concrete masonry 09
TRANSCRIPT
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Concrete & Masonry
Prof Dave Hughes
Taught by lectures, tutorials, lab,
CALCRETE & design sessions
Assessed by Class test multiple choice week
6/7 (30%)2 hour exam - design exercises
(70%)
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Left school when 16 with 7 OLevels
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Left school when 16 with 7 OLevels
Farnborough Technical College OND Engineering (1971)
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Left school when 16 with 7 OLevels
Farnborough Technical College OND Engineering (1971)
Portsmouth Polytechnic BSc (Hons)
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Left school when 16 with 7 OLevels
Farnborough Technical College OND Engineering (1971)
Portsmouth Polytechnic BSc (Hons) (1975)
Surrey University PhD (1982)
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Left school when 16 with 7 OLevels
Farnborough Technical College OND Engineering (1971)
Portsmouth Polytechnic BSc (Hons) (1975)
Surrey University PhD (1982)
Bradford University (1985)First Associate Dean (Learning & Teaching)
Mortars conservation and new build
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Introduction
Tofamiliarise you with concrete and mortar
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What are concrete & mortar?
Composite of
Aggregate
Binder
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What are concrete & mortar?
Composite of
Aggregate
Binder
Gravel
Crushed Rock
Expanded Clay
Sintered PFA
Blast Furnace Slag
Steel Shot
GlassSea shells
Recycled concrete
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What are concrete & mortar?
Composite of
Aggregate
Binder
Portland Cement
Calcium Aluminate Cement
B-CSA-F CementHydraulic Lime
Air Lime
Water
PFA
GGBSSilica Fume
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What is concrete?
0
10
20
30
40
50
% by
Volume
CoarseAggFine Agg
Binde
rWater
Voids
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What is mortar?
% byVolume
0
10
20
30
40
50
60
FineAgg
Binder Water Voids
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What are the attractions of concrete?
In-situ or Pre-cast
Two states
Range of finishes
High compressive strength
Can be durable
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What the down-sides of concrete?
Cement can be guaranteed but not concrete
Low tensile strength & toughness
Can lack durability
Natural Hydraulic Lime is variable between
and within source
Lime mortars are more flexible
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So what are the differences betweengood concrete and bad concrete?
Application of know-how since theingredients are the same
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So what are the differences betweengood concrete and bad concrete?
Application of know-how since theingredients are the same
CEMENT & LIME, COMPOSITION,COMPACTION, CURING, COVER, CARE
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Testing of concrete & mortar
Compressive strength
Workability
but durability is more often the key factor
a function of permeability and composition
and very rarely tested for
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Layout of the rest of the module
Ingredients
Fresh concrete
Hardened concrete - mechanical
Hardened concrete - permeation
Hardened concrete - durability
Mix design
Mortars
Masonry units
Design exercises
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Cements and Limes
To present specifications for hydraulic cements
and hydraulic limes
To discuss their hydration and the formation of
microstructure
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Terminology of Cements and Limes
SiO2 S
Al2O
3A
CaO C
Fe2O3 F
SO3 S
H20 H
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Cements
Portland cement -
Tri Calcium Silicate C3S
Di Calcium Silicate C2S
Tri Calcium Aluminate C3A
Tetra Calcium Aluminoferrite C4AF
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History of Cements and Limes
0
10
20
30
40
50
60
1900 1920 1940 1960 1980 2000
C3
S
C2
S
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Manufacture of Portland Cement
Quarrying
Limestone
Clay/Shale
Grinding &
Blending
H2O CO2 Clinker
Pre-heat 850oC 1400oC
Add Gypsum
Grinding
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Manufacture of Lime
Quarrying
Limestone
Crushing850oC
1000oC
CO2 Reaction
Slaking
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Lime, Portland Cement & Pozzolanas%age by wt
NHL PC GGBS PFA CSF
S 15 21 37 48 92
A 1 7 11 26 1
F 1 3 1 10 1
C 60 66 40 2 0Alk 1 1 1 4 3
CH C3S AS glass AS glass S glass
CaCO3 C2S
C2S C3A
C2AS C4AF
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Cement & BS EN 197-1:2000Composition
CEM I Portland cement
CEM II Portland-composite cement
CEM III Blast furnace cement
CEM IV Pozzolanic cement
CEM V Composite cement
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Cement & BS EN 197-1:2000
CEM I Portland cement
95 - 100% clinker
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Cement & BS EN 197-1:2000
CEM II Portland-composite cement
65 - 94% clinker plus
6 - 35% GGBS, PFA, limestone dust
6 - 10% CSF
6 - 35% mix of any or all
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Cement & BS EN 197-1:2000
CEM III Blast furnace cement
5 - 64% clinker plus
36 - 95% GGBS
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Cement & BS EN 197-1:2000
CEM IV Pozzolanic cement
45 - 89% clinker plus
11 - 55% CSF + PFA
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Cement & BS EN 197-1:2000
CEM V Composite cement
20 - 64% clinker plus
18 - 50% GGBS + 18 - 50% PFA
