Part-II (164 slides)HY - Ki??isel...

SEWER SYSTEM

Hydrogen sulphide formationin oxygen-free surface

Escape of hydrogensulphide

Acidattack on concrete

Bacteriologicalformation of sulphuric acid in O2

containing environment at theconcrete surface

ACID ATTACK

ACID ATTACK

(Typical new and

undeteriorated condition of

sewer pipe)

(Concrete deterioration

of sewer pipe)

Effect of various acids on Concrete

Rate of

Attack

Type of acid

Inorganic Organic

Medium Phosphoric Tannic

Rapid

Hydrofloric,

Hydrochloric,

Nitric, Sulfiric

Asetic,

formic,

lactic

Slow Carbonic -

Negligible - Oxalic, Tartaric

ACID ATTACK

MASS LOSS, STRENGTH LOSS

INCREASE IN PERMEABILITY

SPECIMENS SUBJECTED TO 7% SULFURIC ACIDCONCENTRATIONS FOR 21 DAYS AFTER STANDARD CURING OF 28 DAYS

HNO3 HCl H2SO4 CH3COOH

ACID ATTACK

SURFACE VIEW OF SPECIMENS SUBJECTED TODIFFERENT ACID TYPES AND CONCENTRATIONS

pH meter

ACID ATTACK

Concrete silo

Agriculture Industry

grain silos

Organic acid

attack

humidity

Concrete pits for pickle production

ACID ATTACK

Phosphoric-Acid-Industry

ACID ATTACK

Concrete silo

Rubber- and Brick-Lining

for a concrete Reactor in

the Filtration unit

ACID ATTACK

A mineral processing plant’s

neutralization system pits and

chambers with a throughput of

500,000 litres per hour. The process is

continuous (24 hours a day). Tropical

location, the effluent is never below

45° C.

Concrete pit

ACID ATTACK

Concrete olive pool

Oleic acid attack

Triglyceride esters of oleic acid

compose the majority of olive

oil, although there may be less

than 2.0% as actual free acid in

the virgin olive oil, with higher

concentrations making the olive

oil inedible.

Attack by feed acids (aceticceticlacticlactic acidacid) ) and Urea

Concrete floors and columnsat animal barns

ACID ATTACK

A fertilizer basement in construction for a cow barn

ACID ATTACK

Corrosion of floodgate

due to acidic water

ACID ATTACK

Reinforced concrete floodgates

Precautions against acid attack

Epoxy impregnated

concrete floor or

direct epoxy coating

Coating of concrete

surface with polimer

or bituminous based

materials

ImpermeabilityImpermeability is not a is not a sufficientsufficientprecautionprecaution methodmethod againstagainst acidacid attackattack

SULFATE ATTACKDRY & SOLID SALTS ⇒ NOT DANGEROUS! HUMID ENVIRONMENT⇒DANGEROUS

Diffusion of sulfates into

concrete

Sulfate solutionfrom the

environment

Expansionreaction of

C3A

HydratedC3A

Crackformation

SOURCES OF SULFATE

SOIL (WHITE SALT RESIDUALS ON SURFACE; LAND DRY & WITHOUT TREES & PLANTS EXCEPT SOME BUSHES)

CEMENT (FROM GYPSUM CaSO4.2H2O, max. SO3 ≤≤≤≤ 3%)

SEA WATER, UNDERGROUND WATER

SULFATE ATTACK

General view of sulfate bearing soils

Mortar samples exposed to sulfate

BEFORESULFATE

EXPOSURE

AFTERSULFATEATTACK

SULFATE REACTIONS

IONS OF SO3> 200 (600 ppm) mg/l ⇒⇒⇒⇒ DANGEROUS

Sulfate ions

SO3- + Ca(OH)2 + H2O CaSO4.2H2O (124% Volume increase)

