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Properties of high performance concrete systems incorporating large amounts of high-lime fly ash
Construction and Building Materiolx Vol. 9, No. 4, pp. 195-204, 1995
8 1995 Elsevier Science Limited Printed in Great Britain. AI1 rights reserved 0950-0618/95 $10.00+0.00
o95o-o618(95)oooO!L7
Properties of high performance concrete systems incorporating large amounts of high-lime fly ash Tarun R. Naik, Shiw S. Singh and Mohammad
M. Hossain
Department of Civil Engineering and Mechanics, College of Engineering and Applied Science, The University of Wisconsin - Milwaukee, PO Box 784, Milwaukee, WI 53201, USA Received
1 September
1993; revised 30 November
1994; accepted
16 January
1995
This research was undertaken to evaluate the engineering propenies of high-lime (ASTM Class C) fly ash concretes. An air-entrained reference concrete mixture without fly ash was proportioned to have 28-day compressive strength of 41 MPa. Additionally, concrete mixtures were also proportioned to have cement replacement with Class C fly ash in the range of O-70% by weight. For each concrete mixture, specimens were made to evaluate compressive strength, tensile strength, flexural strength, modulus of elasticity, shrinkage, abrasion resistance, air permeability, water permeability, chloride ion permeability, air-void parameters, freezing and thawing durability, and salt scaling resistance, of hardened concrete. The results of this study established that high-performance concrete incorporating Class C fly ash at 30% cement replacement can be proportioned for high-strength applications. In general, concrete mixtures up to 50% cement replacement with fly ash showed satisfactory performance with respect to strength and physical durability properties appropriate for structural applications. Keywords:
abrasion; air entertainment;
air permeability
It is now well established that inclusion of fly ash is not only desirable for deriving economic, energy conservation and ecological benefits, but it is also highly effective in modifying concrete properties for numerous applications1-25. The use of Class C and F fly ashes as an admixture is desirable in the production of very dense and durable concretes. This is achieved because the presence of fly ash generally reduces heat of hydration and thus helps reduce the adverse effects of rapid hydration reaction resulting from the use of rich mixtures. Additionally, both grain and pore refinements occur due to the fly ash addition’ resulting in increased resistance to permeability of water, CO, and other aggressive agents. This, in turn, improves durability of concrete. More recently, attempts have been made to develop high-performance concrete containing significant amounts of mineral admixtures. In this work, highperformance concrete has been defined as a concrete which exhibits excellent strength and durability properties that are required for a particular application. This research was carried out to establish fly ash concrete mixtures for high-performance and structural applications. To accomplish this, concrete mixtures with and without Class C fly ash were manufactured and their strength and durability properties were determined. Highperformance concrete requires: (1) low-heat cement; (2) high-quality aggregates; (3) supplementary cementing Construction
materials; (4) low water-to-cementitious materials ratio; and (5) chemical additives. These requirements were satisfied for the concrete used for this project by low-cement factor with use of fly ash, addition of high-range water reducers and use of high-quality aggregates. Review of literature For more than half a century fly ash has been used in concrete. Since the late 194Os, significant amounts of Class F fly ash has been used in mass concrete to reduce the heat of hydration and early age cracking. Currently fly ash is being employed in a wide variety of concrete construction projects29 3. Up to a certain level of cement replacement with Class C fly ash, strength properties of concrete are either better than or comparable to concrete without fly ash. More recent investigations have shown adequate strength and durability characteristics of high-volume fly ash systems for structural and other applications2-g. Pioneering work for production of structural concrete with low-lime (ASTM Class F) fly ash was done by Malhotra and his associates. Research work pertaining to the use of large quantities of Class C fly ash in structural and paving concretes started at the University of Wisconsin-Milwaukee, in 19842,4. Shrinkage of concrete containing fly ash has been investigated by a number of and Building
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Properties
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T. R. Naik et al.
