CONCRETE TECHNOLOGY UNIT Modern coal-fired …€¦ · CONCRETE TECHNOLOGY UNIT Modern coal-fired...
Transcript of CONCRETE TECHNOLOGY UNIT Modern coal-fired …€¦ · CONCRETE TECHNOLOGY UNIT Modern coal-fired...
MA/41
CONCRETE TECHNOLOGY UNIT
Modern coal-fired power station ash products
Minutes of the Sixth Steering Committee Meeting, Wednesday 20 August 2014
Present: C Bennett, R Carroll, L J Csetenyi, M R Jones, M J McCarthy and H I Yakub
Actions
1. Welcome
MR Jones welcomed the members to the Sixth Steering Committee meeting.
2. Apologies
Apologies were received from R Boult (Cemex).
3. Minutes of the Fifth Steering Committee Meeting [MA/34]
The Minutes were accepted as a true record of the meeting.
4. Update on Actions Allocated at the Previous Meeting
MJ.McCarthy summarized the status of actions allocated at the previous meeting. It was
noted that two supercritical fly ashes (SCFA1 and SCFA2) have been received from
ECOBA. It had been hoped that a biomass-only fly ash could be included in the project,
but this has not been possible. Further information about the fly ashes in the study, in terms
of which has been air-classified, is still to be established. CTU, RC
The new stainless steel flow table (BS EN 1015-3) has now been motorised and is
operational. Tests using the fly ashes from the study will be carried out and results reported
from these in due course. CTU
Testing is on-going with Fly Ash LFA (produced using similar technology to SNCR),
which was received from C.Bennett towards the end of 2013. The suggested
characterization tests with this have been carried out and are reported under Item 6. Water-
saving concrete tests have also been carried out and are reported under Item 8.
It was noted that the CTU would be able to examine air void parameters using an automated
system and the concretes being tested would be investigated using this to contribute to the
understanding of the freeze/thaw results. CTU
5. Update on Materials for the Project [MA/36]
As noted in Item 4, samples SCFA1 and SCFA2 have been received for the project.
Unfortunately oxyfuel fly ash, which it was hoped would be obtained via ECOBA, is not
available. It was proposed that oxyfuel fly ash from a pilot-scale burner, available from another
project, would be included. No other materials have been obtained since the last meeting.
A discussion was held about other potential materials that might be considered for the project,
but recognising that it is in its final stages. It was suggested that Rugely beneficiated fly ash
should be included. R Carroll agreed to source of this. RC
MA/41
6. Material Characterization and BS EN 450-1 Test Results [MA/37]
It was noted that new information from the characterization work, obtained since the last
meeting, corresponded to LFA, and SCFA1 and SCFA2.
LFA had a moderate LOI and a relatively high BET surface area, although its foam index was
not that high. It appeared to contain agglomerates and a number of unburnt particles.
SCFA1 and SCFA2 had relatively low LOIs, BET surface areas and foam index values. The
majority of particles under the SEM appeared to be spherical.
Much of the material characterization work is now complete, with a few results to come for
activity index.
7. Update of Concrete Strength Results [MA/38]
The data from the concrete strength test results was presented, which have now reached
180 days for many of the fly ashes. There was some discussion about the behaviour of the
Portland cement (PC) used, gave continued strength gains with time in the reference
concrete (approx. 10 MPa at 0.55 w/c ratio between 28 and 180 days). It was felt that this
may be a factor in the fly ash concretes still indicating lower strength by 180 days.
There was a discussion about the water saving concretes and while they demonstrated that
water savings of between 10 and 15 l/m³ are possible, they also indicated lower strength
than the PC concrete to 180 days.
It was suggested that the properties of the PC being used in the study be compared with
those used in previous work to see if underlying effects can be identified. CTU
8. Update of Concrete Durability Results [MA/39]
The concrete durability results were presented. In most cases, these are now moving
towards the advanced stages of their testing. The following were noted.
Chloride testing was on-going and the main data for this property, using chloride profiles,
would be reported in due course. The NT Build test results suggest little effect of fly ash
characteristics on chloride ingress.
Carbonation results (both accelerated and normal exposure) suggest that the characteristics
of fly ash, with one or two exceptions, have little influence on the property.
The sulfate expansion tests indicate that there has been little change in length for the various
fly ash concretes considered for the test period to date. Noticeable expansions and damage
have been obtained for some of the PC reference concretes at high w/c ratio.
Some variations in freeze/thaw and abrasion have been noted between concretes. These
are being examined in more detail to identify whether they relate to the fly ash production
details. PC reference concretes appeared to perform best in these tests.
ASR tests are at their early stages and there is little sign of noticeable expansion or surface
damage to date.
9. Proposed Leaching Study
Details of the leaching study were reviewed. Two leach test methods have been considered,
relevant in the waste acceptance criteria. For fly ash: BS EN 12457-3 and for concrete:
NEN 7375.
The results from these tests will be compared with the limits set by the UK Environment
Agency to determine whether the test materials, in loose (fly ash) or bound (concrete) form,
are hazardous. Concrete leaching tests have been carried out and fly ash tests will be
completed shortly. The leachates from these tests will be analysed using voltammetry for
any harmful species identified from XRF. CTU
MA/41
10. Structure of the Final Report [MA/40]
The structure of the final report covered in MA/40 was considered. At this stage, it was
agreed that its contents were reasonable. It is anticipated that progress on this would be
made in the next 6 months.
11. Research Plan for the Next 6 Months
It was envisaged that testing would continue and be nearing completion. The analysis and
writing stages would be in progress over this period.
12. AOCB
There was no other business.
13. Date of the Next Meeting
The date of the next meeting is Thursday 12 February at 9.00 am, Room H20, Fulton
Building, University of Dundee.
LJC/MJMC
04 February 2015
MA/42
CONCRETE TECHNOLOGY UNIT
Modern Fly Ashes for Concrete Construction
Seventh Project Steering Committee Meeting, 12 February 2015
09.00 -11.00 Thursday 12 February 2015,
Meeting Room H20, Fulton Building, University of Dundee
AGENDA
1. Welcome
2. Apologies
3. Minutes of the Sixth Steering Committee Meeting [MA/41]
4. Update on Actions Allocated at the Previous Meeting
5. Update on Materials for the Project [MA/43]
6. Material Characterization and BS EN 450-1 Tests [MA/44]
7. Update of Concrete Strength Results [MA/45]
8. Update of Concrete Durability Results [MA/46]
9. Leaching Studies
10. Final Report
11. A.O.C.B.
LJC/MJMC
04 February 2015
MA/43
Modern Fly Ash for Concrete Construction
Update on Materials for the Project
MA/43 Page 2 of 2
Modern Fly Ashes for Concrete Construction — Materials for the Project
No. Ash
Ref. Description Source
Date
Sampled
Approx.
