10 YEAR EXPOSURE OF CIMENT FONDU
MORTARS IN A MARINE ENVIRONMENT
P.F.G. BANFILL
School of the Built Environment, Heriot-Watt University, Edinburgh, EH14
4AS, UK
p.f.g.banfill@hw.ac.uk
SUMMARY: A research programme to investigate the durability of Ciment
Fondu mortars mixed with sea and fresh water plus various admixtures has
been described previously, and results have been presented on fresh and
early age hardened properties. This paper presents results on durability tests
in a marine environment for up to 10 years. Mortars, made at 5, 20 and
40°C, were mixed using seawater, artificial seawater and de-ionised water.
The admixtures used were an accelerator, superplasticiser, anti-washout, airentraining and water proofing admixtures and an ethylene vinyl acetate
polymer dispersion. Performance of each combination was monitored for a
total of 10 years at a marine exposure site and is compared to the laboratory
performance in freeze-thaw and wet-dry cycling over one year. The mortars
with polymer latex performed poorly and many specimens had completely
disintegrated, whereas the controls and mortars with accelerator and
superplasticiser performed well on the marine site. Temperature of mixing
and curing is very important in both the early and long term performance of
Ciment Fondu, and it is recommended to carry out durability tests on any
proposed combination before a decision is taken regarding materials
selection.
Keywords: Ciment Fondu, durability, mortar, seawater.
INTRODUCTION
Calcium Aluminates of the Ciment Fondu type have long been known to have superior
qualities in resisting attack by seawater and many other hostile chemical environments.
They are widely recommended as being more durable than Portland cements in seawater
[1,2,3]
. The conversion process occurs but is usually very slow (as low as 15% in 30
years) except in the tidal zone or in warm waters [4]. These CACs are also recommended
for use in cold environments, especially at W/C < 0.4. There may be situations where it
is necessary to mix them with seawater, especially offshore where fresh water is scarce
and of course where there is no embedded metal to pose risks of corrosion. However,
there is disagreement about the effects of seawater for mixing. Gjørv suggests that it
may be better than with fresh water [1], while Neville and Wainwright suggest that the
formation of chloroaluminates preclude its use [5]. Halse and Pratt [6] found that although
Calcium Aluminates: Proceedings of International Conference, Avignon, 18 –21 May 2014. Fentiman CH,
Mangabhai RJ and Scrivener KL (Editors). IHS BRE Press, 2014, EP104. ISBN 978-1-84806-316-7.
Banfill
seawater retarded hydration the later microstructure was very similar to that with fresh
water.
In view of the relative scarcity of information on its durability when admixtures
are used [3], a research programme was established to investigate the durability of
Ciment Fondu mortars mixed with sea and fresh waters, incorporating various
admixtures, with the aim of giving information on the effects of the admixtures when
the mortars were exposed to laboratory conditions and in a marine environment.
Information on the effects on fresh properties [7], early age properties [8] and three-year
field performance [9] has already been reported. This paper reports data on field
performance up to the conclusion of the investigation after 10 years.
EXPERIMENTAL PROGRAMME
Materials
Ciment Fondu, provided by Lafarge Aluminous Cement Co Ltd (now Kerneos), from a
single batch with the chemical and physical properties shown in Table 1, was used with
a siliceous sand whose particle size distribution is shown in Table 2. Three different
mixing waters were used (Table 3): deionised water (DI), water from the Irish Sea,
settled but unfiltered, (SW) and reconstituted seawater (RSW) made from a corrosion
test mixture (BDH Chemicals). To simulate the effect of using unwashed marine sand,
each mix was also repeated using additional sea salts (SS) added at 6.6 kg of corrosion
test mixture per kg of sand, giving mixes designated DI+SS, SW+SS and RSW+SS.
Admixtures were chosen to represent a range of types potentially used in marine
work and were used at the maximum dosage recommended by the respective
manufacturers:






Lithium citrate accelerator at 0.025% by mass of cement (Accel)
Superplasticiser (FEB SP3) at 0.6% by mass of cement (SP)
Anti-washout (Conplast UW) at 1% by mass of cement (AWO)
Air-entrainer (Cormix AE1) at 45ml/50kg of cement (AEA)
Waterproofer (Palace Intrapruf) at 1:30 in the mixing water (WP)
Ethylene vinyl acetate dispersion polymer (Vinamul 3281) at 5% solids by mass
of cement (EVA).