researchers3j8-“. In general, shrinkage of fly ash concrete is either lower than or comparable to no-fly ash concrete. Gebler and Klieger’? proportioned concrete mixtures at 25% cement replacement with Class F and Class C fly ashes. The authors reported that the abrasion resistance of Class C fly ash concrete was generally superior to Class F fly ash concrete. Tikalsky et al.” observed the same trend but up to 35% cement replacement with fly ash. Hadchti et ~1.‘~ reported that at equal strengths, concrete with fly ash is as resistant to abrasion as no-fly ash concrete. Naik et cd.3 reported that concrete made with 50% Class C fly ash attained higher abrasion resistance than concrete with 40% Class F fly ash. Bilodeau and Malhotra’O studied abrasion resistance of concrete incorporating 55 to 60% Class F fly ash of total cementitious materials. Their test results showed lower abrasion for the fly ash concretes compared to a reference concrete without fly ash. Ellis et ~1.‘~showed that concrete made with Class F fly ash was more effective in reducing concrete permeability than concrete incorporating Class C fly ash. Naik et (11.‘~ reported chloride permeability of 918 coulombs for the reference concrete with 20% Class C fly ash, 391 coulombs for 50% Class C fly ash mixture, and 188 coulombs for 40% Class F fly ash at one year age. Other researchers “3 i* also found very low chloride permeability results for fly ash concrete systems. Studiesi9-** have established that inclusion of fly ash in concrete increases the dosage of air-entaining admixtures (AEA) compared to concrete without fly ash. The dosage rate for AEA depends upon the loss-on-ignition (LOI) and chemical composition of fly ash, fineness of fly ash, type and amount of fiy ash used in the mixture, etc. Larson20 reported that fly ash does not have adverse effects on the air void system in hardened concrete. Gebler and Klieger2’ reported that concrete containing Class C fly ash demands less AEA compared to concrete with Class F fly ash. Several studies&*xii, ‘Z 18,?‘-24have shown that properly air entrained fly ash concretes exhibit freezing and thawing resistance similar to no-fly ash concretes. A number of studies33lo, Is, 22 have shown low salt scaling resistance of concrete containing fly ash. More research is needed to establish salt scaling characteristics/resistance of concrete as a function of fly ash inclusion. Some researchers25 have found reduction in sulphate resistance of concrete due to addition of Class C fly ashes. However, other researchers25 did not observe this trend. Additional research is needed to establish sulphate resistance of concrete containing Class C fly ash. In the presence of amorphous silica containing aggregates, addition of Class C fly ash having large amounts of water soluble alkali sulphates can participate in the alkali-silica reactions in concrete. The reaction can produce significant expansion if the value of total amounts of water soluble alkalies in concrete from all sources is greater than 2.5 kg m-3. 196
Construction
Experimental program An experimental program was designed to develop fly ash concrete mixture proportions for high-performance and structural applications. Each concrete mixture was evaluated with respect to compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, shrinkage, air permeability, water permeability, chloride ion permeability, abrasion resistance, air-void system parameters, freezing and thawing resistance, and salt scaling resistance of hardened concrete.
Materials A Type I portland cement conforming to ASTM C 150 requirements was used. The test results are shown in Table 1. An ASTM Class C fly ash obtained from the Pleasant Prairie Power Plant, Kenosha, Wisconsin was used throughout this investigation. The chemical and physical properties of the fly ash were determined in accordance with applicable ASTM test methods (Tuble I). A natural sand with a 6.35 mm maximum size was used as a fine aggregate. A coarse aggregate used in this study was 25 mm nominal maximum size of crushed limestone obtained from one source. Physical properties of the aggregates are given in Table 2. Both the fine and coarse aggregates met the ASTM C 33 gradation requirements. A commercially available melaminebased superplasticizer and a resin type air-entraining admixture were used.
Mixture proportions A total of six different mixtures were produced. One of them was the reference mixture containing no fly ash, and the other five mixtures contained the Class C fly ash. The mixture proportions were developed for producing concrete on a 1.25 to 1, fly ash inclusion to cement replaced, weight basis. The levels of cement replacement ranged from 15-70%. The mixture proportions are given in Table 3. The control mixture without fly ash was proportioned to have 28-day compressive strength of 41 MPa. The water-to-cementitious materials ratio (W/(C+FA)) was maintained at about 0.35 + 0.02 and air content was kept at 6 ?Y1%. Each test batch of 0.76 m3 was mixed in a power-driven revolvingpaddle mixer according to ASTM C 192.
