Roads as Routes to the Future
- Porous Pavement and Other Innovations
TecEco are in the
biggest business
on the planet –
that of solving
global warming
waste and water
problems
Presentation by John
Harrison, managing director
of TecEco and inventor of
Tec and Eco-Cements and
the CarbonSafe process.
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 downloadable from www.tececo.com
1
We have a Planet in Crisis
 In the next 50 years many issues will become
critical:
–
–
–
–
Fresh Water
Global warming
Energy
Waste &
Pollution
– Top soils
– Logistics
This presentation discusses roads. Attempts to point
out where we are going wrong and rethink their
purpose hollistically.
Presentation downloadable from www.tececo.com
2
Fresh Water
 The amount of water in the world is finite. The
number of us is growing quickly and our water use is
growing more quickly.
 A third of the world's population lives in waterstressed countries. By 2025, this is expected to rise
to two-thirds.
 The world's supply of fresh water is running out.
Already one person in five has no access to safe
drinking water.
 Australians are talking about 3 de-salination or deputrification plants yet millions of litres are captured
by our streets and drained away every day.
Presentation downloadable from www.tececo.com
3
Salination of Water
 De-afforestation, agriculture, irrigation, salination,
desertification.
– Is a sequence we seem unable to learn from history to stop.
– It destroyed the fertile crescent and it will destroy much of
Australia’s rivers and agriculture.
Presentation downloadable from www.tececo.com
4
Waste & Pollution
There are various estimates, but globally we produce about 5600 million tonnes of waste each year.
Waste can cause ill health in an
area, leads to the contamination of
land, underground water, streams
and coastal waters (destroying our
fisheries) and gives rise to various
nuisances including increased
traffic, noise, odours, smoke, dust,
litter and pests.
Most damaging is the release of
dangerous molecules to the global
commons.
Presentation downloadable from www.tececo.com
5
Our Road Network
Roads are the veins, arteries and
lymphatic system of cities.
They provide
– The network for
• The transport of resources and wastes
• Drainage
– The route for all services
•
•
•
•
•
Water
Sewerage
Electricity
Gas
Telephone etc.
Presentation downloadable from www.tececo.com
6
Mayhem?
 Roads and associated services as they are today have
not been thought out. They have evolved.
 In the past the agencies that are responsible for these
networks and services have more or less acted
independently of each other resulting in
– Wasted Resources
– Additional Cost
 How often do you see different crews digging up the
same bit of road?
– This is not sustainable!
You never change things by fighting the
existing reality. To change something, build
a new model that makes the existing model
obsolete. – Buckminster Fuller
Presentation downloadable from www.tececo.com
7
Thinking is Supposed to Distinguish us from Other Animals
 The engineering paradigm too prevalent amongst the road
building fraternity is:
– “Roads are for vehicles” “water on roads in dangerous” “collect it and
get rid of it as quickly as possible”
 Given the current water crisis can this limited thinking be
allowed to continue?
 Only a small % of water reticulated through a community is
used for drinking.
– Most is used for washing, laundry, flushing toilets or watering gardens.
 Perhaps the water caught by our road drainage systems
could be used for these purposes.
Presentation downloadable from www.tececo.com
8
Duplication?
 In Australia we run many duplicate services down each
side of a road. Given the high cost of installing
infrastructure it would be smarter to adopt a system
whereby services run down the middle of a road down
what amount to giant box culverts.
– Adding services is easy
• And not involve digging up the whole road
– Repair and maintenance would be easier
• And cost much less
Presentation downloadable from www.tececo.com
9
Hollistically Designed Roads
Conventional
bitumen or
concrete footpath
pavement
Foamed concrete
root redirectors
and pavement
protectors
Porous ecocement concrete
pavement surface
using recycled
aggregates
Possible leakage
to street trees
and underground
aquifers
Services to either
side of the road.
All in same trench
of conduit
Service conduit
down middle of
road
Impermeable
layer (concrete or
plastic liner)
angling for main
flow towards
collection drains
Porous gravel
under for
collection,
cleansing and
storage of water
Collection drains to
transport drain or
pipe in service
conduit at intervals
Its time for a road re think!
Presentation downloadable from www.tececo.com
10
Collecting Water Using Porous Pavement
 An unknown but huge quantity of water is drained away to sea
taking with it polluting substances and articles every time it
rains on our cities.
