Concrete
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Major Topics
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History
Uses
Materials Used To Make Concrete
Cement
 Aggregate
 Water
 Admixture
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Major Topics con’t
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Testing
Slump Test
 Compressive Strength Test
 Air Content Test
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Strength
Placing
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Major Topics con’t
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Transporting
Curing
Finishing
Reinforced Concrete
Pre-cast Concrete
Pre-Stressed Concrete
ICF (Insulated Concrete Form)
4
Concrete History Facts
The History of Concrete: Textual
Noteworthy:
The Hoover Dam, outside Las Vegas, Nevada,
was built in 1936. 3 ¼ million cubic yards
of concrete were used to construct it.
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Concrete Resources
Concrete Admixtures - The Concrete Network
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Uses
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Foundations and Driveways
Architectural Details
CMU (Concrete Masonry Units)
Concrete Roofing (Arches &
Domes)
Columns, Piers, Caissons
Walls and Beams
Bridges
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Materials Used to Make Concrete
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Portland Cement – 5 types
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Should conform to ASTM C150
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Type 1 – standard; widely used; columns,
floor slabs, beams
Type 2 – has a lower heat of hydration;
used in massive pours; e.g. Dam
construction
Type 3 – high early strength; suitable for
cold weather
Type 4 – termed low heat; used in
massive pours to diminish cracking
Type 5 – sulfate resistant; used in sewage
treatment plants & concrete drainage
structures
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Air-Entraining Portland Cement
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Produces billions of tiny bubbles
Greatly reduce segregation of mix
Less water needed to produce a
“workable” mix
Has a better resistance to freezing
and thawing
Classified as Type 1A, 2A, 3A
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Aggregate
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2 classes
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Fine – sand; < 1/4 “ large
Coarse – gravel or crushed stone
Grading should conform to ASTM C33
Sieve analysis test (ASTM C136) and
analyses for organic impurities (ASTM
C40) often done
Represent 60-80% of the concrete
volume
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5 Aggregate Types
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Natural – sand and gravel
By-Product – blast-furnace slag or
cinders
Lightweight – materials heated and
forced to expand by the gas in them
Vermiculite – a type of mica that will
greatly expand
Perlite – a type of volcanic rock which
expands
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The Critical Role of Water in Mix
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Hydration – chemical reaction caused by
mixing the water with cement
Too much – prevents proper setting
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Laitance (bleeding) – white scum or light
streaks on the surface of concrete which
are very susceptible to failure
Too little – prevents complete “chemical
reaction” from occurring
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Proportioning of Mix
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1: 2: 4 – concrete consisting of :
1 volume of cement
 2 volumes of fine aggregate
 4 volumes of coarse aggregate
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Emphasis now on “Water-Cement”
ratio methods of proportioning
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Typical Design Mix (Yield: 1 cu.yd. of
3,000 psi of Concrete) ***
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517 lb. of cement (5 ½ sacks)
1,300 lb. of sand
1, 800 lb. of gravel
34 gal. of water (6.2 gal. per sack)
*** Data from Architectural
Graphics Standards, 2000
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Admixtures
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Materials added into the standard
concrete mixture for the purpose of
controlling, modifying, or impacting
some particular property of the
concrete mix.
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Properties affected may include:
 Retarding
or accelerating the time
of set
 Accelerating of early strength
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Admixtures con’t
 Increase
in durability to exposure
to the elements
 Reduction in permeability to liquids
 Improvement of workability
 Reduction of heat of hydration
 Antibacterial properties of cement
 Coloring of concrete
 Modification in rate of bleeding
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Testing of Concrete May Include
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Slump Test [ASTM C143]
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Compressive (Cylinder) Strength
[ASTM C192]
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Determines the consistency and
workability
Determines the “compressive unit
strength” of trial batches
Air Content
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Slump Test
**Concrete sample is placed into a 12”
sheet metal cone using 3 equal volumes.
**Each layer is tamped 25 times with a
bullet-nosed 5/8” by 24” rod.