Gypsum

Na2SO4

Na2SO4.10H2O + Ca(OH)2 CaSO4.2H2O + 2NaOH + 8.H2O

Gypsum

MgSO4

MgSO4.7H2O + Ca(OH)2 CaSO4.2H2O+Mg(OH)2 + 5.H2O

Gypsum

REACTIONS WITH Ca(OH)2

3(CaSO4.2H2O)+3 CaO.Al2O3.12H2O+20H2O

3CaO.Al2O3.3 CaSO4.32H2O

Ettringite ( Candlot salt) 227% Volume increase

Na2SO4

2(3CaO.Al2O3.12H2O) + 3Na2SO4 . 10H2O

3CaO.AL2O3.3CaSO4.31H2O + 2Al(OH)3 + 6NaOH + 17H2O

MgSO4

REACTION WITH C3A

CaSO4.2H2O

3CaO.2SiO2.aq + MgSO4.7H2O

CaSO4.2H2O + Mg(OH)2 + SiO2.aq

Ettringite

Worst Effect: Attack to CSH besides C3A & Ca(OH)2

SULFATE REACTIONS

* WHITE STAINS

* CRACKS AT CORNERS & EDGES

* PEELING - DROPS

* SOFTENING - FRIABILITY

WATER MOVEMENT (WETTING&DRYINGCYCLES ACCELERATES THE REACTION)

SIGNS

DANGER LIMITS INWATER

INSOIL

TS3440 3000 ppmSO4-2

MILD 600 ppmSO4-2 2000 ppmSO4

-2

SEVERE 2000 ppmSO4-2 5000 ppmSO4

-2

SULFATE ATTACK

DANGER LIMITS ACCORDING TO ACI 201

Negligible 0.00 – 0.10 0 - 150

EffectSoluble (SO4

-2) %

IN SOIL IN WATER

SO4-2 mg/lt

Moderate 0.10 – 0.20 150 - 1500

Severe 0.20 – 2.00 1500 - 10000

Very severe over 2.00 over 10000

DAMAGED WATER CHANNEL

PIPES LEFT ON SOILS RICHWITH SULFATE

DAMAGED BRIDGE COLUMN

DAMAGED SIDEWALK

SULFATE TEST RESULTS(84 days of testing period)

Test specimen Control specimen

PREVENTATIVE MEASURES

IMPERMEABLE CONCRETE

USING CEMENT with LOW C3A CONTENT

STABILIZATION of LIME (Ca(OH)2) with POZZOLANS

CONCRETE MUST BE INSULATED if NECESSARY

C3A ≤ %8 CEMENT MODERATE RESISTANT to SULFATE

C3A ≤ %5 CEMENT HIGHLY RESISTANT to SULFATE

CLASSIFICATION OF ENVIRONMENTALEXPOSURE –TS EN206

AGGRESSIVECHEMICAL

ENVIRONMENT

XA1 XA2 XA3Max.

W/C 0.60 0.50 0.45

XA1 : LOW AGGRESIVE CHEMICAL ATTACK

Min. Strength

(MPa)C25/30 C35/45 C35/45

Min. CEMENT

DOSAGE (kg/m3)280 320 320

OTHER SULFATE RESISTANT CEMENT

XA2 :MODERATE AGGRESSIVE CHEMICAL ATTACK OR SEA WATER

XA3 : EXCESSIVE AGGRESSIVE CHEMICAL ATTACK

DEF (DELAYED ETTRINGITE FORMATION)

What is DEFWhat is DEF ( ( DelayedDelayed EttringiteEttringite FormationFormation ))??

Damage (expansion & cracking) of concrete due to the formation

of ettringite after the concrete has hardened

Damage due to DEF was first reported in heat-cured railway ties in

Germany in the early 1980’s Heinz et al, 1989

HUMIDENVIRONMENT

CEMENTTYPETEMPERATURE

- Wetting and drying cycles- Tightness problems,

- Massive structure- High cement quantity- Exothermic cement- Concreting in summer

- C3A > 7%- SO3 > 2,5%- Na2Oéq > 0,6%

TemperatureCement type

HumidEnvironment

DEFRisk

�� No characteristic properties of visual damages induced by DEF

�� The study of civil engineering structures shows that not onlyprecast concretes are concerned by DEF

�� There is a risk for large civil engineering structures

�� Nevertheless, numerous factors are implicated in the DEFmechanisms.

