require grading and relatively fine rounded sands to minimise voids are required

For carbonating eco-cements and lime mortars on the on the hand the matrix must “breathe” i.e. they must be porous– requiring a coarse fraction to cause physical air voids and some

vapour permeability. Coarse fractions are required in the aggregates used!


57

Roman SpecificationsRoman Specifications The oldest record: Book II, chapter IV of the Ten Books of

Architecture by Vitruvius Pollio.– According to Vitruvius “the best (sand) will be found to be that which

crackles when rubbed in the hand, while that which has much dirt in it will not be sharp enough. Again: throw some sand upon a white garment and then shake it out; if the garment is not soiled and no dirt adheres to it, the sand is suitable” Vitruvious was talking about gritty sand with no fines.

The 16th century architect Andrea Palladio is renowned for "The Four Books of Architecture“– translated into English in the early 18th century– used as a principal reference for building for almost two centuries

(Palladio, Isaac Ware translation, 1738).– In the first book Palladio says, "the best river sand is that which is

found in rapid streams, and under water-falls, because it is most purged". In other words, it is coarse. Compare this with most sand for use in mortar today.

The conclusion form history is that a coarse gritty sand that is not graded for minimum paste is required.


58

Eco-Cement Porous Pavement – A Solution for Water Quality? Eco-Cement Porous Pavement – A Solution for Water Quality?

Before three were cites forests and grassland covered most of our planet.

When it rained much of the water naturally percolated though soils that performed vital functions of slowing down the rate of transport to rivers and streams, purifying the water and replenishing natural aquifers.

Our legacy has been to pave this natural bio filter, redirecting the water that fell as rain as quickly as possible to the sea. Given global water shortages, problems with salinity, pollution, volume and rate of flow of runoff we need to change our practices so as to mimic the way it was for so many millions of years before we started making so many changes.

Porous Pavements are a Technology Paradigm Change Worth Investigating


59



Many wastes and local materials can contribute physical property values.– Plastics for example are collectively light in weight, have tensile

strength and low conductance. Tec, eco and enviro-cements will allow a wide range of

wastes and non-traditional aggregates such as local materials to be used.

Tec, enviro and eco-cements are benign binders that are:– low alkali reducing reaction problems with organic materials.– stick well to most included wastes

Tec, enviro and eco-cements can utilize wastes including carbon to increase sequestration preventing their conversion to methane

There are huge volumes of concrete produced annually (>2 tonnes per person per year)


60

Solving Waste & Logistics ProblemsSolving Waste & Logistics Problems

TecEco cementitious composites represent a cost affective option for– using non traditional aggregates from on site reducing transports costs and

emissions– use and immobilisation of waste.

Because they have– Lower reactivity

• less water• lower pH

– Reduced solubility of heavy metals• less mobile salts

– Greater durability.• denser.• impermeable (tec-cements).• dimensionally more stable with less shrinkage and cracking.

– Homogenous.– No bleed water.

TecEco Technology - Converting Waste to Resource


61

Role of Brucite in ImmobilizationRole of Brucite in Immobilization

In a Portland cement Brucite matrix– PC derive CSH takes up lead, some zinc and germanium– Pozzolanic CSH can take up mobile cations– Brucite and hydrotalcite are both excellent hosts for toxic and

hazardous wastes. – Heavy metals not taken up in the structure of Portland cement

minerals or trapped within the brucite layers end up as hydroxides with minimal solubility.

The Brucite in TecEco cements has a structure comprising electronically neutral layers and is able to accommodate a wide variety of extraneous substances between the layers and cations of similar size substituting for magnesium within the layers and is known to be very suitable for toxic and hazardous waste immobilisation.

Layers of electronically neutral brucite suitable for trapping balanced cations and anions as well as other substances.

Salts and other substances trapped between the layers.

Van de waals bonding holding the layers together.