**Last layer is leveled off with the top of the
cone.
**Cone is removed
**The vertical distance from the top of the
metal cone to the concrete is measured
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Compressive Strength Test
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Comply with ASTM C39
Basic steps:
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# of samples taken vary (no less than 3)
3 layers of concrete placed in a cardboard
cylinder 6” in diameter and 12” high.
Each layer is rodded 25 times with a 5/8”
steel rod
Samples are cured under controlled
conditions
Test ages vary but usually done after 7, 14,
and 28 days
Sample removed from cardboard and placed
in testing apparatus which exerts force by
compressing the sample until it fails (breaks)
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Strength of Concrete:
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Stated as the minimum
compressive strength at 28 days of
age
Design strength:
Typical residential 2,500 – 4,000 psi
 Pre- or Post tensioned typically 5,000
– 7,000 psi
 10,000 – 19,000 psi used in columns
for high- rise buildings
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Placing Concrete
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Temperature
 Optimum temperature for curing is 75 degrees F; may
have problems curing if temperature below 50 degrees F. If
temperature is lower or higher than normal curing ranges
special provisions must be made.
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Forms
 Wood and metal commonly used (reused)
 Clean and sufficiently braced to withstand the forces of the
concrete being placed
 Concrete weighs 135 – 160 pcf; if lightweight then 85 – 115
pcf; often in estimating the figure 150 pcf is used
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Placing Concrete con’t
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Free falling distance should not
exceed 4 feet due to the threat of
“segregation” of aggregates
occurring***
***This is according to the author (see page 103)
In 2001 the ACI (American Concrete Institute)
published research to indicate this is not the case
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Transporting Concrete
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Method selected depends on
quantity, job layout, and equipment
available
Chutes
 Wheelbarrows/Buggies
 Buckets
 Pneumatically forcing through a
hose (shotcrete)
 Pumps
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Curing
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Proper curing is essential to obtain
design strength
Key factor: the longer the water is
retained in the mix – the longer the
reaction occurs – better strength
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Evaporation of Water Reduced
by:
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Cover with:
Wet burlap or mats
 Waterproof paper
 Plastic sheeting
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Spray with curing compound
Leave concrete in forms longer
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Joints
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3 types:
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Isolation (expansion) – allow movement
between slab and fixed parts of building
Contraction (control) – induce cracking at
pre-selected locations
Construction – provide stopping places
between pours
Materials used:
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Rubber/plastic
Vinyl, neoprene, polyurethane foams
Metal/wood/cork strips
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Finishing
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Screeds – used to level the
concrete placed in the forms
Consolidation – may be
accomplished by hand tamping
and rodding or using mechanical
vibration
Floating – done while mix still in
plastic state; provides a smooth
surface
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Finishing con’t
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Final stage may include:
Incorporation of materials for
toppings (adjust the “look”)
 Non-slip finish – use broom to
“rough-up” the surface
 Patterns – accomplished by
pressing form patterns into surface
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Reinforced Concrete
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Concrete has good compression
strength but little tensile strength
Steel excels in tensile strength and
also expands and contracts at
rates similar to concrete
Steel and concrete compliment
each other as a unit
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Reinforcing Steel [Rebar]
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Manufactured as round rods with raised
deformations for adhesion and
resistance to slip in the concrete
Sizes available from #3 to #18 –the size
is the diameter in eighths of an inch
Galvanized and epoxy coatings often
used in corrosive environments (parking
structures & bridge decks – where
deicing agents used)
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Reinforcing Bar
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Placement, size, spacing, and number of
bars used vary according to the specific
project
Markings on bars include:
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Symbol of producing mill
Bar size
Type steel used
Grades (yield & ultimate strength –
grades of 40, 50, 60, & 75 common)
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Welded Wire Reinforcing
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Also may be used as a
reinforcement in concrete
2 sets of wires are welded at
intersections to forms
squares/rectangles of a wire mesh
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Pre-Cast Concrete
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Individual concrete members of
various types cast in separate
forms before placement (may be at
job site or another location)
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Tilt-up slabs are often pre-cast in
the field
Walls and partitions are often
made of pre-cast units
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Pre-Stressed Concrete
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Concrete which is subjected to
compressive stresses by inducing tensile
stresses in the reinforcement
Attributes:
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Concrete strength is usually 5,000 psi at
28 days and at least 3,000 psi at the time
of pre-stressing.