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Cement & BS EN 197-1:2000Strength
Strength Compressive Strength (MPa) Initial Set
Class Early strength Standard strength (Mins)
2 days7 days 28 days32.5 N 16 32.5 52.5 75
32.5 R 1042.5 N 10 42.5 62.5
6042.5 R 2052.5 N 20 52.5 45
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Lime & BS EN 459-1:2010
NHL - from a single source of argillaceous or
siliceous limestone with no additions
HL - from a combination of unspecified sources,may contain PC, GGBS, CSF, natural
pozzolana
FL same as HL but must specify contents
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Lime & BS EN 459-1:2001Strength
Strength Strength (MPa)
Class 7 days 28 days
NHL/FL 1 0.5 - 3
NHL/HL/FL 2 2 - 7
NHL/HL/FL 3.5 3.5 - 10
NHL/HL/FL 5 2 5 - 15
All limes to be sound 2 mmSetting in 1 hour 14 days!!!!!!!!!!!!!
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Basic hydration
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Basic hydration
C3A + H > C3AH6C3A + H + C H2> C6A 3H32S
_S_
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Basic hydration
C3A + H + C H2> C6A 3H32
C3S + H > CSH + CH
S_
S_
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Basic hydration
C6A 3H32 > C4A H18
C3A + H > C4AH19C4A H18 & C4AH19 known as AFm
S_
S_
S_
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Basic hydration
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Slower long term reactions
C2S + H > CSH + CH
CH + S > CSH (pozzolanic reaction)
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Physical Structure Development
Water
Vapour
CapillaryAdsorbed
Interlayer
Combined
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Pore Structure
1 - 5 mm Entrapped air
100 m - 1 mm Entrained air
0.01 m - 15 m Capillary voids
< 0.01 m Interlayer or gel voids
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Pore Structure Development
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Pore Structure Development
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Pore Structure Development
1 10 100 1000
Porosity
Pore size (nm)
1 d PFA
1 d OPC
6 m OPC
6 m PFA
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Types of PC
LHPC
SRPC
White
RHPC - (CEM 1R)
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Types of PC
LHPC Low C3S, high C2S
SRPC 3.5% C3A
White No or trace C4AF
RHPC - (CEM 1R) High C3S or high SSA
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CALCRETE
Read all of section on cements
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Aggregates
To identify key properties as they affect the
properties of concrete
To describe methods of their determination
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Types of aggregates by density
Heavyweight
(4000 - 8500 kg/m3)
Normal
(2300 - 2500 kg/m3)
Lightweight
(350 - 1800 kg/m3)
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Types of aggregates by density
Heavyweight
Normal
Lightweight
Magnetite
Iron shot
Lead shot
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Types of aggregates by density
Heavyweight
Normal
Lightweight
Natural Crushed rock
Sand & gravel
Artificial Air cooled slag
Broken brick
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Types of aggregates by density
Heavyweight
Normal
Lightweight
Natural Pumice
Expanded
clay or shale
Artificial Furnace clinker
Foamed slag
Sintered PFA
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Strength
Concrete 30 - 80 MPa
Aggregate 70 - 350 MPa
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Factors affecting workability of
concrete
Water content
Aggregate type and grading
Mix proportions
Cement fineness
Admixtures
Oven dry
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Porosity
Air dry
Saturatedsurface dry
Moist
Absorptionor porosity
Free
moisture
content
Total
moisture
content
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Aggregate Type
Shape
Rounded
IrregularAngular
Flaky
ElongatedFlaky and elongated
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Aggregate Type
Texture
Glassy
SmoothGranular
Rough
CrystallineHoneycombed
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Aggregate Grading
Maximum size
Continuous grading
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Aggregate Grading
Sieve Size
% age
passing
Continuous
Gap
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Sieve Analysis
Sieve Wt ret % ret Cum % ret Cum % pass
5.00 0 0 0 100
2.36 32 16 16 84
1.18 40 20 36 640.60 42 21 57 43
0.30 46 23 80 20
0.15 32 16 96 4
Pan 8 4 100 0Total 200
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BS classification - Fine aggregate
Sieve Overall C M F
5.00 89 - 100
2.36 60 - 100 60 - 100 65 - 100 80 - 100
1.18 30 - 100 30 - 90 45 - 100 70 - 100
0.60 15 - 100 15 - 54 25 - 80 55 - 100
0.30 5 - 70 5 - 40 5 - 48 5 - 70
0.15 0 - 15*
* 20% for crushed rock sands
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0
20
40
60
80
100
150 300 600 1.18 2.36 5
BS classification - Fine
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0
20
40
60
80
100
150 300 600 1.18 2.36 5
BS classification - Medium
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BS classification - Coarse
0
20
40
60
80
100
150 300 600 1.18 2.36 5
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BS classification - Coarse aggregate
Sieve 20 mm SS 10 mm SS
37.5 100
20.0 85 - 100
14.0 100
10.0 0 - 25 85 - 100
5.0 0 - 5 0 - 25
2.36 0 - 5
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Impurities
Chlorides
Clay
Organic matter
Unsound particles
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CALCRETE
Read aggregate section for winning and
processing and deleterious materials
Revision0.18
