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Copyright 2003 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 21

Introduction

Concrete prisms (76 76 280 mm) and concrete cylinders

(100 200 mm) were cast using four different cementitious mate-

rials during spring and summer of the year 2000 for a comparative

study of sulfate resistance and strength development. The main

purpose was to use the samples and data in the 3rd and 4th year ma-terials courses in civil engineering. The cementitious material in

the four different batches of concrete consisted of high alumina ce-

ment (HAC), (calcium aluminate cement, ciment fondu), Type 10

Portland cement,3 Type 10 Portland cement of which 20% was re-

placed by Sundance fly ash (Type C)4 and Type 50 Portland ce-

ment.3 Available chemical and physical analyses and mix designs

are shown in Table 1a,b,c. The prisms were made for measurement

of length change, which was recorded in triplicate on prisms as a

function of time of immersion in room temperature Na2SO4 solu-

tion. The cylinders were used for estimation of compressive

strength as a function of time in the fog-room, 40C water bath or

Na2SO4 solution. Treatment is summarized in Table 2.

In ASTM C1012-95 a procedure is described that provides ameans of assessing the sulfate resistance of concretes and mortars,

by measurement of length change of mortar bars immersed in a sul-

fate solution. The procedure used in this work differed in that con-

crete, rather than mortar, test specimens were used. Also ASTM

C1012 calls for the use of a container large enough to allow a vol-

ume proportion of sulfate solution to mortar bars of 4 0.5

volumes of solution to 1 volume of mortar bars. In the present work

the volume proportion was about 3.3 volumes of solution to 1 vol-

ume of concrete prisms and the ratio was about 2.1 for solution to

concrete cylinders. The prisms and cylinders were stored in con-

tainers (Fig.1a) but in both cases the volume proportion was lessthan that required by ASTM. This followed because the concrete

specimens occupy a larger volume than a corresponding number of

mortar bars and too few containers were available to compensate

for the difference. A review of ASTM C1012 in assessing sulfate

resistance of different mortars with a view to establishing accep-

tance limits was given by Patzias (1987, 1991).

Objectives

The principal objectives of the work were as follows:

1. To demonstrate to 3rd and 4th year students of civil engineer-

ing the effects of sulfate attack on concrete made with four

types of cementitious material.2. To provide students with evidence of sulfate attack in the

form of:

(a) Cracking and disintegration of test specimens;

(b) Length change of test specimens;

(c) Changes in compressive strength of test specimens.

3. To demonstrate to students:

(a) The differences in sulfate-resistance of the four types of

concrete;

(b) That evidence of sulfate resistance could be obtained

within a reasonably short time-frame (say 6 months) by

means of a practical easy-to-use-test.

4. To provide answers to several questions such as:

(a) Would modification of the standard test (ASTM C1012)impair its utility? In this work specimens were made of

J. E. Gillott1 and T. Quinn2

Strength and Sulfate Resistance of ConcreteMade With High Alumina Cement, Type 10Portland Cement, Type 10 Portland Cement PlusFly Ash and Type 50 Portland Cement

ABSTRACT: Concrete prisms and cylinders were made using four different cementitious materials. These were high alumina cement (HAC), Type10 Portland, Type 10 with 20% replaced with fly ash and Type 50 Portland Cement. Specimens were used for measurement of length change andestimation of compressive strength over a period of about 18 months exposure to fog-room conditions, room temperature Na2SO4 solution or 40Cwater bath. None of the concrete samples made with the 3types of Portlandbased cementitious material showed distress due to sulfate attack. Theconcrete made with HAC and which had probably not undergone the conversion reaction also showed good resistance to sulfate attack but samplesin which conversion had probably occurred cracked and disintegrated in the Na2SO4 solution.

