EXPERIMENTAL STUDY OF FLY ASH- BASED GEOPOLYMER CONCRETE… · Alakaline Solution/Fly ash=0.35 Liquid/Fly Ash = 0.44 Compressive Strenght [MPa] Mixing Time Compressive Strenght [MPa]

EXPERIMENTAL STUDY OF FLY ASH-BASED GEOPOLYMER CONCRETE:

STRUCTURAL APPLICATIONS

Linda Monfardini, PhD [email protected]

UNIVERSITY OF BRESCIADepartment of Civil Engineering, Architecture, Environment, Land Planning

and of MathematicsPhD Course in:

CIVIL AND ENVIRONMENTAL ENGINEERING

2/25Saint QuentinJuly 6-8,2015 Linda Monfardini - [email protected]

EXPERIMENTAL STUDY OF FLY ASH-BASED GEOPOLYMERCONCRETE: STRUCTURAL APPLICATIONS

Brescia



University of BresciaFaculty of Engineering

“Pietro Pisa” Testing Lab



Concrete: one of the most used material in the world

Because of PORTLAND CEMENT, concrete

production has a significant effect on global warming and

CO2 emissions

NEED OF ECO-FRINEDLY MATERIAL

GEOPOLYMER CEMENT/CONCRETE

11

269

0

50

100

150

200

250

300

Ceneri volanti Cemento

Emissioni CO2[kgCO2e - m3]

Louise K. Turner, Frank G. Collins, “Carbon dioxide

equivalent (CO2-e) emissions: a comparison between geopolymer

and OPC cement concrete”.

1 ton Cement ≈ 1 ton CO2


ADVANTAGES

- Cement free

- Use of fine dustderived from industrial processes

- Good mechanical and durability properties

Reduction of CO2 emissions

Reuse of waste materials

ECO-FRIENDLY MATERIAL



Precast structures

Retrofitting of existing structures

University of Queensland’s Global

Change Institute, Australia

STRUCTURAL APPLICATIONS Geopolymer mortar

Self compacting geopolymerconcrete

Fiber reinforced geopolymerconcrete



OUTLINESTEP 1: MIX DESIGN • Study of the optimal mix design• Analysis of curing parametres

STEP 2: MATHERIAL CHARACTERIZATION• Compressive strenght• Young’s Modulus• Stress-strain relationship• Analysis of Modulus of Rupture (MOR)

STEP 3: FULL-SCALE TESTS• Two full-scale beams tested under four point loading system

CONCLUSIONS



ALUMINOSILICATESOURCE

Metakaolin,Slag

Class F Fly Ash(ASTM C618-78)

ALKALINESOLUTION

Potassium Hydroxide

+Potassium

Silicate

SodiumHydroxide

(8M)

+Sodium Silicate

(WR=2Conc. 44%)

AGGREGATES Fine and Coarse aggregates(Maximum size=10 mm)

STEP 1: MIX DESIGN



CLASS F FLY ASH:

FLY ASH USED BY UNIBSTotal SiO2 = 56%

Al2O3 = 28%SiO2+Al2O3 =84 %

SiO2/Al2O3 ≈2CaO= 2%

Fe2O3= 5.5 % LOI = 2.8 %

SUPERPLASTICIZER

NO CONTRIBUTION IN TERMS OF WORKABILITY

J.Davidovits, High-alkali cements for 21st century concretes, in "Concrete technology, past present and future", Proceedings of V. Mohan Malhotra symposium, Ed. P. Kumar Metha, ACI SP-144, 1994, pp. 383-397.

Structural applicationsSi:Al = 2

LOI:It should be less than

5%Inhibition of reaction

Low contentof CaOAvoid fast

settingJ. Davidovits, M. Izquierdo, X. Querol, D. Antennucci, H.

Nugteren, V. Butselaar-Orthlieb, C. Fernández-Pereira, Y.

Luna, The European Research Project GEOASH:

geopolymer cement based on European coal fly ashes,

Technical Paper #22, Geopolymer Institute Library,

www.geopolymer.org, 2014.



Rest period Curing time (60°C)

Extra water content27 26 27

8

0

5

10

15

20

25

30

GC27 (23kg/m3)

GC28 (25kg/m3)

GC30 (30kg/m3)

GC26 (80kg/m3)

Res

isten

za a

com

pres

sione

Rcm

2729

0

5

10

15

20

25

30

35

40

Curing 24 h Curing 48 h

Res

isten

za a

com

pres

sione

Rcm

27

35

0

5

10

15

20

25

30

35

40

Rest period 24 h Rest period 48 h

Res

isten

za a

com

pres

sione

Rcm

22

25

26 26

15

18

21

24

27

30

3 4 5 6 7 8 9 10 11

Res

isten

za a

com

pres

sione

Rcm

Tempo di miscelazione [Minuti]

Materials [kg/m3]

Coarse Aggregate (6-10 mm) 1201

Sand 647

Tot. Aggregates 1848

Class F Fly Ash 408

Sodium Hydroxide 8 M 41

Sodium Silicate 103

Extra H2O 35

Total 2435

Aggregates: 80% by mass

Coarse Aggregate/Sand = 2

Silicate/ Hydroxide= 2.5

Alakaline Solution/Fly ash=0.35

Liquid/Fly Ash = 0.44

Mixing Time

Com

pres

sive

Str

engh

t [M

Pa]

Com

pres

sive

Str

engh

t [M

Pa]

Com

pres

sive

Str

engh

t [M

Pa]

