Multi-Parameter Study of Sulfate Attack in

Transcription

1 Multi-Parameter Study of Sulfate Attack in Blended d Cement Materials Aboozar Bonakdar, PhD Candidate Barzin Mobasher, PhD, PE, FACI School of Sustainable Engineering and the Built Environment Department of Civil, Environmental, and Sustainable Engineering ARIZONA STATE UNIVERSITY Concrete Sustainability Conference, April 13-15, 21, Tempe, AZ 21 Concrete Sustainability Conference 1 National Ready Mixed Concrete Association

2 Cement & Concrete Technology: Temporal, Spatial, and Scientific Span Disciplines nanometers to kilometers (1x1-6 to 1x1 3 meters) Space Materials Science Engineering Chemistry Mechanics Computational Techniques Manufacturing products and systems Sustainable development Technical & non-technical labor pool hydration Early age Seconds to Centuries (1 to 3x1 1 Seconds) Service life Time Long term Performance 21 Concrete Sustainability Conference 2 National Ready Mixed Concrete Association

3 Primary Incentives Research Theme Sustainability Shrinking resources Increasing demand Globalization Social justice & technology transfer Quality of life Provide modern, energy efficient, and economical infrastructure for societies with a growing middle class population Economical Development Conservation of energy, time, resources, & cost Value added products for infrastructure 21 Concrete Sustainability Conference 3 National Ready Mixed Concrete Association

4 Outline Overview of Research Group activities Durability of concrete as a sustainability issue Performance based specification, long term performance, economical materials selection, and life cycle cost Models applicable to a host of transport related problems Sulfate attack- case study Experimental program Macroscopic expansion, what do ASTM results mean? Microstructural studies Transport properties Mechanical properties Modeling Assumptions Parametric study and Verification 21 Concrete Sustainability Conference 4 National Ready Mixed Concrete Association

5 Concrete in Arizona- Pay Factors, Statistical Process Control At $1-$4 per cubic yard, $1.5-6 Billion industry in Arizona Over-strength Level 1 Source: ADOT Database for One ready mix supplier over a course of two years All concrete classes 28 day strength Delivered Stren ngth, psi o = 1 cubic yards Specified f'c, psi Laungrungrong, B., Mobasher, B., Montgomery, D., Development of Rational Pay factors Based on Concrete Compressive strength Data, Arizona Department of Transportation,, SPR 68, 28. B. Laungrungrong, B. Mobasher, D. C. Montgomery, and C. M. Borror, Hybrid Control Charts for Active Control and Monitoring of Concrete Strength ASCE Journal of Materials Engineering Jan Concrete Sustainability Conference 5 National Ready Mixed Concrete Association

6 Housing is a human rights issue Navajo Nation is 27, square miles in the states of AZ, NM, and UT, geographically is the largest Native American reservation in the U.S. The Navajo Nation has the highest poverty rate in the U.S. More than 56% of Navajos live below the poverty level Unemployment rate is 44 percent, median family income is $11,885, Per capita income is $6,217. The population has increased 3.5 times from the 5, people in 194. Most homes do not have electricity, running water, or telephones. 21 Concrete Sustainability Conference 6 National Ready Mixed Concrete Association

7 Aerated Fiber-Reinforced Concrete (AFRC) Block Manufacturing & Construction Methods Demonstration Home in Town of Guadalupe, AZ Designed by ASU Stardust Center Thermal Mass Airtight, Whole wall coverage reduce HVAC Equipment Reduces energy consumption Fire Resistant, 8 Bearing wall, 4 hour UL fire rating 21 Concrete Sustainability Conference 7 National Ready Mixed Concrete Association

8 Properties of AFRC Actuator LVDT-1 LVDT-2 -Energy efficient, Effective R-value, 3.4/in, - Fire, Pest resistant - Durable, no autocalve - Acoustical insulation - Energy absorbing - Easy to use 21 Concrete Sustainability Conference 8 National Ready Mixed Concrete Association

9 Thermal Insulation of Concrete Homes Thermal properties (2x2x2 mm plates) 5 Experiment, T out Experiment, T in Temperature, C 4 3 Simulation, T in Experimental and thermal simulation of insulation of concrete walls Time, h 21 Concrete Sustainability Conference 9 National Ready Mixed Concrete Association