KEYWORDS: concrete, Portland binders, high alumina cement, sulfates, strength, durability

Cement, Concrete, and Aggregates, June 2003, Vol. 25, No. 1Paper ID CCA11842_251

Available online at: www.astm.org

1 Emeritus Professor, Department of Civil Engineering, The University ofCalgary, AB T2N 1N4, Canada.

2 Technologist, Department of Civil Engineering, The University of Calgary,AB T2N 1N4, Canada.

3 CSA Standards, CAN/CSAA54 CSA Standards, CAN/CSAA23.5

Manuscript received 12/13/2002; accepted for publication 4/16/2003;published XX.


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concretethe normal material of constructionrather

than mortar. The point has been made by others that at

least some tests of concrete itself are desirable to assure

satisfactory performance (Struble et al., 2001).

(b) Would the performance of modern high alumina ce-

ment differ from that of the material described in the

literature?

5. The primary objectives were to use the results of this work in

teaching 3rd

and 4th

year materials courses. However, thewrite-up was amplified to include a brief review of the state

of knowledge in this area since student class notes, where

these topics are covered, were not available to people in civil

engineering practice some of whom expressed interest in the

results.

Methodology

The concrete prisms made with high alumina cement were

divided into two groups. One group was cured in the fog room (22C

100% R.H.) for 70 days after casting and then immersed in a room

temperature bath of solution containing 50g/L (0.352 moles/L) of

Na2SO4 (ASTM C1012-95). The other group was precured in the

fog room for 3 days after casting and then placed in a water bath at40C. Then, 70 days after casting, that group of prisms was trans-

ferred into the solution of Na2SO4. The concrete prisms made with

Type 10 cement, Type 10 plus fly ash, and Type 50 cement were pre-

conditioned for 7 days in the fog room and then immersed in the

room temperature bath of Na2SO4 solution (Table 2).

The concrete cylinders made with high alumina cement were di-

vided into groups. One group was cured continuously in the fog

room for about 18 months but 70 days after casting half of that

group was immersed in the room temperature bath of sodium sul-

fate solution. Another group was precured in the fog room for only

3 days after casting and then transferred to a water bath at 40C for

about 18 months. Half the cylinders of that group were transferred,

at an age of 70 days after casting, to the room temperature bath ofsodium sulfate solution.

22 CEMENT, CONCRETE, AND AGGREGATES

TABLE 1aProportions by weight (kg/m3) of ingredients in four concrete mixtures.

Ingredients

CEMENT HAC P.C. Type 10 P.C. Type 50 Fly Ash Water Coarse Agg. Fine Agg. W/cm

High Alumina 400 160 1127 620 0.4

Portland Type 10 370 185 1050 750 0.5Type 10 Fly Ash 296 74 185 1050 750 0.5Portland Type 50 370 185 1050 750 0.5

Abbreviations: HAC High Alumina Cement ; Agg. Aggregate; P.C. Portland Cement; W/cmWater/Cementitious Material

TABLE 1bChemical analyses of portland cements.

Cement Type

Type 10 Type 50Chemical Analysis % %

Silica (SiO2) 20.5 21.4Alumina (Al2O3) 4.1 3.3Iron Oxide (Fe2O3) 2.7 3.8Calcium Oxide (CaO) 63.2 62.5Magnesium Oxide (MgO) 4.5 4.5Sulphur Trioxide (SO3) 2.4 2.2Loss on Ignition at 1050C 2.8 . . .Loss on Ignition at 550C 0.9 . . .Loss on Ignition . . . 1.0Insoluble Residue 0.14 0.10Calcium Oxide, Free (FCaO) 1.01 0.42Equivalent Alkali (As Na2O) 0.55 0.56C3S 62.8 58.0C2S 11.5 17.7C3A 6.3 2.3C4AF 8.3 11.4

TABLE 1cPhysical analyses of portland cements.