62

Lower Solubility of Metal HydroxidesLower Solubility of Metal Hydroxides

Pb(OH) Cr(OH) 3

Zn(OH) 2

Ag(OH) Cu(OH) 2 Ni(OH) 2 Cd(OH) 2

10 -6

10 -4

10 -2

10 0

10 2

Co

nce

ntr

atio

n o

f D

isso

lved

Met

al, (

mg

/L)

14 6 7 8 9 10 11 12 13

Equilibrium pH of brucite is 10.52 (more ideal)*

Equilibrium pH of Portlandite is 12.35

*Equilibrium pH’s in pure water, no other ions present. The solubility of toxic metal hydroxides is generally less in the range pH 10.52 -11.2 than at higher pH’s.

Equilibrium pH of PC CSH is 11.2

There is a 104 difference

All waste streams will contain heavy metals and a strategy for long term pH control is therefore essential


63

Tec-Cement Concretes - The Form of MgO Matters - Lattice Energy Destroys a Myth

Tec-Cement Concretes - The Form of MgO Matters - Lattice Energy Destroys a Myth

Magnesia, provided it is reactive rather than “dead burned” (or high density, crystalline periclase type), can be beneficially added to cements in excess of the amount of 5 mass% generally considered as the maximum allowable by standards prevalent in concrete dogma.– Reactive magnesia is essentially amorphous magnesia with low lattice

energy.– It is produced at low temperatures and finely ground, and– will completely hydrate in the same time order as the minerals contained

in most hydraulic cements. Dead burned magnesia and lime have high lattice energies

– Crystalline magnesium oxide or periclase has a calculated lattice energy of 3795 Kj mol-1 which must be overcome for it to go into solution or for reaction to occur.

– Dead burned magnesia is much less expansive than dead burned lime in a hydraulic binder (Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p 358-360 )


64

Tec-Cement ReactionsTec-Cement Reactions

MgO + 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 PC

MgO + 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??

We think the reactions are relatively independent of PC reactions


65

More Rapid and Greater Strength DevelopmentHigher Strength Binder Ratio

More Rapid and Greater Strength DevelopmentHigher Strength Binder Ratio

Early strength gain with less cement and added pozzolans is of great economic and environmental importance as it will allow the use of more pozzolans.

Tec – Cement Concrete with 10% reactive magnesia

OPC Concrete

HYPOTHETICAL TEC-CEMENT STRENGTH GAIN CURVE MPa

Log Days Plastic Stage

? ?

?

?

7 14 28 3

Concretes are more often than not made to strength. The use of tec-cement results in

– 15-30% more strength or less binder for the same strength.– more rapid early strength development even with added

pozzolans.– Straight line strength development for a long time

We have observed this sort of curve in over 500 cubic meters of concrete now


66

Tec-Cement Strength DevelopmentTec-Cement Strength Development3 14.365 18.095 19.669 5.5163 16.968 19.44 20.196 6.6569 19.466 20.877 13.39 3.4179 24.248 24.408 15.39 4.4349 29.03 27.939 17.39 5.451

21 24.54 35.037 25.493 11.99221 28.403 36.323 28.723 13.93321 32.266 37.609 31.953 15.874

TEC-CEMENT COMPRESSIVE STRENGTH

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12 14 16 18 20 22 24

CURING TIME (days)

ST

RE

NG

TH

( M

Pa

)

OPC(100%)

OPC(90%)+MgO(10%)

WHITTLESEA SLAB

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Days water cured

Str

eng

th,

MP

a

CompressiveStrength

Graphs above by Oxford Uni Student are for standard 1PC:3 aggregate mixes, w/c = .5

WHITTLESEA SLAB (A modified 20 mpa mix)

PC = 180 Kg / m3MgO = 15 Kg / m3Flyash = 65 Kg / m3

0

20

40

60

17 30 56 89

Days

MP

a

Sample 1Sample 2

Rate of strength development is of great interest to engineers and constructors


67

Reasons for Compressive Strength Development in Tec-Cements.Reasons for Compressive Strength Development in Tec-Cements.

