Analytical and numerical prediction of water sorptivity in cement-based materials

Transcription

1 Life Cycle Predictio ad Maagemet of Cocrete tructures, apporo, March Aalytical ad umerical predictio of water sorptivity i cemet-based materials Licheg WANG Dr. Dalia Uiversity of Techology, Dalia Chia

2 Cotets. Itroductio. Usaturated flow theory 3. Effect of iitial water cotet o sorptivity 4. Numerical aalysis model ad result 5. Coclusios

3 . Itroductio Chloride-iduced Deterioratio of RC structures () Marie eviromet Water splashig zoe Frost attack i cold regio

4 Chloride-iduced Deterioratio of RC structures () De-icig salt eviromet Bridge decks ubstructure-beams ad colums Cocrete is rarely saturated!

5 / i =t h = k t x is the sorptivity k is the capillarity coefficiet alt Water chematic illustratio of water absorptio test

6 . Usaturated flow theory = t ( D( ) K ( )) is the ormalized water cotet D() represets the hydraulic diffusivity fuctio ( ) = D e D K() is th hydraulic coductivity. Whe the gravity effect is ot cosidered, K() will be eglected. As a result, = t x D x ( ) < x <

7 Compariso of aalytical profiles whe =6 with test data φ = λ ( ) = D e D e a ( ) da = D = e β a s + ( ) e + 4 = ( e ) s + s + 6D βλ 4β water co otet..8.6 Hall mi 57 mi. 97 mi 8 mi 7 mi x (mm)

8 Relatioship betwee ad k By itroducig the Bolzma variable φ=xt -/ x = φ( ) t h =φ( ) t The capillarity coefficiet k ( ) = φ

9 = t x D x ( ) < x < i = xd = t s φ d d d d dφ dφ dφ φ = D ( ) = ( Θ Θ ) ( ) D( ) d i + k ( =.) φ =. 94 Θ Θ i D = = ( ) De 6

10 If a specime is iitially dried, Θ i will become zoe, thus we have k =.94 Θ Θ is the porosity of cocrete. Porosity k/ Test data Hazic ad Ilic (3) ±

11 3. Effect of iitial water cotet o sorptivity 3. Effect of iitial water cotet o sorptivity 3mm 3mm L Goverig equatio = ψ A t t AL L AD ( ) ( ) = D t

12 x alt Water As Θ i icreases, the advacig wet frot becomes less steep, but the leadig edge of the water absorptio profile advaces rapidly. Normalized water cotet ir =(Θ i -Θ )/(Θ -Θ ). ir =.9.8 ir =.7.6 ir =.5.4 ir =.3. ir =. ir = Depth (mm) The profiles of water cotet at differet iitial water cotet

13 = Θ Θ i D = De Θ Θ Θ Θ Θ Θ ( Θ Θ +Θ) De dθ i Θ Θ ( Θ Θ ) [ ( ) ] D = { Θ Θ +Θ i e [( ) Θ Θ +Θ ] e i Θi Θ Θ Θ D ( ) Θ [( ) ] Θ e = + = [( ) ] e [ ( ) ] ir ( ) e + ir e ir

14 Compariso betwee the proposed model ad some available models..8 /.6.4. Calculated data By Brutsaert 976 By Hall 989 By preset study Iitial water cotet ir

15 4. Numerical aalysis model ad result 4. Mesoscopic model of cocrete Macro scale Meso scale Three-phase composite Homogeeous material Rea al structure Heterogeeous material Aaly ytical model = Mortar + Coarse Aggregate +Iterface

16 4. Truss etwork model Vorooi elemet Truss elemet iside Vorooi elemet Truss elemet o boudary For chloride trasport through the area A ca be represeted by a -D lie elemet. water A Formatio of the truss etwork

17 4.3 Aalysis coditio Water trasport property of the iterface D it = D m t it = µm. water Cocrete sample x

18 4.4 Aalysis result Cumulative absorbed water Absorbed water (g/m ) Wittma et al. 6 Numerical calculatio result Time (hr / )

19 5. Coclusios Coclusios:. The relatioship betwee capillarity coefficiet k ad sorptivity is built up as k/=.94/(θ -Θ i ) ;. A ew model to accout for the effect of iitial water cotet o sorptivity is developed aalytically.. 3. The mesoscale model of cocrete ca be used to predict water absorptio process. This is the basis for predictio of chloride movemet by capillary actio.

20 Dalia Uiversity of Techology, Dalia Chia