Those factors can by classified in 3 groups :

19

•Homogenious paste expansiontheory

•Crystal growth theory

(accumulation of ettringite crystals )

ETTRINGITE

Conversion to monosulfate

Sulfate adsorption by CSH

ettringite

time

DEF EXPANSION MECHANISMS

ettringiteettringite

monosulfoaluminatemonosulfoaluminate

DEF(DELAYED ETTRINGITE FORMATION)

PREVENTATION OF ETTRINGITE FORMATION IN EARLYPERIODS OF HYDRATION

CONTINOUS WETTING-DRYING IN OPEN ATMOSPHERE (HEAT)

LATE FORMATION OF ETTRINGITEC3A.CaSO4.32H2O

CRACKS

Delayed ettringite formation is a form of internalsulfate attack

SHANGHAI JINMAO BUILDING

Binanın yüksekliği: 440 m

Temel betonu sınıfı: C50

Temel yüksekliği: 4 m

Betonun yerleştirilmesinden 40 saat

sonra ölçülen sıcaklık : 97 °C

Beton sülfoaluminat bazlı

genleşen kimyasal katkı içeriyor

DEF Risk !!!





Betonun yerleştirilmesinden 40 saat

sonra ölçülen sıcaklık : 97 °C





Sulfoaluminate based chemical

admixture

40 hours Recorded concrete

temperature after casting : 97 °C


Height: 440 m

Foundation concrete class: C50

Height of foundation: 4 m


PREFABRICATED COLUMNS

TEXAS –prefabricated beam


BESIDES PREFABRICATION

MASS CONCRETE PRODUCTION ON HOT WEATHERS

IN FIRE

CharacteristicDEF Cracks

K9-E

Ettringite formation in void

90x 330x

1000x 3000x

Expansion for 502 days : % 0.86

%4.5 %4.5 SOSO33

5000 5000 cmcm22/g /g BlaineBlaine

Different forms of Ettringite

DU9-E

%4.5 %4.5 SOSO33

5000 5000 cmcm22/g /g BlaineBlaine

OOAlAl

SS

CaCa

CaCa

C3S + Water C-S-H + CH + HeatC3A + Water + Gypsum Ettringite + HeatC3A + Water + Ettringite Monosulfoaluminate

CaCa

SS

SiSi

AlAlMgMgOO CaCa


DEF (DELAYED ETTRENGITE FORMATION)

DEF (DELAYED ETTRENGITE FORMATION)

Cracks & Pores due toDEF

Pores filledwithettrengiteformation


Ettringite has - bydirected crystalgrowth - partlyfilled an air void

Air void completelyfilled with ettringite

crystals in a damaged pavement

concrete

DEFDEF

ASRASR

PREVENTIVE MEASURES AGAINST DEF

ÇİMENTO KLİNKERİNİN SÜLFAT İÇERİĞİ DÜŞÜK OLMALI

KÜR SICAKLIĞI ÇOK YÜKSEK OLMAMALI

DÜŞÜK HİDRATASYON ISILI ÇİMENTO KULLANILMALI

PUZOLANİK MADDE KULLANMAK SURETİYLE SÜLFAT MİKTARINI AZALTMAK

SU İLE TEMAS KESİLMELİ

HAVA SÜRÜKLEYİCİ KATKI KULLANIMI

DİĞER REAKSİYONLARDAN KAYNAKLANAN MİKROÇATLAKLARINOLUŞUMUNUN ENGELLENMESİ





















HAVA SÜRÜKLEYİCİ KATKI KULLANIMI







USING AIR ENTRAINING AGENTS

PROPER CURING TEMPERATURES

USING POZZOLANIC MINERAL ADMIXTURES (REDUCINGSULFATE CONTENT)

CEMENT WITH LOW HEAT OF HYDRATION

PREVENTATION OF MICROCRACK FORMATIONS CAUSED BYOTHER REACTIONS

LOW SULFATE BEARING CEMENT

WATER INSULATION

THAUMASITE ATTACK (TSA)

