YAPI MALZEMESĐNDE ÖZEL KONULAR -2-1-

Doç. Dr. Halit YAZICI

Yüksek Performanslı

betonlarhttp://kisi.deu.edu.tr/halit.yazici/

Dokuz Eylül Üniversitesi Đnşaat Mühendisliği Bölümü

SINIFLANDIRMA� NORMAL AĞIRLIKLI BETON (2400 kg/m3)

� HAFĐF BETON (< 1800 kg/m3)

� AĞIR BETON (>3200 kg/m3)

SINIFLANDIRMA� Düşük dayanımlı (< 20 MPa)

� Orta Dayanımlı (20-50 MPa)

� Yüksek Dayanımlı (> 50 MPa)

Enerji Tüketimi

YÜKSEK PERFORMANSLI

BETON

YÜKSEK DAYANIMLI

BETON

YÜ

KS

EK

P

ER

FOR

MA

NS

LI B

ET

ON

AMACA YÖNELĐK OLARAK UYGUN TASARLANMIŞ BETON

NORMAL BETON YETERSĐZ ĐSE

TAZE HALDE KOLAY ĐŞLENEBĐLME

TOKLUK (ENERJĐ YUTABĐLME), DÜKTĐLĐTE (SÜNEK DAVRANIŞ)

MEKANĐK VE FĐZĐKSEL ETKĐLERE KARŞI DĐRENÇ(EĞĐLME, BASINÇ DAYANIMI, AŞINMA, DARBE ETKĐLERĐ)

DAYANIKLILIK (GEÇĐRĐMLĐLĐĞĐ DÜŞÜK BETON)

(LĐFLĐ KOMPOZĐTLER)(KENDĐLĐĞĐNDEN YERLEŞEN ÇĐMENTOLU KOMPOZĐTLER)

YÜKSEK PERFORMANSLI

BETONLAR

için

TASARIM KRĐTERLERĐ

Tümünün bir arada olması mümkün değil mi acaba?

hedef performansa dayalı tasarım

•Yüksek dayanım

•Yüksek erken dayanım

•Yüksek elastisite modülü

•Yüksek dayanıklılık, uzun servis ömrü

•Donma-çözülme direnci

•Tokluk ve darbe direnci

•Yüksek aşınma direnci

•Boyutsal stabilite

•Kolay yerleşebilirlik, ayrışma direnci…467 m

1.2 milyon

ton

40 MPa uygun boşluk yapısı ve klor iyonu penetrasyonu

dirençli

Doğal gaz platformu

YÜKSEK PERFORMANSLI

BETON

YÜKSEK DAYANIMLI

BETON

Normal beton bileşenleri

Yüksek performanslıbeton bileşenleri

çimentoagregasuakışkanlaştırıcı katkı

çimentoagregasu

mineral katkılar

ince öğütülmüş taş tozları

yüksek oranda su azaltıcı katkılar

viskozite arttırıcı

metalik liflerpolimer kökenli lifler

…

hava sürükleyici

genleşen çimento

kalsine edilmiş killer

priz ayarlayıcı

rötre azaltıcı

karbon lifler

YÜKSEK PERFORMANSLI BETONLARIN GELĐŞĐMĐNĐTETĐKLEYEN BULUŞLAR

akışkanlaştırıcılar

hava sürükleyici katkılar veya

yüksek dayanımlıhafif agregalar

mineral katkılargelişim

Çelik,karbon ve sentetik lifler

S/B<0.35

hafiflik

tokluk

işlenebilirlik

Ingalls Building

64 m 15 kat

Cincinnati, Ohio

1903 Kompozit gökdelenler

80 MPalong-span floor beams that

support concrete-filled metal deck

119 MPa

Taipei 101

Çelik

23.900m3 beton 70 MPa

380 betonarme kazık: 80m derinliğe kadar

660 ton kütleli

sönümleyici

Betonarme – çelik kompozit

Betonarme – çelik kompozit

Betonarme – çelik kompozit

Çelik

Taşıyıcı sistem

199966421Çin5. Jin Mao

1974108442ABD4. Sears

199888452Malezya2-3. Petronas

2004101509 mTayvan1. Taipei 101

Yılkatyükseklik

Two Union SquarePetronas

Çelik tüp

WTC 526m

160Kat sayısı

876,000,000 $Maliyeti

EMAARSahibi

(�ubat ‘05 ~ Haziran ‘09)Süre

800m üstüYükseklik

Burj GökdeleniProje adı

Otel (L39)