Quantity
Available
Status
1 HN1 Pre 1999 Ash Ratcliffe Pre-1999 25 kg Received
2 HN2 Stockpile Ash Ratcliffe Jun-02 100 kg Received
3 HN3 10% Petcoke ash Ratcliffe Mar-04 25 kg Received
4 PM1 German ash fitted with
SNCR
Herne PS,
Germany Sep-11 75 kg Received
5 LS1 UK ash Longannet Sep-04 25 kg Received
6 LS2 UK ash Cottam Oct-04 25 kg Received
8 RFA1 Pre-beneficiation fly ash Rugeley Nov-15 50 kg Received
9 RFA2 Post-beneficiation fly ash Rugeley Nov-15 50 kg Received
10 SCR2 Ash from station fitted
with SCR
Moneypoint
(Eire) Jan-12 50 kg Received
11 PRO1 Ash from wet processed
stockpile material
Fiddlers
Ferry Oct-11 100 kg Received
12 BL1 Ash from base load station West Burton Jan-12 100 kg Received
13 NH1
Ash from station fitted
with ammonium injection
prior to the precip
RWE -
Aberthaw Feb-12 100 kg Received
14 BL2
Ash from station fitted
with ammonium injection
prior to the precip
RWE -
Aberthaw Feb-12 100 kg Received
15 DFA BS EN 450 Type S Ash Drax Sep-12 100 kg Recieved
16 LFA From station that uses
similar tech to SNCR Longannet Sep-13 75 kg Recieved
17 SCFA1
Ash from a station that
uses super critical steam
generators.
ECOBA May-14 50kg Recieved
18 SCFA2
Ash from a station that
uses super critical steam
generators.
ECOBA May-14 50kg Recieved
MA/44
Modern Fly Ashes for Concrete Construction
Material Characterization and BS EN 450-1 Test Results
Concrete Technology Unit
Division of Civil Engineering
University of Dundee
Dundee
DD1 4HN
MA/44 Page 2 of 31
1. Introduction
This document provides a summary of the results from characterisation tests carried out on the fly
ashes received for the project.
The properties described were determined using test methods given in British/European standards,
or following established techniques at the University of Dundee.
2. Test Materials Received
During the last 6 months (December 2014) fly ashes RFA1 and RFA2 from Rugeley power station
were received. The materials being considered for the modern fly ash project (noted in Document
MA/43) are given in Table 1.
3. Summary of Test Results
Tables 2, 3, 4 and 5 provide the data for physical and chemical properties of the above fly
ashes. The results of these are also given in Figures 1 to 13, with scanning electron microscopic
(SEM) images shown in Figures 14 to 29 .
3.1 Fineness
The results of the 45 µm sieve retention tests are given in Figure 1. These indicate that PRO1
(processed material) gave highest fineness, with only 2.6% retained on the 45m sieve, and as
with BL1, RFA1, RFA 2 and LS2, met the fineness requirement of Type S to BS EN 450-1.
HN1, LFA, DFA, HN3, SCR2, LS1, NH1, BL2, SCFA1, SCFA2 and PM1 were all relatively
coarser, but within the limit of Type N to BS EN 450-1. HN2 was from a stockpile and did
not achieve this. Visually, the presence of some agglomerates was also noted in this material.
As indicated by Figure 7, the PSD (d50) results for the fly ashes show general agreement with
the 45 m sieve retention data, with PRO1, RFA1, RFA2, BL1 finest and HN1, HN2, HN3
and BL2 at the coarser end.
The supercritical fly ashes (Figure 1 c) have sieve retentions in the range of 20 to 30%. Post-
combustion low NOx fly ashes (Figure 1 a) have fineness in the range of 12 to 23 %. Since
these are downstream of the boiler, it is anticipated that the fineness would be unaffected by
this technology.
MA/44 Page 3 of 31
The co-combustion fly ashes (Figure 1 b) tend to have relatively high sieve retentions, which
is similar to that found in other studies i.e. this may produce fly ash with larger particle sizes
due to lower burning temperatures and agglomeration of particles. However these materials
were still within the limits of Type N fly ash.
3.2 LOI, N2 Adsorption and Foam Index
The results obtained from the LOI tests are given in Figure 2. All of the fly ashes, except for
NH1, BL2, HN3, LFA and HN2 had LOI’s < 7.0% and, therefore, met the requirements of BS
EN 450-1. The fly ashes of higher LOI tended to be coarser and darker in colour, particularly
NH1. The (BET) N2 adsorption, shown in Tables 2 and 3 ranged from between 0.86-5.94 m2/g
with SCFA2 and LFA having the lowest and highest surface areas respectively. As shown in
Figure 8, these did not necessarily follow the LOI results.
The results shown in Figure 3 are foam index values, obtained using SDBS (0.01M) as the
surfactant and the automatic shaker described in an earlier study. Figure 9 shows the general
agreement between foam index and BET (N2) values. However, as noted with the BET (N2),
the foam index values did not follow the LOI results.
Post-combustion low NOx fly ashes, apart from LFA, have relatively low LOI, BET and foam
index values (< 3.5%, < 1.15 m2/g and < 80l respectively). This suggests that these fly ashes
would be suitable for air-entrainment. Similar behaviour was also observed for supercritical
fly ashes.
The co-combustion fly ashes, BL2 (woodchip), NH1 (woodchip) and HN3 (petcoke), have
relatively high LOI (10 to 18%), which may be due to incomplete combustion of the co-fuel
and lower flame temperatures. Petcoke has been shown to have low volatility, thereby giving
fly ash with higher LOI when used as a co-fuel. In the case of NH1 and BL2, this had an effect
on its foam index (320 and 300 l respectively), which may affect their suitability for air-
entrainment. However, different behaviour was observed from HN3 petcoke fly ash. It had a
low foam index despite its high LOI. This is in agreement with other studies which found that
petcoke carbons are dense and have low surface area, thereby adsorbing little AEA.
MA/44 Page 4 of 31
3.3 Water Requirement and Strength Factor
The water requirement results (using the BS 3892-1 flow table) are given in Figure 4. These
indicate that finer fly ashes generally gave lower water requirements, with values from 93-
98% of the reference PC mortar. However, in cases where the fineness (45µm sieve residue)
exceeded 20%, water requirements were greater than 100%, with a maximum value of 108%
noted for HN2 and NH1. The results indicate that while some of the fly ashes met Type S
requirements for fineness, they did not necessarily achieve the 95% limit for water requirement
(BS 3892-1/BS 4551-1).
A comparison of selective water requirement and strength factor results (BS 3892-1) is given
in Figure 11. These indicate general agreement between the properties, with reducing strength
factor noted at increasing water requirement. It is also evident from the results that the mortars
meeting the 0.85 value for strength factor at 28 days were mainly those with water
requirements less than 100%.
The co-combustion fly ashes (Figure 4 b) had a negative effect on the water requirement of
mortars (requiring 105-108% of the reference). This may be because co-combustion fly ashes
tend to exhibit agglomeration and have larger, less rounded particles which may have an effect
on the cohesiveness and water demand of these fly ashes. This may influence the use of these
materials in concrete, affecting workability.
The low NOx combustion fly ashes (Figure 4 a) and supercritical fly ashes (Figure 4 c) had
water requirements close to 95% suggesting they may have potential water saving properties.
3.4 Activity Index
The results from tests for activity index at 28 and 90 days are given in Figures 5 and 6. These
indicate that the fly ashes all met BS EN 450-1 activity index requirements at both test ages
(75% at 28 days and 85% at 90 days). By 90 days all of the fly ashes, except HN2 and HN3,
had activity index values higher than the reference PC. The results of HN2 may be influenced
by its storage conditions and agglomeration of particles, as noted previously.