Casting and curing of test specimens Cylinders (150 X 300 mm) were cast from each mixture to evaluate compressive strength, modulus of elasticity and splitting tensile strength. Prism specimens of 75 x 100 X 400 mm were cast for flexural strength and shrinkage measurements. Cylinders (100 X 200 mm) were cast for measurement of chloride ion permeability. Prism specimens (75 X 100 X 400 mm) were cast to evaluate freezing and thawing durability. Slab specimens (300 X 300 X 100 mm) were cast for air permeability, water permeability, abrasion resistance and
and Building Materials 1995 Volume 9 Number 4
Properties of high performance concrete: T. R. Naik et al. Table 1 Properties of cement and fly ash used
Cement (“/)
Chemical composition
Silicon dioxide, SiO, Aluminium oxide, Al,O, Ferric oxide, Fe,O, Total, SiO, + Al,O, + Fe,O, Sulphur trioxide, SO, Calcium oxide, CaO Magnesium oxide, MgO Titanium dioxide, TiO, Potassium oxide, K,O Sodium oxide, NarO Moisture content Loss on ignition
ASTM C 150, Type 1
Fly Ash (“~)
ASTM C 618, Class C
_
30.5 17.2 5.5 53.2 _ 28.6 4.7 1.6 0.4 2.0 0.1 0.3
_
20.2 4.7 0.3 25.2 _ 64.1 0.9 0.3 0.1 0.1
_ _ _ 3 max. _ 6 max. _ _ _ 3.0 max.
_
50.0 min 5.0 max. _ 5.0 max. _ _ 1.5 max. 3.0 max. 6.0 max.
Physical properties of cement 7.1 395.8 0.03 3.16
Air content (%) Fineness (m2 kg-‘) Autoclave expansion (%) Specific gravity Compressive strength, (MPa) 1-day 3-day 7-day 28-day Vicat time of initial set (min)
_ _ _
12 max. 280 min. 0.8 max.
_
16.2 25.7 31.5 37.9 145
12.4 min. 19.3 min. _ 45 min., 375 max.
Physical properties of fly ash Fineness retained on No. 325 sieve (%) Pozzolanic activity index with cement 28-day (% of control) Water requirement (% of control) Autoclave expansion (%) Specific gravity
_ _
_ _
18.6 105
34 max. 75 min.
_ _ _
_ _ _
90.4 0.02 2.78
105 max. 0.8 max.
Table 2 Physical properties of aggregates Fine aggregates Sieve size
#4 #8 #16 #30 #50 #loo
Coarse aggregates
% Passing
ASTM C 33, % Passing
Sieve size
% Passing
ASTM c33, % Passing
100 91 74 49 17 4
95-100 80-100 50-85 2560 lo-30 2-10
25 mm 19 mm 13 mm 9.5 mm #4 #8
99 96 43 15 3 2
95 to 100 _ 25 to 60 _ oto 10 0 to 5
Physical properties Aggregates
Fine Coarse
Bulk specific gravity
Bulk specific gravity (SSD)
Apparent specific gravity
2.54 2.76
2.57 2.78
2.62 2.84
deicer salt scaling resistance. All the test specimens were cast according to ASTM C 192. Immediately after casting, all the specimens were covered with plastic to minimize their moisture loss. These specimens were stored at temperatures of about 23°C in the casting room area of a precast concrete plant. After 24 h, the specimens were demoulded. They were then put into a moist curing room at 23°C with 100% relative humidity until the time of test. The 70%
SSD absorption (%) 1.30 1.10
Dry rodded unit weight (kg m-r)
Percent voids
1764 1756
30.5 36.4
fly ash mixture specimens were demoulded after 11 days of curing under room conditions at 23°C due to their slow setting. Testing of specimens Fresh concrete properties
Slump, unit weight, temperature, and air content for each batch were determined according to applicable ASTM test methods. The results are presented in Table 3.
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Table3 Mixture proportions using ASTM class C fly ash - 41 MPa specified strength Mixture no.