Reactive magnesia increases plasticity and therefore should allow skilled operators to use less water.– We admit however that we have done little work with

plasticisers yet. Reactive magnesia requires considerable water to

hydrate resulting in:– Denser, less permeable concrete. Self compaction?– A significantly lower voids/paste ratio.

Higher early pH initiating more effective silicification reactions?– The Ca(OH)2 normally lost in bleed water is used internally for

reaction with pozzolans.– Super saturation of alkalis caused by the removal of water?

Brucite gains weight in excess of the theoretical increase due to MgO conversion to Mg(OH)2 in samples cured at 98% RH.

Dr Luc Vandepierre, Cambridge University, 20 September, 2005.


68

Reasons for Compressive Strength Development in Tec-Cements.Reasons for Compressive Strength Development in Tec-Cements.

Micro-structural strength due to particle packing Cement grains are around 2.5 times the size of magnesia in Australia at around 20 micron. (Magnesia particles at 5-9 micron roughly 2.5 times smaller, which Francois Larrard (1) maintains is a requirement for good packing.)

Formation of MgAl hydrates? Similar to flash set in concrete but slower??

Formation of MSH?? We do not think relevant. Slow release of water from hydrated Mg(OH)2.nH2O

supplying H2O for more complete hydration of C2S and C3S?

(1) de Larrard, F. (1999). Concrete Mixture Proportioning: A Scientific Approach, E & FN Spon.


69

Greater Tensile StrengthGreater Tensile Strength

MgO Changes Surface Charge as the Ph Rises. This could be one of the reasons for the greater tensile strength displayed during the early plastic phase of tec-cement concretes. The affect of additives is not yet known

0

1

2

3

4

5

6

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

CURING TIME (days)

STR

EN

GTH

(MP

a)

OPC(100%)

OPC(90%)+ MgO(10%)

+

+

+

+

++

+

+

+

+

+++

++

+

+

+

+

+Mutual Repulsion

=>

+

+

+

+++

+

+

+

+

+

++

+-

-

-

-

--

-

Ph 12 ?

Cement

Cement

MgO Sand

Sand

MgO

Mutual Repulsion

Mutual Attraction


70

Improved DurabilityImproved Durability

Reasons for Improved Durability:– Reduced shrinkage and Cracking– Greater Density = Lower

Permeability• Physical Weaknesses => Chemical

Attack• Chemical weaknesses

– Removal of Portlandite with the Pozzolanic Reaction.

• Removal of reactive components– Substitution by Brucite => Long

Term pH control• Reducing corrosion

DURABILITY

Durability is a very important property that is significantly improved with TecEco cements.

As Paul Hawkins says in his book, ‘The Ecology of Commerce’ something that is made with half as much energy and last twice as long is 80% more sustainable (1)

The main contributions or our technology are the removal of Portlandite and replacement with a much more stable alkali and reduced shrinkage and cracking.

(1) Hawken, P. (1993). The Ecology of Commerce. New York, HarperCollins


71

Durability. Shrinkage and CrackingDurability. Shrinkage and Cracking

Concretes are said to be less durable when they are physically or chemically compromised.

Physical factors can result in access to water and chemicals resulting in reactions reducing durability e.g.– Porosity and – Cracking due to shrinkage can allow reactive gases and liquids to

enter concrete. Chemical factors can result in physical outcomes reducing

durability e.g. – Reactivity of lime with aggressive agents such as chloride or sulphate– Alkali silica reaction opening up cracks allowing other agents such as

sulfate and chloride in seawater to enter.– Other reactions can also occur as a result of the pH being too high.