The relationships obtained between fly ash fineness and activity index at the two test ages are
shown in Figure 12. The fly ashes exhibiting higher values were generally of greater fineness.
The improved relationship at 90 days also corresponds to the period where fly ash has greatest
MA/44 Page 5 of 31
reactivity. The red markers (Sample PRO1) were not included in the regression analysis,
because they represent processed fly ash, which although fine, did not follow the same trend
at 90 days.
Low NOx fly ashes (Figures 5 a and 6 a) supercritical and oxy-fuel fly ashes (Figures 5 c and
6 c) met the 28 and 90 day requirements of BS EN 450-1. Similarly, the reactivity of the co-
combustion fly ashes (Figures 5 b and 6 b) was largely unaffected, despite their high LOI.
3.5 Oxide Composition and Mineralogy
The bulk oxide composition and mineralogy of the fly ashes are given in Tables 4 and 5. These
indicate that all of the fly ashes were of low lime content (with CaO mainly less than 5%) with
all, except for SCFA1 and SCFA2, achieving the BS EN 450-1 requirement for the sum of the
main oxides (>70%). All of the fly ashes also met those for SO3 and alkali contents. However,
it is interesting to note the relatively high sulfur content of the HN3 (petcoke co-combustion
fly ash).
SCR2, LFA and LS1 contained significantly higher quartz (20.7%, 19% and 17.5%
respectively, range: 3.9-20.7%) than the other fly ash samples, furthermore LS1 had a higher
mullite content (26.0%, range: 7.6-26.0%) than the other materials. The ‘others’ content of
the fly ashes varied mainly between 68.6% and 85.1%, with LFA and BL2 fly ashes at the
lower and upper end of this range. LS1 had a noticeably lower value than the other materials
considered.
3.6 Colorimetry
The lightness values of the fly ashes are given in Tables 2 and 3 and are in the range of 52.8
to 63.4, with NH1 having the lowest and SCR2 the highest values. For reference, the lightness
of Portland cement was 65.5. Table 6 gives examples of colours in the measured range. The
results indicate that there was a relationship between lightness and LOI as shown in Figure 13.
This means that high LOI fly ashes (e.g. co-combustion fly ashes) may produce darker
concrete, potentially making the material unsuitable for projects where this is important.
MA/44 Page 6 of 31
3.7 Fly Ash Morphology
SEM images of the fly ashes are shown in Figures 14 to 28. From the images, Type S fly
ashes generally tended to be more rounded and uniform in appearance than those of Type N.
Similarly, the finer fly ashes with rounded particles tended to perform better in the activity
index tests.
The low NOx fly ashes (Figures 15, 19 and 23), apart from LFA, appeared to be free of carbon
and scoria. They contain, for the most part, smooth, spherical particles, with a good spread of
particle sizes. Similar features were also observed for the supercritical fly ashes (Figures 27
and 28). This shows agreement with the water saving, LOI and BET results for these materials.
LFA contained noticeably more carbon, which appeared to have partially melted surfaces. It
also contained more scoria and irregular particles. However, it is unlikely that these effects
have been caused by post-combustion NOx reduction.
In general, the co-combustion fly ashes (Figures 14, 24 and 26) appear to have remnants of
carbon and scoria present, which may be due to lower flame temperatures and incomplete
combustion of the co-fuel. This shows agreement with the high LOI and BET values observed
for these materials. They also appeared to have rougher surfaces, due to partial crystallisation
of the fly ash surfaces, and the presence of some irregular particles. Furthermore a number of
agglomerates were also observed. These effects may be caused by lower combustion
temperatures and a lack of alkali oxides.
MA/44 Page 7 of 31
3.8 Conclusions
The initial stages of the study have involved physical and chemical characterization of the fly
ashes. It appears, from the testing and literature, that co-combustion may cause the following,
1. Increase in LOI
2. Increased Foam Index
3. Increased coarseness
4. Increase in particle sizes
5. Slight variations in oxide composition and mineralogy
However, the results suggest that coal fired power plants operating post combustion measures
for NOx reduction or supercritical steam generation do not affect fly ash properties, possibly
because they do not influence boiler conditions.
The above effects may influence fly ash behaviour in cementitious systems and there is a need
to evaluate these, to ensure continued suitability of the material as a valuable construction
resource.
MA/44 Page 8 of 31
Table 1. Summary of fly ash test samples
Ash Code Source Date Received Quantity Production/Origin
PM1 Herne PS, Germany Sep-11 75 kg German fly ash
Fitted with SNCR
PRO1 SSE - Fiddlers Ferry Nov-11 100 kg Fly ash from wet processed
stockpile material
HN1 E.ON – Radcliffe
Power Station Nov-11 25 kg Pre 1999 fly ash
HN2 E.ON – Radcliffe
Power Station Nov-11 50 kg Stockpile fly ash
HN3 E.ON – Radcliffe
Power Station July-12 25 kg 10% Petcoke fly ash
LS1 Scotash - Longannet Jan-12 20 kg UK fly ash
LS2 EDF - Cottam Jan-12 20 kg UK fly ash
BL1 West Burton Jan-12 100 kg
Fly ash from station fitted with
Selective Catalytic Reduction
(SCR)
NH1 RWE - Aberthaw Feb-12 100 kg
Fly ash from station fitted with
ammonium injection prior to the
precipitators
SCR2 ESB – Moneypoint
(Eire) Feb-12 100 kg Fly ash from base load Station 1
BL2 RWE – Aberthaw Apr-12 100 kg
Fly ash from station fitted with
ammonium injection prior to the
precipitators
DFA Drax Sep-12 100 kg BS EN 450 Type S Ash
LFA Longannet Sep-13 75 kg From station that uses technique
similar to SNCR
SCFA1 ECOBA May-14 50 kg From a station that uses super
critical steam generators.
SCFA2 ECOBA May-14 50 kg From a station that uses super
critical steam generators.
