L&M Construction Chemicals
Concrete Basics
Filename: concrete long.ppt
AIA/CES Program Number CCL101
Provider Number J280
© 1999 All Rights Reserved,
L&M Construction Chemicals Inc.
Concrete Basics
Presented By
L&M Construction Chemicals, Inc.
I.
II.
What is concrete
What are the ingredients and how do they interrelate
III.
Factors controlling the ratio of ingredients
IV.
Concrete problems
V.
Rules of thumb for concrete
What is Concrete
Concrete is a mixture of portland cement,
fine and coarse aggregate and water.
This mixture may or may not have added
to it chemical and mineral admixtures, airentraining agents, and steel or plastic
fibers.
Concrete Ingredients
Approximate Percent By Volume
50
Precent By Volume
40
30
20
10
10
0
Cement
Stone
Sand
Water
Air
Concrete Ingredients
Approximate Percent By Volume
50
40
Precent By Volume
40
30
20
10
10
0
Cement
Stone
Sand
Water
Air
Concrete Ingredients
Approximate Percent By Volume
50
40
Precent By Volume
40
27
30
20
10
10
0
Cement
Stone
Sand
Water
Air
Concrete Ingredients
Approximate Percent By Volume
50
40
Precent By Volume
40
27
30
17
20
10
10
0
Cement
Stone
Sand
Water
Air
Concrete Ingredients
Approximate Percent By Volume
50
40
Precent By Volume
40
27
30
17
20
10
6
10
0
Cement
Stone
Sand
Water
Air
FLY ASH
Fly Ash reacting with
calcium hydroxide
Silica Fume
Polypropylene Fiber:
Coilated - Fibulated
Polypropylene Fiber:
Monofilament
PORTLAND CEMENT
Cement in its dry
form is made up of
discreet individual
particles.
The cement particles
when mixed with water
do not dissolve they
become dispersed.
Only approximately 65% of the cement in concrete ever
hydrates.
It is the water to cement ratio that determines the
strength of a concrete mix and not the amount of
cement in the mix alone.
The only other requirement is that there is sufficient
cement paste to coat all the aggregate particles.
PORTLAND CEMENT TYPES
ASTM C -150
Standard Specification for Portland Cement
Type I
Type IA
Normal
Normal Air Entraining
Type II
Type IIA
Moderate Sulfate Resistance
Moderate Sulfate Resistance Air Entraining
Type III
Type IIIA
High Early Strength
High Early Strength Air Entraining
Type IV
Low Heat of Hydration
Type V
High Sulfate Resistance
HYDRATION
Hydration is the chemical reaction between portland
cement and water that produces crystalline structures.
Two of which are Tobermortie and Ettringite.
Tobermorite
Ettringite
PERCENT OF 28 DAY STRENGTH
Percent of 28 Day Compressive Strength
Typical Type I and Type III Portland Cement
120%
100%
80%
60%
40%
35%
20%
15%
0%
1D
3D
TYPE I
W/C =0.50
Moist-Cured at 68F
7D
TYPE III
28 D
PERCENT OF 28 DAY STRENGTH
Percent of 28 Day Compressive Strength
Typical Type I and Type III Portland Cement
120%
100%
80%
60%
40%
70%
35%
20%
50%
15%
0%
1D
3D
TYPE I
W/C =0.50
Moist-Cured at 68F
7D
TYPE III
28 D
PERCENT OF 28 DAY STRENGTH
Percent of 28 Day Compressive Strength
Typical Type I and Type III Portland Cement
120%
100%
80%
60%
40%
70%
35%
20%
85%
67%
50%
15%
0%
1D
3D
TYPE I
W/C =0.50
Moist-Cured at 68F
7D
TYPE III
28 D
PERCENT OF 28 DAY STRENGTH
Percent of 28 Day Compressive Strength
Typical Type I and Type III Portland Cement
120%
100%
80%
60%
40%
70%
35%
20%
85%
100% 100%
67%
50%
15%
0%
1D
3D
TYPE I
W/C =0.50
Moist-Cured at 68F
7D
TYPE III
28 D
HEAT OF HYDRATION
Heat of hydration is the heat generated when
cement and water react.
