duncan herfort cementir holding...
TRANSCRIPT
H d h bl f hi hHydrate phase assemblages for high performance low clinker cementsHydrate phase assemblages for low
clinker fit for purpose cementsDuncan Herfort
Cementir Holding
p p
Duncan HerfortCementir HoldinggCementir Holding
Introduction
H d h bl f hi h
Can we replace 50% clinker by a non-calcareous pozzolana (e.g. class F FA) for same concrete performance?
Hydrate phase assemblages for high performance low clinker cements
At first glance the answer is no, because the
• maximum replacement with a non-calcareous pozzolana for same
Duncan HerfortCementir Holding
p pstrength is c. 25%, and
• Except for N.America production of industrial SCMs falls well short of this in any event gy
Solutions to overcome this include developing
• natural pozzolana including calcined clays,• the synergy between limestone and alumino silicate pozzolana for
replacement up to 50%, andreplacement up to 50%, and• alkali activation for replacement higher than 50%
44
oduc
tion
improved kiln efficiency,biofuel,n.gas where practicable
Improved kiln efficiency, use of bio fuels & natural gas (0.93 109 t CO2)
3
cem
ent p
ro p
a
40% SMC for same concreteperformance
40% SCM for same concrete performance (0.88 109 t CO2)
2
issi
on fr
om
109 to
nne
1/3 of RM CO2 recarbonated
1/4 f CO2 i i t d
1/5 of RM CO2 recarbonated (0.34 109 t CO2)
2/5 of CO2 emissions captured
1
obal
CO 2
em
i 1/4 of CO2 emissions storedand captured
Serie1
and stored (0.83 109 t CO2)
Currently 25% is about the limit for non calcareous SCMs
02008 2050
Glo non calcareous SCMs
2008 2050
7580
a
606570
hs, M
Pa
45505560
stre
ngth
30354045
28d
s
300 10 20 30 40
clinker replacement, %clinker replacement, %
silica gelSiO2
20% Silica fume clays
C0 8SHy
pozzolans
0.8 y
C SH
70% GBFS35% basaltic pozzolan25% granitic pozzolan25% calcined clay or PFA
C-S-Hss
C1.7SHx 25% calcined clay or PFA
stratlingite
C3A.CS.H12
C3A.CC.H12
C3A.3CS.H32
CH
gibsite
C3APortland cement
g
CaO Al2O3
silica gel
Max clinker replacement by non calcareous pozzolana for equal concrete performance
20% Silica fume clays
concrete performancec. 25%
C0 8SHy
pozzolans
0.8 y
C SH
70% GBFS35% basaltic pozzolan25% granitic pozzolan25% calcined clay or PFA
C-S-Hss
C1.7SHx 25% calcined clay or PFA
stratlingite
C3A.CS.H12
C3A.CC.H12
C3A.3CS.H32
CH
gibsite
C3APortland cement
g
CaO Al2O3
silica gel
Max clinker replacement by non-calcareous pozzolans for equal concrete performance
20% Silica fume clays
c. 25%
Availability c. 10%
C0 8SHy
pozzolans
0.8 y
C SH
70% GBFS35% basaltic pozzolan25% granitic pozzolan25% calcined clay or PFA
C-S-Hss
C1.7SHx 25% calcined clay or PFA
stratlingite
C3A.CS.H12
C3A.CC.H12
C3A.3CS.H32
CH
gibsite
C3APortland cement
g
CaO Al2O3
World wide availability of Supplementary Cementitious Materials
Metakaolin
x
IEA production data
Silica fume
Rice husk ashIEA production data published 2008:
Cement 2500 tpa
Natural pozzolana
Burnt shale Used in cement
Reserve
Fly ash 300 tpa
BF slag 220 tpa
Blast furnace slag
Natural pozzolana
i.e. max 20% of cement
Cement
Fly ash
Limestone
0 100 200 300 400 500 600Mill. tons/year