OFA Drax Aug-10 25 kg Oxy-fuel ash from trial burner
RFA1 Rugeley Oct-14 50 kg Fly ash produced prior to
beneficiation
RFA2 Rugeley Oct-14 50 kg Fly ash produced after
beneficiation
MA/44 Page 9 of 31
Table 2. Physical properties modern and processed fly ashes
Properties PM1 NH1 SCR2 BL2 HN3 LFA SCFA1 SCFA2 OFA
Loss on Ignition, % 3.4 17.3 2.6 13.7 9.8 7.3 2.4 1.4 5.4
Moisture content, % 0.0 0.2 0.2 0.2 0.3 0.2 0.2 0.2 0.2
Water requirement, % 96 108 96 105 106 98 97 96 101
45 mm sieve residue, % 15.1 27.2 12.1 24.4 29.4 22.5 20.0 29.6 19.1
Nitrogen adsorption, m2/g 0.93 3.43 1.12 3.45 2.24 5.94 1.81 0.86 2.46
Foam index1, µl 40 280 60 260 100 140 100 20 220
Lightness value 60.6 52.8 63.4 53.4 53.6 57.1 63.3 60.1 -
28 Day activity Index, % 79 75 84 83 76 80 81 84 86
90 Day activity Index, % 106 101 106 105 98 101 102 100 101
Strength factor 0.87 0.73 0.97 0.82 0.74 - - - -
PSD d(0.1), µm 2.5 3.4 2.1 2.6 3.1 2.0 3.6 3.8 7.9
PSD d(0.5), µm 19.1 33.1 14.8 29.7 34.0 24.0 46.1 30.8 30.3
PSD d(0.9), µm 77.4 117.6 78.8 94.0 125.7 109.4 231.8 122.7 81.8
1 AEA reagent used: 0.01 M SDBS (sodium salt of dodecyl benzene sulfonate)
MA/44 Page 10 of 31
Table 3. Physical properties of processed and ‘other’ fly ashes
Properties PRO1 LS1 LS2 HN1 HN2 BL1 DFA RFA1 RFA2
Loss on Ignition, % 4.8 4.6 4.8 5.9 8.3 4.4 4.0 3.1 2.4
Moisture content, % 0.4 0.2 0.4 0.6 0.5 0.3 0.3 0.12 0.07
Water requirement, % 94 104 98 102 108 95 93 98 97
45 mm sieve residue, % 2.6 20.5 11.0 32.8 49.5 9.6 13.2 11.6 8.7
Nitrogen adsorption, m2/g 4.25 2.91 1.25 1.81 5.40 1.74 2.29 2.86 2.51
Foam index1, µl 120 140 100 100 140 160 100 240 240
Lightness value 60.1 55.3 57.5 53.6 53.2 60.0 57.4 - -
28 Day activity Index, % 84 83 82 80 76 84 78 75 75
90 Day activity Index, % 103 105 106 103 97 112 105 - -
Strength factor 0.89 0.83 0.93 0.86 0.77 0.97 0.82 - -
PSD d(0.1), µm 1.2 2.6 2.8 3.2 5.6 1.8 2.7 1.7 2.1
PSD d(0.5), µm 8.6 20.4 17.1 28.2 42.7 12.1 14.1 12.4 15.1
PSD d(0.9), µm 33.7 94.2 67.5 106.5 140.5 57.5 65.1 64.1 55.3
1 AEA reagent used: 0.01 M SDBS (sodium salt of dodecyl benzene sulfonate)
MA/44 Page 11 of 31
Table 4. Oxide and mineralogical compositions of modern fly ashes
Component, % PM1 NH1 SCR2 BL2 HN3 LFA SCFA1 SCFA2 OFA
CaO 3.74 2.94 1.91 3.55 4.63 1.64 4.47 4.19 4.2
SiO2 47.07 41.98 51.42 42.86 39.41 45.74 43.97 44.43 49.3
Al2O3 19.93 20.82 17.34 20.92 21.07 16.55 16.34 16.00 19.7
Fe2O3 9.13 8.15 8.96 6.71 12.99 7.72 7.89 8.49 13.4
MgO 1.66 1.17 1.60 1.09 1.40 1.09 1.38 1.37 1.1
MnO 0.09 0.09 0.06 0.12 0.13 0.04 0.05 0.05 0.1
TiO2 1.07 0.94 0.96 0.98 1.03 0.83 0.81 0.87 1.1
K2O 3.37 2.05 2.04 1.55 2.52 1.73 1.79 1.90 2.3
Na2O 1.44 0.75 1.74 0.84 1.19 1.24 1.69 2.88 0.8
P2O5 0.84 0.86 0.23 0.89 0.56 0.15 0.43 0.29 0.2
SO3 1.24 1.24 1.45 0.8 2.55 1.08 0.74 0.91 2.8
Quartz 11.1 4.8 20.7 3.9 7.0 19.0 5.6 10.7 12.8
Hematite 2.7 1.5 2.4 1.4 2.6 1.7 2.4 3.0 4.5
Magnetite 0.2 0.2 0.1 0.1 0.4 0.1 0.2 0.2 0.1
Mullite 8.8 11.8 7.6 9.5 11.9 10.6 5.6 6.2 17.9
Others 77.2 81.8 69.2 85.1 78.1 68.6 86.2 79.9 64.6
MA/44 Page 12 of 31
Table 5. Oxide and mineralogical compositions of processed and ‘other’ fly ashes
Component, % PRO1 LS1 LS2 HN1 HN2 BL1 DFA
CaO 2.74 3.41 5.26 4.03 2.67 3.01 2.31
SiO2 48.28 52.78 46.11 43.40 43.81 48.39 49.81
Al2O3 23.98 25.16 25.93 23.28 23.42 20.12 22.31
Fe2O3 7.64 4.33 6.21 11.01 10.97 8.35 7.94
MgO 1.70 1.24 1.91 1.81 1.77 1.60 1.49
MnO 0.06 0.05 0.08 0.08 0.08 0.06 0.05
TiO2 1.12 1.26 1.30 1.10 1.05 1.03 1.13
K2O 3.15 1.45 2.22 2.67 2.86 2.80 3.42
Na2O 0.74 0.81 1.51 1.71 0.90 2.01 1.33
P2O5 0.38 0.65 1.01 0.54 0.26 0.46 0.23
SO3 0.55 0.45 1.02 1.40 0.80 0.97 0.89
Quartz 7.1 17.5 8.0 8.6 6.8 9.8 11.1
Hematite 1.8 2.0 2.1 3.2 3.4 2.2 2.3
Magnetite 0.0 0.1 0.1 0.1 0.1 0.1 0.2
Mullite 16.9 26.0 19.6 15.6 13.3 10.4 11.0
Others 74.2 54.3 70.2 72.4 76.4 77.6 75.5
MA/44 Page 13 of 31
Table 6. Comparison of lightness values with fly ash colour
Sample Lightness Value Colour
SCR2 63.4
DFA 57.4
NH1 52.8
Portland Cement 65.5
MA/44 Page 14 of 31
(a) (b)
(c) (d)
Figure 1. Fineness (45 µm sieve residue) of fly ash samples
MA/44 Page 15 of 31
(a) (b)
(c) (d)
Figure 2. LOI of fly ash samples
MA/44 Page 16 of 31
(a) (b)
(c) (d)
Figure 3. Foam index of fly ash samples
MA/44 Page 17 of 31
(a) (b)
(c) (d)
Figure 4. Water requirement of fly ash samples
MA/44 Page 18 of 31
(a) (b)
(c) (d)
Figure 5. 28 day activity index of fly ash samples (in order of fineness)
MA/44 Page 19 of 31
(a) (b)
(c) (d)
Figure 6. 90 day activity index of fly ash samples
MA/44 Page 20 of 31
Figure 7
Figure 8 Relationship between specific surface area (by N2 adsorption) and LOI
MA/44 Page 21 of 31
Figure 9. Relationship between specific surface area (by N2 adsorption) and foam index
Figure 10. Relationship between LOI and foam index
MA/44 Page 22 of 31
Figure 11. Relationship between water requirement and strength factor
Figure 12. Relationship between fineness (45 µm sieve residue) and activity index
MA/44 Page 23 of 31
Figure 13. Relationship between LOI and fly ash lightness
MA/44 Page 24 of 31
Figure 14. SEM micrographs of NH1 Fly Ash
Figure 15. SEM micrographs of PM1 Fly Ash
MA/44 Page 25 of 31
Figure 16. SEM micrographs of HN1 Fly Ash
Figure 17. SEM micrographs of HN2 Fly Ash
MA/44 Page 26 of 31
Figure 18. SEM micrographs of PRO1 Fly Ash
Figure 19. SEM micrographs of SCR2 Fly Ash
MA/44 Page 27 of 31
Figure 20. SEM micrographs of BL1 Fly Ash
Figure 21. SEM micrographs of LS1 Fly Ash
MA/44 Page 28 of 31
Figure 22. SEM micrographs of LS2 Fly Ash
Figure 23. SEM micrographs of LFA Fly Ash
MA/44 Page 29 of 31
Figure 24. SEM micrographs of BL2 Fly Ash
Figure 25. SEM micrographs of DFA Fly Ash
MA/44 Page 30 of 31
Figure 26. SEM micrographs of HN3 Fly Ash
Figure 27. SEM micrographs of SCFA1 Fly Ash
MA/44 Page 31 of 31
Figure 28. SEM micrographs of SCFA2 Fly Ash
Figure 29. SEM micrographs of OFA Fly Ash
MA/45
Modern Fly Ashes for Concrete Construction
Update of Concrete Strength Results
Concrete Technology Unit
Division of Civil Engineering
University of Dundee
Dundee
DD1 4HN
MA/45 Page 2 of 27
1 Introduction
This document summarizes the results from the strength tests on the concretes outlined in
Document MA19 (Proposed Durability Study). The series of concretes in this document
are being considered for each fly ash in the study (except for LS1 and LS2, due to limited
material availability). Four w/c ratios covering the range 0.35-0.65, were considered with
a fly ash addition level of 30% and target slump class of S3. Compressive strength tests
were carried out up to 180 days for all w/c ratios and 365 days at 0.45 and 0.55. All fly ash
concrete samples, expect RFA1and RFA2, have been tested to the test ages indicated. The
fly ash sources and characteristics are given in Document MA44 (Material Characterisation
and BS EN 450-1 Test Results).
