Chpt 10 Flashcards
Because concrete is noncombustible, it is widely used in
Fire resistive construction
In almost all structural applications concrete is reinforced with
Steel
Is produced from Portland cement coarse and fine aggregates, and water
Concrete
Concrete must be ____ in order to reach its proper strength
Cured
Hardening or concrete involves a chemical process known as
Hydration
In hydration , water combines with particles of cement to form a microscopic gel. As the concrete hardens, this gel gives off heat, which is known as the
Heat of hydration
In addition to maintaining proper moisture, concrete that is curing must be maintained at the correct temperature, ideally between
50-70f
Theoretically, properly cured concrete continues to harden indefinitely at a gradual rate, however, normal design strength is reached after
28 days
Different types of concrete can be produced for specific purposes. This is accomplished by varying the ingredients or adding chemicals to the concrete mixture, these are generally known as
Admixtures
Like masonry, concrete is strong in compression but weaker in
Tension
Because concrete is weak in tension, it cannot be used where tensile forces occur in a structure. To resist tensile forces, concrete is reinforced with ______ placed within the concrete before it hardens
Steel reinforcing bars
With_____, steel bars are placed in the formwork and the wet concrete is placed in the formwork around the bars
Ordinary reinforcing
The vertical reinforcing of bars are known as _____ and are provided to resist the diagonal tension
Stir ups
Although the primary function of placing reinforcing steel concrete is to resist tensile forces, the steel can also be used to support some of the
Compressive forces
In ____ a compressive load is induced in the concrete before the load is applied
Prestressing
In_____ concrete, steel strands are stretched between anchors producing a tensile force in the steel
Pretensioned concrete
When concrete is ______, the reinforcing steel is not tensioned until after the concrete has hardened
Posttensioned
As a general rule, reinforcing steel should not be cut in the course of fire fighting operations unless it is necessary to
Rescue trapped victims
Concrete can be either
Cast in place or precast
Is placed into forms at the building site as a wet mass and hardens in forms
Cast in place concrete
Is placed in forms and cured at a precasting plant away from the job site.
Precast concrete
Permits the designer to cast the concrete in a wide variety of shapes
Cast in place concrete
This type of concrete does not develop its designed strength until after it has been placed in the location where it will be used
Cast in place concrete