DURABILITY of CONCRETE STRUCTURES - Weebly

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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