 This rapid drainage or rain requires a high cost of investment
in much larger drains than the original natural drainage
replaced because water no longer percolates through natural
vegetation and obstacles.
– In urban and some agricultural areas water gets to the sea in hours not
days!
 This water could be collected by permeable roads also acting
as giant water filters, subterranean reservoirs (the city of
Alexandria had huge underground cisterns over 2000 years
ago) and collection and redistribution network.
 An essential component of this paradigm is porous pavement.
Presentation downloadable from www.tececo.com
11
Permeable or Porous Pavement
 Porous pavement is a permeable pavement surface with a stone
reservoir underneath. The reservoir temporarily stores surface runoff
before infiltrating it into the subsoil or sub-surface drainage and in
the process improves the water quality. Porous materials such as
ancient lime mortars and porous pavements are made using relatively
mono graded materials. In the case of porous pavement this
translates as a lack of "fine" materials. No fines concrete or under
asphalted gravel are names for common materials used.
 Porous pavements allow the earth to breathe, take in water and be
healthy. The stone and soil under them acts as a reservoir and cleans
the water just like the filter on a fish tank. They are safer to drive on
as they do not develop "puddles", have a good surface to grip and
importantly, in Australia, some parts of the US and many other places
in the world subdivisions made with porous pavement that also have
street trees can be several degrees cooler than surrounding suburbs
without.
Presentation downloadable from www.tececo.com
12
The First Eco-Cement Porous Pavement
TecEco's first practical
test (to the right) has now
been improved
dramatically (see next
slide) as too much water
was used tending to wash
the paste off a mono
sized aggregate. We now
make the paste a little
stickier by adding fly ash
and one or two other
additives in small
quantities as the aim is to
emulate the manufacture
of chocolate coated
peanuts or raisins on a
very hot day whereby
they stick together.
(Yum!)
Presentation downloadable from www.tececo.com
13
Eco-Cement Porous Pavement Made with Re-Cycled Aggregate
=> Porous Pavement
Allow many mega
litres of good fresh
water to become
contaminated by the
pollutants on our
streets and pollute
coastal waterways
Or
Capture and cleanse
the water for our use?
TecEco have now perfected porous pavements that can be made
out of mono-graded recycled aggregates and other wastes.
Presentation downloadable from www.tececo.com
14
Purifying Water
 Porous pavements filter water falling on them releasing
it slowly to sub-surface drains or aquifers and finally the
sea. There is little or now surface run-off to carry
rubbish into drains and streams.
 Water quality is purified by the sub-pavement acting as a
giant biofiliter allowing bacteria and oxygen to do their
work and because surface rubbish does not contaminate
it.
Presentation downloadable from www.tececo.com
15
Porous Pavements - An Opportunity for Sustainability
 In years gone by 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 now seriously being considered by
enlightened engineers around the world as a way of reducing runoff and improving safety. TecEco believe they are essential for our
long term survival on this planet.
 Proponents claim that porous pavements reduce the overloading
of our present drainage system, cleanse water before it enters
aquifers or streams and rivers, improve safety, reduce
maintenance on buildings due to seasonal ground movement and
reduce the costs of watering street trees.
Presentation downloadable from www.tececo.com
16
Advantages of Porous Pavement (1)
 Reduced volume and rate of runoff
– Porous pavement would allow the replenishment of aquifers and reduced the
cost of infrastructure to carry water out to sea as the volume and rate of flow
would be less. Not as many pollutants, rubbish and debris would be transported
reducing waterway pollution.
 Cleaner water - less pollution
– A porous pavement with integral bacteria would improve water quality entering
aquifers, streams and rivers. The critical "first flush" of pollutants would be sent
rapidly into the cross-section where constantly available sources of bacteria and
microbes exist and have sufficient air exchange capability to maintain themselves
and perform their cleaning functions. Porous pavements could act as both
pavements and bio-filters at the same time.
 Improved Pavement Safety
– Water penetrates through porous pavements quickly leaving drier and safer
surfaces with no standing water.
– Drier pavements have the obvious effect of increasing friction between shoes or
tyres and the foot, cycle path or road surface in wet weather and at the same
time reducing road noise and spray, improving visibility.