Use hardrock aggregate or light weight
concrete
Low slump controlled mix is required to
reduce shrinkage
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Advantages of Pre-Stressed
Concrete
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Smaller dimensions of members
for the same loading conditions,
which may increase clearances
(longer spans) or reduce story
heights
Smaller deflections
Crack-free members
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ICF’s
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Insulated Concrete Forms
Combines the properties of concrete with the
advantages of insulating material
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History: What is an ICF?
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An ICF is basically a concrete wall that is
constructed by using formed in place
concrete forms.
A resistive foam insulation, such as
polystyrene, is added to the product.
Since the pressure of wet concrete is
high, specialized form ties are used.
They also allow for the attachment of
finishes later in the construction process.
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History cont.
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The ICF technology was first established in
the European marketplace in the late 60’s.
Mr. Werner Gregori patented a “Foam Form
of Canada” in March of 1966.
The Europeans then took his idea to the
scale that it is used today.
Canadian Energy Conservation policies
helped build a strong market for ICF’s in
Canada.
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History cont.
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As problems such as high winds,
high energy bills, fires, and other
natural disasters in the United
States, ICF became more popular.
ICF’s were sold as an alternate
building material since the 1970’s.
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Characteristics of ICF
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Polystyrene
Foam pieces
contain: Plastic
or steel
components
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Uses of Material
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Commercial
Residential
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Specific Uses
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Commercial
Doctor’s Offices
 Malls
 Industrial Park Buildings
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Residential
Homes
 Basements
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Types of ICF’s
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I-Form
E-Form
C-Deck
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Types: I-Form
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Universal Design
6” on Center Tie Placement
Loose Fir, Two Deep Snap-In
Rebar
Multiple Rebar Positioning
Quick Concrete Flow
Superior Tie Fastening Device
Recessed, Full-Length Tie
Open 1” Tooth Design
Versatile Sizes
Universal 90 degrees and 45
degrees Corners
Corner Tie for Attaching Finishes
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Types: E-form
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Perfect curing environment
Ship lap joints
Full-length tie
Efficient Installation
Quick Concrete Flow
Handy Rebar Chair
Trusted Design
Versatile Sizes
Molded 90 degrees and 45 degrees
Corners
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Types: C-Deck
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Customized System
Lightweight Materials
Self-Supporting Panels
Insulate Without Thermal Bridges
Built-in Ventilation Ducts & Utility Passages
Minimize Floor Thickness
Easy to Finish
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Sizes
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Panels often come in sizes of:
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4’ x 8’
Planks—1’ x 8’
Block forms—16” x 4’
When delivered to the job site they are in
separate 2” thick planks of form and then
they are snapped into the wall with
plastic crosspieces called ties.
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Advantages for Builder
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Stability
Versatility
Accuracy
No Moving Parts
Lighter weight
Design Simplicity/ Easy to use
Easily to form curves and ties
Cost Competitive
Internationally Proven & Code-Accepted
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Advantages for Homeowner
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Greater comfort & lower energy
bills
Reduces heating and cooling loads
Solid & lasting security
Peace & quiet
Less repair & maintenance
Healthier home and environment
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Disadvantage
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As it existed 30 yrs ago the same
types of challenges exist today.
The challenge is to convince an
industry that does not readily
accept change and to try
something new by using ICF rather
than the conventional construction.
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Why Consider ICFs?
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ICF has become
increasingly popular for
several reasons:
Energy savings for ICF
homes are in the
neighborhood of 20% in
comparison to wood frame
homes which meet only
minimum thermal
insulation requirements.