World wide availability of Supplementary Cementitious Materials
Metakaolin
x
IEA production data
Silica fume
Rice husk ashIEA production data published 2008:
Cement 2500 tpaPotentially 25% for same concrete
Natural pozzolana
Burnt shale Used in cement
Reserve
Fly ash 300 tpa
BF slag 220 tpaperformance, but only 10% availability.Solution is to exploit existing
Blast furnace slag
Natural pozzolana
i.e. max 20% of cementSolution is to exploit existing landfilled PFA, natural pozzolana, or calcined clay
Cement
Fly ash
Limestone
or calcined clay
0 100 200 300 400 500 600Mill. tons/year
World wide availability of Supplementary Cementitious Materials
Metakaolin
x
IEA production data
Silica fume
Rice husk ashIEA production data published 2008:
Cement 2500 tpaThat still leaves us well short of
Natural pozzolana
Burnt shale Used in cement
Reserve
Fly ash 300 tpa
BF slag 220 tpaour target of 50% replacement
Blast furnace slag
Natural pozzolana
i.e. max 20% of cement
Cement
Fly ash
Limestone
0 100 200 300 400 500 600Mill. tons/year
7580
606570
hs, M
Pa
45505560
stre
ngth
354045
28d
300 10 20 30 40
clinker replacement %clinker replacement, %
The carboaluminate reaction suggests a way out.
7580
606570
hs, M
Pa
45505560
stre
ngth
354045
28d
300 10 20 30 40
clinker replacement %clinker replacement, %
CaSO4gypsum+ CSH + CH + FH+ CSH + CH + FH3+ pore solution
ettringite
monosulfate
thaumasite
Reduced porosity
Ms-ss
porosityIncreased porosity
C4AH13
calcite
MonocarbonateHemicarbonateC3A CaCO3
calcite
higher aluminate content = higher strengths
10
15nd
]
compressive strength measured
5
10
poro
sity
atre
ngth
[%]
increase
-5
0
chan
ge o
f pr
essi
ve s
t
decrease
15
-10
rela
tive
cco
m
total porosity calculated
-150 2 4 6 8 10 12 14 16 18 20 22
amount of CaCO3 added [wt.-%]
Very good correlation between predicted changes of relative porosityand measured compressive strength
H d h bl f hi hHydrate phase assemblages for high performance low clinker cements
Li t d l i d lDuncan Herfort
Cementir Holding
Limestone and calcined clayg
65
55
60
50
55
ngth
, MPa
+ 20%
40
45
28 d
str
en
calcined mixed clay
35
2 calcined mixed clay
Metakaolin
calcined Na bentonite30
0 0,2 0,4 0,6 0,8 1
clay content (wt. fraction of clay/(clay+limestone), clinker + gypsum constant at 65%)
65
55
60
50
55
ngth
, MPa
+ 26%
40
45
28 d
str
en
calcined mixed clay
35
2 calcined mixed clay
Metakaolin
calcined Na bentonite30
0 0,2 0,4 0,6 0,8 1
clay content (wt. fraction of clay/(clay+limestone), clinker + gypsum constant at 65%)
300
240
260
280
nsta
nt
CEM I at same fineness
- 18 %
200
220
240
ete
at c
on
- 33%
160
180
200
m3
conc
retr
engt
h
120
140
ssio
n kg
/m st
mixed clayMetakaolin
1000 0,2 0,4 0,6 0,8 1
CO
2em
is
clay content (wt. fraction of clay/(clay+limestone), clinker + y ( y ( y )gypsum constant at 65%)
300
240
260
280
nsta
nt
CEM I at same fineness
- 18 %
200
220
240
ete
at c
on
- 33%
Most studies have shown that 40% replacement is about the limit before the
160
180
200
m3
conc
retr
engt
h supply of Ca is exhausted.To go further other hydrate phases need to form
120
140
ssio
n kg
/m st
mixed clayMetakaolin
to form.
