PCA R&D SN2897c
Identifying Incompatible Combinations
of Concrete Materials: Volume III—
Additional Appendices
by P.C. Taylor; V.C. Johansen; L. A. Graf; R. L. Kozikowski;
J. Z. Zemajtis, and C. F. Ferraris
Published by the Portland Cement Association in 2008 without copyright.
Table of Contents
VOLUME III – Additional Appendices
INTRODUCTION TO VOLUME III ................................................................................................ 1
KEYWORDS ................................................................................................................................. 1
ABSTRACT ................................................................................................................................... 1
REFERENCE ................................................................................................................................ 1
ACKNOWLEDGEMENTS ............................................................................................................. 2
REFERENCES ............................................................................................................................. 2
APPENDIX G – CALORIMETRY GRAPHS .................................................................................. 3
APPENDIX H – PORE SOLUTION CHEMISTRY REPORT......................................................... 9
APPENDIX I – RING SHRINKAGE GRAPHS ............................................................................ 57
APPENDIX J – FOAM DRAINAGE GRAPHS ............................................................................. 62
APPENDIX K – PORE SOLUTION ANALYSES RAW DATA ..................................................... 68
i
INTRODUCTION TO VOLUME III
KEYWORDS
admixture, ASTM C1581, incompatibility, calorimetry, foam drainage, pore solution chemistry.
ring shrinkage
ABSTRACT
Unexpected interactions between otherwise acceptable ingredients in portland cement concrete
are becoming increasingly common as cementitious systems become more and more complex
and demands on the systems are more rigorous. Such incompatibilities are exhibited as: early
stiffening or excessive retardation, uncontrolled early-age cracking, unstable or unacceptable airvoid systems.
A number of test methods have been reviewed to assess their usefulness in detecting
incompatibility early, thus preventing problems in pavements in the field. A protocol has been
developed to allow product manufacturers, concrete producers, contractors and owners to
monitor their materials and concrete systems. The protocol is phased to allow relatively simple
field tests to provide early warnings of potential problems, and central laboratory tests to support
and confirm the field work.
This is the last of three volumes. The initial two volumes in this series have been published under
the following titles:
• FHWA HRT-06-079, Identifying Incompatible Combinations of Concrete Materials:
Volume I–Final Report (Taylor et al. 2006a).
• FHWA HRT-06-080, Identifying Incompatible Combinations of Concrete Materials:
Volume II–Test Protocol (Taylor et al. 2006b).
This document contains detailed charts and tables portraying data collected during the
development of the protocols. Included are isothermal conduction calorimetry graphs, pore
solution chemistry (including a report with additional explanation), ASTM C1581 ring shrinkage
data, and foam drainage test data.
REFERENCE
Taylor, P.C.; Johansen, V.C.; Graf, L.A.; Kozikowski, R.L.; Zemajtis, J.Z.; and Ferraris, C.F.,
Identifying Incompatible Combinations of Concrete aterials: Volume III—Additional
Appendices, R&D SN2897c, Portland Cement Association, Skokie, Illinois, USA, 2008,
89 pages.
1
ACKNOWLEDGEMENTS
The research reported in this paper (PCA R&D SN2897c) was conducted by CTLGroup with the
sponsorship of the Portland Cement Association (PCA Project Index No. 03-10) and the Federal
Highway Administration (Contract No. DTFH61-03-X-00102). The contents of this report reflect
the views of the authors, who are responsible for the facts and accuracy of the data presented.
The contents do not necessarily reflect the views of the Portland Cement Association or the
Federal Highway Administration.
In addition, the authors wish to acknowledge the work of the following people in completing the
work described in this report: Katie Amelio, Pat Berry, Barb Betke, Javed Bhatty, Fred Blaul,
Phil Brindisi, Roberto Celestin, Rachel Detwiler, Luis Duval, Ken MacLeod, Greg Miller, Max
Peltz, W. Agata Pyc, Brian Szczerowski, Shiraz Tayabji, and John Winpigler.
REFERENCES
Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F.,
Identifying Incompatible Combinations of Concrete Materials: Volume I—Final Report,
FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA, August,
2006a, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.
Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F.,
Identifying Incompatible Combinations of Concrete Materials: Volume II—Test
Protocol, FHWA-HRT-06-080, Federal Highway Administration, Maclean, VA, USA,
August, 2006b, 86 pages., http://www.fhwa.dot.gov/pavement/concrete/pubs/06080/.
2
APPENDIX G – CALORIMETRY GRAPHS
Introduction. Isothermal conduction calorimetry was selected as a technique to monitor the
cement hydration process. The calorimetry testing was performed using a differential heat flow
calorimeter designed to monitor the heat of cement hydration as a function of time. The
conduction calorimetry analyses were performed using 5.0 g (0.18 oz) of a selected sample and a
w/c or w/cm of 0.50. Tests were performed for 24 h at 25 ± 1°C (77 ± 2 °F). Chapter 2 of
Volume I—Final Report contains detailed discussion of the calorimetry testing.
Sample Designation. In summary, each of six cement samples (1 to 6) was blended with Class C
fly ash (C), Class F fly ash (F), and Slag (S) to produce 18 cementitious materials. In addition, 4
selected cement control samples were used consisting of ordinary portland cement (P). Other
variables included admixture type and dosage, and curing temperature. Four rounds of testing
were performed. In round one, the 24 samples were mixed with a single dose of admixture (A).
In round two, selected samples were mixed varying admixture type (B) and dose (DA), resulting
in a total of 15 mixes.
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
14
12
J/gh
10
8
6
4
Sample "1PA"
Sample "1CA"
Sample "1FA"
Sample "1S"
2
0
0:00:00
6:00:00
12:00:00
18:00:00
Tim e of Hydration (hrs)
Figure G.1. Round 1 – Cement 1
3
24:00:00
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
15.00
12.00
J/gh
9.00
\
6.00
Sample "2PA"
Sample "2CA"
Sample "2FA"
Sample "2SA"
3.00
0.00
0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
Figure G.2. Round 1 - Cement 2
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
15.00
Sample "3PA"
Sample "3CA"
Sample "3FA"
Sample "3SA"
12.00
J/gh
9.00
6.00
3.00
0.00
0:00:00
6:00:00
12:00:00
18:00:00
Tim e of Hydration (hrs)
Figure G.3. Round 1 - Cement 3
4
24:00:00
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
15.00
Sample "4PA"
Sample "4CA"
Sample "4FA"
Sample "4SA"
12.00
J/gh
9.00
6.00
3.00
0.00
0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
Figure G.4. Round 1 - Cement 4
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
15.00
Sample "5PA"
Sample "5CA"
Sample "5FA"
Sample "5SA"
12.00
J/gh
9.00
6.00
3.00
0.00
0:00:00
6:00:00
12:00:00
18:00:00
Tim e of Hydration (hrs)
Figure G.5. Round 1 - Cement 5
5
24:00:00
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
15.00
Sample "6PA"
Sample "6CA"
Sample "6FA"
Sample "6SA"
12.00
J/gh
9.00
6.00
3.00
0.00
0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
Figure G.6. Round 1 - Cement 6
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
14
12
J/gh
10
8
6
4
Sample "2C"
Sample "2CDA"
Sample "2PDA"
Sample "2P"
2
0
0:00:00
6:00:00
12:00:00
18:00:00
Tim e of Hydration (hrs)
Figure G.7. Round 2A - Cement 2
6
24:00:00
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
16
14
12
J/gh
10
8
6
4
Sample "4P"
Sample "4PDA"
Sample "5P"
Sample "5PDA"
2
0
0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
Figure G.8. Round 2A - Cement 4 and Cement 5
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
14
12
J/gh
10
8
6
4
Sample "1CB"
Sample "1PB"
Sample "6PB"
2
0
0:00:00
6:00:00
12:00:00
18:00:00
Tim e of Hydration (hrs)
Figure G.9. Round 2B - Cement 1 and Cement 6
7
24:00:00
FHWA Incom patibility Study - Conduction Calorim etry
Hydration Profile
16
14
12
J/gh
10
8
6
4
Sample "2PB"
Sample "2CB"
Sample "4PB"
Sample "5PB"
2
0
0:00:00
6:00:00
12:00:00
18:00:00
24:00:00
Tim e of Hydration (hrs)
Figure G.10. Round 2B - Cement 2, Cement 4, and Cement 5
8
APPENDIX H – PORE SOLUTION CHEMISTRY REPORT
Test Methods
Introduction
The methods employed for extracting pore solution out of cement paste were similar to those
applied in research studies done elsewhere. Depending on the initial time of set for the different
mixes, extractions were done on either plastic-state or hardened-state paste. Mixing procedure
for the paste was adapted from that described in report “Development of an Early Stiffening
Test” (Tang 1997). This method of mixing cement paste was also used for the “mini-slump”
testing. Chemical analysis of the pore solution collected was conducted for sodium, potassium,
calcium, and sulfate ion, as well as pH measurement. In order to obtain the desired amount of
liquid for chemical analysis, trial extraction tests were conducted prior to extractions.
The scope of work for pore solution extraction and analysis followed that for mini-slump,
calorimetry, and all other tests performed under Task 2.1.1. In summary, each of 6 cement
samples (1 to 6) was blended with class C fly ash (C), class F fly ash (F), and slag (S) to produce
18 cementitious materials. In addition, 4 selected cement control samples were also used
consisting of ordinary portland cement (P). Other variables included admixture type and dosage,
and curing temperature. Samples were mixed with water at w/cm ratio of 0.50 to produce paste
and extract solution either in plastic or hardened state, at 5, 10, 30, 60, 360, and 1440 minutes
after mixing.
Four rounds of testing were performed. In round one, the 24 samples were mixed with a single
dose of admixture (A). In round two, selected samples were mixed varying admixture type (B)
and dose (DA), resulting in a total of 15 mixes. In round three, selected samples were mixed to
look at the effect of high temperature (32°C or 90°F), resulting in another group of 8 mixes in
total. Similarly, in round four selected samples were mixed to look at the effect of low
temperature (10°C or 50°F), 8 mixes total.
Paste Mixing
Paste was mixed in a Waring Blender™ mixer at 10,000 rpm for 90 seconds counting from the
time that all cement and admixture were added to the water. Mixing proportions used were 500 g
of cementitious material, 250 ml of water, and varied amounts of WRA admixture. Admixtures
were measured and emptied into the mixer using 5-ml plastic syringes and dosed at single and
double dosages recommended by the manufacturer. Lignin-based WRA admixture “A” was
dosed at 1.62 ml and 3.25 ml per 500 grams of cementitious material. Sugar-based WRA
admixture “B” was dosed at 0.81 ml per 500 g of cementitious material. A 0.50
water/cementitious material ratio was used in all paste mixes.
Because of the different effects on paste consistency experienced on initial time of set and early
stiffening by using different extraction conditions such as time after mixing, combination of
materials, mixing temperature, etc., the solution extractions were performed either in plastic state
where the sample was poured into disposable centrifuge tubes, or in hardened state where
samples were cast in small cylinder molds.
9
Extractions During Plastic-State
An Analytical Centrifuge machine was used for extraction of solution before cement paste
reached initial set. The centrifuge machine, manufactured by Clay Adams and equipped with a
115 volt-, 1.5 amp-, 60 Hz-motor, had a total capacity of 6 tubes. Plastic centrifuge tubes with
gradation scale with a total capacity of 15 ml were used.
Minimum extraction times were previously determined in order to obtain between 10 and 15 ml
of solution. Extraction times of 1 min. for very fluid paste and 3 min. for less fluid paste were
used. Paste was placed inside each of 6 centrifuge tubes with the help of a funnel, and in cases
where the paste would not flow easily, using a vibrating table. For paste mixes not reaching
initial set yet but showing significant stiffening at 6 hours after mixing, 12 tubes were filled in
with paste to obtain the desired amount of liquid.
For most mixes pore solution at ages of 5, 10, 30, and 60 minutes after mixing were centrifuged.
Even some extractions at 6 and 24 hours were also performed using the centrifuge method, when
temperature of the paste was kept at 10ºC (50°F).
Extractions During Hardened-State
An extraction method for squeezing solution out of hardened cement paste was adopted from
previous research studies at Purdue University (Barneyback 1987). A press die manufactured of
steel and designed to receive loads of up to 1335 kN (300 kips), “squeezed” the pore liquid by
applying pressure to the paste specimen through a piston cylinder, and collecting the liquid via
grooves in a base platen that removed the liquid and carried it out into tube receptacles using a
flexible piece of tube flushed with nitrogen gas. Specimens used for this extraction technique
were discs cast in 50-mm (2-in.) diameter by 19-mm (¾-in.) high cylinders that were able to
provide a tight seal. An illustration of the press die set is shown in Fig. H.1, showing on the left
side photo the paste specimen and the cylindrical chamber before introducing the disc and
applying the pressure. Prior to testing, trial extractions were done in order to determine the
approximate volume of hardened paste necessary to obtain 10 to 15 ml (0.34 to 0.51 fl oz) of
solution. Normally 4 or 5 disc specimens were required to obtain the desired volume of liquid.