– Pavements are safer because they are not lubricated with a film of water flowing
across the upper surface to the edge drains. As water does not tend to collect,
sheet ice problems should be less in colder climates.
Presentation downloadable from www.tececo.com
17
Advantages of Porous Pavement (2)
 Less Maintenance
– Aquifers would be more regularly replenished resulting in less variable
ground moisture content, reduced ground movement with wet dry cycles
and less maintenance on buildings and infrastructure.
 Less Watering
– A permeable surface will allow water to penetrate to street trees reducing
the need for watering during dry periods and saving money.
 Durability
– Porous pavements made with TecEco Eco-Cements would not be attacked
by salts and would last considerably longer that conventional binders such
as bitumen ( in some countries referred to as asphalt) and Portland cement.
 Sustainability
– Porous pavements made with TecEco Eco-Cements would utilise a
considerable proportion of wastes such as fly ash and as they would
carbonate, provide substantial abatement. Water entering aquifers, streams
and rivers would be of higher quality and carry less macro pollutants. Fresh
water replenishment of aquifers would reduce salinity and reverse falling
water tables.
Presentation downloadable from www.tececo.com
18
Disadvantages Myths and Research(2)
 The Clogging Myth - Stopping Common Sense to Prevail?
– The experience of many engineers is that with relatively minor
control and maintenance clogging will not reduce the infiltration
rate below a design rate within the lifecycle of the pavement.
Like any other kind of surface, porous pavements have to be
swept periodically to remove debris and water under pressure
can be used.
 Research
– TecEco are looking for governements/research institutions around
the world interested in laying down experimental roads using EcoCement porous pavements and then monitoring run-off, water
quality etc.
Presentation downloadable from www.tececo.com
19
Porous Pavement as Carbon and Waste Sinks?
 With the invention of eco-cements porous pavements can also act
as carbon sinks and be made using waste materials.
– TecEco eco-cements set by absorbing carbon dioxide out of the air and will
therefore set in porous pavement.
– If made with carbon capture as TecEco propose then our roads could become
giant carbon sinks
– Wastes such as mono-graded crushed used build materials and waste
recycled aggregates can easily be used
 Several environmental issues would be addressed at once including
water quality, replenishment of aquifers, "hot city syndrome"
atmospheric carbon reduction and waste.
 If you want to know more about porous pavement go to TecEco
newsletters 29, 35 and 42. A good website about managing
stormwater using porous pavement is to be found at
http://www.greenworks.tv/stormwater/porouspavement.htm
Presentation downloadable from www.tececo.com
20
Making Porous Pavement
 Ideally a porous pavement should be made with mono-graded
stone aggregates and a binder and be similar to asphalt or
concrete to handle and install.
– In cold areas it is important that the pavement should not trap water
otherwise in winter the water would freeze and cause cracking.
– It is also important to detail a porous structural base and sub base for
the pavement that has a high void ratio as this acts as a reservoir, and
provide underground drainage as required.
Eco-Cement Porous
Pavement
Set by absorbing CO2
Can use recycled materials as long
as they are hard and mono-graded
Asphalt
Carcenogenic to workers using it.
Becoming more expensive as
petroleum supplies dwindle.
Presentation downloadable from www.tececo.com
21
Hot City Syndrome and Porous Pavement
 Ever walked up a pebble beach on a hot sunny day? The heat
held by the stones can be unbearable! It’s the same in large
cities. There are so many materials with high specific heat
that during hot sunny weather and with no natural
transpiration, due to the fact that we have paved all the
ground, large cities just get hotter and hotter.
 As architects, engineers and designers of cities we need to
come to grips with the macro impacts of the materials we
use. Hot city syndrome is one of a number of man made
phenomena that the use of porous Eco-Cement pavements
will reduce. The solution is to let the ground breathe and
porous pavements do this. Evaporation after all is still the
principle behind many cooling systems – so why do we pave
the ground and prevent moisture entering or exiting?
Presentation downloadable from www.tececo.com
22
We Must Learn from Nature (Biomimicry)
 Nature is very efficient. The waste from one plant or animal is
the food or home for another.
 By studying Nature we learn who we are, what we are and
how we are to be.” (Wright, F.L. 1957:269)
 In nature photosynthesis balances respiration.