This presentation will describe benchmark improvements in durability as a result of using the new TecEco magnesia cement technologies


72

CrackingCracking

TecEco technology can reduce if not solve problems of cracking:– Related to (shrinkage) through open system loss of water.– As a result of volume change caused by delayed reactions– As a result of corrosion.– Related to autogenous shrinkage

Thermal

PlasticShrinkage

DryingShrinkage

Corrosion Related

Freeze Thaw D Cracks

StructuralSettlement Shrinkage

Photos from PCA and US Dept. Ag Websites

Autogenous or self-desiccation shrinkage(usually related to stoichiometric or chemical shrinkage)

Alkali aggregateReaction

EvaporativeCrazingShrinkage


73

Causes of Cracking in ConcreteCauses of Cracking in Concrete

Cracking commonly occurs when the induced stress exceeds the maximum tensile stress capacity of concrete and can be caused by many factors including restraint, extrinsic loads, lack of support, poor design, volume changes over time, temperature dependent volume change, corrosion or delayed reactions.

Causes of induced stresses include:– Restrained thermal, plastic, drying and stoichiometric shrinkage, corrosion

and delayed reaction strains.– Slab curling.– Loading on concrete structures.

Cracking is undesirable for many reasons– Visible cracking is unsightly– Cracking compromises durability because it allows entry of gases and ions

that react with Portlandite.– Cracking can compromise structural integrity, particularly if it accelerates

corrosion.


74

Graphic Illustration of CrackingGraphic Illustration of Cracking

Combined Effect of Concrete Volume Change (Example Only)

-50

0

50

100

150

200

250

0 12 24 36 48 60 72 84 96 108

120

Time since Cast (Hrs)

Sh

rin

kag

e/(E

xpan

sio

n)

Mic

rost

rain

Max Tensile Strain

Temperature effect

Drying Shrinkage

Autogenous Shrinkage

Total Srain Induced

Total Strain Less Creep

After Tony Thomas (Boral Ltd.) (Thomas 2005)

Autogenous shrinkage has been used to refer to hydration shrinkage and is thus stoichiometric


75

Cracking due to Loss of WaterCracking due to Loss of Water

DryingShrinkage

PlasticShrinkage

Picture from: http://www.pavement.com/techserv/ACI-GlobalWarming.PDF

EvaporativeCrazingShrinkage

Settlement Shrinkage

We may not be able to prevent too much water being added to concrete by fools.TecEco approach the problem in a different way by providing for the internal removal/storage of water that can provide for more complete hydration of PC.

Brucite gains weight in excess of the theoretical increase due to MgO conversion to Mg(OH)2 in samples cured at 98% RH.

Dr Luc Vandepierre, Cambridge University, 20 September, 2005.

Bucket of Water

Fool


76

Solving Cracking due to Shrinkage from Loss of Water

Solving Cracking due to Shrinkage from Loss of Water

In the system water plus Portland cement powder plus aggregates shrinkage is in the order of .05 – 1.5 %.

Shrinkage causes cracking There are two main causes of Portland cements shrinking over

time.– Stoichiometric (chemical) shrinkage and

– Shrinkage through loss of water. The solution is to:

– Add minerals that fill voids preventing shrinkage or compensate by stoichiometrically expanding and/or to

– Use less water, internally hold water or prevent water loss. TecEco tec-cements internally hold water and prevent water

loss.

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)


77

When magnesia hydrates it consumes 18 litres of water per mole of magnesia probably more depending on the value of n in the reaction below:

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s) The dimensional change in the system MgO + PC depends on:

– The ratio of MgO to PC– Whether water required for hydration of PC and MgO is coming from

stoichiometric mix water (i.e. the amount calculated as required), excess water (bleed or evaporative) or from outside the system.

– In practice tec-cement systems are more closed and thus dimensional change is more a function of the ratio of MgO to PC

As a result of preventing the loss of water by closing the system together with possible expansive stoichiometry of MgO reactions (depending on where the water is coming from see below).

MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)40.31 + 18.0 ↔ 58.3 molar mass (at least!)

11.2 + liquid ↔ 24.3 molar volumes (at least!) It is possible to significantly reduce if not prevent (drying, plastic,

evaporative and some settlement) shrinkage as a result of water losses from the system.

The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density (g.L-1).