Rezidans (L108)

Ofis (L123)

Haberleşme (L160)

Ofis (L153)

•260.000 m3 beton

Çekirdek betonu: 80-100 MPa

BETON TEKNOLOJĐSĐ

BETON-iç yapı

Üç farklı faz� Çimento hamuru (Cement Paste)

� Agrega (Aggregate)

� Arayüzey-Geçiş Bölgesi (InterfacialTransition Zone-ITZ)

Beton: Karmaşık iç yapı

Çimento tanesi

Kum tanesi

Kalsiyım hidroksit

Gözenekler

ÇĐMENTOProblem

Dünyadaki CO2salınımının

%7’sinden çimento üretimi sorumludur.

Notasyon� C : CaO

� S : SiO2

� A : Al2O3

� F : Fe2O3

� H : H2O

� C3S : 3CaOSiO2

� C2S : 2CaOSiO2

� C3A : 3CaOAl2O3

� C4AF : 4CaOAl2O3Fe2O3

ÇĐMENTO

SU

ÇÖZÜNME ÇÖKELME

� For a well-hydrated cement paste, the inhomogeneousdistribution of solids and voids alone can perhaps be ignored when modeling the behavior of the material. However, microstructural studies have shown that thiscannot be done for the hydrated cement paste presentin concrete. In the presence of aggregate, themicrostructure of hydrated cement paste in the vicinityof large aggregate particles is usually very differentfrom the microstructure of bulk paste or mortar in thesystem. In fact, many aspects of concrete behaviorunder stress can be explained only when the cementpaste-aggregate interface is treated as a third phase of the concrete microstructure.

Erken yaşlarda hidratasyon

3 saat 10 saat

Hidratasyonun katı ürünleri� Kalsiyum silikat hidrat (CSH)

� C/S oranı : 1.5-2.0

� Büyük yüzey alanı (100-700 m2/g)

� Yüksek Van der Walls kuvvetleri ile dayanım sağlar

� Çimento hacminin %50-60’lık kısmı

CSH

� C-S-H jelleri, zayıf kristalli (amorfa yakın) kolloidal parçacıklardan oluşur. Lif şekilli bu kristallerin dağılımında bir düzen yoktur. C-S-H jelleri bir dantel veya dokuma parçası gibi iç içe büyümüş şekilde yer alırlar. C-S-H jelleri, elektron mikroskobu altında incelendiğinde, Şekil de görüldüğü gibi üzerinde dikenleri olan bir keseye benzer.

� Kalsiyum Sülfoalüminat Hidratlar

� Çimento hacminin %15-20’si

� Önce etrenjit oluşumu

� Daha sonra monosülfat hidrata dönüşüm

Kalsiyum Hidroksit (kireç)

Kalsiyum Hidroksit (kireç)

Etrenjit

Etrenjit

Kalsiyum Hidroksit (kireç)

� The chemical composition of the principalclinker compounds correspondsapproximately to C3S, C2S, C3A, and C4AF. In ordinary portland cement their respectiveamounts usually range between 45 and 60, 15 and 30, 6 and 12, and 6 and 8 percent.

� When portland cement is dispersed in water, thecalcium sulfate and the high-temperature compoundsof calcium begin to go into solution, and the liquidphase gets rapidly saturated with various ionicspecies. As a result of interaction between calcium, sulfate, aluminate, and hydroxyl ions within a fewminutes of cement hydration, the needle-shapedcrystals of calcium trisulfoaluminate hydrate, calledettringite, first make their appearance.

� Afew hours later, large prismatic crystals of calciumhydroxide and very small fibrous crystals of calciumsilicate hydrates begin to fill the empty spaceformerly occupied by water and the dissolvingcement particles. After some days, depending on thealumina-to-sulfate ratio of the portland cement, ettringite may become unstable and will decomposeto form monosulfoaluminate hydrate, which has a hexagonal-plate morphology.