2 Materials and Mix proportions
The Portland cement used in the concretes was a CEM I, 52.5 N, while the aggregates were
a North Fife sand and gravel. The aggregate absorptions for sand, 4/10 and 10/20 aggregate
(from lab dry to SSD) were 0.8%, 1.4% and 1.3% and particle densities (at SSD)
2630 kg/m3, 2600 kg/m³, 2610 kg/m³. The superplasticizing admixture used was based on
a modified polycarboxylic ether. The fine to total aggregate ratios for the concrete mixes
were derived from the BRE mix design method. The mix proportions are given in Table 1.
Water saving mixes were considered using a selection of fly ashes, with compressive
strength tests up to 180 days carried out, following standard water curing. These fly ashes
were chosen because they required significantly lower admixture doses than the reference
concrete to achieve S3 slump. The admixture dose of the fly ash mixes was matched to the
reference concrete and the water was reduced as far as possible while still maintaining an
S3 slump. The water, for the reference, was fixed at 165 kg/m3 and a w/c ratio of 0.55 was
used. The fly ash level was kept at 30%.
The freeze-thaw mixes were air entrained, with a target air content of 5 (+1%, - 0.5%),
using an air entraining agent formulated for use with fly ash. The mix proportions for the
MA/45 Page 3 of 27
freeze-thaw concretes are given in Table 2. The water was kept at 165 kg/m3 and the fly
ash level was 30%. The w/c ratios used were 0.45 and 0.55 and the superplasticiser dose
was fixed at 3ml/kg of cement (or cement + addition).
3 Fresh properties
The plastic density measurements gave general agreement with the sum of the constituents
for the concrete mixes. The slump measurements were in the range of 105-155 mm, i.e.
within the limits of Slump Class S3. The superplasticizer (SP) doses required to achieve
Slump Class S3 were within the range of 0.3-0.9 % by mass of cement (recommended
limits for the admixture 0.25-1.0 %), as shown in Figure 1, with the SCR2 dose at the lower
end of this and NH1 the higher end. Except for HN2, HN3, LFA, SCFA1, SCFA2 and
NH1, all of the fly ashes gave reduced SP dose requirements compared to the PC reference
concretes.
Figure 2 shows the effect of fineness (45 m sieve retention) on these. The results indicate
that finer fly ash, with lower LOI generally required less SP to achieve the target slump
class. The SP dose also gave agreement with water requirement tests carried during
characterization, as shown in Figure 3.
The low NOx fly ashes, with the exception of LFA (dose range: 0.75 to 0.85 % cement
content), had SP doses in the range 0.30 to 0.55 % of the cement content. This is in
agreement with the fineness and water requirement results observed for these materials
from the characterisation. PM1 and SCR2 appear to have potential water saving properties.
The co-combustion fly ashes had relatively high superplasticiser dosages for all w/c ratios
(range: 0.55 to 0.9 % of cement content). Of these, BL2 and NH1 consistently had the
lowest and highest SP doses across all w/c ratios, with BL2 requiring marginally less than
the reference PC mix at 0.55 and 0.65 w/c ratios. Similarly, the supercritical and oxy-fuel
fly ashes had SP doses in the range of 0.55 to 0.8 % of the cement content (cf. PC, in the
range of 0.6-0.7 % cement content). The results suggest that these materials would not
provide any water saving benefits.
MA/45 Page 4 of 27
4 Compressive Strength
Compressive strength tests were carried out on 100 mm concrete cubes at test ages up to
180 days (following standard water curing). Strength tests up to 365 days were carried out
at 0.45 and 0.55 w/c ratios. The strength data are given in Figures 4 to 7 for the different
w/c ratios considered. These show that the fly ash mixes had lower strengths than those of
the PC references, but the differences tended to reduce with increasing test age, particularly
at low w/c ratio. In general, BL1 had the highest compressive strength over the range of
w/c ratios and test ages. HN2 tended to have the lowest compressive strength at all ages
and w/c ratios, which may be because it originates from a long-term stockpile, potentially
affecting its reactivity. Figure 10 gives the strength data up to 365 days at 0.45 and 0.55
w/c ratio. The results show that after 180 days, the strength gain in the PC concretes is
minor, whereas the fly ash concretes continue to gain strength (in the range of 10 to 20%).
After 365 days, PRO1 had the highest strength at both w/c ratios, and at 0.55 exceeded that
of the PC concrete. NH1 and BL2 had the lowest compressive strengths at 365 days for
0.45 and 0.55 w/c ratios respectively.
Figure 8 shows that the fineness of the fly ashes was closely related to the strength of
concrete at all ages and w/c ratios, with reductions noted with coarser fly ash. This is further
noted in Figure 9.
In general, there was little difference observed between the compressive strength of low
NOx fly ashes, however SCR2 and LFA consistently achieved the highest and lowest values
respectively. This shows agreement with activity index and fineness results for these fly
ashes. Similar trends were observed for co-combustion, supercritical and oxy-fuel fly
ashes, with little strength difference between them noted. This suggests that, although there
were variations in production, the resultant impact on concrete strength was minimal.
