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Delivering Concrete to Survive
the Environment
Dr. Peter Taylor
Outline
• What can go wrong?
• How do we prevent it?
2
What Can Go Wrong?
• Internal Expansion• External attack
Durability
• Ability of the concrete to survive the
environment to which it is exposed
Aggressive fluids
Cold weather
Unstable aggregates
Slab deformation
Overload
Aggressive fluids
• Sulfates
• External sulfates (eg soil)
• C3A in the cement
• Softening
• Complex chemistry
Aggressive fluids
• Salt crystallization
• Transported in solution
• Water evaporates leaving solid salt
• Not necessarily cold related
6
Aggressive fluids
• Soft water or acids
• Dissolves calcium compounds
• Problem in:
• Pure water reservoirs
• Some streets
(Bourbon St., New Orleans)
• Industrial settings
7
Cold Weather
• Saturated Freezing and Thawing
• Thin flakes in paste
• Or deep cracks
8
Cold Weather
• De-icing salts
• Calcium oxychloride (MgCl2)
• Friedel’s Salt – Calcium-chloro-aluminate
• Ettringite
9
Cold Weather
• Deicing salts
• Oxychloride
• Causes paste expansion at ~40°F
• Separates aggregate from paste
10
Cold Weather
• Deicing salts
• Ettringite
• Accelerates saturation
11
Stark and Bollmann 2000
Moulzolf
Unstable Aggregates
• Alkali Aggregate Reaction• Chemical reaction with some aggregates,
paste alkali hydroxides and water• Expansion
Unstable Aggregates
• D-Cracking
• Some limestone aggregates hold water
• Freezes
13Marks and Dubberke 1982
Unstable Aggregates
• Popouts
• Porous aggregates
• Freezing
• Surface phenomenon
• May accelerate other
distresses
Slab deformation
• Shrinkage
• Cracking
• Warping
• Expansion
Overload
• Strength
• Support
Slabs on GradeWhat's critical Name What is the
cause
What does it look
like
Where does it
occur
Where does it start How far does it go Prevention Repair Photo Deteriratio
n Type
D-Cracking Water freezing in
coarse
calcareous
aggregate
containing clays
and or with a
pore system that
holds water
Cracks near joints,
often an a curve at
intersection of
joints
Full depth, cracks
are parallel to
free surface, mm
part
Bottom of a joint Up to ~18" from joint Avoid
deleterious
aggregates.
Reducing
maximum size
delays damage
As per ASR
Physical
Freeze thaw Water freezing in
saturated cement
paste with
inadeqaute air
void system
Thin flakes parallel
to free surfaces at
joints
Joints Where water is trapped A few mm Adequate air
void system,
low
permeability
Partial depth repair
Physical
Oxychloride MgCl2 reacts
with some paste
systems at about
40F to form
expansive
oxychloride
compounds
Cracks parallel to
joint faces,
sometimes up to 1"
from previous cut
or crack
Joints Tops of saw cuts or in the kerf Up to ~9" from joint High SiO2
cementitious
systems, low
permeability,
adequate air,
limit use of
MgCl2
Partial depth repair, Full
depth repair
Chemical
Salt Scaling Salts or ice
crystallizing
below the
surface, often
related to poor
surface finishing
Flakes peeling off
the surface of the
slab
Surface only Surface Can cover the whole slab Good finishing
procedures,
curing,
adequate air
void system,
low alkali
cement
Grind
Not sure
Popout Water freezing in
low density
aggregate
Divot above
aggregate particle
At the surface Joints Whole slab surface Avoid
deleterious
aggregates
None
Physical
Checial Reaction
Alkali silica reaction Reaction
between some
silicates in
aggregate, alkali
hydroxides in
pore solution
and water
Cracks mostly
parallel to
longitudinal joint
Full depth Near edges Whole slab surface Avoid
deleterious
aggregates,
low calcium
SCM, Lithium
comounds
Remove and replace, rubblize
and overlay, unbonded
overlay
Chemical
Joint Related
Only Surface
What do we measure now?
•Slump
•Strength
•Air
•Thickness
Performance Engineered Mixtures
• Seeking to:
Understand what makes concrete “good”
Specify the critical properties and test for them
Prepare the mixtures to meet those
specifications
Delivering concrete to
survive the environment
PEM
• A program to make
everyone’s life miserable
The Perfect Specification
You get paid after […] years
Or we do a test that predicts life
Slump?
Strength?
Why bother?
• Currently:
Focused on strength
Struggling to get durability
Wrestling with unintended
consequences
Why bother?
1967 2017
No. of ingredients Cement, water,
rock, sand, AEA
Add SCMs,
admixtures, int.
aggregates,
limestone…
Opening Weeks Days (or hours)
Curing Weeks Days
De-icing Sand, NaCl Other chlorides,
formates, acetates
Design life 20 years 100 years
Knowledge base In house Contracted out
What Really Matters?
• Transport properties (everywhere)
Resistivity / Formation Factor
• Aggregate stability (everywhere)
ASR AASHTO R80
D-Cracking IPA
• Strength (everywhere)
Flex or compression
What Really Matters?
• Cold weather resistance (cold locations)
Air
SAM
LTDSC
• Shrinkage (dry locations)
Prism
Ring
• Workability (everywhere)
VKelly
Box
A Better Specification
Measure the right things at the right time
Prequalification
–This is what will be delivered
Process control
–What was delivered will make it
Acceptance
–Delivered
as promised…
A Better Specification
A buffet of approaches (for the Agency)
Prescriptive: w/cm, paste volume
Performance: Formation factor
Equivalency?