For most mixes, solution extraction at ages of 24 hours after mixing was done using the press
die. Even some extractions at 6 hours were performed using the press die method, when
temperature of the paste was kept at 32ºC (90°F) and the paste had hardened enough to prevent
the use the centrifuge method.
Chemical Analysis
Pore solution samples were submitted to the chemical laboratory for analysis. After the
extraction, samples were sealed and kept in the refrigerator until the next morning before
analysis. After refrigeration samples were allowed to reach room temperature and pH was
measured and solutions acidified to minimize potential changes in chemical composition due
mainly to carbonation upon prolonged exposure to air. Samples were analyzed within the next
24 hours for sulfate, calcium, sodium, and potassium concentration. Sulfate analyses were done
according to ASTM C114 wet method for chemical analysis, determined by the gravimetric
10
method after precipitation with reagent-grade barium chloride. Calcium, sodium, and potassium
analyses were done using Atomic Absorption Flame Emission Spectroscopy (AAS) using Varian
spectrometer model SpectrAA 800. Sample preparation in most cases did not require more than
10 times dilution of the original volume, and in no case exceeded 100 times. Concentrations
were calculated in mg/L of solution and used in ppm for data reduction and analysis.
Figure H.1. Die set for squeezing pore solution out of hardened cement paste specimens.
Reproducibility of Results
Additional selected paste samples were produced in one repetition to evaluate the reproducibility
of the entire method of mixing, extracting, and analyzing the pore solution samples. Samples
2CA and 2CB at 21°C (70°F), 1CA at 32°C (90°F), and 1CB at 10°C (50°F), were randomly
selected to repeat mixing of the paste, extracting of the pore solution at all six different times,
and subsequent analyzing pore solutions for chemical composition. The results of the two
determinations, along with their average value were plotted in the graphs shown in Appendix K.
The reproducibility was evaluated by computing the standard deviation and the average of each
pair of data values determined, and then by calculating the coefficient of variation (COV) in
percentage dividing the standard deviation by the average. Then, the maximum and minimum
COVs over the whole range of six times of extraction and four repeat samples were determined,
11
as well as the average COV over the same data range, for each ionic species and pH. The
resulting COV parameters are shown in Table H1.
Table H.1. Coefficient of Variation (COV)* Parameters for Repeat Samples
pH
SO42-
Ca2+
Na+
K+
MAX.
4.6%
55.6%
60.9%
56.0%
29.4%
MIN.
0.1%
0.4%
0.8%
0.5%
0.7%
AVG.
0.8%
10.2%
16.7%
11.8%
9.7%
*COV = coefficient of variation = standard deviation / average
From Table H.1, the standard deviation of each pair of pH data determined for all the repeat
samples at all six times of extraction, ranged from 0.1% to 4.6% of the corresponding mean
value for that pair of data. The same analysis was applied to the sulfate ion content, where the
standard deviation ranged from 0.4% to 55.6% and averaged 10.2% of the corresponding mean
value. It can be seen from Table H.1 that while variability is larger for ionic concentration
methods than for pH, the overall average coefficient of variation for chemical analysis is around
12%, which may be considered fair for such a labor-intensive methodology and number of
persons involved in each determination.
Results and Discussion
Appendix K shows graphs containing the results of chemical analysis done for each system
under each round of testing described before. Sample notation used throughout this section and
in the graphs has been given before. Concentration and pH results are shown for the different
ionic species analyzed, i.e. sulfate, calcium, sodium, and potassium, for the different times of
extraction tested. The concentration data is plotted on a primary y-axis, from 0 to 20,000 ppm,
whereas pH values are plotted on a secondary y-axis from 12 to 14. Both concentration and pH
are plotted vs. time of extraction or time after mixing, in minutes in the x-axis on logarithmic
scale.
The data was analyzed in two portions, the raw ionic concentration data (trends) and the resulting
calculated saturation factors for gypsum, calcium hydroxide, and syngenite. The data is preceded
by an introduction section, which provides a basic explanation of cement hydration principles
and pore solution chemistry.
Introduction
When portland cement enters in contact with water it hydrates, meaning that the cement particles
dissolve and chemically react in water. The reactants of this chemical dissolution are cement
particles and water. In Type I cements, particles are mainly (above 95% by mass) clinker grains.
Clinker grains are composite particles of the so-called four “cement phases” and other solidified
melts from the kiln. These grains consist of the phases C3S and C2S, held together by C3A and
C4AF that solidify from the kiln melt. Sulfate and alkalies that are part of the clinker reactions in
the cement kiln and originate from raw materials and fuel used, also form solid compounds upon
12
clinker cooling. These compounds are different varieties of alkali sulfates, the most commonly
found being potassium sulfate (K2SO4). These compounds are usually found in cements that
show a high alkali content in their chemical analysis.
Other particles present in cement are gypsum, plaster (resulting from gypsum dehydration in the
cement mill), anhydrite, mineral additions (fly ash, slag), and contaminants. Some of this
particulate matter is not soluble in water, like quartz and other silico-aluminate clays. Gypsum
and plaster are both soluble in water, and plaster dissolves more easily than gypsum.
From the dissolution reactions of all these particles that comprise portland cement, the products
of the chemical dissolution are simply the ionic species derived from all these compounds. For
example: Gypsum (CaSO4•2H2O) dissolves in water to produce calcium ion (Ca2+) and sulfate
ion (SO42-); plaster (CaSO4•½ H2O) dissolves in water to produce the same ionic species as
gypsum; potassium sulfate (K2SO4) produces potassium ion (K+) and sulfate ion. Calcium
silicates from clinker grains dissolve partially to produce solid “gel” calcium-silicate hydrate
(C-S-H), calcium ion (Ca2+) and hydroxyl ion (OH-). Chemical admixtures used in concrete
mixtures also contribute to calcium ion concentration, as they are soluble in water.
The plus or minus sign shown as super indices on the chemical element symbol indicates the
electrical charge of the ion. Essentially this means that the molecular matter is dissociated into
ions, and each ion will tend to find another ion of opposite charge to achieve electrical neutrality.
When there are enough pairs of ions, the solid reforms from the aqueous dissolution in the form
of solid crystal or “phase.”
As cement particles hydrate the mixing water or the water surrounding the particles becomes an
aqueous solution of various ionic species. This explains the term “pore solution” to designate the
water that remains in the porous concrete microstructure after it hardens. Fig. H.2 illustrates
cement particles in close proximity to each other surrounded by water, such as in concrete
mixtures where water/cement ratios normally range from 0.35 to 0.45. The water surrounding
cement particles starts to dissolve the solids at different rates, depending on their rate of
dissolution, which in turn is a function of temperature. The resulting ionic species become more
and more concentrated and start to interact between each other and with the solid phases. Ionic
electrical neutrality must be attained, so in order to balance the electrical charge, as more
negative charge ions are incorporated into solution, more positive charge ions will also be
incorporated and vice-versa. Eventually, solid products of reaction will “precipitate” or form
from the pore solution, such as calcium hydroxide and ettringite phases.
13
OH-
3
Ca
2+
SiO44OH-
SO42-
4
SO42-
K+
Ca2+
5
2
K+
Al(OH)4-
1
OH
Ca2+
Ca2+
SiO44-
SO42-
SO42SO42-
Al(OH)4-
OH-
Na+
SO42Ca
2+
OH-
Ca2+
Na+
7
K+
K+
6
K+
SO42-
-
Na+
Ca
K+
2+
Na+
Ca2+
SiO44-
1=2CaO•SiO2, 2=3CaO•SiO2, 3=3CaO•Al2O3, 4=4CaO•Fe2O3•Al2O3,
5=CaSO4•½H2O, 6=CaSO4•2H2O, 7=SiO2
Figure H.2. Schematic representation of portland cement solid phases and their ionic species in
aqueous dissolution right after cement enters in contact with water.
As cement hydration progresses with time, the trends in ionic concentrations observed are based
on the following typical portland cement hydration processes:
1. During the first 30-minute period high levels of sulfate in solution denote dissolution
of alkali sulfates, plaster, gypsum, and anhydrite.
2. This high level of sulfate ion in solution stays almost unchanged as a result of
precipitation of gypsum from plaster, syngenite, and formation of ettringite.
3. At 6 hours of hydration there should be:
a. Significant decrease of sulfate ion in solution resulting from the reaction of sulfate
and C3A to form the maximum amount of ettringite in the paste.
b. Increase of potassium ion in solution (and subsequent increase in pH), which
results from releasing of potassium ion in solution.
c. Slight decrease of calcium ion concentration is the result of precipitation of solid
calcium hydroxide during the onset of C3S acceleratory hydration (usually
observed as a second peak in a calorimeter heat curve).
14
4. By 24 hours, sulfate and calcium ion concentration decrease significantly, whereas
potassium and sodium ion increase. Formation of calcium hydroxide, calcium silicate
hydrate, and the conversion of ettringite to monosulfoaluminate take place.
The chemical composition of concrete pore solution has been the subject of several studies on
the hydration of portland cement (Tang, et al. 1988; Gartner, et al. 1985; Rothstein, et al. 2002).
Until recently, not many measurements have been reported of the ionic concentration of
solutions when supplementary cementitious materials (SCM) are used in the concrete mix. As
shown on various graphs in Appendix K, sulfate ion concentration is high right after mixing and
remains at a high level until after 6 hours or later, decreasing until it reaches very low
concentration at 24 hours. Potassium and sodium ion concentrations will start at some point
(depending on the alkali content of the cement and other SCM added) and will increase as time
progresses and cement grains react more with water. Calcium ion concentration follows the same
trend as sulfate, being highest at the beginning and slowly decreasing until becoming negligible
after 24 hours of hydration. Of these four ionic species, sulfate and potassium usually show
higher relative concentration levels than sodium and calcium right after mixing. The pH of the
solution increases with time, normally moving in the range from 13 to 13.5 during the first
24 hours.
These are the general trends seen in the pore solution data analyzed during this study. However,
there are variations within different cementitious materials used, dosage and type of admixture
used, and mixing/curing temperatures used. The following sections discuss the particular effects
observed of the variables tested on the pore solution concentration of the ionic species monitored
at different times of hydration.
Round 1 - Effect of Chemical Composition of Cementitious Materials
In round 1 of testing, sulfate ion concentrations during the first 6 hours for pastes made with
cement sample 2 and its combinations (i.e. P, C, F, and S) are about twice as high at
approximately 16,000 ppm than those for paste made with cements 1, 3, 4, and 6, at less than
8,000 ppm. Sulfate ion concentrations are also high for paste made with cement 5 and some of its
combinations. This is a direct effect of cement composition. Fig. H.3 illustrates the relative
proportions of C3A, alkalies, and SO3 in all 6 cement samples. ASTM C150 specification
provides for additional sulfate content when the C3A content exceeds 8%. Cements 2, 3, 4, and 5
are above 8%, while 1 and 6 are below, so sulfate contents are at the expected levels. The alkali
contents are highest in samples 2 and 5, while at normal levels (below 0.6% Na2Oeq., according
to ASTM limits) in all the rest.
Based on Differential Scanning Calorimetry (DSC) analysis results shown in Table H.3,
reasonable assumptions can be made on sulfate distribution (clinker sulfate vs. gypsum sulfate)
that lead to calculations showing that indeed cements 2 and 5 contain the highest amount of
clinker sulfate, or alkali sulfate, as shown in Fig. H.4 (where data is sorted by gypsum content).
Of all sulfate-bearing phases in cement, alkali sulfates contained in clinker (mainly K2SO4) are
the most readily soluble in water, followed by syngenite (K2Ca2(SO4)2•H2O), hemihydrate or
plaster, and gypsum, in that order. Based on this sulfate-bearing phase solubility, sulfate ion
concentrations in pore solution are in agreement with cement composition: samples 2 and 5 are
expected to reach highest levels because of both the higher total sulfate content and the higher
15
alkali sulfate content. While cement 2 has no syngenite present, it has a bigger proportion of
plaster to gypsum than cement 5. Fig. H.5 shows sulfate ion concentration of pore solutions
extracted from paste made with cement samples 1 through 6 without supplementary cementitious
materials and single dose of admixture A.
Table H.2. Chemical composition of cements and supplementary cementitious materials with
calculated Bogue compounds where applicable (weight % of sample)
Sample ID (Cement
Sample No., SCM):
1
2
3
4
5
6
Slag
Class C Class F
Fly ash Fly ash
Oxide XRF Analysis
SiO2
20.51
19.06 20.29 19.48 19.22 20.83
37.6
32.26
52.56
Al2O3
4.46
6.03
5.48
5.95
5.56
4.20
7.95
17.38
20.26
Fe2O3
3.19
2.13
2.8
2.68
2.66
3.3
0.87
6.06
11.46
CaO
63.43
62.45 65.59 64.42 61.63 62.55
38.91
26.8
4.29
MgO
2.99
2.67
1.02
0.85
2.34
3.23
10.87
7.87
1.00
Total SO3
2.72
3.87
2.63
3.32
4.42
2.75
2.49
2.65
0.64
Na2O
0.13
0.23
0.19
0.18
0.27
0.13
0.33
2.03
1.32
K2O
0.65
1.25
0.3
0.53
0.99
0.65
0.37
0.35
1.92
L.O.I. (950oC)
1.44
1.23
0.9
1.41
2.11
1.45
-0.99
0.24
4.22
Total
99.99
99.82 99.86 99.88 99.99 100.24 99.84
98.47
99.1
Alkalies as Na2Oeq.
