wt%

days

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

SCM Phases

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

SCM Phases

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

SCM Phases

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

SCM Phases

Amorphous

AFt

β-C2S

Gibbsite

Minor initialphases

C4A3S

CSH2FW

Vaterite

wt%

days

SCM Phases

Marta García-Maté*, Isabel Santacruz*, Ángeles G. De la Torre, Miguel A.G. Aranda

Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias, Campus de Teatinos s/n, University of Malaga, 29071 Malaga, Spain

*e-mails: martagmate@uma.es, isantacruz@uma.es

Calcium sulfoaluminate (CSA) cements are receiving increasing attention since their manufacture produces less CO2 than ordinary Portland cement (OPC) [1]. These binders may have quite variable compositions, but all of them contain Ye’elimite phase, also called Klein’s salt or tetracalcium trialuminate sulfate (C4A3S) as the main phase [2]. They may also have minor amount of phases such as C2S, CA, C4AF, CS, CSH2 [3], where C=CaO, S=SiO2, A=Al2O3, F=Fe2O3, S=SO3, M=MgO, T=TiO2 and H=H2O. The mortar and concretes derived from these cements show high strength developments at early-ages [4] and could also be used for radioactive element encapsulation [5]. Another environmental strategy for reducing the negative impact of the cement industry is related with the reduction of the clinker content in concretes [6]. This is possible by the partial substitution of cement by supplementary cementitious materials (SCMs) mainly from power stations or metal industry (fly ash, slag or silica fume). The environmental benefits of the use of waste materials are two folds: the clinker reduction will produce lower CO2 emissions; and the valorization of an “useless” product. Furthermore, fly ash improves some properties of OPC mortars and concretes due to the pozzolanic reaction and its role as a micro-filler.

Introducción

Objetive

Acknowledgements

Conclusions References

This work has been supported by Spanish Ministry of Science and Innovation through MAT2010-16213 research grant, which is co-funded by FEDER, and Ramón y Cajal Fellowship (RYC-2008-03523).

This work deals with the study of the “potential pozzolanic” effect of fly ash (FA) on CSA cement pastes and mortars. This will allow the fabrication of environmentally friendly cements (by the use of CSA clinker and its partial substitution with by-products), and mortars with improved mechanical properties at long ages.

CALCİUM SULFOALUMİNATE CEMENT HYDRATİON İN THE PRESENCE OF FLY ASH

Hydration time: 3, 7, 28 days

6 months, 1 year

CSA Clinker (BELITH S.P.R.L., Belgium)

Gypsum 25 wt%

Fly Ash (Lada, Spain)

0 wt% 15 wt% 30 wt%

Water/binder (w/b)

0.50 0.65 (without FA)

Sand

Mortar

Compressive Strength

Cement Pastes

Calorimetry TDA-TGA Porosimetry

LXRD Rietveld methodology Amorphous quantification (G-factor)

Pastes and mortars preparation

10 20 30 40

7d

3d

28d

10 20 30 40

3d

7d

28d

10 20 30 40

3d

7d

28d

Hydration studies (pastes) qualitative approach

10 20 30 40

7d

3d

28d

[1] Gartner E., Cem. Concr. Res. 2004, 34, 1489. [2] Álvarez-Pinazo G., Cuesta A., García-Maté M., Santacruz I., Losilla E.R., De la Torre A.G., León-Reina L., Aranda M.A.G., Cem. Concr. Res., 2012, 42, 960. [3] Sahu S., Majling J., Cem. Concr. Res., 1993, 23, 1331. [4] Glasser F.P., Zhang L., Cem. Concr. Res., 2001, 31, 1881. [5] Zhou Q., Milestone N.B., Hayes M., J. Hazard. Mater., 2006, 136, 120. [6] Bensted J., Barnes P., Structure and performance of cements. 2002, 2nd ed. New York: Spon Press.