Cement Type

Type 10 Type 50Physical Analysis % %

Fineness 45m% Retained 3.1 1.8Blaine m2/kg 379 380Setting TimeInitial (Min.) 108 151False Set % 72 . . .Autoclave Expansion % 0.11 0.10Sulfate Resistance % . . . 0.022Compressive Strength at 1 Day Mpa 15.9 . . .Compressive Strength at 3 Days Mpa 27.5 27.4Compressive Strength at 7 Days Mpa 33.9 34.1Compressive Strength at 28 Days Mpa 43.3 43.1

TABLE 2Treatment of concrete prisms and cylinders made with highalumina cement and portland cementitious materials.

Prisms: Length Change Data

(a)High Alumina CementFog Room (70 Days) Na2SO4 solutionFog Room (3 Days)Water bath 40C (70 Days) Na2SO4 solution

(b) Portland Cementitious MaterialsType 10Type 10 Fly Ash Fog Room (7 Days) Na2SO4 solutionType 50

Cylinders: Compressive Strength Data

(c)High Alumina CementFog Room (18 Months)Fog Room (70 Days) Na2SO4 solutionFog Room (3 Days)Water bath 40C (18 Months)Fog Room (3 Days)Water bath 40C (70 Days) Na2SO4 solution

(d) Portland Cementitious MaterialsType 10 Fog Room (18 Months)Type 10 Fly AshType 50 Fog Room (7 Days) Na2SO4


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Concrete cylinders were also made with each of the other three

cementitious binders (Type 10 Portland cement; Type 10 plus fly

ash; Type 50 Portland cement). In each case some cylinders were

held under fog room conditions throughout the test period (18

months) while half of each set was removed from the fog room

after 7 days and placed in the room temperature bath of sodium

sulfate solution (Table 2).

Results

1. The length change recorded on the concrete prisms made

with high alumina cement and cured in the fog room for 70

days prior to immersion in the sulfate bath showed only avery small expansion (0.02%) and no visible cracks by 433

days after casting (Fig.1b). In contrast the prisms placed in

water at 40C for 70 days prior to immersion in the sulfate

bath expanded by 0.025% by 265 days after casting and

showed excessive expansion (0.25%) with severe cracking

and deterioration by 433 days (Fig. 1c).

2. The concrete prisms made with the other cementitious agents

showed no significant expansion or cracking during 18

months in the Na2SO4 solution (Fig.1d, e,f). Expansion val-

ues at 18 months for prisms made with Type 10 cement, Type

10 plus fly ash and Type 50 cement were 0.006%, 0.008%,

and 0.003% respectively.

3. Concrete cylinders made with high alumina cement and cured

in the fog room gained strength rapidly and reached over50MPa within 5 days and about 65MPa within 14 days. By 8

GILLOTT AND QUINN ON STRENGTH AND SULFATE RESISTANCE 23

FIG. 1Effect of Na2SO4 Solution on Concrete Prisms.


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months and 1 year strengths were lower (about 50MPa) but

by 18 months some strength recovery to about 60MPa had

occurred.

4. HAC concrete cylinders placed in the sulfate bath after

70 days in the fog room also had a strength of about

60MPa by 18 months and were generally in excellent

condition but a few small cracks were visible in one cylinder(Figs. 2a, b).

5. Concrete cylinders made with high alumina cement and

placed in the 40C water bath after 3 days in the fog room

showed a rapid decrease in strength to about 40MPa, which

declined further to slightly more than 30MPa at 8 months and

1 year with recovery to about 40 MPa by 18 months.

6. The corresponding HAC cylinders placed in the sulfate bath

after 70 days at 40C had a strength of a little over 30MPa at

about 1 year. By 18 months the strength had decreased to only

about 20MPa and the cylinders were cracked and disintegrat-

ing (Fig. 2c).