Table 1. Chemical and physical properties of the Ciment Fondu
Setting time (BS915), minutes
Initial
280
Final
293
90 micron residue (%)
3.8
2
Blaine surface area (m /kg)
276
Chemical composition (%)
SiO2
Al2O3
Fe2O3
FeO
TiO2
CaO
Na2O
K2O
SO3
CO2
4.14
38.67
10.43
5.63
1.98
38.5
0.06
0.04
0.19
0.42
Table 2. Particle size distribution of the sand
Sieve size
2.4-1.2 mm
1.2-0.6 mm
600-300 μm
300-150 μm
150-90 μm
% by mass
25.9
37.1
14.8
14.8
7.4
10 year exposure of Ciment Fondu mortars in a marine environment
Table 3. Composition of sea waters (ppm by mass of each species
Cl-
Na+
SO42-
Mg2+
Ca2+
K+
CO32-
Br-
Sea Water (SW, Irish Sea)
19000
10500
2650
1350
400
380
160
65
Reconstituted (RSW)
16200
9960
1830
570
440
-
-
-
Species
Mixing and curing
The mix proportions were standardised for every mortar at water/cement ratio 0.40 and
cement/sand ratio 0.50, giving overall contents of cement 691 kg/m3, sand 1382 kg/m3
and water 276 kg/m3. There was no reduction in water content to take account of the
effect of any admixture. The cement, sand and water were pre-conditioned to the
temperature of curing (5, 20 or 40°C). Each batch was made in two parts in a bench top
mixer (Kenwood Chef), mixed dry for 60 sec at 120 rev/min, followed by addition of
the water and admixture over 60 sec with hand mixing, and a final 60 sec of mixing at
250 rev/min, followed by hand blending of the two parts. 75 mm cubes, 40 mm
diameter x 100 mm long cylinders and 40 x 40 x 160 mm prisms were cast and all
specimens were cured for 7 days under thermostatically controlled fresh water at 5, 20
and 40°C. This resulted in a factorial experiment consisting of 126 combinations – 7
(Control (Nil) plus 6 admixtures) x 6 (3 waters plus 3 with additional sea salts) x 3
temperatures.
Test methods
In addition to the laboratory programme of wetting/drying and freezing/thawing
reported previously [9], one prism of each mix was set up in an exposure trial which ran
from January 1989 for ten years. The specimens were secured in wire baskets at midtide level on a rocky beach on the Irish Sea coast and tested at intervals for ultrasonic
pulse velocity (UPV) using the PUNDIT instrument, for length change by a 100 mm
gauge length Demec instrument, weight change and final strength (flexure on each
prism followed by compression on 40 mm cubes cut from the broken halves of the
prism tested for flexural strength).
RESULTS
While a large amount of data was accumulated, only the most significant features can be
presented here, and appropriate comparisons will be made with laboratory data.
Analysis of variance enabled statistical significance to be established for the relevant
factors. Unfortunately, many specimens were lost or became unidentifiable during the
course of the trial between 4 years and 10 years, and this seriously restricts the amount
of 10 year data that can be shown: only 31 out of 126 combinations are available.
UPV
Figs. 2-7 show changes in UPV with time for each admixture compared to the nil mix
(Fig. 1). Because a constant w/c ratio was used, these trends show the effect of the
admixtures without any confusing factors. The results designated ‘lab’ are taken from
the laboratory freeze/thaw results [9], wherein each 40 x 40 x 160 mm prism was
immersed 100 mm deep on its long dimension in sea water and then subjected to 120
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cycles of alternate -5°C and +20°C over one year. The temperatures shown are the
temperature of mixing / casting and each point is the mean of 6 specimens prepared
with the different mixing waters. The results designated ‘site’ were obtained from
different specimens cast at the same time and are likewise the means of the 6 specimens
prepared with the different waters, but some 10 year (approximately 3400 days) results
are based on only one or two specimens due to the losses mentioned above. Since the
previous results had shown no significant effect of the mixing water type on the
performance of the mortars [9], this process is considered to give representative
comparisons. UPV (v) is a reasonable predictor of cube strength (fcu), as shown by
equation 1 which was constructed from the 10 year test results obtained in this
investigation using 60 points (made up of 31 identifiable and 29 unidentifiable but still
testable specimens). There are too few 10 year strength values to be presented here.
UPV - km/sec
fcu = 0.07 v4 ± 11.0
(1)
5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
Fig. 1: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of Nil mixes cured at different
temperatures.
5.50
5.30
UPV - km/sec
5.10
5 degC (lab)
4.90
20 degC (lab)
4.70
40 degC (lab)
4.50
4.30
5 degC (site)
4.10
20 degC (site)
3.90
40 degC (site)
3.70
3.50
1
10
100
Age - days
1000
10000
Fig. 2: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of Accel mixes cured at different
temperatures.
UPV - km/sec
10 year exposure of Ciment Fondu mortars in a marine environment
5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
UPV - km/sec
Fig. 3: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of SP mixes cured at different
temperatures.