A Better Specification
AASHTO PP84 published in March 2017
Guide Specification / Standard Practice
“Deemed to satisfy”
Avoids bonus discussion – that is local
Provisional = meaning we can
modify as we learn things
Construction
• QC should include
Unit weight
Calorimetry
Maturity
Strength development
Air void stability
And a response…
• Risk management
Test Methods
• Tests for those critical properties
VKelly / Box
SAM
Resistivity / Formation factor
Sorptivity
Ring / Dual ring
30
VKelly
• Measure initial slump (initial penetration)
• Start vibrator for 36 seconds at 8000 vpm
• Record depth every 6 seconds
• Repeat
• Plot on root time
• Calculate slope = VKelly Index
31
Box Test
• A test that examines:
Response to vibration
Filling ability of the grout (avoid internal voids)
Ability of the concrete to
hold an edge
Ley
Box Test
• The edges of the box are then removed and
inspected for honey combing and edge slump
Ley
Super Air Meter
• Reports air content and SAM number
• SAM number correlates well with freeze thaw
testing
Ley
Formation Factor
•F = Resistivity (bulk)
Resistivity (solution)
•Sample is fully saturated
•Solution resistivity = ~0.01 kΩ•cm
ASTM C1202 Classification Charge Passed (Coulombs) Resistivity (kΩ ∙ cm)a Formation Factor
High >4,000 <5.2 520
Moderate 2,000–4,000 5.2–10.4 520–1,040
Low 1,000–2,000 10.4–20.8 1,040–2,080
Very low 100–1,000 20.8–207 2,080–20,700
Negligible <100 >207 20,700
Sorptivity
•Assess capillary absorption (ASTM C 1585)
Condition sample for moisture content
Seal the sides and top
Measure mass increase over time with open
face immersed in water
Ring Test
•Assesses cracking risk
•Starts immediately
37
How do we proportion to achieve
design goals?
Workability Transport Strength Cold
weather
Shrinkage Aggregate
stability
Aggregate System Type, gradation - - - -
Paste qualityAir, w/cm, SCM
type and dose
Paste quantity Vp/Vv - - - -
Doing the Sums
The wonders of
a spreadsheet and a
solver function…
Aggregate System
Project Effect of gradation 9/29/2016
Materials Blue= Input Data
Red = Calculation Don’t touch!
Cementitious 472 Yellow = Output Don’t touch!
Coarse Agg 1" Black = Working Don’t touch!
Fine Agg Sand
Intermediate 3/8"
Sieve Analysis Data
Max nominal aggregate size 1.00 inch (0.75, 1.0 or 1.5)
Coarse 1" Fine Sand Intermediate 3/8" Combined Fineness
Percent Cum. Sieve Modulus
Percent mass 100.0 44.9 45.7 9.4 Passing Retained Retained
Sieve: % Pass % Mix % Pass % Mix % Pass % Mix % % %
2" 100.0 44.9 100.0 45.7 100.0 9.4 100.0 0.0 0.0
1 1/2" 100.0 44.9 100.0 45.7 100.0 9.4 100.0 0.0 0.0
1" 99.0 44.4 100.0 45.7 100.0 9.4 99.6 0.4 0.4
3/4" 73.9 33.2 100.0 45.7 100.0 9.4 88.3 11.7 11.3
1/2" 37.5 16.8 100.0 45.7 100.0 9.4 71.9 28.1 16.3
3/8" 19.7 8.8 100.0 45.7 90.2 8.5 63.0 37.0 8.9 0.0
# 4 3.5 1.6 98.6 45.1 21.6 2.0 48.7 51.3 14.4 1.4
# 8 0.8 0.4 88.3 40.3 2.0 0.2 40.9 59.1 7.8 11.7
# 16 0.4 0.2 68.9 31.5 0.6 0.1 31.7 68.3 9.2 31.1
# 30 0.4 0.2 37.0 16.9 0.4 0.0 17.1 82.9 14.6 63.0
# 50 0.3 0.1 9.7 4.4 0.4 0.0 4.6 95.4 12.5 90.3
# 100 0.3 0.1 0.8 0.4 0.3 0.0 0.5 99.5 4.1 99.2
# 200 0.3 0.1 0.2 0.1 0.3 0.0 0.3 99.7 0.3
2.97
Coarsness Factor 62.55 Power 45 least difference 31.0 Tarantula error 0.0 4.5
Workability Factor 40.89 Power 45 error 350.2 113.7
Adjustments 0.00
Adjusted Workability Factor 40.89 Fine 31.5 24-34 23.9 34.1
Coarse 31.5 >15 15
0
5
10
15
20
25
2"
1 1
/2"
1"
3/4
"
1/2
"
3/8
"
# 4
# 8
# 1
6
# 3
0
# 5
0
# 1
00
# 2
00
Perc
en
t R
eta
ined
Sieve
Tarantula
Greater than 15% on the sum of #8, #16 and #3024-34% of fine sand (#30-200)
0
20
40
60
80
100
2"11/2"
1"3/4"1/2"3/8"# 4# 8# 16# 30# 50# 100# 200
Perc
en
t P
assin
g
Sieve
Individual and Combined Gradations
C33
Sand
3/8"
1"
Combined
0
20
40
60
80
100
% P
assin
g
Sieve (^0.45)
Power 45
Mixture
Max Density
Limits
#50 #16 1" 2"1/2"#4#200
20
25
30
35
40
45
020406080100
Wo
rkab
ilit
y F
acto
r
Coarseness Factor
Shilstone Chart
IVSandy
IGap
II
IIISmall Agg
VCoarse
Measure Va
Does it Work?
• West Des Moines specification
• WI using the proportioning tool
• Other states looking at shadow evaluations in
2018
Are we there yet?
• A framework is in place
• The details need work
Ruggedness
Limits
Correlation with life
Training