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0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.0010.010.11101001000
Mean Pore Diameter (m)
CumulativePoreVolume(ml/gm)
A
B
C F h
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Concrete - Fresh state
To identify the factors which control properties
of concrete in the fresh state
To be able to modify those properties by use ofadmixtures
To be able to perform standard workability tests
K ti
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Key properties
Fluidity
Compactability
Cohesiveness
Workability is the amount of internal work
required to achieve full compaction
Workability
R i t t fl
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Resistance to flow
Friction & Interference Water lubricated
C it i f b t k bilit t t
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Criteria for robust workability tests
Simple equipment
Easily & quickly performed
Appropriate for range of workability sought
Repeatable
Sl
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Slump
Truncated cone Three equal layers
Rod each layer 25 times Scrape off the surface
300 mm
200 mm
Sl
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Slump
slump cone
rod
concrete
Slump
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Slump
Slump
Ruler
Slump
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Slump
Normal range of slump 50 - 100 mm
Medium workability only
Compacting Factor
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Compacting Factor
Two cones Drop through into cylinder
Weigh W1 Fully compact and fill up
Weigh W2
Compacting Factor
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Compacting Factor
CF = W1 / W2
Normal range 0.70 - 0.95
Low workability with zero
slump
VB
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VB
Slump in cylinder
Apply standard vibration
Normal range 4 -35 seconds
Very Low workability
V i b
r a
t i o
n
Flow Table
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Flow Table
For mortars
Compact in 2 layers
15 jolts, 1 per second
Typically 17 cm though no
standard
Flow
Key factors
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Key factors
Free water content (FWC)
Aggregate & cement fineness (grading)
Aggregate shape and textureAggregate moisture state
Proportions of fine to coarse aggregate
Presence of PFA or CSFTemperature and time
Key factors
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Key factors
Presence of PFA or CSF
Admixtures
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Admixtures
Plasticiser
Super-plasticiser
Retarder
Accelerator
Choice of workability
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Choice of workability
Level Slump CF Use
V Low 0.78 Roads heavy vibration
Low 25 -50 0.85 Roads light vibration
Medium 75 Mass & rc construction
High 125 Piling and dense steel
V High Self-levelling concrete
Practical considerations
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Practical considerations
Bleeding
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Practical considerations
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Practical considerations
Bleeding
Plastic settlement
Plastic shrinkage
Practical considerations
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Practical considerations
Bleeding
Plastic settlement
Plastic shrinkage
Curing
Practical considerations
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Practical considerations
Curing
Degree of hydration Efficiency of curing
Strength Permeability Degree of hydration
Practical considerations
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act ca co s de at o s
Bleeding
Plastic settlement
Plastic shrinkage
Curing
Thermal cracking
Practical considerations
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Thermal cracking
Practical considerations
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Thermal cracking
Hardened concrete - mechanical
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To describe the factors affecting strength
To be able to undertake standard strength tests
To describe the factors affecting moisture relatedmovements
Concrete - Strength
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g
See CALCRETE for detaiMost specified by compressive strength
100 mm cubes, steel moulds, compacted in
2 layers, 20o
C water cure, 28 days, standardloading rate
Some by indirect tension (flexure or split cylinder)
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Labcrete - RealcreteA li d t
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curing
shape
Failure cones
of restraint
Applied stress
Induced stress
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Factors affecting strength
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Intrinsic
Production related Compaction
External environment
Properties of materials
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Cement
Aggregates
Water
Cement -
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fineness
Properties of materials
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Cement
Aggregates
Water
Mix proportions
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Water/Cement ratio
Coarse/fine aggregate ratio
Water/Cement ratio
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Strength
w/c ratio
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Age70
80
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0
10
20
30
40
50
60
1 10 100 1000
Age
Strength
High
Low
Pozz
Compaction
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1% voids reduces strength by some 5%
Vital to compact until air no longer present butdont over-vibrate and segregate mix
Deformation in concrete
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Short term
