chapter 10 Flashcards
concrete construction
like masonry concrete doe not ?
burn
concrete also resist “” and the effects of contact w/ ‘’
insects/ soil
concrete is the hardened form of ‘’ produced form ‘’ coarse and fine ‘’ and ‘’.
cement, porland cement, aggregates and water
course aggregates include ‘’
fine aggregates include ‘’
gravel/stone
sand
what make up a large volume of cement
aggregates p. 257
types of admixtures OF CONCRETE are:
S/C - REDUCED DENSITY
S-P- COLORING
shale or clinker - reduce density of concrete
super-plasticizers
coloring
any adhesives material or variety of materials which can be made into paste w/ adhesives and cohesive ro bond inert aggregate materials into solid mass chemical hardening
cement
particulates materials used to provide a stable blend bedding or reinforce a composition material. Used as an extender in concrete can be graded into course and fine grain sizes and material types, including sand, gravel, and stone
aggregates
ingredients or chemicals added to concrete mix to produce to make concrete w/ specific characteristics
admixtures
What ‘’ admixtures is used w/ concrete or mortar mix to make it workable , pliable and soft while using relatively little water, flow more easily
super-plasticizers
types of concrete include:
SC
SLC
ILC
G
HES
E
WPC
ordinary stone concrete
structural lightweight
insulating lightweight
gypsum
high early strength
expansive
water-permeable
concrete walls and slabs act as good
fire barriers
concrete is widely used for what kind of construction
type 1 fire resistant
primary ‘’’ of concrete:
produced fro locally available and low cost raw material
noncombustible
performs well under mild to moderate fire conditions
good insulating properties p. 258
advantage
like masonry, concrete is strong in ‘’ but weaker in ‘’
compression /tension
untimate compressive strength can range from
2500-6000
’’’ concrete includes componets added to the concrete before it hardens to resist tensile force.
reinforced concrete
reinforcing components can include:
R
WM
FG A
rebar, wire mesh or fiberglass additives p259
rebar size are commonly referred to by a standardized ‘’, what is the most common size
number , 5 .625 inch
concrete beams are frequently cast in the shape of
T
what is put at the bottom of a concrete beam to reduce tensile force
reienforced steel
vertical reinforcing bars are known as ‘’, they provided to resist the “”” tension and resist bending forces in the column from such sources as wind and settling
stirrups
Diagonal
.260
when a concrete beam or floor slab supports a load, the concrete in the part of the beam in tension is doin what
no work
tensioning reinforced bar before concrete is pour is
prestressing
2 common methods of prestressing concrete are
pretensioning and postensioning
what should not be cut during FF opts unless necessary to rescue trapped victims
reinforced steel
what is like to happen if post tension reinforced steel is cut in concrete
to spring out of concrete, they are like big rubber bands p. 261
uses steel strands ( cables stretched b’tw anchors producing tensile force in the steel is ?
pretensioning
uses reinforcing steel cables that are not tensioned until after the concrete has hardened to certain strength
posttensioning p. 262
what type of concrete system may be more vulnerable to failure than ordinary reinforced concrete
prestressed concrete
systems use reinforcing cables and rods made of high strength steel that can yield as temps as low as
752
prestressed concrete will fail sooner than
conventional reinforced assembly
what is placed in forms and cured away at a plant away from a job
precast concrete
what is placed in forms at the buildings site as a wet mass and hardens in prepared forms
cast in place concrete
most ‘’ is proportioned at bulk plants and then mixed in a mixing truck enroute to the job site
cast in place
common application for concrete include
pavement , foundations , columns, floors , walls , concrete masonry units
during the curing process concrete will what
shrink slightly
normal design strength is reach how what day
28
single most important factor in determining the intimate strength of concrete is the ‘’ to ‘’ ratio
water to cement
if to much what is added to the mix what happens
water
concrete doesn’t reach desired strength
hardening of concrete involves the chemical process known as ‘’. in which water combines w/ particles of cement to form a microscopic gel
hydration
during hardening of concrete , heat is given off by chemical process
heat of hydration
in the process of curing the correct temp is required which is ideal between
50 and 70 “
concrete above 100 will not what
reach its proper strength
concrete cured at freezing temps will
harden more slowly p. 264
method of evaluating the moisture content of wet concrete by measuring the amount that a small cone shaped sample of the concrete stumps after it is removed from a standard sized test
slump test
concrete with high moisture content has greater ‘’ than dryer concrete
greater slump
uses small test cylinders of a concrete batch to determine the compression strength of that batch
compression testing * most costly p. 265
’’’ of concrete assembly is affected by such variables as:
density
thickness
quality
load
depth over the reinforcing bars
fire resistance
what concrete has a lower density than ordinary concrete and had a lower thermal conductivity which acts as a better insulator against heat
lightweight concrete
non resistive members supporting concrete floor slabs or wall panels
precast walls panels horizontally braced with exposed steel roof beams
opening in concrete slabs / walls w’o rated assembly protecting the opening
force of an explosion p. 266
ARE fire resistance of concrete assemblies THAT ARE ?