10 Durability of concrete Major concerns: Life cycle cost Premature failure and serviceability issues Design codes: Durability- is a black box issue Main criterion: compressive strength, W/C, empirical tests Proper testing ti techniques: What do test t results really mean? Key parameters affecting the durability: multi-scale and multi-variant Transport mechanisms dominate major durability issues Alkali silica reaction (ASR), sulfate attack, carbonation, leaching, frost resistance and corrosion Damage by sulfate attack: building foundations, bridge, piers. Before sulfate exposure After sulfate exposure 21 Concrete Sustainability Conference 1 National Ready Mixed Concrete Association

11 External Sulfate attack Diffusion of sulfate ions into concrete and reaction with cement paste: Dissolution of portlandite (CH) and decomposition of C-S-H phase Formation of gypsum and/or ettringite crystals, vol. expansion Formation of ettringite: topochemical reaction: may cause expansion and cracking of the hardened cement C3 A + 3 CSH H C6 AS 3 H Volume of reaction products >> volume of reactants Need for better mechanics based models Blended cements improve sulfate resistance by reducing the porosity (diffusion) and altering the chemical reactions (less C 3 A) Concrete Sustainability Conference 11 National Ready Mixed Concrete Association

12 Experimental program Hypothesis: Can effect of different fly ash compositions be directly related to performance? How do you measure performance? Type I/II portland cement + 7 different fly ashes (class F, C) Tests: ASTM C 112, XRD, microstructural studies (SEM/EDS), ionic diffusion (EDS, PIXE), micro-hardness, flexural response, fracture parameters Cement F1 F2 F3 C1 C2 O SiO SO Al 2 O Fe 2 O CaO MgO SO Na 2 O K2O Concrete Sustainability Conference 12 National Ready Mixed Concrete Association

13 Properties of studied fly ashes SEM and XRD for fly ash particles 21 Concrete Sustainability Conference 13 National Ready Mixed Concrete Association

14 Expansion (ASTM C 112) Specimen size: 1x1x11 in (standard) vs..4x.4x4 in (modified).1.8 Standard Size Paste with 2% Fly ash, % Expansion, F3 Control F1 F2 F3 C1 C2 O Exposure Time, Days Hypothesis: can smaller specimens be used in order to measure the same material properties for modeling, what does.1% expansion mean? 21 Concrete Sustainability Conference 14 National Ready Mixed Concrete Association

15 Expansion: modified vs. standard paste mixture Normalized Modified Exp pansion, %. mm Experimental Data Initial Linear Fit Final Linear Fit R 2 =.6 R 2 = Normallization Factor = Standard Expansion, % 1 1 x1 x11.4 x.4 x4 Size effect consideration: SA/V ( S tan dard SA/ V ) ( SA/ V ) Modified = Normalization Factor: 2.5 Bonakdar, A., and Mobasher, B., Multi-Parameter Study of External Sulfate Attack in Blended Cement Materials Construction and Building Materials 24 (21) Concrete Sustainability Conference 15 National Ready Mixed Concrete Association

16 Expansion: mortar vs. paste.5 Effect of aggregates is undeniable: ortar Expans sion, % Experimental Data Overall Exponential Fit standard ASTM size ln(y) = X R 2 =.52 - Creating ITZ in mortar - Increase of porosity due to ITZ - Higher rate of diffusion - Higher expansion values Developing specifications for every combination of cement-fly ash-aggregate becomes improbable M.1 Need performance based specifications to address internal mechanisms Paste Expansion, % How to address empirically based effective transport parameters? Bonakdar & Mobasher, Journal of Construction and Building Materials, Concrete Sustainability Conference 16 National Ready Mixed Concrete Association

17 Microstructural studies (SEM/EDS) Specimen size:.4x.4x.4 in (used in expansion test) Formation of ettringite crystals in pores Bonakdar & Mobasher, Journal of Construction and Building Materials, Concrete Sustainability Conference 17 National Ready Mixed Concrete Association

18 Measurement of Other Properties Can we get extra information using the same specimens? 1/4 1 1 Microstructural studies -SEM, EDS or Transport properties -1D diffusion - 2D diffusion 1x1x5 Mechanical properties - Strength - Stiffness - Hardness 21 Concrete Sustainability Conference 18 National Ready Mixed Concrete Association