Long term
Applied stress
Environmental factors
Deformation in Concrete
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Function of Stiffness
Shrinkage
Creep
Elastic behaviourTangent
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Stress
Strain
Initialtangent
g
Secant
Principally related to
strength
Deformation in Concrete
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Function of Stiffness
Shrinkage
Creep
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Deformation in Concrete
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Function of Stiffness
Shrinkage
Creep
Factors affecting creep
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Same as for shrinkage plus
Initial moisture content
Applied stressStorage temperature
Typical values 0 - 1400
CALCRETE
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Hardened Concrete for revision and exercises
Hardened concrete - permeation
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To differentiate between diffusion and
permeability
To relate these to microstructure
Permeation
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Permeability is the ease of flow of a liquid as aresult of a pressure difference (eg flow through
dam)
Diffusion is the ease of flow of a species as a
result of a concentration difference (eg sulphatesflowing from groundwater)
Sorptivity is the uptake of water by capilliary
action in unsaturated concrete or mortar
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Factors affecting permeation
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Porosity
Pore size distribution
Inter-connectivity of poresTortuosity
Factors affecting permeation
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Factors affecting permeation
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Factors affecting permeation
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Factors affecting permeation
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Factors affecting permeation
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CALCRETE
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See Durability for an alternative explanation
So what are the factors that affect
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Porosity
Pore size distribution
Inter-connectivity of pores
w/c ratio
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Age
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Covercrete and Heartcrete
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H
C
Covercrete and Heartcrete
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H
C
Reinforcing
steel Aggressive
agents
CALCRETE
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Read Durability - Permeability and Pore Structure
Hardened concrete - durability
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To recognise some of the major durability
problems facing concrete
To identify means of combating them by referenc
to appropriate microstructures
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Protection of reinforcement
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Correct cover
High quality covercrete
High alkalinity
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Carbonation
D th
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Depth
Period of exposure
Curing, cement
content, rh
w/c, CO2, temp
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Chloride corrosion
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Marine aggregates
De-icing salt
Sea sprayCaCl2 - accelerator
Chloride corrosion
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Marine aggregates
De-icing salt
Sea spray
CaCl2 - accelerator
Chlorides
Free in solution
Physically absorbedChemically bound
Chloride corrosion
Cl-/OH- >0.6Fe
++
+2Cl
-
= FeCl2
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Cl2, O2H2O
Metal
Fe++
Fe
Anode
OH--
Cathode
Cl-Fe +2Cl = FeCl2FeCl2 + 2H2O = Fe(OH)2 +2HC
2e
Corrosion control
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Permeation properties
Cover
Chloride binding capacityBinder content
Binder type
Curing
Sulphate attack
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AFm + CH + + H > C6A 3H32
Na2SO4 + CH + H > C H2 + 2NaOHMgSO4 + CH + H > C H2 + Mg(OH)2
MgSO4 + CSH + H > C H2 + Mg(OH)2 + SH
S_
S_
S
_
S_
S
_
Solutions
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Low C3A
Permeation properties
CH binding (PFA, GGBS, CSF)
Frost attack
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Frost attack
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Hydraulic pressure
Osmotic pressure
Ice
Water
Solutions
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Drainage
Permeation
Air entrainment
Air entrainment
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Air entrainment
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Alkali Silica Reaction (ASR)
Hi h lk li l l
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High alkali levels
Reactive silica
Water
Alkali Silica Reaction (ASR)
High alkali levels NaOH KOH Ca(OH)
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High alkali levels
Reactive silica
Water
NaOH, KOH, Ca(OH)2
Na2O equivalent > 0.6%
= Na2O + 0.658 K20
Alkali Silica Reaction (ASR)
High alkali levels Amorphous silica eg opal
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High alkali levels
Reactive silica
Water
Amorphous silica, eg opal,
volcanic glass
Cherts, siliceous limestone,flint
Alkali Silica Reaction (ASR)
High alkali levels
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High alkali levels
Reactive silica
Water > 75% relative humidity
Temperature
Alkali Silica Reaction (ASR)
W t
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Alkali
Water