 We have nothing that balances our emissions in the technoprocess
 There is a strong need for similar efficiency and balance
By learning from
Nature we can all
live together
Presentation downloadable from www.tececo.com
23
Biomimicry
 The term biomimicry was popularised by the book of
the same name written by Janine Benyus
 Biomimicry is a method of solving problems that uses
natural processes and systems as a source of
knowledge and inspiration.
 It involves nature as model, measure and mentor.
The theory behind biomimicry is that natural processes
and systems have evolved over several billion years
through a process of research and development
commonly referred to as evolution. A reoccurring theme
in natural systems is the cyclical flow of matter in such a
way that there is no waste of matter or energy.
Nature is very economical about all Processes.
We must also be MUCH more economical
Presentation downloadable from www.tececo.com
24
Re - Engineering Materials – What we Build With
Environmental
problems are
the result of
inherently
flawed
materials,
materials flows
and energy
systems
 To solve environmental problems
we need to understand more
about materials in relation to the
environment.
– the way their precursors are derived and
their degradation products re assimilated
• and how we can reduce the impact of
these processes
– what energies drive the evolution,
devolution and flow of materials
• and how we can reduce these energies
– how materials impact on lifetime energies
 With the knowledge gained redesign materials to not only be
more sustainable but more
sustainable in use
Presentation downloadable from www.tececo.com
25
Huge Potential for Sustainable Materials
Reducing the impact of the take and
waste phases of the techno-process.
– including carbon in materials
they are potentially carbon sinks.
– including wastes for
physical properties as
well as chemical composition C
they become resources.
Waste
– re – engineering
materials to
reduce the lifetime C
energy
C
Many wastes can
contribute to
physical properties
reducing lifetime
energies
C
Waste
C
Presentation downloadable from www.tececo.com
26
Utilizing Carbon and Wastes (Biomimicry)
 During earth's geological history large tonnages of
carbon were put away as limestone and other
carbonates and as coal and petroleum by the activity of
plants and animals.
 Sequestering carbon in magnesium binders and
aggregates in the built environment mimics nature in that
carbon is used in the homes or skeletal structures of
most plants and animals.
We all use carbon and wastes to
make our homes! “Biomimicry”
In eco-cement blocks
and mortars the
binder is carbonate
and the aggregates
are preferably wastes
Presentation downloadable from www.tececo.com
27
Biomimicry - Ultimate Recyclers
 As peak oil looms and the price of transport is
set to rise sharply
– We should not just be recycling based on chemical property
requiring sophisticated equipment and resources
– We should be including wastes based on physical properties
as well as chemical composition in composites whereby they
become local resources.
The Jackdaw recycles all sorts of things it finds nearby based on physical
property.
The bird is not concerned about chemical composition and the nest it
makes could be described as a composite material.
TecEco cements are benign binders
that can incorporate all sort of wastes
without reaction problems. We can
do the same as the Jackdoor
Presentation downloadable from www.tececo.com
28
TecEco Formulations
 Tec-cements (5-15% MgO, 85-95% OPC)
– contain more Portland cement than reactive magnesia. Reactive magnesia
hydrates in the same rate order as Portland cement forming Brucite which uses
up water reducing the voids:paste ratio, increasing density and possibly raising
the short term pH.
– Reactions with pozzolans are more affective. After all the Portlandite has been
consumed Brucite controls the long term pH which is lower and due to it’s low
solubility, mobility and reactivity results in greater durability.
– Other benefits include improvements in density, strength and rheology, reduced
permeability and shrinkage and the use of a wider range of aggregates many of
which are potentially wastes without reaction problems.
 Eco-cements (15-95% MgO, 85-5% OPC)
– contain more reactive magnesia than in tec-cements. Brucite in porous
materials carbonates forming stronger fibrous mineral carbonates and therefore
presenting huge opportunities for waste utilisation and sequestration.
 Enviro-cements (5-15% MgO, 85-95% OPC)
– contain similar ratios of MgO and OPC to eco-cements but in non porous
concretes brucite does not carbonate readily.
– Higher proportions of magnesia are most suited to toxic and hazardous waste
immobilisation and when durability is required. Strength is not developed
quickly nor to the same extent.