-Sulfate or sulfide source

-Ground CaCO3 Carbonationor bicarbonates from groundwater

-water

-CSH

-Low tempeature (<15oC)

Bridge and tunnel structures

Scandinavian countries, England, North America, in particular cold climates

THAUMASITE ATTACK (TSA)

Deterioation of CSH structure

Loss of strength

Mushy like concrete

C-S-H + C-S-A-H + CaCO3

(CaSiO3.CaCO3.CaSO4.15H2O)

THAUMASITE FORMATION

Ferenc Puskas Stadium in Budapest (1954)

The planned limestone content of the cement amounted to 15%, but contaminated soft limestone was used

THAUMASITE

FERENC PUSKAS STADIUM

After World War II, in order to minimise the significant cement deficiency a clinker saving cement mix named Sigma Cement’ was produced to use in

construction of stadium in Hungary.

The average temperature in Hungary is about 70% of the year

longer than 15oC which is advantageous for thaumasite

formation!

EnvironmentalEnvironmental effectseffects, , corrosioncorrosion, , alsoalso thaumasitethaumasiteformationformation !!!!

cement produced has low strength and high fineness !

separation of the coarse fraction of the cement clinker is insufficient

the strength of the concretedecreased

gradually afterten year

construction

THAUMASITE


THAUMASITE


Specimens was exposed to highconcentration of MgSO4 solution


LimestoneLimestone ratioratioincreasesincreases (%0(%0--40)40)

Tübitak 104I083

20oC MgSO4 (200 g/l) – 1 year

20oC Na2SO4 (200 g/l) – 1 year

Limestone increases

5oC Na2SO4 (200 g/l) – 1 year

5oC MgSO4 (200 g/l) – 1 year

C3A

%11.2

C3A

%4.6

C3A

%11.2

C3A

%4.6

C3A

%11.2

C3A

%4.6

C3A

%11.2

C3A

%4.6

Limestone increases

Limestone increases Limestone increases

C3A %4.6

5oC Na2SO4 – 1 year 5oC MgSO4 – 1 year


C3A %11.2


20oC MgSO4 - 1 year20oC Na2SO4 – 1 year

Limestonereplacement : %40

MgSO4 solution

(III-M-40)

THAUMASITETHAUMASITE

CaCa

CaCa

Mg Mg

SiSi S S

Al Al

PREVENTIVE MEASURES AGAINST


FROM THE VIEW POINT OF STRENGTH AND DURABILITY, THE MAXIMUM LIMESTONE INCORPORATION AMOUNT SHOULD NOT EXCEED 10%, ESPECIALLY FOR THE STRUCTURES THAT ARE

CONSTRUCTED IN SULFATE BEARING SOILS AT COLD REGIONS.

LOW C3A CEMENT

MINERAL ADMIXTURES

REDUCE THE PERMEABILITY of CONCRETE

LOW SULFATE BEARING CEMENT

WATER PROOFING

ALKALIALKALI -- SILICASILICA REACTIONREACTION

ASRASR

ASR CAN BE EXPLAINED IN A TWO-STEP PROCESS

Diffusion of waterand alkalis into

concrete

Water and/or alkalisfrom the environment

(e.g. from de-icingsalts)

Crack formation(map cracking and

surface parallelcracking)

Diffusion of alkalis(e.g. from cement

and admixtures)

ASR gel; expansion

Reactive aggregate

1. ALKALI + SILICA ASR GEL2. ASR GEL + WATER EXPANSION

DETERIORATION OF CONCRETE

ASR REACTIVITY

3 REQUIREMENTS MUST BE MET !1) HIGH ALKALI OXIDE CONTENT

(Na2O + 0.658 K2O) > %0.6

2) REACTIVE SILICA(OPAL, TRIDYMITE, CRISTOBALITE, VOLCANICGLASS, RIYOLITE, ANDESITE & THEIR TUFFS)

GEL FORMATION (YEARS AFTER)(SODIUM + POTASSIUM + CALCIUM SILICATE)

SWELLING

MAP CRACKS

3) WATER

Part-II (164 slides)HY - Ki??isel...

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