reconstruction and maintenance of concrete and reinforced conctrete...
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Reconstruction and maintenance of concrete and
reinforced conctrete structure
Examples of desintegration of visual concrete and
corrosion of reinforcement – small thickness of cover,
low-quality of concrete (weak concrete), carbonation of
concrete
Examples of desintegration of visual concrete and
corrosion of reinforcement – small thiskness of cover,
low-quality of concrete (weak concrete)
Carbonation of concrete pH < 11 – alkaline of concrete –
increasing the possibility of corrosion of reinforcement
high moisture of environments small thiskness of cover =
drop out of cover, breaking-out and follow corrosion of
reinforcement
corrosion of reinforcement - small thiskness of cover,
in-leak
Effect of corrosion of reinforcement
moisture
Expansion of capacity of
bar by corrosion
Increased effects of adverse of environment
reinforced bar
Pressure till 30 Mpa
(cause = expansion of
capacity)
Carbonation of concrete
Plan of electrochemical
corrosion
Conta
min
ated
concr
ete
by
chlo
ride
Rough defects during realization of reinforced of column – found
during demolition of structure
Examples of disturbance
(desintegration) reinforced
elements after earthquake (Taiwan)
Examples of desintegration of visual
concrete and corrosion of reinforcement –
small thiskness of cover, low-quality of
concrete (weak concrete) Examples of desintegration
(disturbance) of concrete by agressive
material
Low-class stairs element prepare in factory
Examples of roof from finish 19th
century
Examples of using anchor elements independance on bearing reinforcement
Variations of make-up sheare reinforcement
Examples of realisation reinforcement of
older reinforced concrete structure
steel profile
sheare reinforcement
Defect of reinforcemet of reinforced conctrete structure
Reinforcement of rod elements
Transversal
reinforcement of
column from steel
profile
Diagonal brace in
place of stirrup
Bracing of opposite
vertical bar by wire
Substitution of brace by loop
Transversal reinforcement
of column circuit section
brace in column with polygon
section
Unsuitable shape of brace
Continuous roof slab
with reinforcement by
lower surface
Using bearing
reinforcement of
bracket as brace
Incorrect reinforcement of roof
slab by loop in dilatation
Large distance
of brace
Incorrect storage sheare
reinforcement
Insufficient anchorage of
reinforcement ahead support Examples of defects realisation
reinforced concrete structure
Different shape of brace use in strucrure from year 1929
Incorrect location of bearing
reinforcement
Insufficient contact of
reinforcement of column by
overlap
small thiskness of cover
Incorrect make-up
reinforcement in
frame corner
Incorrect make-up
sheare
reinforcement and
reinforcement in
dilatation
Examples of defects realisation reinforcement of older reinforced
concrete structure
Incorrect make-up
reinforcement
Incorrect anchor
logitudinal reinforcement
in block foundation
Incorrect anchor
reinforcement above
support
absent anchor
reinforcement
absent
reinforcement of
frame joint with
haunch
Failures of concrete structure
-Tension and shear cracks, branching of cracks, crushing of concrete and exfoliation of surface
layers, exfoliation of covering layers, buckling of reiforcement and failure of covering, over strain
(deformation) of structure, carbonatation, increase (expansion) of porosity, changing pH, corrosion
of reinforcement
- Technological cracks – cause concrete shrinkage
- High tepmetrature during fire – 800°C till 60 min – disturbance (destruction) of surface layer, when
the covering is min. 15 mm – no changing of load bearing capacity
- from 1000°C till 1200°C – marked (extremly) deformation, cracks and
surface desintegration to depth 30 – 50 mm
- from 1400°C and 60 min and more loss of stability and load bearing
capacity, total desintegration
- rapid cooling of surface layers of concrete by water – desintegration
of layers and large decrease of cohesion between steel and concrete
- Bending moment while rise of cracks rectangular crossection with 0,8 – 1,15% of reinforcement
running at cca 100 MPa. Rise of cracks wider than 1,5 – 2 mm show, that strain is near by yield
limit
- During rise of cracks decrease bending rigidity – increase of deformation