Presentation downloadable from www.tececo.com
29
Tec & Eco-Cement Theory
 Many Engineering Issues are Actually
Mineralogical Issues
– Problems with Portland cement concretes are usually resolved
by the “band aid” engineering fixes. e.g.
• Use of calcium nitrite, silanes, cathodic protection or stainless steel
to prevent corrosion.
• Use of coatings to prevent carbonation.
• Crack control joins to mitigate the affects of shrinkage cracking.
• Plasticisers to improve workability.
– Portlandite and water are the weakness of concrete
• TecEco remove Portlandite it and replacing it with magnesia which
hydrates to Brucite.
• The hydration of magnesia consumes significant water
Presentation downloadable from www.tececo.com
30
Tec & 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
Presentation downloadable from www.tececo.com
31
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 raise the early Ph.
– Increasing non hydraulic strength giving reactions
 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
32
Strength with Blend & Porosity
150
Tec-cement concretes
100
Eco-cement concretes
50
High OPC
Enviro-cement
concretes
STRENGTH ON
ARBITARY SCALE 1-100
100-150
50-100
0-50
0 High Porosity
High Magnesia
Presentation downloadable from www.tececo.com
33
Solving Waste & Logistics Problems
 TecEco cementitious composites represent a cost affective option
for
– using non traditional aggregates from on site reducing transports costs and
emissions
– use and immobilisation of waste.
 Because they have
– lower reactivity
• less water
• lower pH
– Reduced solubility of heavy metals
• less mobile salts
– greater durability.
• denser.
• impermeable (tec-cements).
• dimensionally more stable with less shrinkage and cracking.
– homogenous.
– no bleed water.
TecEco Technology - Converting Waste to Resource
Presentation downloadable from www.tececo.com
34
Eco-Cements
 Eco-cements are similar but potentially superior to lime mortars
because:
– The calcination phase of the magnesium thermodynamic cycle takes
place at a much lower temperature and is therefore more efficient.
– Magnesium minerals are generally more fibrous and acicular than calcium
minerals and hence add microstructural strength.
 Water forms part of the binder minerals that forming making the
cement component go further. In terms of binder produced for
starting material in cement, eco-cements are much more
efficient.
 Magnesium hydroxide in particular and to some extent the
carbonates are less reactive and mobile and thus much more
durable.
Presentation downloadable from www.tececo.com
35
Eco-Cements
 Have high proportions of reactive magnesium oxide
 Carbonate like lime
 Generally used in a 1:5-1:12 paste basis because much more
carbonate “binder” is produced than with lime
MgO + H2O <=> Mg(OH)2
Mostly CO2
and water
Mg(OH)2 + CO2 + H2O <=> MgCO3.3H2O
58.31 + 44.01 <=> 138.32 molar mass (at least!)
24.29 + gas <=> 74.77 molar volumes (at least!)
 307 % expansion (less water volume reduction) producing much
more binder per mole of MgO than lime (around 8 times)
 Carbonates tend to be fibrous adding significant micro
structural strength compared to lime
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”.
Presentation downloadable from www.tececo.com
36
CO2 Abatement in Eco-Cements
For 85 wt%
Aggregates
15 wt%
Cement
Eco-cements in
porous products
absorb carbon
dioxide from the
atmosphere.
Brucite carbonates
forming lansfordite,
nesquehonite and
an amorphous
phase, completing
the thermodynamic
cycle.
Portland
Cements
15 mass%
Portland
cement, 85
mass%
aggregate
Emissions
.32 tonnes to
the tonne.
After
carbonation.
Approximately
.299 tonne to
the tonne.
No
Capture
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.37 tonnes to
the tonne. After
carbonation.
approximately
.241 tonne to
the tonne.
Capture
CO2
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.25 tonnes to the
tonne. After
carbonation.
approximately
.140 tonne to
the tonne.
Capture
CO2. Fly and
Bottom Ash
11.25% mass%
reactive magnesia,
3.75 mass%
Portland cement,
85 mass%
aggregate.
Emissions
.126 tonnes to the
tonne. After
carbonation.
Approximately .113
tonne to the tonne.
Greater Sustainability
.299 > .241 >.140 >.113
Bricks, blocks, pavers, mortars and pavement made using eco-cement, fly
and bottom ash (with capture of CO2 during manufacture of reactive
magnesia) have 2.65 times less emissions than if they were made with
Portland cement.