MA/45 Page 5 of 27
5 Water-Saving Compressive Strength Results
The fly ashes used and their corresponding water savings are shown in Figure 11. All fly
ashes concretes achieved a water reduction of 15 kg/m3, except for DFA, where this was
10 kg/m3. Strength results up to 180 days are shown in Figure 12. From this, it is apparent
that at all ages the water saving fly ash mixes had lower strengths than those of the PC
reference, with reducing differences at later test ages. PRO1 and BL1 had the highest
compressive strengths at 28 and 90 days respectively, while DFA was lowest due to its
higher w/c ratio. Figures 13 to 17 show the strength development of the water saving fly
ash concretes, compared with their non-water saving counterparts and Figure 18 shows the
strength increase associated with the water saving concretes. These indicate that all water
saving fly ash concretes had higher strengths than their equivalent non-water saving
concretes and were therefore closer to the strength of the reference PC concrete at all ages.
At 90 days, the water saving fly ash concretes, excluding DFA, achieved 88-91% of the
reference concrete strength (cf. 76-86% for non-water saving mixes). Similarly at 180 days
the fly ash concretes achieved 94-96% (cf. 77-87%) of the PC reference concrete strength.
6 Freeze-Thaw Compressive Strength Results
The freeze-thaw (FT) mixes were tested for compressive strength up to 90 days (following
standard water curing). The FT strength data is shown in Figures 19 and 20. As with non-
air entrained concrete, the air entrained fly ash concretes at a given w/c ratio had lower
strengths than the PC (REF). The 28 day strength of the fly ash concretes at 0.45 w/c ratio
varied between 26.5 and 34.0 MPa with LFA and DFA being at the lower and upper end
of this range respectively. At 0.55 w/c ratio, BL2 had lowest 28 day compressive strength
DFA highest, with values of 15.5 and 20.0 MPa respectively. Figure 21 shows a
comparison between air entrained and non-air entrained concrete. The air entrained
concretes at 0.45 w/c ratio typically had strengths 24-36% lower than the non-air entrained
concrete at 28 days (This corresponds to about 5% reduction per 1% air entrained), whereas
at 0.55 w/c ratio the air entrained concretes had strengths 37-48% lower than the
corresponding non-air entrained concretes at this age.
MA/45 Page 6 of 27
7 Comparison with 1990s Test Data
Fly ashes to BS EN 450, covering various UK sources and a range of properties, from an
investigation carried out at the CTU during the 1990s were also considered, where possible,
to provide older materials as part of the evaluation.
A comparison of compressive strength with respect to fly ash fineness is shown in Figure
22, while the range of strengths for the fly ashes to 28 days is given in Figure 23. The
results of the fly ash concretes from the 1990s study (w/c ratio 0.5, with similar aggregates,
slump class S2, without SP admixture) are also shown.
The results show that 28 day strength increases with fineness (range 2.6 to 49.5 %). A
similar trend is observed with the 1990s fly ashes covering a similar range of fineness (2.8
to 41.5 %). The results at 28 days show that there were differences between the fly ash
concretes of up to 5 MPa (range 34 to 39 MPa). As before, similar effects were noted in
the data from the 1990s with regard to the range of strengths (range 31 to 36 MPa). The
difference in absolute strength values may be due to material variations (e.g. aggregate and
cement). These results suggest that the modern fly ashes tend to follow established
behaviour.
MA/45 Page 7 of 27
Table 1. Concrete mix proportions
MIX Water/Cement
Ratio
CONCRETE MIX PROPORTIONS1, kg/m³
Free water Cement / Addition Aggregate
Total2
PC Fly ash Total Sand 10 mm 20 mm Total
PC reference
Mixes
1 0.65 165 255 0 255 910 375 695 1975 2395
2 0.55 165 300 0 300 850 380 705 1935 2400
3 0.45 165 365 0 365 790 380 710 1880 2410
4 0.35 165 470 0 470 720 375 700 1795 2430
Fly Ash
Mixes
1 0.65 165 180 75 255 895 370 685 1945 2365
2 0.55 165 210 90 300 845 375 695 1915 2380
3 0.45 165 255 110 365 775 375 695 1850 2380
4 0.35 165 330 140 470 700 365 680 1745 2380
1 Superplasticizer used in quantities necessary to achieve Slump Class S3
2 Typical measured plastic densities for the fly ash mixes was in the range of 2370-2395 kg/m3 and 2415-2420 kg/m3 for the PC mixes.
MA/45 Page 8 of 27
Table 2. FT Concrete mix proportions
1 Superplasticizer dosage was fixed at 0.3% by mass of the cement+addition (Glenium 51)
MIX Water/Cement
Ratio
CONCRETE MIX PROPORTIONS1, kg/m³
Free water Cement / Addition Aggregate
Total
PC Fly ash Total Sand 10 mm 20 mm Total
PC reference
Mixes
1 0.55 165 300 0 300 790 365 680 1840 2305
2 0.45 165 365 0 365 730 370 685 1785 2315
Fly Ash
Mixes
1 0.55 165 210 90 300 780 360 670 1810 2275
2 0.45 165 255 110 365 715 360 670 1745 2275
MA/45 Page 9 of 27
(a) (b)
(c) (d)
Figure 1. Superplasticiser dosages for concrete mixes
MA/45 Page 10 of 27
(a) (b)
(c) (d)
Figure 2 Relationship between superplasticiser dosage and fineness (45m sieve retention)
MA/45 Page 11 of 27
(a) (b)
(c) (d)
Figure 3 Relationship between superplasticiser dosage and water requirement
MA/45 Page 12 of 27
(a) (b)
(c) (d)
Figure 4. Compressive strength results at 0.35 w/c ratio
MA/45 Page 13 of 27
(a) (b)
(c) (d)
Figure 5. Compressive strength results at 0.45 w/c ratio
MA/45 Page 14 of 27
(a) (b)
(c) (d)
Figure 6. Compressive strength results at 0.55 w/c ratio
MA/45 Page 15 of 27
(a) (b)
(c) (d)
Figure 7. Compressive strength results at 0.65 w/c ratio
MA/45 Page 16 of 27
(a) (b)
(c) (d)
Figure 8. Relationship between compressive strength and fineness (45m sieve retention)
MA/45 Page 17 of 27
(a)
(b)
Figure 9. Relationship between fineness (45 m sieve retention) and
compressive strength
MA/45 Page 18 of 27
Figure 10. Strength results up to 365 days at 0.45 and 0.55 w/c ratios
(a)
(b)
MA/45 Page 19 of 27
Figure 11. Water saving per m3 of fly ash concretes
Figure 12. Compressive strength results for water saving fly ash mixes
MA/45 Page 20 of 27
Figure 13. Strength development comparison of SCR2 and SCR2 water saving concretes
Figure 14. Strength development comparison of PM1 and PM1 water saving concretes
MA/45 Page 21 of 27
Figure 15. Strength development comparison of DFA and DFA water saving concretes
Figure 16. Strength development comparison of BL1 and BL1 water saving concretes
MA/45 Page 22 of 27
Figure 17. Strength development comparison of PRO1 and PRO1 water saving concretes
MA/45 Page 23 of 27
(a) (b)
(c) (d)
Figure 18. Compressive strength results for water saving fly ash concretes
MA/45 Page 24 of 27
(a)
(b)
Figure 19. Freeze-thaw compressive strength results at 0.45 w/c ratio (air-entrained)
MA/45 Page 25 of 27
(a)
(b)
Figure 20. Freeze-thaw compressive strength results at 0.55 w/c ratio (air-entrained)
MA/45 Page 26 of 27
(a)
(b)
Figure 21. Comparison between 28 day strength results for air entrained and non-air
entrained concretes
MA/45 Page 27 of 27
Figure 22 Relationship between fly ash fineness and concrete strength
Figure 23 Strength development ranges up to 28 days
MA/46
Modern Fly Ashes for Concrete Construction
Update of Concrete Durability Results
Concrete Technology Unit
Division of Civil Engineering
University of Dundee
Dundee
DD1 4HN
MA/46 Page 2 of 28
1 Introduction
This document describes results obtained from the durability tests outlined in Document
MA/19 (Proposed Durability Study). Comparisons in this document are made at equal w/c ratio
and in some cases equal strength. To date, chloride migration, carbonation, sulfate attack,
abrasion, freeze-thaw and alkali aggregate reaction (AAR) tests have been carried out on
selected materials at a range of w/c ratios. The concretes used, described in MA/46 (Update of
Concrete Strength Results; see Tables 1, 2 and 3), have a fly ash level in cement of 30%, a
target slump class of S3 and were water and/or air-cured according to that required by the test
method.