19 1-D diffusion using PIXE Element Co unts Si 1-4-1, w/c=.7 PIXE (Particle Induced X- S Ca Position 1 Position 2 Position 4 Position 5 Position 6 Position 7 Position 8 ray Emission) 4 Na Al K Ca Ti Energy, KeV Sulfur Area Cou unt Concentration of Sulfates (Mortar) Control: D = 2.4 x1-11 k = 4.4 x1-8 Blended: D = 1.6 x1-11 k = 2.22 x1-8 Control (Experiment) Blended (Experiment) Error Function (Fitted) Specimen size: 2x2 in cylinders Specimen Depth, mm. 21 Concrete Sustainability Conference 19 National Ready Mixed Concrete Association

20 2-D diffusion using EDS Specimen size: 1x1x.25 in (used in expansion test) 1/ mm Diffusion of sulfur Leaching of calcium.9 Sulfur Content, % (Interpolated Data) 12.9 Calcium Content, % (Interpolated Data) Interpolated contour plots for different elements Y, in Y, in X, in X, in 21 Concrete Sustainability Conference 2 National Ready Mixed Concrete Association

21 Mechanical properties 16 Control (no fly ash) No 1: Control (Mortar) S/C=2., W/C=.5, Curing=1 Month Blended (3% class F fly ash) 16 No 2: Blended (Mortar) S/C=2., W/C=.5, Curing=1 Month Flexural l Load, lbf 12 8 Before Exposure 3 Months Exposure 12 Months Exposure Flexural l Load, lbf 12 8 Before Exposure 3 Months Exposure 12 Months Exposure Specimen size: 1x1x5 in (used in expansion test) CMOD, in CMOD, in Ratio: Blended/Control MOR Elastic Flex. Stiffness Before exposure m exposure m exposure Concrete Sustainability Conference 21 National Ready Mixed Concrete Association

22 Modeling Steps Components of a diffusion reaction-micromechanics based damage model. Tixier & Mobasher, ASCE, Materials Journal, Concrete Sustainability Conference 22 National Ready Mixed Concrete Association

23 Diffusion/Reaction Based Model U Plane of symmetry Calcium Aluminates U U Sulfates,U at t> at t= Concentration Profile C C 4 4 AH ASH L CSH CSH + 14H C H C AS H 6 3 AS H CH 32 X CA+ qs C 6AS3H32 C A + 3CSH H C 6 AS H 3 32 summarize ettringite CA = C 4 AH 13 (monosulfate and residual C 3 A combined) q = equivalent stoichiometric coefficient Tixier & Mobasher, ASCE, Materials Journal, Concrete Sustainability Conference 23 National Ready Mixed Concrete Association

24 Transport properties Durability-related phenomena: one or more transport mechanisms: movement of water and chemicals in to or out of concrete Ionic diffusion: predominant transport mechanism in most cases Sulfate attack: ionic diffusion + chemical reaction 2 C C ( x, t ) C ( x, t ) D : = D + R( t x 1 C 2 C/C, % Concentration Profile - with reaction ) without reaction with reaction D=1-12 (m 2 /s) k=1-8 (1/s) C ( x, y, t ) C ( x, y, t ) C ( x, y, t ) 2 D : = D { + } + R ( C ) 2 2 t x y 1D Solution using error function 2D Solution using series Concentration Contour - with reaction 21 Concrete Sustainability Conference 24 National Ready Mixed Concrete Association Y-Depth, mm X-Depth, mm

25 Volumetric Changes & Damage Evolution The result of reaction between sulfates and C 3 A is formation of delayed ettringite which has a lot more water molecules and consequent volume change. M i (g/mole) ρ i (g/cm 3 ) a i C 3 A C 3A + CSH H C ASH 6 32 Gypsum Ettringite ΔV = Vi = ± i ΔV = ΔV. i ai. M ρ reacted S reacted Δ εv = εv (t) t = V i V reacted specimen i r) Te ensile Stress (σ r f t E E' 'E' decreasing Stress-Strain Curve Degraded Slope Damage Function E' = E (1- ω) u(x) x σ ( x ) =σ.[1 ( ) ] d q n Da amage Function (ω) Tixier & Mobasher, ASCE, Materials Journal, 22 d 21 Concrete Sustainability Conference 25 National Ready Mixed Concrete Association