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Why consider ICF’s (cont.)
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Structural stability and soundness is also
another major advantage of the ICF
structure.
Studies have shown, noise levels from
exterior sources tend to be lower in the
interior of ICF homes. Design
considerations such as “sound tightness”
and number of windows and doors help
the overall noise reduction.
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Application/Installation
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Most important step is correctly installing
footings.
They should be smooth, square, and
level.
A line is chalked inside and outside the
edges of a wall.
Vertically rebar reinforcements are
critical to the strength of an ICF wall.
Light gauge metal guides are placed
horizontally against the footings to hold
the ICF form straight.
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Application cont.
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Vertical rebar is tied to
reinforcement dowels.
Minimum bracing is required every
10’ of wall space where there are no
windows or doors to support the
forms while the concrete is being
poured and cured.
Place all door and window framing
in place making sure they are
securely braced, level, and plumb.
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Application cont.
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Installation of a ledger board allows
framers to correctly lay out floor joist as
required (several method are required).
Concrete is then pumped in multiple lifts
approximately 4’ high to insure proper
consolidation of concrete.
After proper curing an approved
basement exterior sealant that is
compatible with expanded polystyrene is
applied to the exterior walls.
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Application cont.
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Stucco may be applied directly to
the exterior walls or the recessed
fastening strips are clearly marked
by raised beads to attach wood,
vinyl, or metal siding or any type
masonry that is desired.
Any desired interior wall finish may
be attached directly to furring strips
with regular drywall screws.
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Related Technologies
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ICF have been recognized by the
American Lung Association for its
participation for clean air
environment.
ICF withstand measure wind
speeds of more than 200 mph with
virtually no wind damage.
In fire tests, ICF withstood intense
flames and heat for as much as 4
hrs.
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Related Technologies (cont.)
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ICF have been engineered to
have excellent performance
seismic zones.
ICF wall systems have been
singled out by the American
Architectural Review for
promoting progress in the
world of Architecture.
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New Developments
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As technology advancements in
technology, many companies are
starting to manufacture ICF.
The number of ICF’s are
increasing, it is estimated that
between 23 and 40 manufacturers
exist in North America.
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Additional Concrete Products
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Stamped concrete
Flowable fill
Pervious concrete
Tilt-up
Translucent concrete—for
information about this click on the
link below
http://www.litracon.hu/
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References
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Construction Materials and Processes, 3rd Edition. Watson, Don
A.. McGraw-Hill, 1986. Imprint 2000. ISBN: 0-07-068476-6
Construction Principles, Materials, and Methods, Seventh
Edition. H. Leslie Simmons, John Wiley and Sons, Inc., 2001.
Architectural Materials for Construction, Rosen, Harold J. and
Heineman, Tom. McGraw-Hill, 1996. ISBN: 0-07-053741-0
Basic Construction Materials, 6th Edition. Marotta, Theodore W.
Prentice Hall, 2002. ISBN: 0-13-089625-X
Building Construction: Materials and Types of Construction, 6th
Edition, Ellison, Donald C., Huntington, W.C., Mickadeit, Robert
E.. John Wiley & Sons. ISBN: 0-13-090952-1.
Architectural Graphic Standards: Student Edition, Abridgment of
9th Edition. The American Institute of Architects. John Wiley &
Sons. ISBN: 0-471-34817-1
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References
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Concrete Homes and Buildings. (1998). Insulated
Concrete Forms (ICF). Retrieved March 15, 2003 from
www.crmca.org/ICF/default.htm.
Eco-Block Installation Manual
Reward Wall Systems. (2002). www.rewardwalls.com.
ICF Web. (2001). www.icfweb.com.
NAHB Research Center. (2001-2003).
www.nahbrc.org.
Alby Material Incorporated. www.alby.com.
American Conform Industries. (2003). Smartblock.
www.smartblock.com.
Insulating Concrete Form Association. www.forms.org.
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