2 Chloride Migration
This test was carried out according to the Nordtest method (NT Build 492) and gives a
measure of the resistance of concrete to chloride penetration. Initial tests considered four
fly ash samples at 0.35 w/c ratio and seven at 0.55 w/c ratio. The results from these are
given in Figure 1. At 0.35 w/c ratio, fly ash BL1 concrete had the lowest migration value
(12.9 × 10-12 m²/s), while that of PRO1 the highest value (15.5 × 10-12 m²/s). At 0.55 w/c
ratio, DFA concrete had the lowest value (20.0 × 10-12 m²/s) and, as before, that of PRO1
the highest (24.4 × 10-12 m²/s).
Figure 2 compares fly ash fineness (45 m sieve retention) and chloride migration data.
There appeared to be only small differences between fly ash concretes with respect to
fineness. Fly ash PRO1 was not included in the comparison, as it was wet processed and
appeared to behave differently to the other fly ash concretes. The findings are similar to
those from two compartment chloride diffusion tests carried out in the 1990s study looking
at a range of fly ashes, using equal strength concrete. This also supports other work, which
suggests that the quantity of fly ash in cement, rather than its properties, is the important
factor influencing chloride transportation.
Further chloride testing on concretes at 0.35, 0.45 and 0.55 w/c ratios has been carried out
according to BS EN 14629. This is a uni-directional chloride diffusion test and involves
immersing concrete in 30.0 g/l sodium chloride solution for 90 days and determining the
MA/46 Page 3 of 28
diffusion coefficient from chloride profiles obtained by grinding layers from the concrete
surface. Some of the results from this will be considered during the meeting.
3 Carbonation
The non-accelerated carbonation and accelerated carbonation tests follow CEN 12390-10
and BS 1881-131 methods respectively. The depth of carbonation was determined by
spraying the cross section of fractured concrete surfaces with thymolphthalein indicator
solution, and measuring the colourless region. To date, carbonation testing has been carried
out on 0.65, 0.55 and 0.45 w/c ratio concretes up to 360 days, with the results shown in
Figures 3 to 5. Further testing is planned at 540 days in March.
Accelerated carbonation results have been obtained for 0.45 and 0.55 w/c ratio concretes
at test ages up to 140 days. The carbonation rates for the concretes at 0.45 and 0.55 w/c
ratio are given in Figures 6 and 7 respectively. The general behaviour observed was similar
to that normally found for carbonation, i.e. increasing carbonation depth in concrete with
time, but at a reducing rate. After 140 days of exposure for 0.45 w/c ratio concretes, HN3
had the highest carbonation depth (5.2 mm) and BL2 the lowest (3.9 mm). For 0.55 w/c
ratio concretes, at 140 days, LFA (6.9 mm) and HN2 (8.2 mm) had the lowest and highest
carbonation depths respectively.
In general, all fly ash concretes performed similarly, with only slight variations noted
between materials. It appears that the modern fly ashes did not affect this aspect of
concrete. The Portland Cement (PC) reference concrete performed better than the fly ash
concretes at all test exposure ages during accelerated and non-accelerated tests. However,
as shown in Figure 8, when considering accelerated carbonation for a concrete meeting the
requirements of the standard, (BS8500-1, minimum grade 35N/mm2, max w/c ratio 0.6 and
minimum cement 280 kg/m3) the fly ash concretes performed similarly to the reference
concrete (6.6 mm), with LFA and SCR2 having the lowest carbonation depth at 6.2 mm
and HN2 and HN3 highest at 6.8 mm. Previous results from the 1990s study considering
MA/46 Page 4 of 28
this property for a range of fly ashes, with different characteristics in equal strength
concrete, gave general agreement with the data
4 Sulfate Attack
The sulfate exposure tests were carried out according to CEN 15697-2008. This was
determined by measuring the length and weight change of concrete samples exposed to
68.0 g/l sodium sulfate solution (46.0 g/l of sulfate). Sulfate tests have been initiated for all
fly ash samples, with results obtained up to 420 days for all w/c ratios. Due to the nature
of the sulfate attack test, it tends to take some time before results indicative of damage are
available. The expansion curves of Type S and Type N fly ash concretes and their
corresponding mass changes at 0.35, 0.45 and 0.55 w/c ratios are shown in Figures 9 to 11
respectively.
The results show that the fly ash concretes are performing similarly to the reference
concrete or better. Furthermore there seems to be little variation between the fly ash
concretes at this stage of the test. As before, it appears that the sulfate resistance of the fly
ashes is unaffected by the technology associated with their production. Visually there were
no signs of deterioration in the fly ash test concretes, however, the reference concrete gave
surface discoloration and minor deterioration at edges and corners (see Figure 12). The PC
reference samples at 0.55 w/c ratio are breaking apart, resulting in significant mass change
and expansion as noted in Figure 11.
5 Abrasion
The abrasion testing was performed according to the Modified BCA Method developed at
the CTU. The depth of tread recorded after 15 minutes of rolling and impacting action on
the surface of the concrete slab by the steel wheels is taken as the depth of abrasion (average
of 10 points). Abrasion tests have been carried out for all fly ashes at 0.45 and 0.55 w/c
ratios. The results for these are shown in Figure 13. At 0.45, BL1 had the highest abrasion
and DFA lowest in the range of 0.47 – 0.81 mm. For 0.55 fly ash concretes, the abrasion
depths ranged from between 0.67 - 1.10 mm, with SCR2 at the lower end and BL2 at the
upper end.
MA/46 Page 5 of 28
Figure 15 shows the variation in abrasion depth across the two w/c ratios tested. The area
shaded in grey represents the range of fly ash abrasion depths and the blue line the abrasion
depths for the Reference PC concrete. As shown in Figure 14, when considering a concrete
that meets the requirements (BS8500-1) for abrasion (minimum grade C40, minimum
cement content 325 kg/m3) DFA performed best, with an abrasion depth 0.63 mm (PC
reference: 0.55 mm), while BL1 performed worst with an abrasion of 0.88 mm.