Preventing Shrinkage through Loss of WaterPreventing Shrinkage through Loss of Water


78

With TecEco Tec-Cements it is important to take advantage of the increased plasticity to add less water so the water for hydration of magnesia is substantially coming from the excess water added to concretes to fluidise them.

Portland cements stoichiometrically require around 23 -27% water for hydration yet we add approximately 45 to 60% at cement batching plants to fluidise the mix sufficiently for placement.

If it were not for the enormous consumption of water by tri calcium aluminate as it hydrates forming ettringite in the presence of gypsum, concrete would remain as a weak mush and probably never set.– 26 moles of water are consumed per mole of tri calcium aluminate to from a

mole of solid ettringite. When the ettringite later reacts with remaining tri calcium aluminate to form monosulfoaluminate hydrate a further 4 moles of water are consumed.

The addition of reactive MgO achieves water removal internally in a closed system in a similar way.

Preventing Shrinkage through Loss of WaterPreventing Shrinkage through Loss of Water



79

Other Benefits of Preventing Shrinkage through Loss of Water

Other Benefits of Preventing Shrinkage through Loss of Water

Internal water consumption also results in:– Greater strength

• More complete hydration of PC .• Reduced in situ voids:paste ratio

– Greater density• Increased durability• Higher short term alkalinity• More effective pozzolanic reactions.

More complete hydration of PC .– Small substitutions of PC by MgO result in water being trapped

inside concrete as Brucite and Brucite hydrates which can later self desiccate delivering water to hydration reactions of calcium silicates (Preventing so called “Autogenous” shrinkage).


80

Bleeding is a Bad ThingBleeding is a Bad Thing Bleeding is caused by:

– Lack of fines– Too much water

Bleeding can be fixed by:– Reducing water or adding fines– Air entrainment or grading adjustments

Bleeding causes:– Reduced pumpability– Loss of cement near the surface of concretes– Delays in finishing– Poor bond between layers of concrete– Interconnected pore structures that allow aggressive agents to enter later– Slump and plastic cracking due to loss of volume from the system– Loss of alkali that should remain in the system for better pozzolanic

reactions– Loss of pollutants such as heavy metals if wastes are being incorporated.

Concrete is better as a closed system

Better to keep concretes as closed systems


81

Dimensional Control in Tec-Cement Concretes over Time

Dimensional Control in Tec-Cement Concretes over Time

By adding MgO volume changes are minimised to close to neutral.– So far we have observed significantly less shrinkage in

TecEco tec - cement concretes with about (8-10% substitution OPC) with or without fly ash.

– At some ratio, thought to be around 15-18% reactive magnesia there is no shrinkage.

– The water lost by concrete as it shrinks is used by the reactive magnesia as it hydrates eliminating shrinkage.

Note that brucite is > 44.65 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.


82

Reducing Cracking as a Result of Volume Change caused by Delayed Reactions

Reducing Cracking as a Result of Volume Change caused by Delayed Reactions

Photo Courtesy Ahmad Shayan ARRBAn Alkali Aggregate Reaction Cracked Bridge Element


83

Types of Delayed ReactionsTypes of Delayed Reactions

There are several types of delayed reactions that cause volume changes (generally expansion) and cracking.– Alkali silica reactions– Alkali carbonate reactions– Delayed ettringite formation– Delayed thaumasite formation– Delayed hydration or dead burned lime or periclase.– Other delayed reactions with aggregates

Delayed reactions cause dimensional distress, cracking and possibly even failure.


84

Reducing Delayed ReactionsReducing Delayed Reactions

Delayed reactions do not appear to occur to the same extent in TecEco cements.– A lower long term pH results in reduced reactivity after the

plastic stage.– Potentially reactive ions are trapped in the structure of

brucite.– Ordinary Portland cement concretes can take years to dry

out however the reactive magnesia in Tec-cement concretes consumes unbound water from the pores inside concrete.

– Magnesia dries concrete out from the inside. Reactions do not occur without water.