Gel + water =
expansion
S
AS gel
ASR cracking
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Pop-out Map cracking
Solutions
Non reactive aggregates
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Non reactive aggregates
Low alkali cement
Use of PFA, GGBS, PFA
Remove water
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Masonry
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Masonry
Prof Dave Hughes
Brick types
Clay
C l i Sili t
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Calcium Silicate
Concrete
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Frost
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Soluble salts
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Soluble salts
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Water threat
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Water threat
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Walls
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Freestanding wal
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Retaining wal
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Weepholes in Austria
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Reinforced walls
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Reinforced walls
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Movement joints
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Movement joints
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Movement joints
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Movement joints
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Durability of masonry
Design
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Design
Material specification
BS EN 771-1
Clay
Density
1000 k / 3 (LD) f t t d
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1000 kg/m3 (HD) for un-protected
masonry
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BS EN 771-1
Clay
Durability Frost
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Exposure
F0 Passive
F1 Moderate
F2 Severe
BS EN 771-2
Calcium Silicate
Strength
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7, 7.5, 10, 15, 20 50, 60, 75
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Sands
Principal quality factors
Average particle size
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Range of sizes
Shape
Impurities, particularly clay
Sands
Impurities
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Annex D of BS EN 13139:2002
Concrete vs Mortar sands
60
80
100
g
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0
20
40
0.1 1 10
Sieve Size (mm)
%passin
Premise of mix design
Voids between aggregate particles are
filled with binder
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By way of example
Unrendered external wall, high
saturation
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1: 3 to 4 if using PC:sand mortar
For a finer sand tend towards 1:3 rather than 1:4
to achieve desired workability, strength and
durability
New advances in silo mortar
Low energy for sustainability
Bi d h
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Binder phase
Sand drying
New advances in silo mortar
Binder phase
P tl d t i hi h b di d
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Portland cement is high embodied energy
Hydraulic lime is high embodied energy
New advances in silo mortar
Sand drying
Kil i ffi i t
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Kilns are inefficient
Lime has potential
CaO + H20 Ca(OH)2
New advances in silo mortar
So what binder could be added to
Ca(OH)2 which is low energy?
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ggbs
Context - strength
50
60
70
80
P
Bradford research
M12?
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0
10
20
30
40
50
0.5 1 2 3 4 5 6
Sand:binder ratio
Strength(MP
NHL
OPC
1:2
1:3
M12?
Context - strength
NHL
FL
10
15
PNHL
Bradford research
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0
5
0.5 1 2 3 4 5 6
Sand:binder ratio
Strength(M
NHL
OPC
1:2
1:3
Context - sorptivity
2.0
2.5
3.0
/min0.5)
NHL
NHL
FL
Bradford research
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0.0
0.5
1.0
1.5
0.5 1 2 3 4 5 6
Sand:binder ratio
Sor
ptivity(mm NHL
OPC
1:2
1:3
Context - wvp
2.0E-11
2.5E-11
3.0E-11
Pa-
1)
NHL
NHL
FL
Bradford research
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0.0E+00
5.0E-12
1.0E-11
1.5E-11
0.5 1 2 3 4 5 6
Sand:binder ratio
WV
P(kgm-
2s
-1 NHL
OPC
1:2
1:3
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Realcrete in mortars?
Bricks
Differing capacity to absorb water
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Mortars
Differing capacity to retain water
Realcrete in mortars?
1840
1850
1860
1870
1880
1890
ensity(kg/m3)
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1800
1810
1820
1830
1840
0 1 2 3 4 5 6 7 8 9 10
Root time (min0.5
)
ODDe
Realcrete in mortars?
25%
30%
orosity
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15%
20%
0 1 2 3 4 5 6 7 8 9 1
Root time (min0.5
)
Po
Realcrete in mortars?Comp Strength
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Mortar
S ti it
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0 0.5 1 1.5 2 2.5
Sorp of Substrate
Sorptivity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 0.5 1 1.5 2
Sorp of Substrate
SorpofMortar
Substrate Comp strength
(MPa)
Flex strength
(MPa)
Steel 4.7 1.3
Realcrete in mortars?
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Steel 4.7 1.3
OD Ibstock 8.1 2.5
OD Blue 5.6 2.1Sat Ibstock 4.6 1.4
Sat Blue 4.4 1.6
Binder NHL 3.5
The End of knowledge acquisition
From next week design sessions to
d l d t di f d i d
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develop understanding of design and
application of knowledge