0.56
1.06
2.26
2.58
0.38
0.53
0.92
0.56
0.58
Calculated Compounds per ASTM C150-02a.
C3S
60
55
65
61
51
56
C2S
13
13
9
10
17
18
C3A
6
12
10
11
10
6
9
8
8
10
C4AF
10
6
* Determined by X-ray diffraction (XRD)
16
11
Bogue C3A
Eq. Alkalies
% SO3
14
4.5
Bogue C3A, wt. %
12
4.0
10
3.5
3.0
8
2.5
6
2.0
1.5
4
1.0
2
0.5
0
Eq. alk. and SO 3, wt. %
5.0
0.0
0
1
2
3
4
5
6
7
Cement sample number
Figure H.3. Selected cement composition.
4.0
14
3.5
12
Sum of K2SO4
+ Na2SO4
3.0
10
Syngenite
2.5
8
2.0
6
1.5
4
1.0
0.5
2
0.0
0
2
3
1
6
4
C3A, wt %
Sulfate-bearing phases, wt %
Table H.3. DSC results for cement samples showing Gypsum, Plaster, and Syngenite amounts
(weight % of sample)
Sample ID:
1
2
3
4
5
6
Gypsum
0.6
0.2
0.2
2.1
3.7
1.1
Plaster
0.4
2.6
2.8
2.0
0.9
1.9
Syngenite
1.1
0.0
0.0
0.0
0.4
1.0
Gypsum/Plaster
1.50 0.08 0.07 1.05 4.11 0.58
ratio
Plaster
Gypsum
C3A
5
Cement Sample Number
Figure H.4. Sulfate distribution (read Y-axis on the left side) and C3A content (read Y-axis on the
right side) in cement samples.
17
Of the SCMs used, class C fly ash and slag are the type of materials that could usually make
important contributions to sulfate ion concentration in solution. The class C fly ash and slag
contained 2.65% and 2.49% SO3 respectively, although the form of sulfate differed substantially
from the form of sulfate in cement. X-ray diffraction (XRD) coupled with selective chemical
dissolution methods performed as part of Task 2.1.1, reported class C fly ash containing about
4% by mass of calcium sulfate. This amount of calcium sulfate represents 2.36% of the total
percent SO3 obtained by XRF analysis (2.65%, see Table H.2 above), or 89%. This calcium
sulfate is relatively soluble in water due to its fine particle size, since it forms in the coal-fired
power generation process during cooling of the flue gas, and is captured in the electrostatic
precipitators of as part of the fly ash. This means that a significant portion of the sulfate present
in the ash (89%) is relatively soluble and contributes to sulfate ion concentration in pore solution
in a relatively short period of time.
As for the distribution of sulfate in the slag, it is mostly part of the amorphous structure of the
slag and not immediately soluble in water. The amount of slag replacement by cement (40%,
twice as much as that for the ashes) does have some impact on sulfate ion and other ionic
concentrations just by the account of a dilution effect of the contribution from the cement
components.
Particularly high concentrations of sulfate ion are observed in pore solutions made with cement 2
(2P) and cement 2 combined with fly ash C (2C) up to 6 hours after mixing. Sulfate
concentration in pore solution declines drastically as expected for all cement systems treated at
21ºC (70ºF) after 6 hours.
2-
Ionic concentration (ppm)
SO4 ion
20000
16000
23°C 1 P A
23°C 2 P A
12000
8000
23°C 3 P A
23°C 4 P A
4000
23°C 5 P A
23°C 6 P A
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.5. Sulfate ion concentration in pore solutions extracted from paste made with all cements
without SCM and admixture A, at 21ºC (70°F).
Alkali ion concentration (potassium more than sodium) was also observed to be high in pastes
made with cements 2 and 5 and their combinations, somewhat less for combinations with slag
and class F fly ash, reflecting mainly the cement amount they replaced (i.e. alkali sulfate). Fly
ash replacement levels were only 20% for both class C and F, whereas slag replacement level
18
was 40%. Alkali content of the SCMs may not contribute directly to sodium or potassium ion
concentration in solution because the form of alkali is not readily soluble in water. Note from
Table H.2 that the total equivalent alkali content of both fly ashes and the slag were not only
comparable with total equivalent alkali in the cement samples, but even twice as much.
However, the nature of this alkali in SCMs is different from that of a water-soluble form;
therefore their contribution to ionic concentration was very limited.
As explained before, pH is a direct function of the hydrogen [H+] and hydroxyl [OH-] ion
concentration in solution. Because of the greater affinity of OH- for Na+ and K+ than for Ca2+,
more than any other ion present in hydrated cement pore solution, potassium and sodium ions
greatly affect hydroxyl ion concentration. As the potassium and/or sodium ionic concentration
increases, the hydroxyl ion concentration will increase, thus increasing the pH of the pore
solution. This increase on hydroxyl ion occurs simultaneously to the reaction of calcium
hydroxide formation, from calcium [Ca2+] and hydroxyl [OH-] ions in solution, consuming
hydroxyl ions from solution and competing with other reactions. However, an overall increasing
effect in pH should be noticeable in systems with high amount of alkali ion in solution, i.e.
cements 2 and 5 with high contents of alkali sulfate in cement. As shown in Fig. H.6, the pH for
pastes made with cement samples 2, 5, and 6 is noticeably higher (approx. 13.3 to 13.7) than that
measured in pastes made with all other cementitious materials. Looking at sulfate-phase
distribution in cement samples (Fig. H.4), pH values for cements 2 and 5 are easily explained
again by a very high, very soluble alkali sulfate content. In cement 6, perhaps the high pH
measured results from a combination of alkali sulfate content and the cement’s high content of
readily soluble syngenite, a potassium-bearing phase. Fig.H.7 shows potassium and sodium ion
concentration for the same pore solutions. Again, pore solution pH is highest for those solutions,
made with cement samples 2, 5, and 6 showing highest concentration of alkali ion.
pH
13.8
13.6
70F 1
70F 2
70F 3
70F 4
70F 5
70F 6
pH
13.4
13.2
13.0
12.8
12.6
PA
PA
PA
PA
PA
PA
12.4
1
10
100
1000
Time after mixing (min)
10000
Figure H.6. Measured pH of pore solution made with cement samples 1 to 6 and admixture A at
21°C (70°F).
19
+
+
Ionic concentration (ppm)
K ion
Na ion
20000
3000
16000
2500
70F 1 P A
70F 2 P A
2000
12000
70F 3 P A
1500
8000
70F 4 P A
1000
4000
500
0
0
1
10
100
1000 10000
70F 5 P A
70F 6 P A
1
10
100
1000 10000
Time after mixing (min)
Time after mixing (min)
Figure H.7. Alkali ionic concentration of pore solution of pastes made with different cement
samples (admixture A and 21°C (70°F)).
Regarding calcium ion concentration, there seemed to be an additive effect when combining
class C fly ash and cement sample 3 that resulted in higher concentrations. Fig. H.8 shows
calcium ion concentration in pore solutions extracted from pastes made with samples 1CA, 2CA,
3CA, 4CA, 5CA, and 6CA, using single dose of admixture A and curing at room temperature. It
is apparent there was a sustained higher calcium ion concentration for pore solution extracted
from paste sample 3CA. To a lesser degree, a higher concentration of calcium ion was also
observed when comparing pore solutions extracted from pastes made with other SCMs and
cement 3, as shown in Fig. H.9, where the effect of the class C ash in calcium ion concentration
is apparent. As seen in Table H2, cement sample 3 has a higher Bogue C3S content (65%) mainly
due to its higher CaO (65.6%) content.
It is interesting to note here that reported as part of Task 2.1.1, conduction calorimetry data
related to C3S hydration, as well as 24-hour mortar cube compressive strength data from
specimens made with samples 3CA, 3FA, and 3SA at 21°C (70°F), seem to show some positive
correlation between enhanced hydration properties and calcium ion concentration in pore
solution.
20
Ionic concentration (ppm)
Ca2+ ion
2500
70F 1 C A
2000
70F 2 C A
1500
70F 3 C A
1000
70F 4 C A
70F 5 C A
500
70F 6 C A
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.8. Calcium ion concentration in pore solutions extracted from paste made with all 6
different cement samples and class C fly ash (admixture A, 21°C (70°F)).
Ionic concentration (ppm)
Ca2+ ion
2500
2000
70F 3 C A
1500
70F 3 F A
1000
70F 3 P A
70F 3 S A
500
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.9. Calcium ion concentration in pore solutions extracted from paste made with cement 3
and all SCMs including control paste (admixture A, 21°C (70°F)).
This observation hints perhaps to the importance of proper balance between sulfate and calcium
ion in pore solution, because in the case of cement 3PA, sulfate ion concentration (see Fig. H.5)
is at a relatively low level, pointing to the safe assumption of a well-controlled aluminate
reaction to form a very stable hydration product (ettringite), thereby reducing the potential for
false set or flash set. This may be further substantiated by the analysis of the data using activities
and ionic activity products to determine the corresponding saturation factors of gypsum, calcium
hydroxide, and ettringite. Note that cement 3 is low in clinker alkali sulfate and unusually high in
hemihydrate (plaster) proportion to gypsum (see Fig. H.4). This means that plaster relatively
quick dissolution in water brings both sulfate and calcium ion into solution while little additional
sulfate is brought from the more-soluble alkali sulfate, which in turn contributes with only
21
limited amounts of calcium ion into solution. These contrasts with pore solution data of paste
made with cements 2 and 5, for example, where alkali sulfate concentrations are much higher.
The drastic drop in calcium ion concentration between 6 and 24 hours observed in most pore
solutions (see Fig. H.8) has a direct relationship to the sudden increase of hydroxyl ion
concentration by 24 hours indirectly measured as pH (see Fig. H.6). This sudden drop in calcium
ion is partly due to calcium hydroxide formation as reviewed before, but also due to the so-called
“common ion effect” by which calcium ion solubility is suppressed because of the presence of
more alkali ion in solution competing for the increasing hydroxyl ion. The increase in alkali ion
between 6 and 24 hours is apparent from Fig. H.7, and is more pronounced in pore solutions
made with cement samples 2 and 5, containing the very soluble alkali sulfate. To illustrate this
typical part of the cement hydration process, the following two chemical equations depict these
competing reactions:
Na+ + K+ + 2OH- ↔ NaOH + KOH
Ca2+ + 2OH- ↔ Ca(OH)2
Because Ca(OH)2 is much less soluble than NaOH or KOH, the final outcome is that Ca(OH)2
precipitates as hexagonal crystals, while Na+, K+, and OH- remain in solution making for the
high pH environment of portland cement hardened paste.
Round 2 - Effect of chemical admixture type and dosage
It is known that chemical admixtures used in concrete will affect the pore solution chemistry,
especially the ionic concentrations of calcium and alkali. Even at the very small dosages typical
of this type of admixtures (in the range from 0.1 to 0.4 ml per 100 g of cementitious material),
the effect of these concentrated substances is to significantly increase ionic concentration and
therefore contribute to ionic balance and influence the saturation condition for the different
products of reaction (i.e. gypsum, calcium hydroxide, ettringite, etc.).
The effect on calcium ion concentration comparing between paste samples made with admixture
A, with double dosage of admixture A, and with admixture B is apparent from Figs. H.10 to
H.14. In these figures, the calcium ion concentration of pore solution is shown for samples made
with selected cementitious samples 2C, 2P, 4P, and 5P. These four samples were selected after
round one of testing because they exhibited strong tendency to early stiffening problems, and to
test the effect (commonly referred as “admixture compatibility”) that a different dose and type of
admixture would have on these problems. Early stiffening properties were measured by
conduction calorimetry, the mini-slump test, setting time, and other tests as reported in other
sections of this report under Task 2.1.1. Also, cementitious samples 1P, 1C, and 6P were selected
to test the effect that a single dosage of a sugar-based admixture would have, if any, on early
stiffening properties. These later samples did not show tendency to early stiffening, but were
taken as a reference of “normal” performance. All these tests were performed at room
temperature, 21ºC (70oF).
The relative effect on Ca2+ ion is shown on Figs. H.10 to H.13. In Fig. H.11, the apparent sudden
drop in concentration at 10 min. and 30 min. for samples 2PDA and 2P respectively, are
considered outlier data points. The effects of admixture in Ca2+ ion are more marked in the
22
period of time starting right after mixing to up to 360 minutes (6 hrs). On Figs. H.10 and H.11,
the concentration is highest for pore solutions containing double dosage of admixture A (DA),
intermediate for pore solutions containing single dosage of admixtures A and B (A, B), and
lowest for pore solutions containing no admixture (control). This is the case for samples made
with cementitious materials 2P and 2C, while for those made with 5P (Fig. H.13) the
concentration is only slightly changed by the dose and or type of admixture. In the case of
sample 4P (Fig. H.12), it is noticeable that the addition of more admixture A, or the use
admixture B, seemed to have a decreasing effect on calcium ion concentration relative to the use
of a single dose of admixture A.