5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
UPV - km/sec
Fig. 4: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of AEA mixes cured at different
temperatures.
5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
Fig. 5: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of WP mixes cured at different
temperatures.
UPV - km/sec
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5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
UPV - km/sec
Fig. 6: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of EVA mixes cured at different
temperatures.
5.50
5.30
5.10
4.90
4.70
4.50
4.30
4.10
3.90
3.70
3.50
5 degC (lab)
20 degC (lab)
40 degC (lab)
5 degC (site)
20 degC (site)
40 degC (site)
1
10
100
1000
10000
Age - days
Fig. 7: Effect of exposure (lab up to 1 year, site up to 10 years) on UPV of AWO mixes cured at different
temperatures.
The 40°C mixes show consistently the lowest UPV in both lab and site exposure
because they were already converted at the start of the tests, while the 20°C mixes start
highest but typically drop below the 5°C mixes over the one year lab exposure period,
also due to conversion. There is no consistent trend between the 5 and 20°C mixes in
site exposure and it should be noted that some values are identical at 4 years and the
symbols coincide on the graphs: there are no missing points in the 4 year data. In
general the site values are what would be expected from extrapolating the lab trends but
the UPV of many mixes decreased between one and 10 years.
Mass change
Most specimens gained mass after exposure to the marine environment, with the
exception of about half of those from groups of mixes made at 40°C. Mass loss did not
correlate with spalling, most notably with the group of mixes containing waterproofer
cured at 40°C, which lost mass but did not spall. This is presumably as a result of
developing porosity. Fig. 8 shows the results, averaged over 6 specimens prepared with
different mixing waters.
10 year exposure of Ciment Fondu mortars in a marine environment
5.00
5°C
20°C
40°C
5°C
20°C
40°C
5°C
20°C
40°C
5°C
20°C
40°C
5°C
20°C
40°C
5°C
20°C
40°C
5°C
20°C
40°C
Mass change - %
0.00
-5.00
Nil
Accel
SP
AEA
WP
EVA
AWO
-10.00
-15.00
-20.00
Fig. 8: Mass change at 4 years (means of 6 specimens made with different mixing waters).
Dimensional change
Establishing reliable trends of expansion and contraction is difficult because many
specimens lost their Demec spots during the exposure trial: only a few spots remained
after 10 years. Most 5°C cured specimens expanded over time and most 40°C
specimens contracted.
Visual inspection
All the severe spalling occurred in the 40°C mixes and was particularly severe with
those made with accelerator and anti-washout admixture: an unidentified expansive
chemical reaction occurred but no further information is available. Conversion seems to
accelerate spalling as shown by the trend from 5 to 40°C specimens. The only 40°C
specimens to completely escape spalling were those containing air-entrainer and
waterproofer. Table 4 summarises the condition, as assessed visually, of the specimens
at 4 and 10 years.
Table 4. Visual condition score of specimens at 4 and 10 years exposure. (Key: 5=sound, 4=slight
spalling, 3=significant spalling and/or cracking, 2=extensive deteriorations, spalling, cracking and loss,
1=very little of specimen left.)
Mixing temperature
5°C
20°C
40°C
4
10
4
10
4
10
Nil
5
5
5
-
4
-
Accel
5
5
5
5
2
-
SP
5
5
5
-
4
4
AEA
5
5
4
3
4
4
WP
4
-
5
5
5
5
EVA
4
-
4
4
2
2
AWO
5
5
5
3
1
-
Years
Admixture
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DISCUSSION
Tables 5-6 attempt to bring together the test findings relating to the effects of
admixtures and mixing temperatures on performance in the marine exposure
environment. Just as the visual scores for the nil mixes without admixture (Table 4) are
high, so also are the test parameters (Table 5): mortars without admixture performed as
well as the best of those with admixture. In contrast, the EVA polymer dispersion
performed uniformly badly, while air-entraining agent, waterproofer and anti-washout
admixture performed better but still failed to offer protection against spalling, despite
performing well in laboratory freeze-thaw testing [9]. Overall, the anti-washout
admixture performed less well than the air-entraining agent and the waterproofer,
particularly at 40°C. In hindsight, it is possible that the air content or spacing factor
were not high enough to enhance the durability of the mortars with air-entraining
admixture. A more detailed investigation of this point would be useful in any further
work. Mortars with superplasticiser maintained similar strength and durability as those
without any admixture, with the sole exception of the 10 year cube strength, which is,
however, based on only two specimens. Finally, despite achieving high early strengths,
mortars containing accelerator were not more durable than the nil mixes.
Temperature of mixing and curing is important in the long term performance of
Ciment Fondu mixes (Table 6). Mortars stored at 40°C are highly converted and
strength is correspondingly lower. Those at 5°C, with low conversion levels, performed
well in the marine environment despite performing poorly in lab durability tests [9].