Presentation downloadable from www.tececo.com
37
Eco-Cement Strength Development
 Eco-cements gain early strength from the hydration of
PC.
 Later strength comes from the carbonation of brucite
forming an amorphous phase, lansfordite and
nesquehonite.
 Strength gain in eco-cements is mainly microstructural
because of
– More ideal particle packing (Brucite particles at 4-5 micron are
under half the size of cement grains.)
– The natural fibrous and acicular shape of magnesium carbonate
minerals which tend to lock together.
 More binder is formed than with calcium
– Total volumetric expansion from magnesium oxide to lansfordite
From air and water
is for example volume 811%.
Mg(OH)2 + CO2  MgCO3.5H2O
Presentation downloadable from www.tececo.com
38
Eco-Cement Strength Gain Curve
HYPOTHETICAL STRENGTH
GAIN CURVE OVER TIME
(Pozzolans added)
MPa
?
OPC Concrete
?
Eco – Cement Concrete with
50% reactive magnesia
?
?
3
Plastic
Stage
7
14
28
Log Days
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
39
Chemistry of Eco-Cements
 There are a number of carbonates of magnesium. The main ones
appear to be an amorphous phase, lansfordite and nesquehonite.
 The carbonation of magnesium hydroxide does not proceed as readily
as that of calcium hydroxide.
– Gor Brucite to nesquehonite = - 38.73 kJ.mol-1
– Compare to Gor Portlandite to calcite = -64.62 kJ.mol-1
 The dehydration of nesquehonite to form magnesite is not favoured by
simple thermodynamics but may occur in the long term under the right
conditions.
 Gor nesquehonite to magnesite = 8.56 kJ.mol-1
– But kinetically driven by desiccation during drying.
 Reactive magnesia can carbonate in dry conditions – so keep bags
sealed!
 For a full discussion of the thermodynamics see our technical
documents.
TecEco technical documents on the web
cover the important aspects of carbonation.
Presentation downloadable from www.tececo.com
40
Eco-Cement Reactions
In Eco - Cements
Magnesia
Amorphous Lansfordite
Brucite
Nesquehonite
MgO + nH2O  Mg(OH)2.nH2O + CO2  MgCO3.nH2O + MgCO3.5H2O + MgCO3.3H2O
Form: Massive-Sometimes Fibrous Often Fibrous Acicular - Needle-like
crystals
Hardness:
2.5 - 3.0
2.5
Solubility (mol.L-1): .00015
.01
.013 (but less in acids)
Compare to the Carbonation of Portlandite
Portlandite
Calcite
Aragonite
Ca(OH)2 + CO2  CaCO3
Form: Massive
Massive or crystalline
Hardness:
Solubility (mol.L-1):
More acicular
2.5
.024
3.5
.00014
Presentation downloadable from www.tececo.com
41
Eco-Cement Micro-Structural Strength
Elongated growths of
lansfordite and
nesquehonite near the
surface, growing inwards
over time and providing
microstructural strength.
Flyash grains (red)
reacting with lime
producing more CSH and
if alkaline enough
conditions bonding
through surface
hydrolysis. Also acting as
micro aggregates.
Portland clinker minerals
(black). Hydration
providing Imperfect
structural framework.
Micro spaces filled with
hydrating magnesia
(→brucite) – acting as a
“waterproof glue”
Mysterious amorphous
phase?
Presentation downloadable from www.tececo.com
42
Carbonation
 Eco-cement is based on blending reactive magnesium oxide with
other hydraulic cements and then allowing the Brucite and
Portlandite components to carbonate in porous materials such as
concretes blocks and mortars.
– Magnesium is a small lightweight atom and the carbonates that form contain
proportionally a lot of CO2 and water and are stronger because of superior
microstructure.
 The use of eco-cements for block manufacture, particularly in
conjunction with the kiln also invented by TecEco (The Tec-Kiln)
would result in sequestration on a massive scale.
 As Fred Pearce reported in New Scientist Magazine (Pearce, F.,
2002), “There is a way to make our city streets as green as the
Amazon rainforest”.