7. Concrete cylinders made with Type 10 and Type 50 Portland

cement gained strength more rapidly than the cylinders made

with the Type 10 plus fly ash binder but by 28 days all three

types of concrete had compressive strengths in excess of40MPa. At an age of about 18 months the compressive

strength of all cylinders was about 55MPa regardless of the

storage conditions. Hence in these tests concrete cylinders

made with the three types of Portland cementitious material

and immersed in the Na2SO4 solution had virtually no differ-

ence in compressive strength from that of the cylinders stored

continuously in the fog room and no cracks were visible

(Figs. 2d, e,f).


FIG. 2Effect of Na2SO4 Solution on Concrete Cylinders.


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Discussion

Sulfates occur in ground water, soils, sea water, fertilizers, and

industrial pollutants and also form by oxidation of sulfides. When

present in significant amounts they have long been a recognized

cause of durability failure of Portland cement concrete. More

recently sulfates have been associated with internal causes of dura-bility problems such as delayed ettringite formation and thaumasite

attack (Parker, 2000; Gillott & Rogers, 2003; Day, 1992; Collepardi

1999). In an attempt to address the sulfate problem Bied (1926) de-

veloped high alumina cement, which was patented by Ciments La-

farge in 1908 in France following earlier work and patents in Ger-

many and England.

High alumina cement (calcium aluminate cement, ciment fondu)

is made in a kiln by the fusion of bauxite and limestone with

some compounds of iron, which acts as a flux. The principal min-

erals formed in the kiln are CA (CaO.Al2O3) and C12A7(12CaO.7Al2O3). The material formed in the kiln is ground to a

fine powder which when mixed with water to a paste hardens and

gains strength rapidly with considerable evolution of heat. Strength

may reach 80 per cent of ultimate within 24 hours. On hydration,pseudohexagonal calcium aluminum hydrates (CAH10, C2AH8)

and aqueous alumina gel (AH3) are formed. Unlike hydrated Port-

land cement Ca(OH)2 is not present in the hydrated paste of high

alumina cement. The hexagonal Caaluminum hydrates are

metastable and with time in the presence of moisture they trans-

form to the denser C3AH6 (hydrogarnet) and alumina gel. The

transformation takes place by a through solution mechanism so wa-

ter has to be present for the reaction to occur.

This transformation is known as the conversion reaction, which

occurs more rapidly with increase of temperature and concentra-

tion of lime and alkalies, which is why contact with Portland ce-

ment concrete may accelerate conversion. The increase in density

of the individual crystallites on conversion causes an increase inporosity and permeability and a significant decrease in strength of

the cementitious material. Prior to conversion high alumina cement

concrete has excellent resistance to sulfate attack attributed in part

to the absence of Ca (OH)2, to the presence of aqueous alumina gel

and to the low reactivity of CAH10 with sulfate ions. After conver-

sion however the increased permeability renders the material much

more liable to poor durability performance since aggressive ions

such as SO3 and CO2 may enter via the pore system. Also sulfate is

said to react expansively with C3AH6 and if CO2 is present it may

lead to formation of calcium carbonate (Neville, 1997, p.101).

Strength loss attributed to conversion has been considered to be the

cause of actual structural collapse in various countries. In other

applications high alumina cement has excellent refractory proper-

ties. There are various descriptions of its nature and behaviorin standard texts (Neville, 1997; Neville and Wainwright, 1975;

Robson, 1962).

In the present work the concrete prisms made with high alumina

cement and cured in the fog room prior to being placed in the

Na2SO4 bath showed virtually no expansion, cracking or other

signs of deterioration to an age of about 18 months (Fig. 1 b).

The prisms immersed in a water bath at 40C, however, showed

greatly increased susceptibility to sulfate attack since expansion

and cracking occurred in the Na2SO4 bath (Fig. 1c).

The fog-room cured HAC cylinders showed rapid strength

development though strengthloss occurred at an age of about 1

year followed by strength recovery at a greater age. Immersion in a

water bath at 40C, however, led to considerable loss of strengthpresumably due to conversion though, as with the fog-room cured

cylinders, some strength recovery occurred at about 18 months.