- Desintegration of concreate by chemically effect is manifested rise crystallic new formation or
leach part of cement stone
Failures of concrete structure
- Reduction pH under 9,6 increase dangerous of corrosin of reinforcement
- Number, length and density of cracks on bending element (beam,…) are depend on number and
way of reinforcement. Increasing of ratio of reinforcement – increasing density of cracks (smaller
width, shorter than case with smaller reinforcement)
- Slope (inclination) of crack in bending beam depend on dominant strian of crossection (shear and
normal strain)
Chracteristic failures of vertical concrete structure
Failure of tension reinforced
concrete elements
Ten
sile
cra
cks
Lar
ge
dis
tance
of
stir
rup
Ver
tica
l te
nsi
le c
rack
s
Failure of concrete and reinforced concrete centric press elements
a) Concrete elements b) Reinforced concrete elements obli
que
crac
ks
Mas
siv
e p
iers
colu
mn
Poss
ibil
ty o
f buck
ling m
ain
rein
forc
emen
t
hai
rlin
e
wra
pp
ed c
olu
mn
Svislé prvky namáhané mimostředným tlakem vertical elements subjected to excentric compression
Failure of vertical elements subjected to excentric compression
Sta
tic
pla
n
Sta
tic
pla
n
Ten
sile
cra
ck
Cru
shin
g o
f co
ncr
ete
Incorrect
location of
reinfocement
Different
qaulity of
concrete
Initiative
deflection
of
column
Tensile
crack
Crushing
of
concrete
Deterioration
and drop of
surface layer
1. start crack 2. Failure of column on failure limit
3. Lightly
reinforcement column
4. mediumly
reinforcement column 5. hardly
reinforcement column
Failure of bearing rod elements subjected to bending moment –
dependence of ratio of reimforcement
Concrete wall (press) elements - Lightly reinforcement
Rise of surface technological
cracks in massive wall
Plan of
reinforcement of
element
Part of
larger
shrinkage
Part of smaler
shrinkage
normal strain
from shrinkage
Plan of deformation
of element –
shrinkage influence
Original size
Real
deformation –
rise of cracks
(tension strain)
teoretical
deformation –
ideal plasticity
Failure of monolitic concrete
wall in middle part by hairline
Course of moisture in time
Course of primary proportional
shortening in time
Course of strain from shrinkage
Rise of cracks – cause =
shrinkage of surface layer
Interaction wall –
roof = shaer tension
Failures caused by effect of
volume change of
temperature and shrinkage –
wrong location of stiffening
construction in load bearing
system
Shrinkage of roof slab
Stiffening core Frame structure
volume change of temperature
Stiffening core, walls Reinforced
concrete
roof
column
Effect of temperature (Straining of
stiffening structure) summer
winter
Effect of shrinkage of roof structure
Straining of roof structure
Straining of
stiffening
structure
Straining of
stiffening
structure
Chracteristic failures of horizontal concrete structure
Failure by
bending moment
Failure by
sheare
Dominate
bend
Spectrum of gradient
of cracks in
dependence on
dominate straining
Failure of beam with
haunch - critical load
Dependence of direction and
characrek of cracks on load
Lightly reinforcement beam
mediumly reinforcement beam
hardly reinforcement beam
Dimension and density of cracks on bending beam –
influence of reinforcement ratio
Characteristic failure of beam slab
Lightly reinforcement slab
hardly reinforcement slab
Tensile cracks
Vie
w f
om
bas
e (l
ow
er)
Characteristic failure of two-way slab
Cracks in two-way
slab, immovable
support by 4 side
(from base
(lower))
View overhead View overhead Cracks in roof slab
by reach ultimate
strength, (from
base (lower))
A) Lift of corner
of floating slab
(deflection about
35% larger than B
B) Prevention lift of corner Ordering of reinforcement resistent on torsion
moments in corner of slab
torsion
moments
Cracks in direction main reinforcement
Tensile cracks in part of
concrete cover of two-way
slab (in part of support is
smallr shrinkage of concrete
from
bas
e (l
ow
er))
Technological cracks rise in places
and direction of main bearing
reinforcement
Cracks caused by effect of
temperature
tensile cracks (in attic) sheare cracks (in attic)
Cracks caused by shrinkage and verical load
Cracks in hardly reinforcement element caused by shrinkage
Cracks in lightly reinforcement element caused by
shrinkage