� Calcium silicate hydrate. The calcium silicate hydrate phase, abbreviated as CSH, makes up 50 to 60 percent of the volumeof solids in a completely hydrated portland cement paste and is, therefore, the most important phase determining the propertiesof the paste. The fact that the term C-S-H is hyphenatedsignifies that C-S-H is not a well-defined compound; the C/S ratio varies between 1.5 and 2.0 and the structural watercontent varies even more. The morphology of C-S-H alsovaries from poorly crystalline fibers to reticular network. Due to their colloidal dimensions and a tendency to cluster, C-S-H crystals could only be resolved with the advent of electronmicroscopy. In older literature, the material is often referred toas C-S-H gel. The internal crystal structure of C-S-H alsoremains unresolved; previously it was assumed to resemble thenatural mineral tobermorite and that is why C-S-H wassometimes called tobermorite gel.

� Although the exact structure of C-S-H is not known, several models have been proposed to explain theproperties of the materials. According to the Powers-Brunauer model,the material has a layer structure witha very highsurface area. Depending on themeasurement technique, surface areas on the orderof 100 to 700 m2/g have been proposed for C-S-H, and the strength of the material is attributed mainly tovan der Waals’ forces. The size of gel pores, or thesolid-to-solid distance, is reported to be about 18Å.The Feldman-Sereda model visualizes the C-S-H structure as being composed of an irregular orkinkedarray of layers which are randomly arranged to createinterlayer spaces of different shapes and sizes (5 to 25 Å).

� Calcium hydroxide. Calcium hydroxide crystals (alsocalled portlandite)constitute 20 to 25 percent of thevolume of solids in the hydrated paste. In contrast tothe C-S-H, calcium hydroxide is a compound with a definite stoichiometry, Ca(OH)2. It tends to form large crystals with a distinctive hexagonal-prismmorphology. The morphology usually varies fromnondescript to stacks of large plates, and is affectedby the available space, temperature of hydration, andimpurities present in the system. Compared with C-S-H, the strength-contributing potential of calciumhydroxide is limited as a result of considerablylower surface area.

� Calcium sulfoaluminates hydrates. Calcium sulfoaluminatehydrates occupy 15 to 20 percent of the solid volume in thehydrated paste and, therefore, play only a minor role in themicrostructure-property relationships. It has already been statedthat during the early stages of hydration the sulfate/aluminaionic ratio of the solution phase generally favors the formationof trisulfate hydrate, C6AS3H32, also called ettringite, whichforms needle-shaped prismatic crystals. In pastes of ordinaryportland cement, ettringite eventually transforms to themonosulfate hydrate, C4AS−H18, which forms hexagonal-plate crystals. The presence of the monosulfate hydrate in portland cement concrete makes the concrete vulnerable tosulfate attack. It should be noted that both ettringite and themonosulfate contain small amounts of iron, which can substitute for the aluminum ions in the crystal structure.

� Unhydrated clinker grains. Depending on the particle sizedistribution of the anhydrous cement and the degree of hydration, some unhydrated clinker grains may be found in the microstructure of hydrated cement pastes, even long afterhydration. As stated earlier, the clinker particles in modern portland cement generally conform to the size range 1 to 50 µm. With the progress of the hydration process, the smallerparticles dissolve first and disappear from the system, thenthe larger particles become smaller. Because of the limitedavailable space between the particles, the hydration productstend to crystallize in close proximity to the hydrating clinkerparticles, which gives the appearance of a coating formationaround them. At later ages, due to the lack of available space, in situ hydration of clinker particles results in the formation of a very dense hydration product, the morphology of which mayresemble the original clinker particle.

� Interlayer space in C-S-H. Powers assumed thewidth of the interlayer space within the C-S-H structure to be 18 Å and determined that it accounts for 28 percent porosity in solid C-S-H; however, Feldman and Sereda suggested thatthe space may vary from 5 to 25 Å. This voidsize is too small to have an adverse effect on the strength and permeability of the hydratedcement paste. However,as discussed below, water in these small voids can be held byhydrogen bonding,and its removal under certainconditions may contribute to drying shrinkageand creep.