Ca2+
Ionic concentration (ppm)
1400
1200
1000
70F 2 C A
800
70F 2 C
600
70F 2 C DA
400
70F 2 C B
200
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.10. Calcium ion concentration for pore solutions made from cement sample 2C and
varying dose and type of admixture, at 21°C (70°F).
23
Ca
2+
Ionic concentration (ppm)
1400
1200
70F 2 P A
1000
70F 2 P
800
70F 2 P DA
600
70F 2 P B
400
200
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.11. Calcium ion concentration for pore solutions made from cement sample 2P and
varying dose and type of admixture, 21°C (70°F).
Ca2+
Ionic concentration (ppm)
1400
1200
70F 4 P A
1000
70F 4 P
800
70F 4 P DA
600
70F 4 P B
400
200
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.12. Calcium ion concentration for pore solutions made from cement sample 4P and
varying dose and type of admixture, 21°C (70°F).
24
Ca2+
Ionic concentration (ppm)
1400
1200
70F 5 P A
1000
70F 5 P
800
70F 5 P DA
600
70F 5 P B
400
200
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.13. Calcium ion concentration for pore solutions made from cement sample 5P and
varying dose and type of admixture, 21°C (70°F).
Fig. H.14 shows calcium ion concentration with time of hydration for samples 1P, 1C, and 6P.
As explained before, these samples were considered as reference regarding early stiffening
behavior when tested prior to the second round, because of the normal performance they
exhibited. In these solutions, it can be seen from Fig. H.14 that ionic concentration starts high at
around 1000 ppm and goes down by 10 minutes to around 600 ppm. This is similar to what it is
observed in Figs. H.10 and H.11 for samples 2C and 2P respectively, except perhaps that
calcium ion seems to remain at higher concentration for longer period of time when admixtures
have been used. A reference threshold concentration for Ca2+ would be around 1080 ppm, which
represents the calcium ion concentration of a saturated pure calcium hydroxide solution at 23ºC
(73ºF), indicating that higher than this there would be precipitation of calcium hydroxide in that
simplified scenario. It is important to note that precipitation of calcium hydroxide is also
governed by hydroxyl ion concentration and that both concentrations are a function of other ionic
concentrations, such as alkalies.
25
Ionic concentration (ppm)
Ca
2+
1400
70F 1 C A
1200
70F 1 C B
1000
70F 1 P A
800
70F 1 P B
600
70F 6 P A
400
70F 6 P B
200
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.14. Calcium ion concentration for pore solutions made from cement samples 1C, 1P, and
6P, and varying type of admixture, at 21ºC (70°F).
Although cement 1 had a higher C3S/C2S ratio, both cement samples 1 and 6 were very similar in
chemical composition. Their total percent SO3 was at the same level, however, sulfate
distribution was different. The cement samples had the same alkali sulfate content, about the
same syngenite content, but gypsum to plaster ratios were different. Plaster was higher than
gypsum in sample 6, while it was lower than gypsum in cement 1. In addition, it was reported
that cement 1 contained significant amounts of natural anhydrite, analyzed by XRD. Naturaloccurring anhydrite is far less soluble than gypsum, plaster, syngenite, or alkali sulfate.
Round 3 and 4 - Effect of Temperature
By testing pore solution chemistry at 32°C (90°F) and 10°C (50°F), the objectives were to
address the effects on mixes showing early stiffening, normal stiffening, and mixes that were
slow in reaching initial setting time. Mixing and curing paste specimens at 32°C (90°F) was
applied to those mixes showing strong tendency to early stiffening for looking at possible
aggravating effects, and to those mixes exhibiting normal behavior. Mixing and curing paste
specimens at 10°C (50°F) was applied to mixes showing a tendency for early stiffening but to a
lesser degree, looking at possible retardation effects, and also applied to those mixes exhibiting
normal behavior as in the 32°C (90°F) treatment.
Mixing and curing at 10°C (50°F) shows a marked effect on sulfate ion concentration compared
to room temperature. For the group of paste mixes showing early stiffening (2CA, 2CDA, 2FA,
and 1CB) sulfate ion concentration remained relatively high after 6 hours (360 min) at 50°F,
contrasting with the observed drop in concentration after 6 hours at room temperature. This is in
effect retardation of hydration reactions because of lower temperature. Fig. H.15 shows an
example of this trend in sulfate ion, where data at 10°C (50°F) and 21°C (70°F) for sample 1CB
is plotted on the right side of the figure.
Furthermore, on the left side of Fig. H.15, the same temperature comparison is shown but for
sample 1CA, which is only different to 1CB in the type of admixture used, and was considered
26
as normal stiffening behavior. It is clearly seen here that the lower temperature does not seem to
have the same effect on sulfate ion concentration observed before. Therefore, the particular
combination of admixture A with these cementitious materials indeed does not seem to represent
a risk of retardation because of lower temperature. When saturation factors for gypsum and
syngenite are considered in the analysis to interpret stiffening characteristics, as explained and
shown in the following sections, the variation in ionic concentrations of pore solutions take a
more practical meaning.
The effect of low temperature on sulfate ion concentration observed for the group described
above (2CA, 2CDA, 2FA, and 1CB) is not observed for samples in the group of mixes exhibiting
normal stiffening rates (1PA, 1PB, 1CA, and 6PA), except for sample 6PA, where sulfate ion
concentration remains relatively high after 6 hours (360 min) at 10°C (50°F).
2-
SO4 ion
2-
SO4 ion
10000
Ionic concentration (ppm)
Ionic concentration (ppm)
10000
8000
6000
4000
50F 1 C A
2000
70F 1 C A
0
1
10
100
1000
10000
Time after mixing (min)
8000
6000
4000
50F 1 C B
2000
70F 1 C B
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.15. Effect of low temperature and type of admixture on sulfate ion concentration for
"slow" mixes
Comparing with mixes at 21°C (70°F), when mixing and curing at 32°C (90°F), sulfate ion
concentration tended to drop earlier than 6 hours after mixing, only after 1 hour, as seen in the
example shown in Fig. H.16. This behavior was observed for all samples in the group that were
selected for testing at 32°C (90°F), i.e. 2PA, 5PA, 5P, and 5PB. The group exhibiting normal
stiffening rates was also tested at 32°C (90°F) as a reference. From this group, the effect on
sulfate ion concentration was also to drop earlier, only after 1 hour after mixing, but to a lesser
degree and starting from a much lower initial sulfate ion concentration. Sample 1PB is shown in
Fig.H.16 as an example of this reference group. In terms of saturation factors, the implication of
sulfate ion concentrations dropping from 6000 ppm to around 2000 ppm is likely less significant
when compared to concentrations dropping from 16000 ppm to also around 2000 ppm. This
means that the level of pore solution super saturation with respect to sulfate-bearing phases like
gypsum and syngenite is much higher at concentrations around 16000 ppm, therefore creating
more potential for precipitation of these phases that would consequently increase early stiffening
problems.
27
Ionic concentration (ppm)
20000
16000
70F 1 P B
12000
90F 1 P B
8000
70F 2 P A
4000
90F 2 P A
0
1
10
100
1000
10000
Time after mixing (min)
Figure H.16. Sulfate ion concentration as a function of time after mixing for pastes 1 and 2 with
admixtures A and B at two temperatures 21ºC (70ºF) and 32ºC (90ºF).
Aside from the individual ionic concentration of the chemical ionic species, calculations can be
made to take into consideration the interactions that these ions have with each other in aqueous
solution, what is known as ionic activity. This ionic activity can be used to calculate the ion
activity products for each phases of interest, such as gypsum, calcium hydroxide, syngenite, etc.
The ion activity products (IAP) are calculated based on the measured ionic concentration using
ionic activities, by multiplying ionic activities of the species present in the phase.
In the following section, the analysis of pore solution data is made based on the calculation of
IAPs and the findings are summarized based on the saturation factors for gypsum, syngenite, and
calcium hydroxide.
Ion Activity Product and Saturation Factor
Introduction
The pore solution chemistry was examined in terms of the ion activity product, IAP. The activity
of each species (ai) is given by;
ai = ciγi
where ci is concentration and γi is activity coefficient of a given species i.
In the following paragraphs, activities of a species are given by it chemical symbol in rounded
parentheses and its concentration in square parentheses e.g. (Ca2+) and [Ca2+]. In order to
determine the activity coefficients, the ion strength, I, has to be determined. This is calculated
from the concentrations of the solution by the following equation;
I = 0.5Σzi2ci
28
where zi is the charge of a given species, and ci its concentration. From this the activity
coefficient (γi) can be calculated by Davies equation:
log γi = -Azi2 (√I/(1+√I)-0.3I))
where A is Debye-Huckel solvent parameter (equal to 0.5).
The (OH-) activity is determined from the pH of the pore solution:
pH = log10(10-14/(OH-))
and is assumed to be equal to its concentration, which was applied as a first approximation for
the concentration to obtain ionic strength and from these the activity coefficients. These values
were used to recalculate the OH- concentration from the relation (OH-)/γOH. The calculations
were repeated in a second iteration and again in a third iteration of the ion strength and activity
coefficients. The results indicated that two iterations are sufficient and the values did not
significantly change on the third iterations. Speciation was not considered.
The IAP was calculated for calcium hydroxide, gypsum and syngenite from the activity of each
species:
IAPCH = (Ca2+)(OH-)2
IAPgyp = (Ca2+)(SO42-)
IAPsyng = (K+)2(Ca2+)(SO42-)2
Refer to Fig. H.17 for a summary of the ion activity product concept.
29
Ion Activity Product, IAP
z
OH- OHCa++
++
Ca
OHOH-
z
z
Ca(OH)2
z
For CH in water at equilibrium (25 oC) the
solution is saturated and the IAP:
(Ca++)(OH-)2 is a constant, KCH=9*10-6
For gypsum, (Ca++)(SO4--), the constant is
KGyp=2.6*10-5
For syngenite, (K+)2(Ca2+)(SO42-)2, the
constant is Ksyng=13.6*10-8
If the value of IAP is smaller than the
saturated value, e.g. KCH, the crystal will
dissolve, if it is larger the crystal will
grow.
Figure H.17. Summary of ion activity product concept.
The IAP was further used to determine the saturation factor (SF) as a measure of the degree of
saturation:
SF = (IAP/Ksp)
Where Ksp is the value of the IAP at saturation. SF = 1 indicates saturation, SF > 1 indicates
supersaturation, and SF < 1 indicates under-saturation. The Ksp values used are 9 x10-6 Mole3
for calcium hydroxide, (2.547+2.258 I) x10-5 Mole2 for gypsum, and (13.9I-0.3) x10-8 Mole5 for
syngenite (Gartner et al., 1985).
As an example of the meaning of SF, consider a gypsum crystal introduced into a solution with
SFgypsum<1. It would dissolve immediately since the solution is under-saturated with respect to
gypsum; and in a solution with SFgypsum>1 it would grow because of the super-saturation.
Applying this to hydrating cement paste or mortar it would be expected that SFgypsum would be
larger than or equal to 1 in the first part of the hydration reactions after mixing cement and water.
The presence of hemi-hydrate and/or alkali sulfates would add to the sulfate concentration in
addition to that from the gypsum, and hydrating calcium silicates will contribute calcium ions to
the solution, so the IAPgypsum = (Ca2+)(SO42-) could be high resulting in a SFgypsum>1. In such
situations there is a potential for precipitation of gypsum leading to change in rheology of the
paste (false setting, etc.). This is depending on the rate with which the aluminate phase reacts in
forming ettringite. Later, as the aluminate phase reacts, and the sulfate is consumed, the SFgypsum
will decrease to below 1 at which time there is no more gypsum present.
30
For cements with high potassium and sulfate content the SFsyngenite may be larger than one in the
pore solution early after mixing and result in a potential for precipitation of syngenite. This will
compete with the aluminate phase for the sulfate and as result calcium aluminate hydrates may
form instead of ettringite causing changes in stiffening behavior.
During the first part of hydration the calcium ion concentration in general increases in the pore
solution and calcium hydroxide, CH, does not precipitate until later. It is therefore to be expected
that SFCH is larger than one. This is the case and in the literature is reported that it stays above
one for a long time (Gartner, et al. 1985).
Pore Solution Chemistry for 2P, 2C, 4P, and 5P, Rounds 1 and 2
The following section shows results from analyses of pore solution from systems without
admixture hydrated at room temperature, 21°C (70 °F).
Gypsum (CaSO4.2H2O):
The SF for all systems are shown in Fig. H.18 and cross the value 1 between 360 and
1440 minutes indicating gypsum is consumed at this time (the point at 30 minutes for 2P is likely
caused by an outlier data point for Ca2+).
The SF for system 4P is the lowest ~2.3 compared to ~6.5 for the others. Hence a greater
potential for precipitation of gypsum and relative faster setting or changed workability for these
systems.