Ancient and modern carbonating lime
mortars are based on this principle
Presentation downloadable from www.tececo.com
43
Aggregate Requirements for Carbonation
 The requirements for totally hydraulic limes and all hydraulic
concretes is to minimise the amount of water for hydraulic
strength and maximise compaction and for this purpose
aggregates that require grading and relatively fine rounded
sands to minimise voids are required
 For carbonating eco-cements and lime mortars on the on the
hand the matrix must “breathe” i.e. they must be porous
– requiring a coarse fraction to cause physical air voids and some vapour
permeability.
 Coarse fractions are required in the aggregates used!
Presentation downloadable from www.tececo.com
44
CO2 Abatement in Eco-Cements
For 85 wt%
Aggregates
15 wt%
Cement
Eco-cements in
porous products
absorb carbon
dioxide from the
atmosphere.
Brucite carbonates
forming lansfordite,
nesquehonite and
an amorphous
phase, completing
the thermodynamic
cycle.
Portland
Cements
15 mass%
Portland
cement, 85
mass%
aggregate
Emissions
.32 tonnes to
the tonne.
After
carbonation.
Approximately
.299 tonne to
the tonne.
No
Capture
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.37 tonnes to
the tonne. After
carbonation.
approximately
.241 tonne to
the tonne.
Capture
CO2
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.25 tonnes to the
tonne. After
carbonation.
approximately
.140 tonne to
the tonne.
Capture
CO2. Fly and
Bottom Ash
11.25% mass%
reactive magnesia,
3.75 mass%
Portland cement,
85 mass%
aggregate.
Emissions
.126 tonnes to the
tonne. After
carbonation.
Approximately .113
tonne to the tonne.
Greater Sustainability
.299 > .241 >.140 >.113
Bricks, blocks, pavers, mortars and pavement made using eco-cement, fly
and bottom ash (with capture of CO2 during manufacture of reactive
magnesia) have 2.65 times less emissions than if they were made with
Portland cement.
Presentation downloadable from www.tececo.com
45
TecEco Cement LCA
TecEco
Concretes
will have a
big role post
Kyoto as they
offer potential
sequestration
as well as
waste
utilisation
The TecEco LCA model is
available for download under
“tools” on the web site
Presentation downloadable from www.tececo.com
46
Rosendale Concretes – Proof of Durability



Rosendale cements contained 14 – 30% MgO
A major structure built with Rosendale cements commenced in 1846 was Fort Jefferson near
key west in Florida.
Rosendale cements were recognized for their exceptional durability, even under severe
exposure. At Fort Jefferson much of the 150 year-old Rosendale cement mortar remains in
excellent condition, in spite of the severe ocean exposure and over 100 years of neglect. Fort
Jefferson is nearly a half mile in circumference and has a total lack of expansion joints, yet
shows no signs of cracking or stress. The first phase of a major restoration is currently in
progress.
More information from http://www.rosendalecement.net/rosendale_natural_cement_.html
Presentation downloadable from www.tececo.com
47
The TecEco Dream – A More Sustainable Built Environment
CO2
CO2 FOR
GEOLOGICAL
SEQUESTRATION
CO2
MINING
MAGNESITE
+ OTHER
INPUTS
“There is a way to
make our city streets
as green as the
Amazon rainforest”.
Fred Pearce, New
Scientist Magazine
TECECO
KILN
MgO
OTHER
WASTES
PERMANENT
SEQUESTRATION &
WASTE
UTILISATION (Man
made carbonate
rock incorporating
wastes as a
TECECO CONCRETES building material)
RECYCLED
BUILDING
MATERIALS
SUSTAINABLE CITIES
We need materials that
require less energy to
make them, that last
much longer and that
contribute properties
that reduce lifetime
energies
Presentation downloadable from www.tececo.com
48
Sustainable Materials in the Built Environment - 2007
Technical Focus
This Conference will focus on:
 The impacts and connectivity
of different parts of the supply
chain.
 Fabrication, performance,
recycling and waste
 New developments in
materials and processes
 Reviewing existing materials
assessment tools
 Future directions in regulation
 Opportunities/barriers to
introduction of sustainable
materials and technologies in
the building industry.
 New materials and more
sustainable built
environments: the evidence?
Joint Venture Websites
ASSMIC Website: www.aasmic.org
Materials Australia Website: www.materialsaustralia.com.au
Presentation downloadable from www.tececo.com
49