26 Parametric study Effect of reaction term (on the concentration) Effect of diffusion term (on the stiffness and expansion) D = 5x1-13 m 2 /s Modulus of Elasticity Expansion /U U/ U/U month 12 months 12 months without reaction (k=) D = 5x1-13 m 2 /s with reaction (k=1-7 ) 1 month X, mm of Elasticity, MPa Modulus D =1-12 D =1-13 D = w/c =.4 E /E 1 = 75% k = 1-7 'D' decreasing D 1 =1-12 D 2 =1-13 D 3 = Exposure Time, Days Expansion, % 21 Concrete Sustainability Conference 26 National Ready Mixed Concrete Association

27 Parametric study Effect of W/C ratio (on the expansion values) Effect of C 3 A content (on the expansion values) Ex xpansion, % W/C =.8 (Experiment) W/C =.8 (Model) W/C =.6 (Experiment) W/C =.6 (Model) W/C =.45 (Experiment) W/C =.45 (Model) Ouyang et al. Data (1988) pansion, % W/C =.8 D = 7.5x1-12 k = 4.x1-7 S/C = 4.2 E /E 1 = 8% α = 75% W/C =.6 C 3 A = 5% D = 6x1-12 k = 3.x1 f t = MPa -7.1 W/C =.45 D = 5x1-12 k = 2.5x Exposure Time, % Ex D = 5x1-12 k = 1-1.5x1-7 W/C =.6 S/C = 4. α = 8% f t = 2 MPa C 3 A = 8.8% (Experiment) C 3 A = 8.8% (Model) C 3 A = 7.% (Experiment) C 3 A = 7.% (Model) C 3 A = 4.3% (Experiment) C 3 A = 4.3%(Model) Ouyang et al. Data (1988) C 3 A = 8.8% 7.% Exposure Time, % 4.3% 21 Concrete Sustainability Conference 27 National Ready Mixed Concrete Association

28 Model Verification Prediction of modulus of elasticity Prediction of expansion 5.3 f Elasticity, GP Pa Modulus o Ferraris et al. Data (26) SF: D = 1x1-13 k = 1x1-7 Control (Experiment) Control (Model) SF (Experiment) SF (Model) Control D = 2x1-12 k = 2.5x1-7 w/c =.485 C 3 A = 5% Expa ansion, % Ferraris et al. Data (26) Control D = 2x1-12 k = 2.5x1-7 SF (Silica fume): D = 1x1-13 k = 1x1-7 S/C = 2.75 W/C =.485 C 3 A = 5% FA_F(Class F flyash): D = 7x1-13 k = 1.5x1-7 Control (Experiment) Control (Model) FA_F (Experiment) FA_F (Model) SF (Experiment) SF (Model) Exposure Time, Days Exposure Time, % 21 Concrete Sustainability Conference 28 National Ready Mixed Concrete Association

29 Model Verification Prediction of expansion (current study) Effect of D and k in modeling Expansion, %.1 5E Control (Experiment) Control (Model) 3% Flyash (Experiment) 3% Flyash (Model) Control: D=8x1-13 E /E 1 =.45 Current Study: Expansion of Pastes 3% Class F: D=4x1-13 E /E 1 =.5 W/C =.4 α = 7% k = 1x1-7 f t = 2 MPa Exposure Time, Days Rate of Reaction, m 3 /(mole.s) 4E-7 3E-7 2E-7 1E-7 Ouyang Data (OPC) Sahamaran Data (OPC) Current Study (OPC) Ferraris Data (Blended) Sahamaran Data (Blended) Current Study (Blended) Zone 1: Fly ash Blended Zone 2: OPC Zone 1 Zone 2 1E-14 1E-13 1E-12 1E-11 Coeffidient of Diffusion, m 2 /s 21 Concrete Sustainability Conference 29 National Ready Mixed Concrete Association