The approximate amount of heat generated
during the first seven days, based on 100% for
Type I, Portland Cement, is as follows:
Type II
moderate
80% to 85%
Type III
high early strength
Type IV
low heat of hydration 40% to 60%
Type V
sulfate resistant
up
to 150%
60% to 75%
PORTLAND CEMENT
Typical Percentage
Compound Composition
60%
50%
40%
30%
20%
10%
0%
Type I
Type II
Type III
Type IV
Type V
Types of Portland Cement
C3S
C2S
C3A
C4AF
White
PORTLAND CEMENT
Typical Percentage
Compound Composition
60%
50%
40%
30%
20%
10%
0%
Type I
Type II
Type III
Type IV
Type V
Types of Portland Cement
C3S
C2S
C3A
C4AF
White
PORTLAND CEMENT
Typical Percentage
Compound Composition
60%
50%
40%
30%
20%
10%
0%
Type I
Type II
Type III
Type IV
Type V
Types of Portland Cement
C3S
C2S
C3A
C4AF
White
PORTLAND CEMENT
Typical Percentage
Compound Composition
60%
50%
40%
30%
20%
10%
0%
Type I
Type II
Type III
Type IV
Type V
Types of Portland Cement
C3S
C2S
C3A
C4AF
White
PORTLAND CEMENT
Typical Blaine Fineness
Blaine Fineness cm2/g
6000
5000
3700
4000
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
PORTLAND CEMENT
Typical Blaine Fineness
Blaine Fineness cm2/g
6000
5000
4000
3700
2800
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
PORTLAND CEMENT
Typical Blaine Fineness
5400
Blaine Fineness cm2/g
6000
5000
4000
3700
2800
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
PORTLAND CEMENT
Typical Blaine Fineness
5400
Blaine Fineness cm2/g
6000
5000
4000
3800
3700
2800
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
PORTLAND CEMENT
Typical Blaine Fineness
5400
Blaine Fineness cm2/g
6000
5000
4000
3800
3700
3800
2800
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
PORTLAND CEMENT
Typical Blaine Fineness
5400
4900
Blaine Fineness cm2/g
6000
5000
4000
3800
3700
3800
2800
3000
2000
1000
0
Type I Type II Type III Type IV Type V
Types of Portland Cement
White
SETTING OF PORTLAND CEMENT
Initial Set:
The degree of stiffening of a mixture of cement
and water after which placement should not be
attempted.
Final Set:
The time after which the mixture should not be
worked.
If the mixture is disturbed, strength
development will be adversely affected.
FALSE SETTING OF PORTLAND CEMENT
False Set:
The rapid development of rigidity in a freshly
mixed portland cement paste without the
evolution of much heat.
Plasticity can be regained by further mixing
without addition of water or loss of strength.
Plaster of Paris: CaSO4 + 1/2H2O
A form of gypsum CaSO4 + 2H2O in which
three-quarters of the chemically bound water
has been driven off by heating.
The Function of an Aggregate
in
Concrete
1. Contributes volume to the concrete mix
2. Contributes its own physical strength
to the concrete mix
3. Affords a good bond plane for the
cement
The Characteristics of a Good
Aggregate
1. Must be chemically inert
2. Free of organic matter
3. Must have a good grading ( particle-size
distribution)
4. Must have good particle shape
5. Must have a low volume of voids
6. Grading and particle shape must work together to
reduce the effects of aggregate thixotropy
7. Particle surface texture and strength must afford a
good bond plane for the cement
Air Entrainment for Protection
The proper size air
voids are produced
when the total volume
of air in the concrete
mix equals 5 to 7 % of
the total volume of the
concrete resulting in
an air void every 0.016
inches in the cement
paste.
0.016”
The Function
of
Air Entrainment in Concrete
Air is placed in concrete to protect the concrete
from internal expansive forces.
These forces are produced when water is frozen to
form ice and when alkali-silica reactivity occurs.
Hardened cement paste is very rigid and will
disintegrate, if internal expansive pressure
becomes too great.
Entrained air in concrete protects concrete by
producing void areas in the cement paste in which
the expanding materials can escape.
This reduces the internal expansive forces thereby
preventing damage to the cement paste .
AIR CONTENT:
The total volume of air in a concrete mix is
expressed as a percentage of the total volume of the
mix.
The air in a concrete mix is found in one of two forms:
Entrapped air:
The natural air in the mix.
It is approximately 1/2% to 3 %.
This form of air does not give freeze-thaw
protection.
Entrained Air:
This air is chemically placed in the mix for
freeze- thaw protection.
This form of air may vary from 4% to 8%
depending on the level of protection needed.
LAWS & RULES
All concrete mixes behave in
accordance specific laws and rules.
