durability of concrete structures - weebly
TRANSCRIPT
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DURABILITY of CONCRETE
STRUCTURES
Assist. Prof. Dr. Mert Yücel YARDIMCI
Part- I
INTRODUCTION
This presentation covers the subjects in CEB Durable Concrete Structures Guideline and has been prepared by the graduate students under the supervision of Prof.Dr.Bülent BARADAN in Dokuz Eylul University.
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GENERAL KNOWLEDGE
- CONCRETE STRUCTURES SHOULD CONTINUE TO PERFORM
ITS EXPECTED FUNCTIONS (STRENGTH & SERVICEABILITY)
DURING THEIR SERVICE LIFE WITHOUT MAJOR REPEATED
REPAIRS
- ARTIFICIAL CONSTRUCTION MATERIALS ARE USUALLY
UNSTABLE. THEY ARE LIABLE TO CONVERT TO THEIR
ORIGINAL FORMS.
- NATURAL MATERIALS (MILLIONS YEARS OLD) ARE MORE STABLE.
EXAMPLE: NATURAL STONE
EXAMPLE:
IRON OXIDE ENERGY
STEEL RUSTING
IRON OXIDE
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SYMBOLS OF DURABILITY
ST. SOPHIA (ISTANBUL)
SERVICE LIFE :
537 AC COMPLETION DATE
(941 YEARS CHURCH + 422
YEARS MOSQUE & MUSEUM)
PYRAMIDS
(CHEOPS, KHEFREN,
MYKRENOS)
4500 YEARS OLD
EGYPTIAN PROVERB:
MANKIND IS AFRAID of TIME
TIME IS AFRAID of PYRAMIDS
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GENERAL KNOWLEDGE
ARTIFICIAL STONE (CONCRETE OR REINFORCED CONCRETE)
NEGATIVE FACTORS
DETERIORATION
SERVICE LIFE
P
E
R
F
O
R
M
A
N
C
E Time
Minimum
Before repair
After repair
Before repair
After repair
INITIAL
FINAL
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BS 7543: Guide to durability of building
elements, products and component
Monumental Constructions, Bridges,
Dams, etc. 100 4
Normal Buildings, Public Buildings 50 3
Demontable Construction elements,
Prefabricated beams, columns, etc. 25 2
ENV 1991-1 = BS 7543 Minimum
service life (year) Example Class
Temporary Buildings 1-5 1
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PHYSICAL & MECHANICAL
DETERIORATION of REINFORCED CONCRETE by
EXTERNAL & INTERNAL FACTORS
CHEMICAL & BIOLOGICAL
CORROSION of REINFORCEMENT
CRACKS SPALLINGS, POP-OUTS
LOSS of STRENGTH & RIGIDITY
DEFORMATIONS
CHANGE OF PORE STRUCTURE, INCREASE in PERMEABILITY
ACCELERATION of DETERIORATION PROCESS
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PHYSICAL & MECHANICAL FACTORS
CAUSES of MASS LOSS
CAUSES of CRACKS
WEARING, EROSION,
CAVITATION FIRE, HIGH TEMPERATURES
EXCESSIVE LOADING, REPEATED LOADING, FATIQUE LOADING, IMPACT LOADS
FREEZE-THAW, DE-ICING AGENTS, WETTING & DRYING, CHANGE of LENGTH & VOLUME
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CHEMICAL & BIOLOGICAL FACTORS
-SULFATE ATTACK
-DEF
-THAUMASITE ATTACK
-ASR and ACR
-DELAYED REACTIONS of CaO & MgO
-CORROSION of REINFORCEMENT
I. GROUP
HYDROLYSIS, WASHING OUT
II. GROUP
IONIZATON REACTIONS WITH AGGRESSIVE CHEMICALS
III. GROUP
PRODUCTS of REACTIONS of EXPANSIVE NATURE
REPLACEMENT of Ca++ IONS with
Mg++ in CSH
REMOVAL of Ca++ IONS by
FORMATION of SOLUBLE or UNSOLUBLE PRODUCTS
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PRINCIPLES of CONCRETE DESIGN
FACTORS
WORKABILITY
SLUMP, MIN. ENERGY for COMPACTION, COHESIVENESS, NO SEGREGATION, MIN. BLEEDING, HOMOGENIETY
OPTIMIZATION
PROBLEM
ECONOMY EFFECTIVE USE of SOURCES
STRENGTH CONCRETE CLASS (PROJECT)
DURABILITY IMPERMEABILITY + EXPECTED SERVICE LIFE
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COMBINED ATTACKS
Example: Sea water effect
(Physical+Mechanical+Chemical+Biological effects)
Trigger effect of one attack over others
Mechanical Attack
Cracks
Chemical Attack
Increase in permeability
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IN MOST CASES;
THE DIFFUSION OF WATER &/OR HARMFULL CHEMICALS &/OR GASES ARE REQUIRED
FOR CONCRETE DETERIORATION
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DIFFUSION
PERMABILITY of CONCRETE
DURABILITY
The main agents that can cause deterioration (BS 7543)
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• Temperature • Radiation: infrared, visible, ultraviolet and thermal radiation • Water: in both solid and fluid forms • Normal air constituents: oxygen, CO2 and sea spray • Air contaminants • Freezing/thawing • Wind • Biological factors: bacteria, insects, fungal attack, rodents and birds, surface growths and plants and trees • Stress factors: sustained and intermittent stresses • Chemical incompatibility: leaching, solvents, contaminated land and expansive materials • Use factors: normal wear and tear or abuse by the user