COMPROMIZED
expansion of moisture w/in concrete when heated or frozen is ( weakens concrete and exposed steel to fire )
spalling
concrete tends to retain heat of an exposing fire and release it slowly, in an effect called
heat sink effect
a simple system that consist of a concrete slab w/ concrete columns for support ( 6-12 inch ) ( good for building supporting hvy loads
flat slab concrete frame
building supporting light loads don’t need as much reinforcing so they use a system called
flat plate p. 267
what type of beam frame consist of concrete slabs supported by concrete beams also called
slab and beam ( light floor loads) 2 inch thick
Concrete joist construction
what are highly susceptible to fire damage because of slab thickness
slab and beam
when concrete beams run one way its know as
one way reinforced slab
slab and beam concrete framing featuring concrete beams running 2 ways is know as
2 way slab construction * looks like waffle ) also called waffle construction
when is slab and beam concrete framing used when ‘’ are short and ‘’ are high.
when spans are short and floors are high
’’’ structural shapes included:
slabs
wall panels
columns p. 268
precast
advantages to using ‘’’
higher degree of quality possible than cast in place
work can be proceed faster
polystyrene core improves insulating
precast concrete:
major disadvantage of concrete
transporting it and cost for it p. 269
’’’’ systems can be cast in standard shapes including:
solid slabs
hollow core
single try
double tee slabs
precast floor
common form of construction used w/ precast concrete, reinforced wall panels are cast at the job site in horizontals casting beds, after cured a crane tilts the wall panels up
tilt up construction
a variety of techs such as ‘’’ can be used to connect precast structural components to each other
bolts, welds, and posttensioning p270
precast concrete is commonly used in construction of
parking garages,
choices of material used in curtain wall may be influenced by style, thermal properties and cost material may include:
A
G
S
M
alumna , glass, steel and masonry. 271
Examples of details that are difficult to determine after construction /?
ordinary reinforcing vs psotention
cast in place vs precast
stucco vs concrete
supports for precast beams by include
corbels ( brackets ) short steel beams cast into poured colums p. 272
What is an example of a reason to add coloring to concrete? (p. 258)
Indicate buried electrical cables
What uses steel bars placed in formwork and concrete is placed in the formwork around the bars… concrete must be properly compacted as it is placed in the forms to surround the reinforcement bars and avoid cavities in the Harding concrete… what are used to ensure that the concrete fills the space within the framework?
Ordinary reinforcing
Mechanical vibrators 259
Reinforcement allows concrete to resist which type of forces?
tensile force
Vertical reinforcing bars are designed to resist what type of tension?
Diagonal tension
What is the simplest and most economical floor system used in concrete buildings? (p. 266
flat plate
In a flat-slab concrete frame, what range of thicknesses may be used?
6-12 inch
Precast concrete sandwich panels have which type of core?
Disadvantage?
Polystyrene
Expensive transport
Solid slabs are used for short spans up to ‘’’ while slabs can be used for spans up to ‘’’
30
120
In the simplest of precast design, precast slab simply rest on ‘’’’ or ‘’’ simple designs of this type, not inherently, rigid and laterally ‘’’ together to resist horizontal forces
Bearing wall
column
tied
What kind of support for precast beams can be cast into concrete columns?
Corbel
