Concrete Technology 2/4. Aalto University School of Engineering Department of Civil and Structural Engineering Building Materials Technology

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1 /4 Aalto University Shool of Engineering Department of Civil and Strutural Engineering Building Materials Tehnology

2 Hydration in a losed system Water is not transferred with the surroundings Variables v volume fration (0 1) hydration degree (0 1) 1- solid onentration (0 1) Volume of unhydrated ement v = ( 1 θ )(1 α ) Solid volume of the gel v (1 θ) α + (1 0,25)0,26ρ 1 θ α / ρ v gs gs 1,6(1 θ) α ( ) w

3 Volume of gel water v gw 0, 75 0, 26 ρ ( 1 θ) α / ρ w v gw 0, 6 ( 1 θ) α Volume of apillary water θ 0, 26 ρ ( 1 θ) α / ρ 0, 6( 1 θ) α v kw w v kw θ 1, 4( 1 θ) α Volume of the ontration pores ρ θ α ρ v p 0, 25 0, 26 ( 1 ) / w v p 0, 2( 1 θ) α

4 Hydration in an open system Transfer of water an take plae with the environment rate of rate of evaporation from thesurfae diffusionfrom insideof the struture The water volume transferred between the environment and struture (ement + water) is denoted by v the formulae of apillary water and porosity are hanged ' v θ 1,4(1 θ ) α + v = v + v kw kw ' v 0,2(1 θ ) α v = v v p p v kw v v p

5 Conversion of the volume variables to weight based variables (kg/ onrete m 3 ) -total volume of the system -the volume variables are multiplied by the total volume of the system 3 0,32 0, m l Q Q v Q v Q Q Q v w w w w tot = + = ρ ρ ρ ρ

6 Volume of hydration produts Initial porosity θ = w w + ρ ρ w Volume of unhydrated ement v = ( 1 θ ) (1 α )

7 Solid volume of the gel v gs = 1,6 (1 θ ) α Volume of gel water v gw = 0,6 (1 θ ) α Volume of apillary water v kw = θ 1,4 (1 θ ) α Volume of the ontration pores v p = 0,2 (1 θ ) α

8 Maximum degree of hydration 1. No external water v kw =0 α max = 1,4 θ (1 θ ) 1 2. Wet uring θ 1,2 (1 θ ) v kw +v p =0 α = 1 max

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10 Volume of hydration produts when ondensed silia fume is applied Hydration of ondensed silia fume -hemial shrinkage is 22 ml/100 g silia fume -amount of gel water is 0.50 g/ g silia fume -water amount onsumed in the reation 0 g/ g silia Densities of the omponents -ρ = kg/m 3 -ρ w = 1000 kg/m 3 -ρ s = 2200 kg/m 3

11 Initial porosity oeffiient θ = w + ρ ρ w w + ρ ρ w s s k = ,4 s

12 Volume of unhydrated ement v = k 1 θ ) Solid volume of the gel v gs Volume of gel water v gw Volume of apillary water v kw ( (1 α ) s = k (1,6 + 0,7 ) (1 θ ) α s = k (0,6 + 1,6 ) (1 θ ) α s = θ k (1,4 + 1,6 ) (1 θ ) α

13 Volume of the ontration pores v p s = k (0,2 + 0,7 ) (1 θ ) α Volume of the unreated ondensed silia fume v s s = k 1,4 (1 θ ) (1 α ) Maximum degree of hydration 1. No external water v kw =0 α max = k (1,4 θ + 1,6 s ) (1 θ ) 1

14 2. Wet uring v kw +v p =0 α max = k (1,2 + θ 0,9 s ) (1 θ ) 1

15 Capillary pores -represent that part of the total volume of the ement paste that is not filled by the hydration produts -volume of apillary pores is dependent on water-ement ratio and degree of hydration Volume proportions during different phases of hydration If v/ > 0,38-0,42, the hydration produts of ement paste annot fill all of the apillary pores. Capillary pores - have approximately diameter < 1,3 µm - shape is variable - an be onneted with eah other

16 - are distributed randomly in the ement gel - have a major effet on permeability and freeze-thaw durability As hydration proeeds the onnetivity to other apillary pores an be broken and they are onneted to eah other only through gel pores - v/ -ratio - uring in wet onditions The hydration degree and water-ement ratio whih makes it possible to break the onnetivity of the apillary pores are - if v/ 0,7 not even omplete hydration degree enables the intereption

17 - when ement is finely ground v/ < 0,8 - applying oarse ements v/ < 0,7 The average uring time (hardening time) for apillary pores to break a ontinuous pore system v/ Time d d d months year >0.70 impossible

18 Conrete is not usually onsidered to be proper if apillary pores form a ontinuous pore system. - spaes between gel partiles - φ Å (Å = m) Gel pores - a deade larger ompared to water moleules they are affeted by partial pressure and mobility of water vapor - - the volume ontent of gel pores is 28 % of gel total volume depending on the hardening onditions.