1.00E+02
IAP(gyp)/solubility product
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Gyp. Sat. Fac 2P 2nd
Gyp. Sat. Fac 2C 2nd
Gyp. Sat. Fac 4P 2nd
1.00E-02
Gyp. Sat. Fac 5P 2nd
1.00E-03
1.00E-04
Time after mixing minutes
Figure H.18. Saturation factor for gypsum as a function of time for pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in
these specimens.
31
(SO4--) mole/liter
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
2P
2C
4P
5P
1
10
100
1000
10000
Time after mixing minutes
Figure H.19. Sulfate ion concentrations in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these
specimens.
0.035
2P
2C
4P
5P
0.03
Ca++ mol/liter
0.025
0.02
0.015
0.01
0.005
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.20. Calcium ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these
specimens. Note the low value at 30 minutes for the paste made with cement 2 is a likely outlier.
Syngenite (K2Ca(SO4)2):
As detailed in Fig. H.21, the SF for system 4P is around 1 for the first 10 minutes after mixing
and then becomes smaller than 1, indicating no syngenite is formed as opposed to the other
systems where the SF is around 10, which in turn indicates large potential for syngenite
precipitation with possible change in workability relative to 4P. Between 360 and 1440 minutes
the SF for all systems falls to low values caused by the decrease in sulfate concentration.
32
IAP(syng.)/solubility product
1.00E+02
1.00E+01
1.00E+00
1.00E-01
1
10
100
1000
10000
1.00E-02
1.00E-03
Syng Sat.fac.2P 2n
Syng Sat.fac. 2C nd
Syng Sat.fac. 4P 2nd
Syng Sat.fac. 5P 2nd
1.00E-04
1.00E-05
1.00E-06
Time after mixing minutes
Figure H.21. Saturation factors for syngenite in pore solutions of pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in
these specimens.
1
0.9
(K+) mole/liter
0.8
2P
2C
4P
5P
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.22. Potassium concentration as a function of time for in pore solutions of pastes made
with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were
used in these specimens.
Calcium hydroxide (Ca(OH)2):
The SF values (Fig. H.23) are from 2.5 to about 10 at ten minutes and increase to about 26 for
2C and 5P at 360 minutes. Except for system 2P the SF values decrease between 360 and
1440 minutes. At this time calcium hydroxide is known to be present in hydrating cement
systems so the reason for SF>1 is that Ca2+ still is produced by the on-going hydration and the
(OH-) is high (see Fig. H.20).
33
IAP(Ca(OH)2)/solubility product
1.00E+03
1.00E+02
Sat. Fac CH 2P 2nd
Sat. Fac CH 2C 2nd
1.00E+01
Sat. Fac CH 4P 2nd
Sat. Fac CH 5P 2nd
1.00E+00
1
10
100
1000
10000
1.00E-01
time after mixing minutes
Figure H.23. Saturation factors for calcium hydroxide in pore solutions of pastes made with
portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were
used in these specimens.
1.4
(OH-) mol/liter
1.2
2P
2C
4P
5P
1
0.8
0.6
0.4
0.2
0
1
10
100
1000
10000
Tim e after m ixing m inutes
Figure H.24. Hydroxyl (OH-) ion concentration in pore solutions of pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in
these specimens.
Pore solution chemistry for 2P, 2C, 4P, and 5P with admixture A, rounds 1 and 2
Gypsum:
The addition of the water reducer A, as single, A, and double dosage, DA, causes SFgyp to
increase for all systems except cement 4. The relative position of the plots are the same at all
dosages, and between 360 and 1440 minutes the value decreases to below 1, indicating gypsum
is no longer present in the systems. If a given system had shown tendency for early stiffening or
other quick setting symptoms, the increase in SFgyp by addition of admixture A might indicate
an strengthening of this effect.
34
1.00E+02
IAP(gyp)/solubility product
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Gyp. Sat. Fac 2P 2nd
Gyp. Sat. Fac 2C 2nd
Gyp. Sat. Fac 4P 2nd
1.00E-02
Gyp. Sat. Fac 5P 2nd
1.00E-03
1.00E-04
Time after mixing minutes
Figure H.25. Saturation factors for gypsum in pore solutions of pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in
these specimens. Note the low value at 30 minutes for the paste made with cement 2 is a likely
outlier.
IAP(gyp)/solubility product
1.00E+02
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Gyp. Sat. Fac. 2PA
Gyp. Sat. Fac. 2CA
Gyp. Sat. Fac. 4PA
Gyp. Sat. Fac. 5PA
1.00E-02
1.00E-03
1.00E-04
Time after mixing minutes
Figure H.26. Saturation factors for gypsum in pore solutions of pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.
IAP(gyp)/solubility product
1.00E+02
1.00E+01
1.00E+00
1
10
100
1000
1.00E-01
1.00E-02
1.00E-03
Gyp. Sat. Fac. 2PDA 2nd
Gyp. Sat. Fac. 2CDA 2nd
Gyp. Sat. Fac.4PDA 2nd
Gyp. Sat. Fac.5PDA 2nd
1.00E-04
Time after mixing minutes
35
10000
Figure H.27. Saturation factors for gypsum in pore solutions of pastes made with portland
cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.
The sulfate concentration is not changed by the addition of admixture A (see Figs. H.29 and
H.30), the increase in SFgyp is caused by increase in the Ca2+ concentration (see Figs. H.20, H.31
and H.32).
(SO4--) mole/liter
0.2
0.15
2P
2C
4P
5P
0.1
0.05
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.28. Sulfate ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these
specimens.
0.2
0.18
(SO4--) mole/liter
0.16
0.14
2PA
2CA
4PA
5PA
0.12
0.1
0.08
0.06
0.04
0.02
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.29. Sulfate ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.
36
0.2
0.18
(SO4--) mole/liter
0.16
0.14
2PDA
2CDA
4PDA
5PDA
0.12
0.1
0.08
0.06
0.04
0.02
0
1
10
100
1000
10000
Time after mixing minutes
(Ca++) mole/liter
Figure H.30. Sulfate ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.
0.035
2PA
0.03
2CA
4PA
0.025
5PA
0.02
0.015
0.01
0.005
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.31. Calcium ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.
(Ca++) Mole/liter
0.035
0.03
2PDA
0.025
2CDA
4PDA
0.02
5PDA
0.015
0.01
0.005
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.32. Calcium ion concentration in pore solutions of pastes made with portland cements 2,
4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.
37
It is interesting to note that the Ca2+ concentration for cement 5 does not change with addition of
admixture A, where it increases by addition of A and then decreases to the original level by
double addition of A (DA) for cement 4. (The variation in the Ca2+ concentration at 10 and
30 minutes for system 2P is due to outlier data points.)
Syngenite:
For cement 4 the effect of adding admixture A as single or double dosage is to decrease the
SFsyn, it is however below 1 indicating no syngenite is present. For the other systems the SFsyn
changes from 21 to 5 to 15 at 10 minutes by addition of a single dosage, and increases to about
27 by double dosage.
IAP(syng.)/solubility product
1.00E+02
1.00E+01
1.00E+00
1.00E-01
1
10
100
1000
10000
1.00E-02
1.00E-03
Syng Sat.fac.2P 2n
Syng Sat.fac. 2C nd
Syng Sat.fac. 4P 2nd
Syng Sat.fac. 5P 2nd
1.00E-04
1.00E-05
1.00E-06
Time after mixing minutes
Figure H.33. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5,
and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.
IAP(syng)/solubility product
1.00E+02
1.00E+01
1.00E+00
1.00E-01
1
10
100
1000
10000
1.00E-02
1.00E-03
1.00E-04
1.00E-05
Syng.Sat.fac.4PA
Syng.Sat.fac. 5PA
Syng.Sat.fac. 2PA
Syng.Sat.fac. 2CA
1.00E-06
Time after mixing minutes
Figure H.34. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5,
and cement 2 with class C fly ash, and single dosage of admixture A.
38
iap(syng)/solubility product
1.00E+02
1.00E+01
1.00E+00
1.00E-01
1
10
100
1000
10000
1.00E-02
1.00E-03
1.00E-04
1.00E-05
Syng Sat.fac. 2PDA 2nd
Syng Sat.fac. 2CDA 2nd
Syng Sat.fac. 4PDA 2nd
Syng Sat.fac. 5PDA 2nd
1.00E-06
Time after mixing minutes
Figure H.35. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5,
and cement 2 with class C fly ash, and double dosage of admixture A.
Thus, relative to cement 4, these systems might have a tendency for early stiffening which, based
on the potential for precipitation of syngenite, compared to systems with no addition may be less
pronounced with addition a single dosage, and stronger with double dosage.
Calcium Hydroxide:
By adding admixture A the SFCH increases for all systems of which cement 4 has the lowest SFvalues. The Ca2+ concentrations generally decrease and the increase in SF-values is caused by
the continued increase in OH- concentration.
1.00E+03
IAP(Ca(OH)2)/solubility product
Sat. Fac CH 2P 2nd
Sat. Fac CH 2C 2nd
1.00E+02
Sat. Fac CH 4P 2nd
Sat. Fac CH 5P 2nd
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
time after mixing minutes
Figure H.36. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4,
and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.
39
1.00E+03
IAP(CH)7solubilita product
Sat. Fac CH 2PA
Sat. Fac CH 2CA
1.00E+02
Sat. Fac CH 4PA
Sat. Fac CH 5PA
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Time after mixing minutes
Figure H.37. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4,
and 5, and cement 2 with class C fly ash, and single dosage of admixture A.
IAP(CH)/solubility product
1.00E+03
Sat. Fac CH 2PDA 2nd
Sat. Fac CH 2CDA 2nd
Sat. Fac CH 4PDA 2nd
1.00E+02
Sat. Fac CH 5PDA 2nd
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Time after mixing minutes
Figure H.38. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4,
and 5, and cement 2 with class C fly ash, and double dosage of admixture A.
1.4
(OH-) mol/liter
1.2
2P
2C
4P
5P
1
0.8
0.6
0.4
0.2
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.39. Hydroxyl ion concentration in pore solutions of pastes made with portland cements
2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these
specimens.
40
1.4
(OH-) mol/liter
1.2
2PA
2CA
4PA
5PA
1
0.8
0.6
0.4
0.2
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.40. Hydroxyl ion concentration in pore solutions of pastes made with portland cements
2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.
1.4
2PDA
2CDA
4PDA
5PDA
(OH-) Mole/liter
1.2
1
0.8
0.6
0.4
0.2
0
1
10
100
1000
10000
Time after mixing minutes
Figure H.41. Hydroxyl ion concentration in pore solutions of pastes made with portland cements
2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.
Pore Solution Chemistry for 2P, 2C, 4P, and 5P with Admixture B, Rounds 1 and 2
The variations of SF-values for systems with addition of water reducer B are similar to those
with addition of a single dosage A.
Pore Solution Chemistry for Selected Systems Hydrated at 90 oF, Round 31
Based on rounds 1 and 2 four systems considered "Fast" and four systems considered "Normal"
with respect to workability were selected for testing at 32°C (90°F). The "Fast" systems were
2PA, 5PA, 5PB and 5P; the "Normal" systems were 1PA, 1CA, 1PB and 6PA.
1
The SF values at 32ºC (90ºF) and 10ºC (50ºF) are calculated using the room temperature value of the
ion activity product at saturation for the relevant compound.
41
Gypsum & Syngenite:
For the period up to about 60 minutes for the systems treated at 32°C (90°F) and to 360 minutes
for systems treated at 21°C (70°F), the SF values are generally highest for the "fast" systems. For
the "fast" systems SFgyp >5 and for the "normal" systems SFgyp <3, and the temperature increase
has only small effect on the saturation factor. The SFsyn for the "fast" systems is around 10,
whereas it is ~1 or smaller for the "normal" systems. This reflects the general high potential for
the "fast" systems to precipitate gypsum and syngenite during the first period of hydration.
Comparing the two systems the difference in SFgyp might be an indicator of whether a system
will exhibit changes in workability in a negative way.
The effect of temperature is the earlier drop in SF values for the systems treated at 32°C (90°F)
compared to those treated at 21°C (70°F) which is reflecting the higher hydration rates caused by
the higher temperature. The hydration of C3A forming AFt (and AFm) is accelerated by the
temperature increase, and as a result the sulfate of the pore solution is depleted earlier.
1.00E+01
IAP(gyp)/solubility product
70
1.00E+00
1
10
100 90
1000
10000
1.00E-01
Gyp. Sat. Fac. 2PA
Gyp. Sat. Fac. 5PA
Gyp. Sat. Fac 5P 2nd
Gyp. Sat. Fac. 5PB
Gyp. Sat. Fac 2PA 3rd
Gyp. Sat. Fac 5PA 3rd
Gyp. Sat. Fac 5P 3rd
Gyp. Sat. Fac 5PB 3rd
1.00E-02
1.00E-03
Time after mixing minutes
Figure H.42. Saturation factors for gypsum in pore solutions of “fast” pastes treated at 21°C (70°F)
and 32°C(90°F).
