Chapter 10 Concrete Construction Flashcards
Concrete is the hardened form of _______ produced from Portland cement
Cement
Inert mineral ingredients that reduce the amount of cement that would otherwise be needed
Aggregates
Course aggregates
Fine aggregates
Gravel, stone
Sand
Ingredients or chemicals added to concrete with specific characteristics
Admixture
Admixture that used to produce a mixture that flows more freely
Superplasticizers
Concrete structure elements usually retain their integrity and concrete slabs and walls act as good
Fire barriers widely used in type 1 construction
Concrete is at one in compression but weaker in
Tension
What’s the ultimate compressive strength of concrete
2,500 to 6,000 psi
Reinforcing components can include what for concrete
Steel bars ( rebar)
Wire mesh
Fiber glass additives
Ordinary reinforcing uses ________ placed in the framework and wet concrete placed in the framework
Steel bars
Used to ensure that the wet concrete fills all the spaces within the framework
Mechanical vibrators
When concrete is hardened it adheres to the reinforcing bars because of what
Textural shaping of the surface of the bars
Reinforcing concrete uses a planned grid of structural reinforcing materials to provide
Lateral and tensile support
Are commonly referred to by a standardized number instead of the actual diameter
Rebar sizes
Largest size is #18
Most common size #5
Concrete beams usually cast the shape of a
Tee
Vertical reinforcing bars are known as
Stirrups and are provided to resist the diagonal tension
To avoid buckling ___________ is provided around the vertical bars
Lateral reinforcing
This technique is more efficient use of concrete than ordinary reinforcing
Prestressing
Two common types of prestressing
Pretensioning
Post-tensioning
Reid forces steel should not be cut durning firefighting operations unless to
Rescue a victim
Uses steel strands (cables) stretched between anchors producing a tensile force in the steal concrete
Pretensioned reinforced concrete
Uses reinforcing steel cables that are not tensioned until after the concrete has hardened
Post tensioning
Prestressed concrete systems may be more vulnerable to failure that
Ordinary reinforced concrete
Placed in a form and cured at a plant away from the job site
Precast concrete
Placed into forms at the building site as a wet mass and hardens in prepare forms
Cast in place concrete usually stronger that precast because of continuity in intersecting members
Using sand from the beach in concrete over time cans _________ and ________ overtime to the reinforcing steel
Corrode and deteriorate
Normal design strength is reached after
28 days
The quality of concrete must be tested to ensure the ____________ of the mixture for the purpose
Suitability
Single most important factor in determining the ultimate strength of concrete
Water to cement ration
If too much too much water has been used in the mix the final product will not achieve its
Desired strength
Hardening of concrete involves a chemical process know as
Hydration
Water combines with the particles of of cement to form _________ this gel releases heat of hydration
Microscopic gel
The moist curing produces a
Stronger concrete
Concrete in the process of curing mist be maintains in the correct temp
Between 50-70 degrees.
100 degrees will not reach its proper strength
Method of evaluating the moisture content of wet concrete by measuring the amount that small cone shaped sample when removed from a standard sized test mold
Slump test
Concrete structural systems can have fire resistance rating of
1-4 hours
Structural lightweight concrete is not used for the
Load bearing application
Construction technique using concrete slabs supported by concrete columns
Flat slab concrete frame
Plain floor slab about 8 inches thick that rests on columns spaced up to 22 feet
Flat plate
The primary cause of spalling is the expansion of the
Moisture with in the concrete when heated or frozen
Concrete tends to retain the heat of an exposing fire then releases heat slowly
Heat sink effect
Flat slab concrete frame ranges in thickness
6 to 12 inches
Frame consists of a concrete slab and supported by concrete beams
Slab and beam framing
This framing system is extremely lightweight and is best suited for buildings with light floor loads
Slab and beam framing
Concrete beams run mainly in one direction - one way reinforced slab
Sometimes referred to joist construction - similar to wood framing
Slab could be as thin as 2 inches
Slab and beam framing
Slab and beam concrete framing featuring concrete beams tuning in two directions is known as
Two way slab construction or waffle construction
This construction is used where spans are short and flood loads are high
Waffle construction or two way framing system
Can be produced using polystyrene core to improve the insulating properties of the precast concrete
Precast concrete sandwich panels
Precasting concrete became a common practice after
World War II
Precast concrete slabs for floor systems I’m standard shapes of
Solid slabs
Hollow core slab
Single tee slabs
Double tee slabs
Precast concrete solid slab are used for short spans of
Approx 30 feet
Tee slabs can be used for spans up to
120 ft
Type of construction in which concrete wall sections (slabs) are cast on the concrete floor of a building then tilted up to vertical position
Tilt up construction
Also known as tilt slab construction
Supports for precast beams may include
Corbels ( brackets ) cast into the columns