19 -the volume ontent of gel pores is somewhat dependent on ement type but does not depend on -water-ement ratio nor -hydration degree Hydration does not affet on the previously generated hydration produts and the gel omposition is invariant of the age at whih it is forming -the surfae area of the ement gel is about m 2 /kg, while the surfae area of unhydrated ement is about 300 m 2 /kg -the surfae area of ement gel whih has hydrated in high temperature is about 7000 m 2 /kg The dimensions and morphology of the hydration produts are quite different the struture is mirorystalline

20 Supplementary binders Fly ash -oal ash -peat ash -wood ash pozzolani reation Commonly used in Finland is oal ash produed in heat and eletriity power plants % unburnt oal residues -olleted from the exhaust gases -bottom ash not suitable

21 Composition of oal ash in a typial power plant Component Variation area % Average value % SiO Al2O Fe2O Requirement (S + A+ F) Together > 70 % CaO MgO % Na2O+K2O SO % Cl % Loss of ignition %

22 Maximum allowable supplementary binder amounts Seosaineiden käytön sallitut enimmäismäärät riippuen rasitusluokista ja käytettävästä sementistä on esitetty taulukossa 4.4. Taulukko 4.4 Betonin valmistuksessa suurimmat sallitut seosainelisäykset lasketaan seuraavista kaavoista, joissa Q II on sementin sisältämät seosaineet [%]. Rasitusluokka X0 XC1 XC3 XS1 XD1, XA1 XF1, XF3 Suurin sallittu seosainelisäys [%] Masuunikuona Lentotuhka Silika 1) QII 0, QII 0, QII 9 XC4, XS2, XS3 XD2, XD QII 08, QII 0, XF2, XF QII 100 0, QII 14 1) Lisäksi on varmistuttava, että syntyvän sideaineseoksen klinkkeripitoisuus on vähintään 65 % rasitusluokissa X0, XC1 XC3, XS1, XD1 ja XA1 ja 80 % muissa rasitusluokissa.

23 Partile size distribution and properties -between the distributions of fillers and ement % spherial ash partiles, part of whih are hollow -density of the solid ontent 2.2 kg/m 3 -partile density kg/m 3 -dusty -pozzolani binder having effiieny oeffiient of in ompressive strength ompared to Portland ement Utilization of oal fly ash 1. Raw material in linker prodution -intermediate produt -already in fine partile form -residual oal ats as additional energy soure

24 2. As a supplementary binder with ement -maximum ontent in CEM IIA is 10 % -maximum ontent in CEM IIB is 35 % -maximum ontent with CEM I is 60 % -mixed with ement before or after grinding 3. Substitute for natural filler -aggregate -pneumati transport and water tight filler silos -good homogeneity

25 Properties in fresh onrete Coal fly ash improves -workability -pumpability -ohesion Good quality oal fly ash -possesses a small loss of ignition and fine partile size -dereases water demand of the mix When oal fly ash is applied -onrete beomes denser -air ontent is dereased -olor is greener -hydration heat is dereased

26 -dereases ement ontent -reats with and binds alium hydroxide -improves durability in some ases Properties in hardened onrete -latent hydrauli properties (pozzolani reation with Ca(OH)2, 1kg fly ash binds 875 g of Ca(OH)2) -when used as supplementary binder as a replaement of ement early age strength dereases and final strength inreases -when used as a filler the pozzolani reation improves strength (not neessarily 28 d strength) -heat treatment improves hardening rate (even early strength)

27 -improves hemial durability of onrete, espeially durability against sulfates -dereases the suseptibility for alkali-aggregate reation and improves the volume stability of ements ontaining too large amounts of MgO Large fly ash ontent dereases Ca(OH)2 ontent in hydrated onrete whih inreases the risk of reinforement orrosion. Maximum fly ash ontent is restrited to 60 % of Portland ement (CEM I).

28 Large oal ontent in fly ash -diminishes the pozzolani reation -inreases water demand -auses olor variations -oal partiles absorb admixtures, for example, airentraining admixture dosage must be inreased fold Fly ash and admixtures -plastiizers and retarding plastiizers generate higher 91 d strength and derease water segregation, Young s modulus, and 90 d shrinkage. Setting time inreases by 1 2 hours.

29 Advantages of fly ash as a filler -diminished water demand -partile omposition is finer whih diminishes water segregation -smaller density Disadvantages of fly ash -quality ontrol -diffiulties in quality variations -umbersome handling ompared to natural fillers -seasonal variation whih auses storage needs -transport osts -additional dosage amount of admixtures

30 Utilization of wood fly ash Reyled material from energy prodution of wood and paper industry Annual prodution about tons in Finland Raw material onsists of bark, saw dust, and different fiber or leftover sludges Has similar properties as fly ash produed from oal in eletriity and heat prodution

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32 SO 3 [%] Cl - [%] SiO 2 [%] Na 2 O- equivalent [%] SiO 2 +Al 2 O 3 +Fe 2 O 3 [%] MgO [%] CaO [%] Loss of ignition ([%]) Wood ash 1 8 0,4 35 4, = 56 Wood ash 2 3 0,2 43 3, = 69 Wood ash ,3 20 4, = 38 Wood ash 4 8 0,3 28 5, = 51 Wood ash 5 2 0,2 36 3, = 67 Limit values in (SFS-EN 450-1) for fly ash < 3,0 % < 0,1 % reative > 25 % 3 15 C (7) 3 15 A (1) 3 31 A (2) 5 15 A (3) 2 14 B (5) < 5 % > 70 % < 4 % free < 2,5 % reat. < 10 % A < 5 % B 5-7 % C 7-9 %

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35 Properties Density [kg/ dm 3 ] Powder density [kg/dm 3 ] Ativity index 28 d Expansion of paste 14 d [µm] Setting time [min] Wood ash 1 2,79 0,69-0,72 0,86 67 Wood ash 2 2,61 0,85-0,87 0,61 13 Wood ash 3 3,00 0,95-0,97 0, Wood ash 4 2,77 0,75-0,78 0,75 60 Wood ash 5 2,62 0,68-0,72 0, Fly ash 0,96 54 Class B 2, Class C 2,14 Portland ement

36 Compressive strength

37 Compressive strength

38 Freeze-thaw durability Quality ontrol