Com

pres

sive

Str

engh

t [M

Pa]

25-35 kg/m3

MIX DESIGN & CURING PARAMETRES



39 (5656) 40 (5801) 41 (5946) 40 (5801)43 (6236)

42 (6091) 43 (6236)45 (6526)

8 (1160)

14 (2030)

20 (2900)

0

1000

2000

3000

4000

5000

6000

7000

0

5

10

15

20

25

30

35

40

45

50

0 7 14 21 28 35

Com

pres

sive

cub

ic st

reng

ht [p

si]

Com

pres

sive

cub

ic st

reng

ht [M

Pa]

Time [days]

GC1, HCGC2, HCGC2, AC

fcm=0.83 Rcm

Cylinder compressive strength:

33-37 MPa

HC:Heat CuringAC: Ambient Curing

STEP 2: MATERIAL CHARACTERIZATIONCUBIC COMPRESSIVE STRENGHT

3 Days: End of Curing



STEP 2: MATERIAL CHARACTERIZATIONYOUNG’S MODULUS

UNI 6556BEAM 1

GC1BEAM 2

GC2

24 GPa 25 GPa

3.0

1022000

cm

cmfE

For ordinary concrete, Eurocode 2 recommends the following relation:

EXPERIMENTAL RESULTS

ANALYTICAL RESULTS

Ecm = 31- 32.5 GPaMaximum Aggregate size = 10 mm



ANALYTICAL FORMULAS

UNI 6556

STEP 2: STRESS-STRAIN RELATIONSHIP

THORENFELDT et al.

EUROCODE 2

Test run in stroke control



GC1-#1

GC1-#2

GC1-#3

GC1-#4

0

1000

2000

3000

4000

5000

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16

Stre

ss σ

[psi]

Stre

ss σ

[MPa

]

Strain ε [‰]

Thorenfeldt et al.Eurocode 2Mean Curve

fcm = 29 MPa [4206 psi]εcm = 2.24 ‰

Ductile behavior in the post-peak phase

STEP 2: STRESS-STRAIN RELATIONSHIP



• CMOD (Crack Mouth Opening Displacement)

• 2 CTOD (Crack Tip Opening Displacement)

• 2 MPD (Mid Point Displacement)

UNI EN 14651

STEP 2: MODULUS OF RUPTURE (MOR)

Goal:

Indirect analysis of tensile strenght

MODULUS OF RUUTURE



0.00 0.01 0.02 0.03 0.04 0.05

0

100

200

300

400

500

0

1

2

3

4

0.0 0.3 0.6 0.9 1.2 1.5

CMOD [in]

Nom

inal

Str

ess σ

N[p

si]

Nom

inal

Str

ess σ

N[M

Pa]

CMOD [mm]

GC1OPC 40

Geopolymer Concreteσn= 3.3 MPaFL=10.6 kN

STEP 2: MODULUS OF ROPTURE



STEP 3: FULL-SCALE TESTS

As = 4.02 cm2 fsy = 545 MPa

A’s = 0 σst,max,es = 260 MPa

ρl = 0.77 %ρv = 0.67 % Ast = 0.50 cm2

Mu = 0.9·d·As·fsy=51 kNmPu = 2 Mu / a = 89 kN

StirrupsØ 8/7.5

Four point bending test



CURING CHAMBER


After a rest period of 48 hours Curing: 60° C for 24 hours


TEMPERATURE MONITORING



COMPARISON OF RESULTS

Test Day:

31 days

Pu = 95 kN

δu = 156 mm

E = 24 GPa

Test Day:

8 days

Pu = 92 kN

δu = 127 mm

E = 25 GPa

Beam GC1

Beam GC2



LOAD-DISPLACEMENT

0 1 2 3 4 5 6 7

0

5000

10000

15000

20000

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

Mis-span displacement [in]

Loa

d [lb

]

Loa

d [k

N]

Mid-span displacement [mm]

GC1GC2

Pu,GC1 = 95 kN

Pu,GC2 = 92 kN

δu,GC1 = 156 mm

δu,GC2 = 127 mm

Py,GC1 = 85 kN

Py,GC2 = 86 kN

δy,GC1 = 37 mm

δy,GC2 = 38 mm

Pu, predicted = 89 kN

Ductility: δu / δyGC1 = 4.16GC2= 3.26



Beam GC1 Baem GC2

Experiental result

Srm = 113 mm

Experimental result

Srm = 102 mm

CRACK PATTERN




COLLAPSE


• Compression strength had a limited increase in time after the heat curing;• Experimental Young’s modulus is lower than ordinary concrete;• Constitutive law: in pre-peak phase, a trend similar to analytical formulas proposed

for ordinary concrete. In post-peak response GC presented a more ductile behavior;• MOR tests pointed out a rather brittle behavior coincident to ordinary concrete;• Despite difference in testing time, flexural behavior of full-scale beams did not

show differences in terms of ultimate load; on the contrary there are minordifference in terms of ultimate displacement and ductility;

• As expected for ordinary concrete, full-scale beams reached failure because ofconcrete crushing with yielded steel;

• Experimental mean crack spacing fits well with analytical formulas for ordinaryconcrete.

CONCLUSIONS


25/16

Thank you for your kind attention!

University of Brescia, Italy

Documents

EXPERIMENTAL STUDY OF FLY ASH- BASED GEOPOLYMER CONCRETE… · Alakaline Solution/Fly ash=0.35 Liquid/Fly Ash = 0.44 Compressive Strenght [MPa] Mixing Time Compressive Strenght [MPa]