IAP(gyp)/solubility product
1.00E+01
70 F
1.00E+00
1
10
100
90 F
1.00E-01
1.00E-02
Gyp. Sat. Fac 1PA
Gyp. Sat. Fac 1CA
Gyp. Sat. Fac. 6PA
Gyp. Sat. Fac. 1PB 2nd
Gyp. Sat. Fac. 1PA 3rd
Gyp. Sat. Fac. 1CA 3rd
Gyp. Sat. Fac.1PB 3rd
Gyp. Sat. Fac.6PA 3rd
1.00E-03
Time after mixing minutes
42
1000
10000
Figure H.43. Saturation factors for gypsum in pore solutions of “normal” pastes treated at 21°C
(70°F) and 32°C(90°F).
1.00E+02
IAP((syng)/solubility product
1.00E+01
90
1.00E+00
70
1
1.00E-01
10
100
1000
10000
Syng.Sat.fac. 2PA
Syng.Sat.fac. 5PA
Syng Sat.fac. 5P 2nd
Syng Sat.fac. 5PB 2nd
Syng. Sat.fac.2PA 3rd
Syng. Sat.fac. 5PA 3rd
Syng. Sat.fac. 5P 3rd
Syng. Sat.fac. 5PB 3rd
1.00E-02
1.00E-03
1.00E-04
1.00E-05
time after mixing minutes
Figure H.44. Saturation factors for syngenite in pore solutions of “fast” pastes treated at 21°C
(70°F) and 32°C(90°F).
1.00E+02
IAP(syng)/solubility product
1.00E+01
1.00E+00
1
10
100
90 F
1.00E-01
1.00E-02
1.00E-03
1.00E-04
70
F
1000
10000
Syng.Sat.fac.1PA
Syng.Sat.fac. 1CA
Syng.Sat.fac. 6PA
Syng Sat.fac.1PB 2nd
Syng. Sat.fac. 1PA 3rd
Syng. Sat.fac. 1CA 3rd
Syng. Sat.fac. 1PB 3rd
Syng. Sat.fac. 6PA 3rd
1.00E-05
Time after mixing minutes
Figure H.45. Saturation factors for syngenite in pore solutions of “normal” pastes treated at 21°C
(70°F) and 32°C(90°F).
Calcium Hydroxide:
The SFCH for the "fast" systems increases as a result of the temperature change from 21 to 32°C
(70 to 90°F). For 21°C (70°F) at 5 minutes the values are from 5 to 15 and increases slowly to
between 13 and 30 at 360 minutes, where after they decrease to between 9 and 20 (the value for
5P may be an outlier result). By increasing the temperature to 32°C (90°F) the SF values all
increase.
For the "normal" systems the SF values for 1PA and 1CA two increase and decrease for 6PA and
1PB and as a result all the SF-values are in a relative narrow band at 32°C (90°F).
43
IAP(CH)/solubility product
1.00E+03
Sat. Fac CH 2PA
Sat. Fac CH 5PA
Sat. Fac CH 5P 2nd
Sat. Fac CH 5PB 2nd
Sat. Fac CH 2PA 3rd
Sat. Fac CH 5PA 3rd
Sat. Fac CH 5P 3rd
Sat. Fac CH 5PB 3rd
1.00E+02
1.00E+01
1.00E+00
1
10
100
1000
10000
Arrows indicate direction from 70 to 90 deg F
1.00E-01
Time after mixing minutes
Figure H.46. Saturation factors for calcium hydroxide in pore solutions of “fast” pastes treated at
21°C (70°F) and 32°C(90°F).
IAP(CH)/solubility product
1.00E+03
Sat. Fac CH 1PA
Sat. Fac CH 1CA
Sat. Fac CH 6PA
Sat. Fac CH 1PB 2nd
Sat. Fac CH 1PA 3rd
Sat. Fac CH 1CA 3rd
Sat. Fac CH 1PB 3rd
Sat. Fac CH 6PA 3rd
1.00E+02
1.00E+01
1.00E+00
1
10
100
1000
10000
Arrows indicate direction from 70 to 90 deg F
1.00E-01
Time after mixing minutes
Figure H.47. Saturation factors for calcium hydroxide in pore solutions of “normal” pastes treated
at 21°C (70°F) and 32°C(90°F).
Pore Solution Chemistry for Selected Systems Hydrated at 50 °F, Round 4
Four systems, 2CA, 2FA, 2CDA, 1B considered “slow”, were selected together with the
"normal" systems for testing at 10°C (50°F).
Gypsum:
"Slow" systems: Up to 360 minutes the SFgyp for 1CB at 21°C (70°F) is around 2. The remainder
of the systems have SF-values from around 5 to 13. After 360 minutes all the 21°C (70°F)
treated samples decrease sharply, whereas the 10°C (50°F) treated systems only decrease slightly
44
and stay larger than SF=1. This is reflecting the retardation in hydration reactions due to the
lower temperature.
"Normal" systems: The SF-values are generally lower than for the "slow" systems, except for
two: 1CA and 6PA treated at 10°C (50°F), all the other values are within a narrow interval and at
level with 1CB described above. Only 6PA treated at 10°C (50°F) has SFgyp>1 after 360 minutes.
1.00E+02
IAP(gyp)/sol.prod.
1.00E+01
50
F
1.00E+00
1
10
100
701000
F
10000
1.00E-01
Gyp. Sat. Fac 2CA 4th
Gyp. Sat. Fac 2FA 4th
Gyp. Sat. Fac2CDA 4th
Gyp. Sat. Fac1CB 4th
Gyp. Sat. Fac. 2CA
Gyp. Sat. Fac. 2FA
Gyp. Sat. Fac. 2CDA 2nd
Gyp. Sat. Fac. 1CB 2nd
1.00E-02
1.00E-03
1.00E-04
Time aftwer mixing minutes
Figure H.48. Saturation factors for gypsum in pore solutions of “slow” pastes treated at 21°C
(70°F) and 10°C(50°F).
1.00E+02
IAP(gyp)/sol. prod.
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
1.00E-02
1.00E-03
Gyp. Sat. Fac. 1PA 4th
Gyp. Sat. Fac. 1CA 4th
Gyp. Sat. Fac.1PB 4th
Gyp. Sat. Fac.6PA4th
Gyp. Sat. Fac 1PA
Gyp. Sat. Fac 1CA
Gyp. Sat. Fac. 6PA
Gyp. Sat. Fac. 1PB 2nd
1.00E-04
Time after mixing minutes
Figure H.49. Saturation factors for gypsum in pore solutions of “normal” pastes treated at 21°C
(70°F) and 10°C(50°F).
Syngenite:
"Fast" systems: The SF-values are in a band from around 4 to around 10. An exception is 1CB
treated at both temperatures with SFsyn < 1 indicating no syngenite can form. The other exception
is system 2CDA treated at 21°C (70°F) with SF-values around 30. After 360 minutes all values
decrease to below 1.
45
1.00E+02
1.00E+01
50 F
1.00E+00
IAP(syn)/sol. prod.
1
10
100
1000
10000
1.00E-01
Syng. Sat.fac.2CA 4th
Syng. Sat.fac. 2FA 4th
Syng. Sat.fac.2CDA 4th
Syng. Sat.fac. 1CB 4th
Syng.Sat.fac. 2CA
Syng.Sat.fac. 2FA
Syng Sat.fac. 2CDA 2nd
Syng Sat.fac. 1CB 2nd
1.00E-02
1.00E-03
1.00E-04
1.00E-05
70 F
1.00E-06
Time after mixing minutes
Figure H.50. Saturation factors for gypsum in pore solutions of “slow” pastes treated at 21°C
(70°F) and 10°C(50°F).
1.00E+02
1.00E+01
IAP(syn)/sol. prod.
1.00E+00
1
10
100
1000
10000
1.00E-01
50 F
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
Syng. Sat.fac. 1PA 4th
Syng. Sat.fac. 1CA 4th
Syng. Sat.fac. 1PB 4th
Syng. Sat.fac. 6PA 4th
Syng.Sat.fac.1PA
Syng.Sat.fac. 1CA
Syng Sat.fac.1PB 2nd
Syng.Sat.fac. 6PA
70 F
Time after mixing minutes
Figure H.51. Saturation factors for syngenite in pore solutions of “normal” pastes treated at 21°C
(70°F) and 10°C(50°F).
Calcium Hydroxide:
"Slow" systems: The SFCH in general increases for the “slow” systems as temperature changes
from 21 to 10°C (70 to 50°F). Contrary to the 21°C (70°F) treated systems, the 10°C (50°F)
treated systems do not show any decrease in SF-values after 360 minutes. This could be caused
by the lower rate of hydration reactions.
"Normal" systems: The situation is a bit more complicated for these systems. For two systems,
1PA, and 1CA, the level of SF-values increases, and for 6PA and 1PB it decreases.
46
1.00E+03
Sat. Fac CH 1PA 4th
Sat. Fac CH 1CA 4th
Sat. Fac CH 1PB4th
Sat. Fac CH 6PA 4th
Sat. Fac CH 1PA
Sat. Fac CH 1CA
Sat. Fac CH 6PA
Sat. Fac CH 1PB 2nd
IAP(CH)/sol. prod.
1.00E+02
1.00E+01
1.00E+00
1
10
100
1000
10000
1.00E-01
Arrows indicate 70 - 50 oF
1.00E-02
time after mixing minutes
Figure H.52. Saturation factors for calcium hydroxide in pore solutions of “normal” pastes treated
at 21°C (70°F) and 10°C(50°F).
1.00E+03
50 F
1.00E+02
IAP(CH)/sol.prod.
70 F
1.00E+01
Sat. Fac CH 2CA 4th
Sat. Fac CH 2FA 4th
Sat. Fac CH 2CDA 4th
Sat. Fac CH 1CB 4th
Sat. Fac CH 2CA
Sat. Fac CH 2FA
Sat. Fac CH 2CDA 2nd
Sat. Fac CH 1CB 2nd
1.00E+00
1
10
100
1000
10000
1.00E-01
1.00E-02
Time after mixing minutes
Figure H.53. Saturation factors for calcium hydroxide in pore solutions of “slow” pastes treated at
21°C (70°F) and 10°C(50°F).
Pore Solution Chemistry for the "Normal" Systems Treated at 50, 70 and 90oF
In the following section the SF-values for the systems 1PA, 1CA, 1PB and 6PA treated at 10, 21
and 32°C (50, 70 and 90°F) are compared.
Gypsum:
The SFgyp for all systems treated at 32°C (90°F) decreases after 60 minutes compared to systems
treated at the other temperatures where the SFgyp decreases after 360 minutes. This is caused by
the accelerated hydration reactions due to increased temperature.
For 1CA and 6PA the SFgyp values are about the same at 5 minutes for all temperatures. Then
they decrease for the 21°C and 32°C (70°F and 90°F) treated systems but stay the same or
increase for the 10°C (50°F) treated systems until about 60 minutes from when they slowly
decrease. This behavior could be explained by the retardation in hydration reactions at 10°C
47
(50°F); and the slight increase for 1CA could be caused by sulfate containing phases still
dissolving. The two other systems show a similar behavior, however to a much smaller effect.
The higher values of the SFgyp for the 10°C (50°F) treated systems indicate a higher potential for
precipitation of gypsum at early times after mixing relative to the systems treated at higher
temperatures. The same effect that slows the hydration reaction down may possibly also slow
down the nucleation and/or growth of gypsum crystals, and as result no change in the workability
may be observed.
1.00E+02
1.00E+01
IAP(gyp)/sol. prod.
50 F
1.00E+00
1
10
100
90 F
1.00E-01
1000
10000
70 F
Gyp. Sat. Fac 1PA
Gyp. Sat. Fac. 1PA 3rd
Gyp. Sat. Fac. 1PA 4th
1.00E-02
1.00E-03
Time after mixing minutes
Figure H.54. Saturation factors for gypsum in pore solutions of pastes made with cement 1 and
single dose of admixture A, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
1.00E+02
1.00E+01
IAP(gyp)/sol. prod.
50 F
70 F
1.00E+00
1
10
100
90 F
1000
10000
1.00E-01
1.00E-02
Gyp. Sat. Fac 1CA
Gyp. Sat. Fac. 1CA 3rd
Gyp. Sat. Fac. 1CA 4th
1.00E-03
Time after mixing minutes
Figure H.55. Saturation factors for gypsum in pore solutions of pastes made with cement 1, single
dose of admixture A, and class C fly ash, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
48
1.00E+02
IAP(gyp)/sol. prod.
1.00E+01
50 F
90 F
1.00E+00
1
10
100
1000
10000
70 F
1.00E-01
Gyp. Sat. Fac. 6PA
Gyp. Sat. Fac.6PA 3rd
Gyp. Sat. Fac.6PA4th
1.00E-02
1.00E-03
Time after mixing minutes
Figure H.56. Saturation factors for gypsum in pore solutions of pastes made with cement 6 and
single dose of admixture A, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
1.00E+02
IAP(gyp)/sol. prod.