85

Reduced Steel Corrosion Related CrackingReduced Steel Corrosion Related Cracking

Steel remains protected with a passive oxide coating of Fe3O4 above pH 8.9.– A pH of over 8.9 is maintained by the equilibria

Mg(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)2

Ca(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.

Rusting Causes Dimensional Distress


86

Reduced Steel CorrosionReduced Steel Corrosion

Brucite is less soluble and traps salts as it forms resulting in less ionic transport to complete a circuit for electrolysis and less corrosion.

Free chlorides and sulfates originally in cement and aggregates are bound by magnesium– Magnesium oxychlorides or oxysulfates are formed.

( Compatible phases in hydraulic binders that are stable provided the concrete is dense and water kept out.)

As a result of the above the rusting of reinforcement does not proceed to the same extent.

Cracking or spalling due to rust does not occur


87

Long Term pH controlLong Term pH control TecEco add reactive magnesia which hydrates forming brucite

which is another alkali, but much less soluble, mobile or reactive than Portlandite.

Brucite provides long term pH control at a lower level in Tec-Cement concretes, but still sufficiently high to prevent corrosion of steel reinforcing .

13.7

pH

Log Time

10.5

Tec – Cement Concrete with 10% reactive magnesia (red). Ph maintained by brucite

OPC Concrete

HYPOTHETICAL pH CURVES OVER TIME (with fly ash)

Plastic Stage

? ?

?

Tec-Cement (red) - more affective pozzolanic reactions

11.2

OPC Concrete – Lower long term pH due to consumption of lime and carbonation

Surface hydrolysis and more polymeric species?

A pH in the range 10.5 (the equilibrium pH of brucite and 11.2 (the equilibrium pH of CSH) is ideal in a concrete


88

Steel Corrosion is Influenced by Long Term pHSteel Corrosion is Influenced by Long Term pH

Eh-pH or Pourbaix Diagram The stability fields of hematite, magnetite and sideritein aqueous solution; total dissolved carbonate = 10-2M.

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 Fe3O4 stable in reducing conditions.

Steel corrodes below 8.9

Equilibrium pH of Brucite and of lime


89

Reducing Cracking Related to Autogenous ShrinkageReducing Cracking Related to Autogenous Shrinkage

Autogenous shrinkage tends to occur in high performance concretes in which dense microstructures develop quickly preventing the entry of additional water required to complete hydration.– First defined by Lynam in 1934 (Lynam CG. Growth and movement in

Portland cement concrete. London: Oxford University Press; 1934. p. 26-7.)

The autogenous deformation of concrete is defined as the unrestrained, bulk deformation that occurs when concrete is kept sealed and at a constant temperature.


90


The main cause of autogenous shrinkage is stoichiometric or chemical shrinkage as observed by Le Chatelier.– whereby the reaction products formed during the hydration of

cement occupy less space than the corresponding reactants.

A dense cement paste hydrating under sealed conditions will therefore self-desiccate creating empty pores within developing structure. If external water is not available to fill these “empty” pores, considerable shrinkage can result.

Le Chatelier H. Sur les changements de volume qui accompagnent Ie durcissement des ciments. Bulletin de la Societe d'Encouragement pour I'Industrie Nationale 1900:54-7.


91


Autogenous shrinkage should not occur in high strength tec-cement concretes because:– The brucite hydrates that form desiccate back to brucite delivering water in

situ for more complete hydration of Portland cement.

Mg(OH)2.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).


40.31 + 18.0 ↔ 58.3 molar mass (at least!)

11.2 + liquid ↔ 24.3 molar volumes (at least 116% expansion, probably more initially before desiccation as above!)


92

Reduced PermeabilityReduced 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 SO4

--, Cl- and CO2 TecEco tec - cement concretes are a closed

system. They do not bleed as excess water is consumed by the hydration of magnesia.– As a result TecEco tec - cement concretes dry

from within, are denser and less permeable and therefore stronger more durable and less permeable. Cement powder is not lost near the surfaces. Tec-cements have a higher salt resistance and less corrosion of steel etc.