6 Freeze-Thaw Scaling
The freeze-thaw tests were carried out according to CEN/TS 12390-9 and involve
measuring the amount (mass) of scaled material at regular intervals following exposure to
± 20ºC over 24 hours (with salt water as the freezing medium) for 56 cycles.
Figure 16 shows the air content and air entrainment dosage of each concrete mix. The air
entraining agent used for all concrete mixes was formulated for use with fly ash. All fly
ash concretes had air contents in the range of 4.8-6% and required air entrainment dosages
of between 2.7 – 5.5 (ml/kg of cement + addition) for 0.45 w/c ratio concretes and 4.3 –
11.0 (ml/kg of cement + addition) for those of 0.55. PRO1 is at the lower end for both w/c
ratios and NH1 at the upper end of the dosage range for 0.45 w/c ratio concretes, while
BL2 and LFA are at the upper end for those of 0.55. Figure 17 indicates that, as noted in
previous studies, there was a good correlation between fly ash specific surface area and
admixture dose to achieve the target air content.
The results show that the co-combustion fly ashes (BL2 and NH1) and LFA had the highest
AEA dosages. This is in agreement with the high LOI, BET and foam index values
observed for these materials.
The freeze-thaw results are shown in Figures 18 and 19 for concretes of 0.45 and 0.55 w/c
ratios respectively. At 0.45, LFA gave the least scaled material at 0.22 kg/m3 while NH1
the most at 0.87 kg/m3, whereas, at 0.55, BL2 had the least with 0.8 kg/m3 and DFA the
MA/46 Page 6 of 28
most with 1.64 kg/m3. The results also show that the PC reference concrete gave the lowest
scaling of the concretes tested.
7 Alkali Aggregate Reaction Results
AAR tests were carried out according to BS812-123:1999 and involve measuring the
expansion of concrete prisms at regular intervals, while being stored at high temperature
(38ºC) / humidity conditions for 1 year. So far, testing up to 39 weeks has been carried out
for 9 fly ash samples.
Figure 20 shows the expansion results for the AAR concretes. All of the fly ash concretes
have lower expansions than the PC reference. The level of expansion observed at this stage
of the test is small and therefore there is little difference between the fly ashes. In addition,
visually and reflecting the levels of expansions obtained, there were no signs of cracking
or deterioration in any of the concretes.
ASR mortar results are given in Figure 21 and show similar trends to those observed for
the concrete mixes. Little expansion has occurred, with only slight differences between the
fly different fly ashes, which were lower than the PC references for both aggregates. In
general, it appears that for concrete and mortar the method of fly ash production has not
had an effect on its AAR performance.
MA/46 Page 7 of 28
Table 1. Concrete mix proportions
MIX Water/Cement
Ratio
CONCRETE MIX PROPORTIONS1, kg/m³
Free water Cement / Addition Aggregate
Total PC Fly ash Total Sand 10 mm 20 mm Total
PC control
Mixes
1 0.65 165 255 0 255 910 375 695 1975 2395
2 0.55 165 300 0 300 850 380 705 1935 2400
3 0.45 165 365 0 365 790 380 710 1880 2410
4 0.35 165 470 0 470 720 375 700 1795 2430
Fly Ash
Mixes
1 0.65 165 180 75 255 895 370 685 1945 2365
2 0.55 165 210 90 300 845 375 695 1915 2380
3 0.45 165 255 110 365 775 375 695 1850 2380
4 0.35 165 330 140 470 700 365 680 1745 2380
1 Superplasticizer used in quantities necessary to achieve Slump Class S3
MA/46 Page 8 of 28
Table 2. AAR mix proportions
MIX
CONCRETE MIX PROPORTIONSa, kg/m3
Free waterc Cement / Addition Aggregateb
Total Cem Fly ashd Total K2SO4 Sand 10 mm 20 mm Total
Reference 228 699 0 699 7.5 413 415 590 1417 2345
Fly ash 228 447 192 639 10.2 413 415 590 1417 2284
Table 3. FT Concrete mix proportions
MIX Water/Cement
Ratio
CONCRETE MIX PROPORTIONS1, kg/m³
Free water Cement / Addition Aggregate
Total
PC Fly ash Total Sand 10 mm 20 mm Total
PC reference
Mixes
1 0.55 165 300 0 300 790 365 680 1840 2305
2 0.45 165 365 0 365 730 370 685 1785 2315
Fly Ash Mixes
1 0.55 165 210 90 300 780 360 670 1810 2275
2 0.45 165 255 110 365 715 360 670 1745 2275
MA/46 Page 9 of 28
(a)
(b)
Figure 1. Chloride migration results for selected concretes
MA/46 Page 10 of 28
Figure 2
chloride migration results
Figure 3. Carbonation results for concretes at 0.65 w/c ratio
MA/46 Page 11 of 28
(a)
(b)
Figure 4. Carbonation results for concretes at 0.55 w/c ratio
MA/46 Page 12 of 28
(a)
(b)
Figure 5. Carbonation results for concretes at 0.45 w/c ratio
MA/46 Page 13 of 28
(a)
(b)
Figure 6. Accelerated carbonation results for concretes at 0.45 w/c ratio
MA/46 Page 14 of 28
(a)
(b)
Figure 7. Accelerated carbonation results for concretes at 0.55 w/c ratio
MA/46 Page 15 of 28
(a)
(b)
Figure 8. Accelerated carbonation results for concretes at equal strength (35 N/mm2)
MA/46 Page 16 of 28
(a) (b)
(c) (d)
Figure 9. Sulfate expansion curves of 0.35 w/c ratio concretes with their corresponding mass changes
MA/46 Page 17 of 28
(a) (b)
(c) (d)
Figure 10. Sulfate expansion curves of 0.45 w/c ratio concretes with their corresponding mass changes
MA/46 Page 18 of 28
(a) (b)
(c) (d)
Figure 11. Sulfate expansion curves of 0.55 w/c ratio concretes with their corresponding mass changes
MA/46 Page 19 of 28
Figure 12. The deterioration of PC reference samples due to sulfate attack
MA/46 Page 20 of 28
(a)
(b)
Figure 13. Abrasion results for concretes at 0.45 and 0.55 w/c ratios
MA/46 Page 21 of 28
(a)
(b)
Figure 14. Abrasion results for concretes at equal strength (40N/mm2)
MA/46 Page 22 of 28
Figure 15. Relationship between w/c ratio and abrasion depth
MA/46 Page 23 of 28
(a)
(b)
Figure 16. AEA dosages and air contents for freeze-thaw concretes
MA/46 Page 24 of 28
(a)
(b)
Figure 17. Relationship between BET specific surface area and AEA dosageNote: Air
entraining agent used was BASF Micro Air 115
MA/46 Page 25 of 28
(a)
(b)
Figure 18. Mass of scaled material for freeze-thaw concretes at 0.45 w/c ratio
MA/46 Page 26 of 28
(a)
(b)
Figure 19. Mass of scaled material for freeze-thaw concretes at 0.55 w/c ratio
MA/46 Page 27 of 28
(a)
(b)
Figure 20. ASR Expansion curves of concretes
MA/46 Page 28 of 28
(a)
(b)
Figure 21. ASR Expansion curves of mortars