Strength recovery has been noted in the literature and attributed by

some to growth of hydration products from previously unreacted

cement. It has also been pointed out that if this is the correct expla-

nation some of the strength recovered may be subsequently lost due

to later conversion. It is possible, however, that strength recovery

may result from other causes such as a decrease in stress concen-trations associated with blunting or shortening of small cracks or

from stress relaxation due to creep and microstructural changes.

The HAC concrete cylinders cured in the fog room showed good

resistance to sulfate attack though small cracks were noted in one

cylinder by about 18 months.

The cylinders placed in the 40C bath prior to immersion in the

sulfate solution showed severe cracking and deterioration by an age

of about 18 months (Figs. 2b, c). These results for the HAC con-

crete prisms and cylinders agree with previous findings reported in

the literature which have attributed strength loss and increased

susceptibility to sulfate attack to acceleration of the conversion

reaction by elevated temperatures in the presence of moisture. This

conclusion could not be confirmed in this work as neither thermal

nor X-ray diffraction data were available.Sulfates occur in soils in many parts of Canada such as the

Prairie Provinces and Canadian researchers, together with their

colleagues in the U.S.A. and Europe made early contributions to

the understanding and remediation of the sulfate problem (Bates

et al., 1913; Mackenzie, 1920; Thorvaldson et al., 1927). The

recognition of the part played by the individual cement minerals

paved the way to the development of sulfate resistant Portland ce-

ment and provided a logical explanation for the role of pozzolans

in improving resistance of Portland cement concrete to sulfate at-

tack. The principal cementitious phases in Portland cement paste

are calcium silicate hydrates (C-S-H) but Ca(OH)2 and calcium

sulphoaluminate hydrates are also present. The latter compounds

have been shown to be the most readily attacked by SO4 ionsthough C-S-H itself becomes unstable under some conditions so

the cement may lose its cementitious properties and all that re-

mains of the concrete may be aggregates with little or no bond be-

tween the particles.

Resistance of Portland cement concrete to sulfate attack may be

improved by reducing the content of Ca(OH)2 and calcium

sulphoaluminate hydrates in the cement paste. One approach is to

decrease the ratio of C3S to C2S in the Portland cement since on

hydration C3S produces three times as much Ca(OH)2 as is

formed by hydration of the C2S. Alternatively pozzolanic materi-

als such as fly ash or silica fume may be incorporated in the con-

crete mixture. Under favorable conditions of hydration those ma-

terials react with the Ca(OH)2 forming C-S-H so a sulfate

susceptible compound with poor cementitious properties is re-placed by a more resistant and better bonding agent. The amount

of calcium sulpho-aluminate hydrates in the cement paste may be

reduced by decreasing the quantity of C3A in the Portland ce-

ment. This is achieved by suitable adjustments to the composition

of the charge entering the kiln during manufacture of the Portland

cement. In sulfate resistant cement (e.g., CSA Type 50) both the

C3S to C2S ratio and the C3A content are lower than in Normal

Type 10 Portland cement.

As stated in the section of this paper dealing with the three types

of Portland cement concrete tested none of the prisms showed any

marked change in length during approximately 18 months in the

bath of Na2SO4 solution. Likewise compressive strengths of the

concrete cylinders made with all three types of Portland cementi-tious binders exceeded 50MPa regardless of whether conditioned



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in the fog-room or immersed in the bath of Na2SO4 solution. These

results indicate that the concrete made here under laboratory con-

ditions has very satisfactory properties, which may well be superior

to that sometimes encountered in the field. Also concrete used in

practice is generally subjected to more severe and variable condi-

tions of exposure which no doubt affects performance. One of the

reviewers of this paper suggested that another aspect to consideris the small specific surface of concrete specimens relative to

mortar-bar specimens.