The magnesia component of TecEco cements will always carbonate near the surface of concretes and because of the high mass of hydrated carbonates that forms, expansion will seal that surface.– On carbonation to nesquehonite brucite expands

307% sealing the surface.


93

Concretes have a high percentage (around 18% – 22%) of voids.

On hydration magnesia expands >=116.9 % filling voids and surrounding hydrating cement grains => denser concrete.

Lower voids:paste ratios than water:binder ratios result in little or no bleed water, lower permeability and greater density.

Greater Density – Lower PermeabilityGreater Density – Lower Permeability


94

Densification During the Plastic PhaseDensification During the Plastic Phase

Water

Observable Characteristic

Relevant Fundamental

Binder + supplementary cementitious materials

High water for ease of placement

Less water for strength and durability

Variables such as % hydration of mineral, density, compaction, % mineral H20 etc.

Consumption of water during plastic stage Voids

Hydrated Binder Materials

Unhydrated Binder

Less water results in increased density and concentration and early reaction of alkalis - less shrinkage and cracking and improved strength and durability.

Water is required to plasticise concrete for placement, however once placed, the less water over the amount required for hydration the better. Magnesia consumes water as it hydrates producing solid material.


95

Brucite has always played a protective role during salt attack. Putting it in the matrix of concretes in the first place makes sense.

Brucite does not react with salts because it has a lower pH and is a least 5 orders of magnitude less soluble, mobile or reactive. – Ksp brucite = 1.8 X 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 AttackDurability - Reduced Salt & Acid Attack


96

Less Freeze - Thaw ProblemsLess 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) + H2O (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 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 concretes TecEco concretes are not attacked by the salts used on roads


97

Rosendale Concretes – Proof of DurabilityRosendale Concretes – Proof of Durability

Rosendale cements contained 14 – 30% MgO A major structure built with Rosendale cements commenced in 1846 was Fort Jefferson

near key west in Florida. Rosendale cements were recognized for their exceptional durability, even under severe

exposure. At Fort Jefferson much of the 150 year-old Rosendale cement mortar remains in excellent condition, in spite of the severe ocean exposure and over 100 years of neglect. Fort Jefferson is nearly a half mile in circumference and has a total lack of expansion joints, yet shows no signs of cracking or stress. The first phase of a major restoration is currently in progress.

More information from http://www.rosendalecement.net/rosendale_natural_cement_.html


98

Easier to Finish ConcretesEasier to Finish Concretes

Easier to pump and finish concretes are likely to have less water added to them resulting in less cracking


99

Shear Thinning RheologyShear Thinning Rheology

O

O

O

O Mg++

+

- +

+

+

+

+

+

+

+

+

O +

+

+

+

+

+

O

O O

- -

- -

-

-

The strongly positively charged small Mg++ ions attract water (which is polar) in deep layers introduce a shear thinning property affecting the rheological properties and making concretes less “sticky” with added pozzolan

It is not known how deep these layers get

Etc.

Etc.

Ca++ = 114, Mg++ = 86 picometres


100

Understanding Water - Bingham Plastic RheologyUnderstanding Water - Bingham Plastic Rheology

TecEco concretes and mortars are:– Very homogenous and do not segregate easily.– Exhibit good adhesion and have a shear thinning property.– Exhibit Bingham plastic qualities and– React well to energy input displaying good workability

TecEco concretes with the same water/binder ratio have a lower slump but greater plasticity and workability.

TecEco tec-cements are potentially suitable for mortars, renders, patch cements, colour coatings, pumpable and self compacting concretes.

A range of pumpable composites with Bingham plastic properties will be required in the future as buildings will be “printed.”

Second layer low slump tec-cement concrete Tech Tendons

First layer low slump tec-cement concrete

Date post:	15-May-2015
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Materials and Molecules - Behind What You See

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