1.00E+01
1.00E+00
1
10
100 90 F
1000
70 F
10000
50 F
1.00E-01
1.00E-02
Gyp. Sat. Fac. 1PB 2nd
Gyp. Sat. Fac.1PB 3rd
Gyp. Sat. Fac.1PB 4th
1.00E-03
Time after mixing minutes
Figure H.57. Saturation factors for gypsum in pore solutions of pastes made with cement 1, single
dose of admixture B and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
Syngenite:
All the SFsyng values are around 1, which means that syngenite as crystalline phase cannot exist
in these systems.
Calcium Hydroxide:
No clear trend is seen for the SFCH values. For 1PA, the SFCH for the 10°C (50°F) treated system
is around 10 times higher than for the 21°C (70°F) treated system, and for the 32°C (90°F)
treated system it is about 5 times higher. For 1CA the 10°C (50°F) as well as 32°C (90°F) values
of SFCH are between 10 and 15 times larger than the 21°C (70°F) values.
49
For 1PB the 21°C (70°F) values are the highest. The 32°C (90°F) values are about 0.5 times the
21°C (70°F) values, and the 10°C (50°F) values are about 0.1 times the 21°C (70°F) values. The
system 1PA is somewhat similar to 1PB, the 21°C (70°F) values are the highest.
1.00E+03
IAP(CH/solubility product
1.00E+02
50 F
90 F
1.00E+01
70 F
1.00E+00
1
1.00E-01
10
100
1000
10000
Sat. Fac CH 1PA
Sat. Fac CH 1PA 3rd
Sat. Fac CH 1PA 4th
1.00E-02
time after mixing minutes
Figure H.58. Saturation factors for calcium hydroxide in pore solutions of pastes made with
cement 1, single dose of admixture A and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
1.00E+03
1.00E+02
IAP(CH)/sol. prod.
50 F
90 F
1.00E+01
70 F
1.00E+00
1
1.00E-01
10
100
1000
10000
Sat. Fac CH 1CA
Sat. Fac CH 1CA 3rd
Sat. Fac CH 1CA 4th
1.00E-02
time after mixing minutes
Figure H.59. Saturation factors for calcium hydroxide in pore solutions of pastes made with
cement 1, class c fly ash, single dose of admixture A, and treated at 10°C(50°F), 21°C (70°F), and
32°C (90°F).
50
1.00E+03
IAP(CH)/sol. prod.
1.00E+02
70 F
90 F
1.00E+01
50 F
1.00E+00
1
10
100
1000
10000
1.00E-01
Sat. Fac CH 6PA
Sat. Fac CH 6PA 3rd
Sat. Fac CH 6PA 4th
1.00E-02
Time after mixing minutes
Figure H.60. Saturation factors for calcium hydroxide in pore solutions of pastes made with
cement 6, single dose of admixture A and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
1.00E+03
IAP(CH)/sol. prod.
1.00E+02
70 F
90 F
50 F
1.00E+01
1.00E+00
1
1.00E-01
10
100
1000
10000
Sat. Fac CH 1PB 2nd
Sat. Fac CH 1PB 3rd
Sat. Fac CH 1PB4th
1.00E-02
Time after mixing minutes
Figure H.61. Saturation factors for calcium hydroxide in pore solutions of pastes made with
cement 1, single dose of admixture B and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).
51
Summary
Based on the results from analysis of pore solutions, the pore solution chemistry was examined
for a selected number of cementitious systems without and with chemical admixtures and at
different temperatures. In most cases the systems were examined at 21°C (70°F). Systems
considered "fast" in regards to their stiffening characteristics were studied at 21°C and 32°C
(70°F and 90°F). Systems considered "slow" were studied at 21°C and 10°C (70°F and 50°F). In
both cases they were compared with the same set considered "normal".
The setting or stiffening behavior of hydrating portland cement or cements with SCMs during the
first ~10 minutes after mixing cement and water, is generally attributed to the reactions involving
the C3A and the sulfate from the added gypsum and from alkali sulfates in the clinker. In cases
when the system is not in "balance" with respect to these reactions changes in rheology of the
mixture may result, and the mixture may exhibit "early stiffening," "false setting" or "flash
setting." The false setting is related to precipitation of gypsum due to a high concentration of
sulfate in the pore solution. Flash setting is the result of too little sulfate available in the pore
solution and caused by formation of C3A hydrates instead of ettringite, which is the normal
hydration product.
Early after mixing, the concentration of the constituent ions in pore solution varies according to
the specific cement. For example for cements high in alkali sulfates the concentration of sulfate
ions as well as alkali ions will be high. At the same time the hydration of the C3S will contribute
calcium ions as well as hydroxyl ions to the pore solution. In special cases where the
concentration of sulfate and calcium ions are high, the pore solution can be super-saturated with
respect to for example gypsum, and this may cause gypsum to precipitate. The criteria for this is
whether the so-called solubility product for gypsum is higher than corresponding to gypsum in
equilibrium with the pore solution, which in this case is said to be saturated with respect to
gypsum. The solubility product of gypsum is calculated according to Kgyp = [Ca2+][SO42-], where
[Ca2+] and [SO42-] are the concentrations of calcium ions and sulfate ions respectively in the pore
solution. Solubility products for other compounds can be calculated in similar ways, and for
saturated solutions the solubility product at a given temperature are constants specific for the
considered compound. Strictly taken, “activity” should be used instead of “concentration”.
Activity is another measure of concentrations, which takes the presence of other ionic
constituents of the pore solution into consideration, and ion activity product, IAP, is used instead
of solubility product. For gypsum it is
IAPgyp = (Ca2+)(SO42-),
where (Ca2+) and (SO42-) respectively are the activities of the calcium ions and the sulfate ions of
the pore solution, and these can be calculated from the total composition of the pore solution.
One way to characterize the pore solution regarding possible super-saturation with respect to for
example gypsum or other constituents is to define the saturation factor, SF, as the ratio between
the actual IAPgyp of the pore solution and the corresponding value for the saturated condition.
52
SF values larger than 1 indicate super-saturation, SF=1 corresponds to the saturated solution, and
for SF smaller than 1 the solution is under-saturated. A crystal cannot exist in a solution with
SF<1, it is not stable and will dissolve. In a solution with SF>1 it will grow, it cannot dissolve.
For the selected systems the saturation factors for gypsum (CaSO4•2H2O), SFgyp, syngenite
(K2Ca(SO4)2•H2O), SFsyn, and calcium hydroxide (Ca(OH)2), SFCH, were studied. Syngenite is a
potassium-calcium-sulfate that can precipitate in systems with cements with high sulfate and
potassium concentrations.
For cement pastes of grey and white portland cement it is known from the literature (Gartner, et
al. 1985, Rothstein, et al. 2002) that SFgyp and SFsyn can be larger than one for up to about
10 hours or later and SFCH is larger than 1 for up to 28 days or more. The super-saturation of
gypsum is related to the dehydration of gypsum to hemihydrate (plaster of Paris) in commercial
cements during grinding. The plaster is much more soluble than gypsum and can deliver sulfate
to the pore solution faster than it can be consumed by the reaction with C3A phase. Extra sources
of sulfate like alkali sulfates can contribute to the super-saturation situation as well. The reason
for the prolonged super saturation with respect to calcium hydroxide is probably the continued
hydration of C3S and C2S.
Water reducers are in many ways similar to retarders. Taylor (1991) makes references to work
showing that calcium ion concentration and hydroxyl ion concentrations increase in pore solution
when such chemical admixtures are used. The mechanism is probably that they modify the
reaction products by being adsorbed, and allow the calcium ion concentration in solution to be
higher than in pore solutions with the unmodified hydration product.
For the 4 systems 2P, 2C, 4P, and 5P (no admixture) considered "early", in terms of their
stiffening behavior at 21°C (70°F), the SFgyp values for 2P, 2C, and 5P were similar ~6.5 and for
4P it was ~2.5 without any significant change up to 360 minutes. After this time all values
decreased to below 1, signaling all gypsum had been consumed. During the period from mixing
until 360 minutes the SFgyp values indicate super-saturation and hence a potential for
precipitation of gypsum with possible effect on the workability. The super-saturation in 4P is
lower than in the other systems and it would be expected that this system would show less early
stiffening compared to the others.
With regards to the SFsyn system 4P again is the lowest: around 1 up to 10 minutes and then for
later times smaller than 1, indicating no presence of syngenite. This makes sense since cement
4P is low in potassium. The other systems all have SFsyn higher than 10 indicating potential for
precipitation of syngenite, which can cause same effects as precipitation of gypsum. Since it is a
sulfate-bearing phase, it might compete with the C3A for the sulfate ion in the pore solution and
cause flash set (Taylor 1991).
Regarding calcium hydroxide the SFCH values for 4P again is the lowest of the set, with values
from 2.5 increasing to about 10 at 360 minutes after which time it decreases but maintain values
>1. The other systems have values from around 9 increasing to 26 at 360 minutes. As mentioned
above the pore solution is expected to be super-saturated by calcium hydroxide for some time
after mixing. But the individual differences in super-saturation cannot be explained at this time.
The reasons can be many: Different reactivity of the clinker minerals of the cement contributing
53
calcium ions and hydroxyl ions at different rate to the pore solution, effect of alkalies on the
calcium ion concentration, different ratios between calcium and silica in the calcium-silicatehydrate formed during the early hydration process.
Addition of water reducers A and B (single (A) and double dosage (DA) of A and single dosage
of B) generally resulted in increase of the hydroxyl ion concentration of the pore solution for all
systems and in calcium ion concentration except for 4PA and 4PDA. The SFgyp for 4PA and
4PDA was not changed significantly, but for the other systems it increased with increasing
addition of water reducer A. Addition of B had similar effect as addition of a single dosage A.
This indicates increasing tendency for early setting with increasing addition of water reducer. For
SFsyn the addition of water reducers had similar effects.
For SFCH the addition of water reducer had an effect for all systems: the SFCH increased with
increasing addition. The increases in SF values are in line with the findings reported in literature
referred to above. However the effect of the super-saturation with respect to calcium hydroxide
on the early stiffening behavior is not understood.
One set considered "Fast": 2PA, 5PA, 5PB and 5P, and a set considered "Normal": 1PA, 1CA,
1PB and 6PA at 21°C (70°F), were additionally tested at 32°C (90ºF). Up to 60 minutes after
mixing the "fast" systems have higher SFgyp and SFsyn values than the "normal.” The "fast" have
SFgyp>5 and the "normal" <3. Changing the temperature from 21 to 32°C (70 to 90°F) has only
small effect on the level of individual SF values until about 60 minutes after mixing. Then the
SFgyp and SFsyn values decrease to smaller than 1 for the 32°C (90ºF) treated systems. This
indicates
•
The "fast" systems have higher potential for precipitation of gypsum and syngenite
with the possible effects on workability and early stiffening behavior,
•
The higher temperature accelerates hydration of C3A and hence the consumption of
gypsum at a much earlier time. This will for both the "fast" and "formal" set lead to
shorter setting time in general.
The SFsyn values for the "normal" systems are around or below 1 in all cases indicating the nonexistence of syngenite and hence no negative effect of this phase on the rheology. For the SFCH
no clear tendency was observed other than that of the "fast" systems increased at 32°C (90°F)
relative to 21°C (70°F).
Four systems considered "slow" at 21ºC (70ºF): 2CA, 2FA, 2CDA, and 1B together with
"normal" systems mentioned above were tested at 10°C (50°F). Regarding the gypsum the SFgyp
values for the "slow" systems with the exception of 1CB were around 10 to 14 and the "normal”
systems slightly lower. The effect of decreasing the temperature from 21ºC to 10°C (70 ºF to
50ºF) was a slight increase in SF values for the "slow" as well as the "normal" set up to
360 minutes after mixing. With the exception of 6PA, after this time the SFgyp values for the
"normal" systems decreased to less than 1, indicating total consumption of gypsum; but the SFgyp
values for the "slow" system treated at 10°C (50°F) remained almost un-changed at their levels
larger than one indicating that gypsum still was present at 1440 minutes after mixing. For the
"slow" set the SFsyn behavior was similar. The values for the system 1CB indicated no existence
54
of syngenite either at 21°C or 10°C (70°F or 50°F), which was also the case for the "normal"
systems. No clear trend could be observed regarding calcium hydroxide.
Based on the study of saturation factors with respect to gypsum, syngenite and calcium
hydroxide the following findings can be summarized:
•
Addition of water reducers results in an increase in the saturation factors for gypsum,
syngenite, and calcium hydroxide in the systems studied.
•
For "fast" systems treated at 32°C (90oF), the saturation factors for gypsum and
syngenite were not affected until after 60 minutes after mixing comparing to those of
samples treated at 21°C (70oF). After 60 minutes the 32°C (90oF) saturation factors
decreased to below one, indicating total consumption of gypsum. When treated at
21°C (70oF) this change took place after 360 minutes after mixing.
•
Treating "slow" systems at 10°C (50oF) had only minor effect on the saturation
factors for gypsum and syngenite up to 360 minutes after mixing when compared to
samples treated at 21°C (70oF). After 360 minutes the saturation factors decreased to
below 1 for samples treated at 21°C (70oF) indicating the presence of gypsum at least
up to 1440 minutes after mixing.