30 Conclusions Effect of various fly ashes on the sulfate resistance of concrete was studied using traditional and developed test methods. ASTM C112 test method using 1x1x11 inch specimens can take up to 12 months for results. Using modeling, smaller size specimens accelerates the reactions and provides results in much shorter times. Supplementary tests were performed in order to obtain the diffusivity (D) and reactivity (k) of sulfate ions in 1-D and 2-D cases using characterization techniques. Flexural tests were performed on exposed samples which showed quantitative measurements of the damage evolution from sulfate attack. 21 Concrete Sustainability Conference 3 National Ready Mixed Concrete Association

31 Conclusions A predictive model is presented based on cement chemistry, concrete physics and solid mechanics. Key factors in modeling are: C 3 A content and reactivity, internal porosity and ionic diffusivity. Input parameters are compatible with experimental data. Effects of degradation, specimen size, curing duration, and material ingredients can be verified using the model. SULFATE2 computer program can be downloaded on the link to the web site is as follows: html 21 Concrete Sustainability Conference 31 National Ready Mixed Concrete Association

32 Acknowledgement Work Conducted under support from ADOT Project SRR- 633 Economical Concrete Design, (Christ Dimitroplos, Program manager). Support of Salt River Materials Group, SRMG, (Jeff Hearne) for the experimental portions of the project is greatly appreciated. 21 Concrete Sustainability Conference 32 National Ready Mixed Concrete Association

33 ASR Reaction Products Control: swelling gels fly ash Blended: safer gels Bonakdar, Mobasher, Dey, Roy (21), ACI Materials Journal, V. 17, No. 21 Concrete Sustainability Conference 33 National Ready Mixed Concrete Association

34 Chemical Composition vs. Expansion Days 28 Days.2 14 Days 28 Days Ex xpansion, %.15.1 Y =.114 (C eq /S eq ) R2 = 75% Ex xpansion, %.15.1 Y =.94 (C eq /S eq ) R 2 = 85%.5 Y =.99 (C eq /S eq ) -.96 R2 = 81% Total C eq /S eq Ratio C CaO = S SiO + Al O eq ( ) simplified eq C Total C eq /S eq Ratio (ML) 21 Concrete Sustainability Conference 34 National Ready Mixed Concrete Association.5 CaO + 6.(.95Na O +.595K Y =.81 (C eq /S eq ) R 2 = 89% O +.7SO ) eq ( ) ML = S eq SiO2 + 1.(.589 Al2 O Fe2 O3 ) One can use this fitted equation to estimate the optimum Ceq/Seq ratio for a required expansion limit Note: ML formula includes molar equivalents and reaction factors (Malvar and Lenke, 26) Bonakdar, Mobasher, Dey, Roy (21), ACI Materials Journal, V. 17, No.

35 Effect of Fiber-Reinforcement Flexural properties on 15x15x45 mm prisms time = min COD=. mm f R =. MPa time =3 min COD=.9 mm f R =.24 MPa time =6 min COD=3.6 mm f R =.28 MPa time =12 min COD=9.2 mm f R =.25 MPa time =24 min COD=18 mm f R =.13 MPa 21 Concrete Sustainability Conference 35 National Ready Mixed Concrete Association

36 Full-Scale Testing of AFRC Shear wall test results 8 6 Note: Ф s.v n : factored shear capacity, V u : un-factored shear capacity, Ф s.v u : factored service load Shear Wall Test (2.4x2.4x.2 m setup) φ s.v n = 68.7 kn 8 6 Shear Wall Test (2.4x2.4x.2 m setup) Shear Load, kn 4 V u = 54.9 kn φ s.v u = 34.3 kn Shear S Load, kn LVDT-1, mm magnified LVDT-1, mm 21 Concrete Sustainability Conference 36 National Ready Mixed Concrete Association

37 21 Concrete Sustainability Conference 37 National Ready Mixed Concrete Association

38 AAC vs. AFRC AAC (plain, autoclaved) AFRC (fiber-reinforced, non-autoclaved) 6 6 Flexural Response for AAC Beams (6x6x18 in) Flexural Response for AFRC Beams (6x6x18 in) f Fle exural Load, lbf 4 2 AAC - Samples 1-4 Average σ R = 93 psi f Fle exural Load, lbf 4 2 AFRC - Samples 1-4 Average σ R = 77 psi CMOD, in CMOD, in Note the difference between scales on X-axis 21 Concrete Sustainability Conference 38 National Ready Mixed Concrete Association