1000 0,2 0,4 0,6 0,8 1
CO
2em
is
clay content (wt. fraction of clay/(clay+limestone), clinker + y ( y ( y )gypsum constant at 65%)
silica gelSiO2
20% Silica fume clays
C0 8SHy
pozzolans
0.8 y
C SH
70% GBFS35% basaltic pozzolan25% granitic pozzolan25% calcined clay or PFA
C-S-Hss
C1.7SHx 25% calcined clay or PFA
stratlingite
C3A.CS.H12
C3A.CC.H12
C3A.3CS.H32
CH
gibsite
C3APortland cement
g
CaO Al2O3Ca needed to form AFm, AFt phases
300
240
260
280
nsta
nt
CEM I at same fineness
- 18 %
200
220
240
ete
at c
on
- 33%
Calcined clays normally require more water for the same consistency and
160
180
200
m3
conc
retr
engt
h therefore more cement for the same strength.However this can be overcome by the
120
140
ssio
n kg
/m st
mixed clayMetakaolin
However, this can be overcome by the correct sequence of mixing with water reducers.
1000 0,2 0,4 0,6 0,8 1
CO
2em
is
clay content (wt. fraction of clay/(clay+limestone), clinker +
reducers.
y ( y ( y )gypsum constant at 65%)
0.6% SP w/b = 0.535% replacement
80
100 cement without SP cement + SP early addition (reference) cement + SP late addition
60
80
Pa)
40
ar S
tress
(P
20
She
a
0 50 100 150 200
0
Shear Rate (s-1)
60
50
55
60
35
40
45
Pa)
25
30
ear S
tress
(
10
15
20
cement early addition
She
0 50 100 150 2000
5
y cement+CB early addition cement+CB late addition
Shear Rate (s-1)
STRUCTURAL EVOLUTION ASSESSMENT
Increasing NS (0 16%)
Futurecem –Workshop 7Aalborg – August 26 -2010
40% clinker, MK/(MK+ls) ratio = 0.96, sodium sulfate content = 0, 4, 10, 16%
Constant water/binder ratio of 0.57
EFFECT OF MK/LIMESTONE RATIO ON STRUCTURE
X-RAY DIFFRACTION – 90 DAYS OF CURING – 40% CLINKER
MK/(MK+ls) ratio: a) 0.80 and b) 0.96
Futurecem –Workshop 7Aalborg – August 26 -2010
STRUCTURAL EVOLUTION ASSESSMENT2
Aluminosilicategel
27Al MAS NMR – 40% CLINKER14.1T, R = 13.0 kHz4 3
2
1
180 days
g
90 days
1
2
Third aluminate
AFm phases
28 days
90 days
3
4
AFt phases
Al(IV) in C-S-H
7 days
28 days
7 days
Futurecem –Workshop 7Aalborg – August 26 -2010
NS = 0% NS = 16%
STRUCTURAL EVOLUTION ASSESSMENT2
Aluminosilicategel
27Al MAS NMR – 40% CLINKER14.1T, R = 13.0 kHz4 3
2
1
180 days
g
Sodium sulfate is an effective activator in mixed CSH – zeolitic systems if the right b l b f d f ffi i tl
90 days
1
2
Third aluminate
AFm phases
balance can be found for a sufficiently high pH for activation and the content of Na needed to balance Al in the framework
28 days
90 days
3
4
AFt phases
Al(IV) in C-S-H
Na needed to balance Al in the framework silicates (must be 1:1).
7 days
28 days
7 days
Futurecem –Workshop 7Aalborg – August 26 -2010
NS = 0% NS = 16%
Conclusion
By combining limestone and alumino silicate pozzolana (FA, calcined clay etc.), the levels of clinker replacement for the same concrete performance canreplacement for the same concrete performance can be extended from about 25% to 40%.
F f th l l f l t lk li f ti tiFor further levels of replacement, alkalis for activation and stabilisation of framework silicates are needed.