•
Comparison of "fast" and "normal" systems showed that the levels of gypsum
saturation factors were highest for the "fast." The difference in saturation factor
values might be an indicator of whether a system could be considered “fast” or
“normal”. However when comparing "normal" with "slow" systems the gypsum
saturation factors for the "slow" are slightly higher than for the “normal.” Based on
the present study it is not possible to characterize early stiffening behavior based
solely on pore solution chemistry.
REFERENCES
Barneyback, Jr., R. S.; Alkali-Silica Reaction in Portland Cement Concrete, Ph.D. Thesis,
Purdue University, 1987, 256 pages.
Tang, F. J. and Bhattacharja, S.; Development of an Early Stiffening Test, RP346, Portland
Cement Association, Skokie, Illinois, 1997, 94 pages.
Gartner, E. M.; Tang, F. J.; and Weiss, Stuart J.; “Saturation Factors for Calcium Hydroxide and
Calcium Sulfates in Fresh Portland Cement Pastes,” Journal of the American Ceramic Society,
Vol. 68, No. 12, 1985, pages 667 to 673.
Rothstein, D.; Thomas, J.; Christensen, B. J.; Jennings, H. M.; “Solubility behavior of Ca-, S-,
Al-, and Si-bearing solid phases in Portland cement pore solutions as a function of hydration
time,” Cement and Concrete Research, Vol. 32, 2002, pages 1663 to 1671.
55
Tang, F. J.; Gartner, E. M.; “Influence of Sulphate Source on Portland Cement Hydration,”
Advances in Cement Research, Vol. 1, No. 2, April 1988, pages 67 to 74.
56
APPENDIX I – RING SHRINKAGE GRAPHS
Introduction: Detailed information on the ring shrinkage tests is found on pages 20 and 98 of
Volume I of this series:
Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris,
C.F.; Identifying Incompatible Combinations of Concrete Materials: Volume I—Final
Report, FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA,
August, 2006, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.
57
0.0
#1
Strain, millionths
-20.0
-40.0
1
2
3
4
5
-60.0
9/20/04
9/22/04
9/24/04
9/26/04
9/28/04
9/30/04
10/2/04
10/4/04
10/6/04
10/8/04
10/10/04
Date, time
Figure I.1. Plots of Strain Gage Data for 5 Samples From Mix WRA1
0.0
#2
Strain, millionths
-20.0
-40.0
1
2
3
4
5
-60.0
8/31/04
9/2/04
9/4/04
9/6/04
9/8/04
9/10/04
9/12/04
9/14/04
Date, time
Figure I.2. Plots of Strain Gage Data for 5 Samples From Mix WRA2
58
0
#3
Strain, millionths
-20
-40
1
2
3
4
5
-60
10/4/04
10/6/04
10/8/04
10/10/04 10/12/04 10/14/04 10/16/04 10/18/04 10/20/04 10/22/04 10/24/04
Date, time
Figure I.3. Plots of Strain Gage Data for 5 Samples From Mix FA1
0
#4
Strain, millionths
-20
-40
1
2
3
4
-60
10/11/04
10/13/04
10/15/04
10/17/04
10/19/04
10/21/04
10/23/04
10/25/04
10/27/04
10/29/04
Date, time
Figure I.4. Plots of Strain Gage Data for 5 Samples From Mix FA2
59
0.0
Strain, millionths
#5
-20.0
-40.0
1
2
3
4
5
-60.0
11/9/0 11/11/ 11/13/ 11/15/ 11/17/ 11/19/ 11/21/ 11/23/ 11/25/ 11/27/ 11/29/ 12/1/0 12/3/0 12/5/0 12/7/0 12/9/0
4
04
04
04
04
04
04
04
04
04
04
4
4
4
4
4
Date, time
Figure I.5. Plots of Strain Gage Data for 5 Samples From Mix 25FA90
0
#6
Strain, millionths
-20
-40
1
2
3
4
5
-60
11/16/04
11/18/04
11/20/04
11/22/04
11/24/04
11/26/04
11/28/04
11/30/04
Date, time
Figure I.6. Plots of Strain Gage Data for 5 Samples From Mix 4FA90
60
0
#7
Strain, millionths
-20
-40
1
2
3
4
5
-60
12/14/04
12/16/04
12/18/04
12/20/04
12/22/04
12/24/04
12/26/04
12/28/04
Date, time
Figure I.7. Plots of Strain Gage Data for 5 Samples From Mix 25FA70
0
#8
Strain, millionths
-20
-40
1
2
3
4
5
-60
12/14/04
12/16/04
12/18/04
12/20/04
12/22/04
12/24/04
12/26/04
12/28/04
Date, time
Figure I.8. Plots of Strain Gage Data for 5 Samples From Mix 4FA70
61
APPENDIX J – FOAM DRAINAGE GRAPHS
Introduction: Detailed information on the foam drainage tests in this program is found on
pages 118 to120 of Volume I of this series:
Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris,
C.F.; Identifying Incompatible Combinations of Concrete Materials: Volume I—Final
Report, FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA,
August, 2006, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.
62
Admixture A
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
150
"AEA+C+WR+F-ASH"
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
Time, hr:min:sec
Figure J.1. Admixture A
Admixture B
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
150
"AEA+C+WR+F-ASH"
100
50
0
0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00
Time, hr:min:sec
Figure J.2. Admixture B
63
Admixture C
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
150
"AEA+C+WR+F-ASH"
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
Time, hr:min:sec
Figure J.3. Admixture C
Admixture D
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
150
"AEA+C+WR+F-ASH"
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
Time, hr:min:sec
Figure J.4. Admixture D
64
1:10:00
Admixture E
300
Water Drainage, ml
250
200
AEA
AEA+C
150
AEA+WR
AEA+C+WR+C-ASH
"AEA+C+WR+F-ASH"
100
50
0
0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00
Time, hr:min:sec
Figure J.5. Admixture E
Admixture F
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
150
"AEA+C+WR+F-ASH"
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
Time, hr:min:sec
Figure J.6. Admixture F
65
1:10:00
Admixture G
350
Water Drainage, ml
300
250
AEA
AEA+C
AEA+WR
AEA+C+WR+C-ASH
"AEA+C+WR+F-ASH"
200
150
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
Time, hr:min:sec
Figure J.7. Admixture G
Admixture H
350
Water Drainage, ml
300
250
AEA
200
AEA+C
AEA+WR
AEA+C+WR+C-ASH
"AEA+C+WR+F-ASH"
150
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
Time, hr:min:sec
Figure J.8. Admixture H
66
1:10:00
Admixture I
300
Water Drainage, ml
250
200
AEA
AEA+C
AEA+WR
AEA+C+WR+C-ASH
"AEA+C+WR+F-ASH"
150
100
50
0
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
Time, hr:min:sec
Figure J.9. Admixture I
Admixture J
350
Water Drainage, ml
300
250
200
AEA
150
AEA+C
AEA+WR
AEA+C+WR+C-ASH
"AEA+C+WR+F-ASH"
100
50
0
0
0.00694 0.01389 0.02083 0.02778 0.03472 0.04167 0.04861
5
5
5
5
Time, hr:min:sec
Figure J.10. Admixture J
67
APPENDIX K – PORE SOLUTION ANALYSES RAW DATA
68
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 1
Sample 1CA
Sample 1PA
20000
14.0
16000
13.5
14.0
20000
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 1FA
Sample 1SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
69
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 2
Sample 2CA
Sample 2PA
14.0
20000
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 2FA
Sample 2SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
70
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 3
Sample 3CA
Sample 3PA
14.0
20000
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 3FA
Sample 3SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
71
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 4
Sample 4CA
Sample 4PA
14.0
20000
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 4FA
Sample 4SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
72
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 5
Sample 5CA
Sample 5PA
14.0
20000
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 5FA
Sample 5SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
73
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 1 Cement 6
Sample 6CA
Sample 6PA
20000
14.0
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 6FA
Sample 6SA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
74
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 2
Sample 2C
Sample 2P
20000
14.0
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 4P
Sample 5P
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
75
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 2
Sample 2CDA
Sample 2PDA
20000
14.0
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 4PDA
Sample 5PDA
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
76
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 2
Sample 2CB
Sample 2PB
20000
14.0
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 4PB
Sample 5PB
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
77
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 2
Sample 1CB
Sample 1PB
20000
14.0
16000
13.5
20000
14.0
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
12.0
10000
1000
12.5
4000
0
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 6PB
20000
14.0
16000
13.5
12000
13.0
8000
12.5
4000
0
1
10
100
12.0
10000
1000
Time after casting, minutes
SO4=
Ca++
78
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 3
Sample 5PA @ 90°F
Sample 2PA @ 90°F
14.0
20000
16000
13.5
14.0
20000
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 5P @ 90°F
Sample 5PB @ 90°F
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
12.0
10000
0
1
10
100
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
79
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 3
Sample 1CA @ 90°F
Sample 1PA @ 90°F
14.0
20000
16000
13.5
14.0
20000
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 1PB @ 90°F
Sample 6PA @ 90°F
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
12.0
10000
0
1
10
100
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
80
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 4
Sample 2FA @ 50°F
Sample 2CA @ 50°F
14.0
20000
16000
13.5
14.0
20000
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 2CDA @ 50°F
Sample 1CB @ 50°F
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
12.0
10000
0
1
10
100
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
81
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Round 4
Sample 1CA @ 50°F
Sample 1PA @ 50°F
14.0
20000
16000
13.5
14.0
20000
16000
13.5
12000
12000
13.0
13.0
8000
8000
12.5
0
1
10
100
1000
12.5
4000
12.0
10000
0
14.0
20000
1
10
100
1000
12.0
10000
pH
Concentration, ppm
4000
Sample 1PB @ 50°F
Sample 6PA @ 50°F
20000
16000
13.5
12000
14.0
16000
13.5
12000
13.0
8000
13.0
8000
12.5
4000
12.0
10000
0
1
10
100
1000
12.5
4000
0
1
10
100
1000
12.0
10000
Time after casting, minutes
SO4=
Ca++
82
Na+
K+
pH
Task 2.1.1 Pore Solution Analysis
Reproducibility
pH
Sample 2CB - Round 2
Sample 2CA - Round 1
14.0
14.0
13.8
13.8
13.6
13.6
13.4
13.4
13.2
13.2
13.0
13.0
10
100
1000
10000
1
10
100
1000
10000
1000
10000
pH
1
Sample 1CA - Round 3
Sample 2FA - Round 4
14.0
14.0
13.8
13.8
13.6
13.6
13.4
13.4
13.2
13.2
13.0
13.0
1
10
100
1000
10000
1
10
100
Time after mixing, minutes
Repeat 1
Average
83
Repeat 2
Task 2.1.1 Pore Solution Analysis
Reproducibility
=
SO4
Sample 2CB - Round 2
SO4= concentration, ppm
Sample 2CA - Round 1
20000
20000
16000
16000
12000
12000
8000
8000
4000
4000
0
0
1
10
100
1000
10000
1
Sample 1CA - Round 3
10
100
1000
10000
1000
10000
Sample 2FA - Round 4
20000
20000
16000
16000
12000
12000
8000
8000
4000
4000
0
0
1
10
100
1000
10000
1
10
100
Time after mixing, minutes
Repeat 1
Average
84
Repeat 2
Task 2.1.1 Pore Solution Analysis
Reproducibility
Ca
++
Sample 2CB - Round 2
Ca++ concentration, ppm
Sample 2CA - Round 1
2000
2000
1500
1500
1000
1000
500
500
0
0
1
10
100
1000
10000
1
Sample 1CA - Round 3
10
100
1000
10000
1000
10000
Sample 2FA - Round 4
2000
2000
1500
1500
1000
1000
500
500
0
0
1
10
100
1000
10000
1
10
100
Time after mixing, minutes
Repeat 1
Average
85
Repeat 2
Task 2.1.1 Pore Solution Analysis
Reproducibility
Na
+
Sample 2CB - Round 2
Na+ concentration, ppm
Sample 2CA - Round 1
3500
3500
3000
3000
2500
2500
2000
2000
1500
1500
1000
1000
500
500
0
0
1
10
100
1000
1
10000
Sample 1CA - Round 3
10
100
1000
10000
1000
10000
Sample 2FA - Round 4
3500
3500
3000
3000
2500
2500
2000
2000
1500
1500
1000
1000
500
500
0
0
1
10
100
1000
10000
1
10
100
Time after mixing, minutes
Repeat 1
Average
86
Repeat 2
Task 2.1.1 Pore Solution Analysis
Reproducibility
K
+
Sample 2CB - Round 2
K+ concentration, ppm
Sample 2CA - Round 1
20000
20000
16000
16000
12000
12000
8000
8000
4000
4000
0
0
1
10
100
1000
1
10000
Sample 1CA - Round 3
10
100
1000
10000
1000
10000
Sample 2FA - Round 4
20000
20000
16000
16000
12000
12000
8000
8000
4000
4000
0
0
1
10
100
1000
10000
1
10
100
Time after mixing, minutes
Repeat 1
Average
87
Repeat 2