Additional salt in the mixing water appears not to have any effect although, of course,
the risk of corrosion of embedded metal where sea water is used for mixing
cementitious materials makes this undesirable.
100
90
28 day cube strength - MPa
80
70
60
50
5 degC
40
20 degC
30
40 degC
20
10
0
-5
-4
-3
-2
-1
0
1
2
3
4
5
Mass change - %
Fig. 9: Relationship between 28 day cube strength and mass change at four years.
10 year exposure of Ciment Fondu mortars in a marine environment
Table 5. Summary of exposure performance (admixtures).
Admixture type
Test
parameter
Nil
Accelerator
Superplasticiser
Air entrainer
Water-proofer
EVA
dispersion
Anti-washout
UPV 3 years
high
high
high
medium
medium
low
UPV 4 years
high
high
high
medium
medium
low
UPV 10 years
high
high
high
medium
medium
low
Cube strength
10 years
(MPa)
Flexural
strength 10
years (MPa)
Length
change 4
years
Mass change
4 years
Mass change
10 years
30-40
(1 specimen)
40-50
25-35
20-35
20-35
20-35
medium but
40°C low
medium but
40°C low
medium but
40°C low
50
(1 specimen)
1.9
(1 specimen)
1.8-2.0
1.6-3.0
1.1-3.2
1.2-3.2
1.2-2.0
3.0
(1 specimen)
none
expansion
none
contraction
contraction
expansion
small
expansion
gain
small gain
gain
gain
gain
gain
loss
-
small gain
-
small gain
gain at 5 and
20°C
gain
Loss
(1 specimen)
Table 6. Summary of exposure performance (mixing temperatures).
Mixing temperature
Test parameter
5°C
20°C
40°C
UPV 3 years
high
high
medium
UPV 4 years
high
high
medium
UPV 10 years
high
high
low
Cube strength 10 years
(MPa)
Flexural strength 10 years
(MPa)
30-40
20-50
25-50
1.1-3.0
1.2-2.3
1.6-3.3
Length change 4 years
expansion
EVA and AWO expanded,
AEA and WP contracted
contraction
Mass change 4 years
gain
large gain
Mass change 10 years
gain
large gain
loss except small gain in
SP and AEA mixes
neutral
Fig. 9 shows that, while there is a reasonable positive correlation between 28 day cube
strength and mass increase on exposure to the marine environment for higher strength
mortars (above about 30 MPa), there is a significant effect of curing temperature. The
points on the graph fall into three broad zones, delineated by the dashed lines: (i)
mortars cured at 20°C exhibit high strength and mostly a small mass increase, (ii) mixes
at 5°C exhibit lesser strength and small mass increase, and (iii) mixes at 40°C achieved
strengths of 10-30 MPa and in some cases showed considerable mass loss (there are an
additional 8 points offscale with mass loss more than 5%). Presumably strong
specimens can resist abrasion, wetting and drying, and freezing and thawing, and
continue to gain mass as a result of continuing reactions between cement and water.
This suggests that 28 day strength remains a good predictor of durability: mixes with
less than about 30 MPa at 28 days are more likely to be non-durable. Furthermore, there
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is reasonable qualitative agreement in the UPV against age graphs (Figs. 1-7) between
the early stages (up to one year), where laboratory freeze-thaw tests in seawater are
shown, and the later stages, showing site exposure. This suggests that laboratory freezethaw results could also be useful to predict field performance.
CONCLUSIONS
This investigation on mortars exposed to the marine environment shows that the effects
of admixtures on Ciment Fondu are complex: potential users should carry out trials of
the combinations being considered. Laboratory trials should represent the most severe
exposure anticipated. Laboratory freeze-thaw in seawater and 28 day cube strength
(cured at the anticipated temperature of exposure) are useful predictors for long term
field performance in the marine environment. In general the ethylene vinyl acetate
polymer dispersion performed badly, and air-entraining agent, waterproofer and antiwashout admixtures all failed to protect the specimens against deterioration. In fact, it is
hard to improve upon the performance of plain Ciment Fondu, possibly with
superplasticiser or accelerator, as a binder for marine applications.
ACKNOWLEDGEMENTS
The experimental assistance of Dr Nina Baker and Tom Scott is gratefully
acknowledged, as is the access granted to the exposure site by the Unit for Coastal and
Estuarine Studies, University of North Wales, Bangor. The project was made possible
by a CASE studentship awarded by the (then) Science and Engineering Research
Council and Lafarge Aluminous Cement Co (now Kerneos). I am also grateful to an
anonymous referee for helpful comments.
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[2]
[3]
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[9]
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