To understand these laws and rules is to
better understand the interworkings of
concrete.
LAWS & RULES
Abrams Law (Water Cement Ratio Law):
For a given amount of cement as the
water content is increased the strength of
the mortar or concrete mix decreases.
The optimum amount of water for strength
is 1/4 lb. per lb. of cement.
LAWS & RULES
Constant Strength Rule:
For a given water cement ratio, the
strength of a concrete mix remains the
same regardless of the aggregate
content of the mix.
As long as there is sufficient cement
paste to coat all the aggregate particles.
LAWS & RULES
Constant Water Content Rule:
For a given aggregate and consistency,
the quantity of mixing water per cubic
yard of concrete will remain essentially
constant, regardless of the cement
content.
LAWS & RULES
Water Requirement Rule:
The water requirements of a concrete
mix, for a given consistency, will
increase as the surface area of the
aggregate increases per unit volume of
concrete.
LAWS & RULES
Air Content vs Water Content Rule:
For a given concrete mix of given
consistency, the water requirements of
the concrete mix will decrease as the
air content increases.
LAWS & RULES
Air Content vs Strength Rule:
For a given concrete mix of given
consistency, as the air
content
increases
the
strength
of
the
concrete mix will decrease .
As the cement content of a concrete
mix increases, the rate of strength
loss will increase.
Concrete Problems
Concrete Problems
BLISTERING:
The irregular raising of a a thin
layer of material at the surface of
placed concrete or mortar during
or soon after, completion of the
finishing operation.
This condition is caused by the
premature closing of the surface
and the entrapment of air or
water just below the surface.
Blisters
Concrete Problems
CARBONATION:
Carbonation of concrete is a process by
which carbon dioxide from the air penetrates
the concrete and reacts with hydroxides,
such as calcium hydroxide, to form
carbonates.
Concrete Problems
CRAZING:
Network of fine Cracks.
Also referred to as map
cracking.
Cause by early drying of
the concrete surface.
Concrete Problems
CRUSTING:
•The drying out of the surface of concrete or
mortar before set occurs.
•This condition gives a false sense of setting.
•The surface of the slab will not have enough
moisture at the surface of the finishing
operation.
Concrete Problems
CURLING:
Curling is the distortion of an originally
essentially flat member into a curved shape.
This warping is caused by differences in
temperature or moisture content between the
top and bottom of the slab.
Concrete Problems
PLASTIC SHRINKAGE
CRACKS:
Plastic shrinkage cracks form prior to
final set.
They are the results of rapid
evaporation of moisture from the
surface of the concrete slab.
Concrete Problems
SCALING:
The deterioration of the
surface of concrete.
Primary causes low air
content , exposer of
concrete surface while
wet to freezing and
thawing and repeated
use of deicing salts.
Rules of Thumb
for
Concrete
RULES OF THUMB
FOR CONCRETE
Water vs. Slump Change:
The addition of 1 to 1 1/2 gallons of water per yard of
concrete will increase the slump by one inch.
Water vs. Strength:
One gallon of water added to a yard of well mixed
and proportioned concrete mix will decrease the
compressive strength approximately 300 to 450 psi.
RULES OF THUMB
FOR CONCRETE
Minimum Water Cement Ratio:
Minimum water cement ratio is approximately 0.25.
It takes approximately 1/4 pound of water to hydrate
one pound of cement.
Water of Convenience: Water in addition to that of
the minimum water required for hydration but
required for a workable consistency.
RULES OF THUMB
FOR CONCRETE
Temperature Change vs. Setting Time:
An increase of 20oF will decrease the set time by onehalf.
A decrease of 20oF will double the set time.
Yield vs. Air Content:
A increase of one percent air will increase the yield of
one yard of concrete by 0.27 cubic feet.
Air Content vs. Strength:
As the concrete mix increases in air content, starting
at approximately 5%, each percent of air will result in
a strength loss of approximately 5% at a mid-range
cement factor.
RULES OF THUMB
FOR CONCRETE
The strength required for one freeze thaw cycle:
If the concrete is properly entrained the minimum
compressive strength required to resist damage
from one freeze thaw cycle is 500 psi.
Temperature vs. Strength Gain:
As the temperature of concrete decreases, the
rate of strength gain decreases. As the concrete
temperature approaches 40oF the rate of strength
gain virtually stops.
© 1999-2000, All rights reserved L&M Construction Chemicals, Inc