AFt Gibbsite C4A3S CSH2

Minor initial phases: CT + M + C2MS2 +C4AF

Minor initial phases: CT + M + C2MS2 +C4AF SCM crystalline phases: Mullite + Quartz

Minor initial phases: CT + M + C2MS2 +C4AF SCM crystalline phases: Mullite + Quartz

To be measured

2 θ days

0 wt% FA, w/b=0.65 0 wt% FA, w/b=0.50 15 wt% FA, w/b=0.50 30 wt% FA, w/b=0.50

Com

pres

sive

Str

engt

h (M

Pa)

Compressive Strength - Mortars

0 wt% FA, w/b=0.65

0 wt% FA, w/b=0.50

15 wt% FA, w/b=0.50

30 wt% FA, w/b=0.50

0 wt% FA, w/b=0.50

15 wt% FA, w/b=0.50

30 wt% FA, w/b=0.50

AFt Gibbsite C4A3S CSH2

AFt Gibbsite C4A3S CSH2

AFt Gibbsite C4A3S CSH2

2 θ

2 θ

2 θ

PASTE

Open Porosit

y* (vol %)

0 wt% FA, w/b=0.65 20.3

0 wt% FA, w/b=0.50 14.7

15 wt% FA, w/b=0.50 17.4

30 wt% FA, w/b=0.50 18.8

Porosimetry (pastes)

0 2 4 6 8 10 12 140.0

2.0x10-3

4.0x10-3

6.0x10-3

8.0x10-3

1.0x10-2

0 wt% FA, w/b=0.50 15 wt% FA, w/b=0.50 30 wt% FA, w/b=0.50

Nor

mal

ized

Hea

t Flo

w (W

/g)

time (days)

0.0 0.5 1.0 1.5 2.00.0

2.0x10-3

4.0x10-3

6.0x10-3

8.0x10-3

1.0x10-2

0 wt% FA, w/b=0.50 15 wt% FA, w/b=0.50 30 wt% FA, w/b=0.50

Nor

mal

ized

Hea

t Flo

w (W

/g)

time (days)

0 2 4 6 8 10 12 140

50

100

150

200

250

300

0 wt% FA, w/b=0.50 15 wt% FA, w/b=0.50 30 wt% FA, w/b=0.50

time (days)

Calorimetry (pastes) – 7 days

- Pastes (≤ 28 days). By Increasing FA content: Normal heat flow decreases (due to the lower hydraulic active matter) Amorphous/non-diffractive matter content increases. Weight loss decreases (for the same w/b) according to TGA. Open porosity increases. - Mortars (≤ 28 days). By Increasing FA content: Compressive strength values decrease. However, it may be expected a different behaviour at longer hydration times (≥6 months). In any case the decreasing in compressive strengths is small

Minor initial phases: CT + M + C2MS2 +C4AF

0 wt% FA, w/b=0.65

Amorphous

AFt

? - C 2 S

Gibbsite

Minor Initial phases

C 4 A 3 S

C S H 2 FW

Vaterite

days

β - 2 S

C 4 A S

C S 2

days

wt%

15 wt% FA, w/b=0.50

DTA-TGA

Gibbsite

28 days

CO2

Rietveld

AFt

15 wt% FA, w/b=0.50 3 days

28 days

Gibb

site

Gibb

site

C 4A 3

S

Gyps

um

Gyps

um

Gyps

um

Gyps

um

AFt

AF t AF

t

AFt

AFt

AFt AF

t AF

t

AFt

AFt

AFt

AFt AF

t AFt

AFt

Vate

rite

Vate

rite

Qua

rtz

0 wt% FA, w/b=0.50 28 days

Gibbsite CO2

AFt

Hydration studies (pastes) quantitative approach

15 wt% FA, w/b=0.50

Gibb

site

Gibb

site

C 4A 3

S

Gyps

um

Gyps

um

Gyps

um

Gyps

um

AFt

AFt

AFt

AF t AF

t

AFt

AFt

AFt

AFt

AFt

AFt

AFt A

Ft

AFt

AFt

Vate

rite

Vate

rite

Qua

rtz

* Mercury Intrusion Porosimetry

2-Theta, deg

Cou

nts

20.0 30.0 40.0

X10E

3

0.0

1.0

2.0

3.0

Mul

lite

Mul

lite

Mul

lite

Mul

lite

Mul

lite

Mul

lite

Mul

lite Mul

lite

Mul

lite

Qua

rtz

Qua

rtz

Qua

rtz

Qua

rtz

Hem

atite

s M

agne

sium

ferr

ite

Lim

e

Peric

lase

Qua

rtz

Gyps

um

Gyps

um

Gyps

um Gy

psum

C 4A 3

S

C 4A 3

S

C 4A 3

S

C 4A 3

S

3d3 0

20

40

60

80

1 2 33 7 28