� Capillary voids. Capillary voids represent the spacenot filled by the solid components of the hydratedcement paste. The total volume of a typical cement-water Microstructure and Properties of HardenedConcrete mixture remains essentially unchangedduring the hydration process. The average bulkdensity of the hydration products is considerablylower than the density of anhydrous portland cement; it is estimated that 1 cm3 of cement, on complete hydration, requires about 2 cm3 of space toaccommodate the products of hydration.

� Thus, cement hydration may be looked upon as a process during which the space originallyoccupied by cement and water is beingreplaced more and more by the space filled byhydration products. The space not taken upby the cement or the hydration productsconsists of capillary voids, the volume and size of the capillary voids being determined by theoriginal distance between the anhydrouscement particles in the freshly mixed cementpaste (i.e., water/cement ratio), and the degreeof cement hydration.

� In well-hydrated, low water-cement ratio pastes, thecapillary voids may range from 10 to 50 nm; in highwater-cement ratio pastes, at early ages of hydration, thecapillary voids may be as large as 3 to 5 µm. It has been suggested that the pore size distribution, not thetotal capillary porosity, is a better criterion forevaluating the characteristics of a hydrated cementpaste. Capillary voids larger than 50 nm, referred toas macropores in modern literature, are probably moreinfluential in determining the strength andimpermeability characteristics, whereas voidssmaller than 50 nm, referred to as micropores, playan important part in drying shrinkage and creep.

� Air voids. Whereas capillary voids are irregularin shape, air voids are generally spherical. Asmall amount of air usually gets trapped in thecement paste during concrete mixing. Forvarious reasons, admixtures may be added toconcrete to entrain purposely tiny air voids. Entrapped air voids may be as large as 3 mm; entrained air voids usually range from 50 to200 µm. Therefore, both the entrapped andentrained air voids in the hydrated cement pasteare much bigger than the capillary voids, andare capable of adversely affecting the strength.

Water in the hydrated cement paste� Capillary water. This is the water present in voids larger

than about 50 Å. It may be pictured as the bulk water that is free from the influence of the attractive forces exerted bythe solid surface. Actually, from the standpoint of thebehavior of capillary water in the hydrated cement paste, it is desirable to divide the capillary water into two categories: thewater in large voids of the order of >50 nm (0.05 µm), which may be called free water (because its removal doesnot cause any volume change), and the water held bycapillary tension in small capillaries (5 to 50 nm), theremoval of which may cause shrinkage of the system.

� Adsorbed water. This is the water that is close to thesolid surface. Under the influence of attractiveforces, water molecules are physically adsorbed ontothe surface of solids in the hydrated cement paste. Ithas been suggested that up to six molecular layersof water (15 Å) can be physically held by hydrogenbonding. Because the bond energies of the individualwater molecules decrease with distance from the solidsurface, a major portion of the adsorbed water can be lost when hydrated cement paste is dried to 30 percent relative humidity. The loss of adsorbedwater is responsible for the shrinkage of thehydrated cement paste.

� Interlayer water. This is the water associatedwith the C-S-H structure. It has beensuggested that a monomolecular water layerbetween the layers of C-S-H is strongly heldby hydrogen bonding. The interlayer wateris lost only on strong drying (i.e., below 11 percent relative humidity). The C-S-H structure shrinks considerably when theinterlayer water is lost.

� Chemically combined water. This is thewater that is an integral part of themicrostructure of various cementhydration products. This water is not lost on drying; it is evolved when the hydratesdecompose on heating. Based on theFeldman-Sereda model, different types of water associated with the C-S-H areillustrated in Fig. 2-9.

YAPI MALZEMESĐNDE ÖZEL KONULAR -2-1-

Doç. Dr. Halit YAZICI

Yüksek Performanslı

betonlarhttp://kisi.deu.edu.tr/halit.yazici/

Dokuz Eylül Üniversitesi Đnşaat Mühendisliği Bölümü