Technological cracks in beam
caused by shrinkage
Maintenance of failure surface of concret structure
Reinforcement disturbed by corrosion
Removing of failure layer of concrete
1- carbonization of concrete
2- corrosion of reinforce
High pressure water jet (HPWJ)
Repaire by technology of air-placed concrete
3- layer of failure concrete, 4-
original reinforcement, 5- basis
treated by HPWJ, 6- additing
reinforcement, 7- air-palced
concrete, 8- adhesive bridge, 9-
maintenance material, 10-
impregnation
Protection of reinforcement before
corrosion
Clean reinforcement
Reinforcement with layer of
impregnation matrial
Using adhesive bridge on
surface concrete
Local repaire of concrete
Maintenance of concrete column, pier and wall
Passive cracks – corrosion of reinforecement and speeding of degradation of concrete – water vapour penetration concrete in larger depth
– depth filling, grouting, sheathing
grouting by polymer resin using for maintenance of cracks smaller than 1 mm, else need using resin with filling mass
grouting by epoxy resin are limitation by temperature of structure and surrounding, weather, moisture of structure and time
limit for working of resim after additing of accelerator
Polymercement mortar and concrete
Maintenance mortar (strength in tension with bending till 10 MPa, strenght in pressure till 60 MPa, modulus of elasticity till 30 000
MPa)
Additing of polypropylen fiber decrease rise of technological cracks and failures of surface concrete maintenance layer by effect of
shrinkage, water and frost
Steel-fiber-reincorced concrete (increase strength in tension with bending, higher ductility, strength in pressure, decrease water
permeability and decrease resistance against rise cracks)
Repaire mortar – markendly higher cohesion with basis than normal mortar about 70 till 100 %)
Horizontal structure – additional switching by prestress free cabel
Transversal bracing concrete element
pin
Cement mortar
Angel iron strap
Strap before welding preheating from
500 till 700 °C,
After cooling on normal temperature –
steel structure prestress masonry
Cement
mortar
Strengthening of
concrete column
and wall
concrete, Air-
placed concrete
Additing main
reinforcement
Additing strrup
Additing
strengthening
reinforcement
concrete, Air-placed
concrete
reinforced concrete
prefabricated
element
Grouting (cemet,
epoxy mortar)
Strengthening
steel profile
Cemet mortar
Welding steel
column
Influence of creep for distribution normal strain in
strenghtening cocrete column
Str
ain
aft
er s
tren
gth
enin
g
Str
ain a
fter
str
ength
enin
g –
long t
ime
afte
r re
alis
atio
n
Month
Original
concrete
New
concrete
year
Month
Month
Month
year
age
of
concr
ete
Diagram of work – carbonic fiber, polyester, aramid and
glass fiber
polyester
glass aramid carbon
steel
steel
polyester glass
aramid
carbon
Tensile
strength Modulus
of
elasticity
steel
Epoxy stick
Examples of strengthening by carbonic fabric(cloth), lamella CFRP
Maintenance of horizontal and roof concrete structure
Bending beams
Welding additing
reinforcement
Extending of section and
additing of
reinforcement, water
jetting surface
Extending of section and
additing of reinforcement,
water jetting surface
Supplying of failures
part of beam by new,
reinforcement
Strengthening by
steel profile and steel
diagonal
additing stick
reinforcement
pin
pin
Anchor plate
1 - Cement mortar (grouting epoxy resin)
2 - Hole – filling by cement mortar (grouting epoxy resin)
3 - Anchor pin
Strengthening of
beam by stick
reinforcement
additing angel profile
reinforcement
maitenance of reinforced concrete slabs
Epoxy resin
Strengthening by
reinforced cocrete layer
Loop from reinforcement
Channel in lower
surface
Guarantee of cohesion
by loop in thin slab
Guarantee of
cohesion by loop in
thick slab
Guarantee of cohesion
by thorn in thick slab
pin
Guarantee of
cohesion by
loop welding by
pin
hollow, filling by cem. mortar
Steel net
concreting hollow, filling by
cem. mortar
Zesílení betonových ohýbaných prvků uhlíkovými lamelami
strengthening of concrete bending elements by carbonic lamella
"Zesílení" ohýbaných nosníků (průvlaků) dodatečným podepřením
strengthening of bending beam by additing support
1 New supports of beam
2 Prestressing cable
3 Steel loop
4 Steel crossbeam
5 Steel tie
6 secondary beam
7 secondary column