It is also possible that the excellent performance of all varieties

of Portland cement concrete, including that made with Type 10

cement, was influenced by the smaller volume ratio of solution to

solid than is recommended in ASTM C1012-95. Since this paper

was submitted for publication additional cylinders (4 in. 8 in.;

100 200 mm) have been cast using the same mix design as in

the previous work but made only with Type 10 Portland cement.

About 1/3 of the cylinders are being held under fog-room condi-

tions while about 2/3 of the cylinders were removed from the fog-

room after 7 days and divided into two sets of 1/3 each. One set

was placed in a room temperature bath (bath #1) of sodium sul-

fate solution (concentration 50 g/L) in which the volume of solu-tion was about twice the volume of the concrete cylinders i.e., the

same as in the original work. The second set of cylinders removed

from the fog-room was placed in a room temperature bath (bath

#2) of sodium sulfate solution (concentration 50g/L) but in which

the volume of solution was about four times the volume of the

concrete cylinders as recommended by ASTM C1012. At an age

of 90 days the average compressive strength of the cylinders was

51.6MPa (fog-room), 49.7MPa (sulfate bath #1) and 48.1MPa

(sulfate bath #2) and no cracks were visible in any of the speci-

mens. Hence it seems unlikely that the lower volume ratio of so-

lution to solid than is recommended by ASTM C1012 is the fac-

tor responsible for the high resistance of the concrete to sulfate

attack.

Conclusions

The three types of concrete made with Portlandbased cemen-

titious materials showed no cracking and no differences in visual

appearance, length change characteristics or compressive strength

whether specimens were immersed in the sulfate solution or stored

in the fog room. Hence the test procedure did not demonstrate sig-

nificant differences in resistance to sulfate attack between these

three types of concrete and indeed all three types appeared to be un-

affected by the Na2SO4 solution. Results such as those reported in

this paper could convey a false sense of security since, if the evi-

dence has been correctly interpreted, the presence of sulfates seems

to be a relatively common cause of durability problems in concreteparticularly when it is made with Normal (Type 10) Portland ce-

ment. Field exposure in many civil engineering applications no

doubt subjects concrete to harsher conditions than that of the

controlled environment of the sulfate bath. Also concrete is

required to remain durable for much longer than the 18 months of

this experiment.

The reported shortcomings of Type 10 Portland cement in the

presence of sulfates may become evident for purposes of test or

demonstration if leaner concrete mix designs than those used in the

present work were employed. Such mixes would be expected to be

weaker, more permeable and absorptive with higher voids ratio and

lower density than those used in this work (Patzias, 1987; Robson,

1962). However, it would be preferable to be able to test the sulfatesusceptibility of concrete made with job-mix designs so possibly a

change in concentration, composition or temperature of the solu-

tion may be better alternatives. It is also possible that continuously

circulating the Na2SO4 solution may increase its effectiveness by

reducing the likelihood that conditions of local equilibrium are

established.

Concrete made with high alumina cement and cured in the fog

room gained strength rapidly and reached higher strength values(65MPa at 28 days) than any of the Portland cement concretes

tested (4045 MPa at 28 days). However the high alumina ce-

ment concrete showed a rapid loss of strength and poor resistance

to sulfate attack after exposure to conditions favoring the conver-

sion reaction. Hence these results appear to support those who

consider it prudent to avoid the use of high alumina cement partic-

ularly for structural applications in civil engineering practice

(Neville, 1998). The close parallel between the performance of this

modern high alumina cement and that reported in previous liter-

ature was disappointing since I had nurtured the hope that changes

may have been made to this material, which would overcome or

moderate its reported drawbacks.

Acknowledgments

Sincere thanks are expressed to Don McCullough and Gerd

Birkle for help with the photography and to Chrissy Ziegler for sec-

retarial support. Rick Ketcheson, Canada Cement Lafarge, is

thanked for his interest in the work and for the supply of the

cements used in the project. Lafarge Canada, Inc. is also thanked

for the average chemical and physical analyses of the cements.

References

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