c-3
P4-2
P4-3
P4-6
P4-7
P4-8
Cement (kg m-9 Fly ash (kg mm’) Water (kg m-3)
315 0 136 0.36 682
259 139 133 0.34 677
220 182 150 0.37 659
320 71 129 0.33 693
180 226 135 0.33 655
110 316 155 0.36 607
1183 120 6.3 2.9 270 21 23
1173 159 5.2 2.x 348 21 23
1153 121 6.4 2.7 514 21 26
1181 146 6.7 2.8 416 19 21
1138 114 7.0 2.7 886 22 26
1146 121 6.4 2.6 1380 21 25
2381
2393
2360
2400
2337
2365
2470
2432
2416
2440
2342
2326
W/(C+FA)I Sand, SSD (kg mm3) 25 mm aggregates, SSD (kg mm3) Slump (mm) Air content (%) Superplasticizer (1 m-‘) Air entraining agent (ml m 3, Air temperature (“C) Concrete temperature (“C) Fresh concrete destiny (kg m-‘) Hardened concrete density, SSD (kg mm3)
Hurdened concrete properties
Compressive strength tests of test specimens were performed according to ASTM C 39. The static modulus of elasticity of concrete was determined in accordance with ASTM C 469. The tensile strength test was carried out in accordance with ASTM C 496. Flexural strength measurements were made using the third-point loading according to ASTM C 78. The water storage test method was used to evaluate the shrinkage characteristics of concrete specimens in accordance with ASTM C 157. Three specimens were tested for each experimental condition for evaluation of the above properties. Air and water permeabilities of the test specimens were evaluated by using the Figg method. A detailed description of this test technique is presented elsewhere26*27.This method involved drilling a hole typically 40 mm deep by 10 mm in diameter from the top of concrete surface. These holes were plugged with a polyethylene foam pad and the head sealed with a silicone sealant. A hypodermic needle was then pushed into the plug. For the air permeability testing the hypodermic needle was subjected to a vacuum pressure of about minus 55 kPa by a hand vacuum pump. The time taken for the pressure change from minus 55 kPa to minus 50 kPa was taken as a measure of air permeability of concrete. For water permeability testing a water head of 100 mm was applied to the concrete through the needle. Then the time taken to absorb 0.02 ml of water was recorded as a measure of water permeability. Typical air and water permeability qualitative interpretations normally used26 are given in Tables 4 and 5. Chloride ion permeability of concrete was determined in accordance with ASTM C 1202. Three 100 X 200 mm cylinders were cast for each experimental condition. From each cylinder, three 100 mm diameter X 50 mm thick slices were cut from the middle portion using a diamond tipped saw. Each mixture was evaluated for resistance to chloride permeability according to criteria presented in Table 6. Abrasion tests were conducted on the moulded surface of the slab specimens to maintain uniform 198
surface of the specimens. All the specimens were tested in a dry condition by the ASTM C 994 test method. Three separate areas were tested on the same face of the specimen. The rotating cutter consisted of 24 grinding dressing wheels. The rotating cutter, having washers with a diameter equal to that of the dressing wheels, produced depths of abrasion of about 1 mm after about 60 min of exposure to the abrasive force. This was considered too slow. Therefore, it was decided to develop an accelerated technique, especially for concretes having high resistance to abrasion similar to the ones used in this investigation. The developed method was equipped with washers having a smaller diameter relative to the dressing wheels. Furthermore, approximately one teaspoon of silica sand (‘Ottawa Sand’) was added to the concrete surface subjected to abrasion at an interval of one minute. At each wear location (circle of wear), for each wear time, readings were taken at two points in the circle. At each point, three readings were recorded, and the average of these six readings was reported as one data point for each wear circle at the measured time of wear. The parameters of the air-void system in hardened concrete were measured in accordance with ASTM C 457. The linear traverse method was employed in this work. Test specimens (75 X 100 X 19 mm) were obtained from the prism specimens used for flexural strength tests. Each sample was polished to obtain a surface suitable for microscopic examination as required by the ASTM procedure. Freezing and thawing resistance of concrete was evaluated according to ASTM 666, Procedure A. Each mixture was evaluated for freezing and thawing durability at different testing ages. This was done to test them at an equivalent strength/maturity level with a minimum specified strength of 28 MPa. Mixture Nos C-3 and P4-2 were tested after 14 days of moist curing. Mixture No. P4-3 was tested at a 56-day age, and the other mixtures (P4-6, P4-7 and P4-8) were tested at 66 days of age. Specimens (300 X 300 X 100 mm) were tested for deicer salt scaling resistance in accordance with ASTM C 672. The specimens were subjected to the deicer salt
Construction and Building Materials 1995 Volume 9 Number 4
Properties of high petfotmance concrete: T. R. Naik et al. Table 4 Classification of air permeability of concrete (specimens conditioned to constant weight and temperature)% Quality category
0
I 2 3 4
Time for pressure change (s)
Interpretation
Typica material
< 30 30-100 100-300 300-1000 > 1000
Poor Moderate Fair Good Excellent
Porous mortar 21 MPa concrete 41 MPa concrete 62 MPa concrete Polymer-modified concrete
Table 5 Typical water permeability qualitative classification26 Time for absorption (s)
Concrete category
Protective quality
Typical material
Poor Moderate Fair Good Excellent
Mortar 21 MPa concrete 41 MPa concrete 62 MPa concrete Polymer-modified concrete
4zO 100-200 200-1000 > 1000
Table 6 Chloride permeability based on the charge passed in accordance with ASTM C 1201 Charge passed (Coulombs) >4000 2OOO4000 1000-2000 100-1000 c 100
Chloride permeability
Typical material
High Moderate
High water-cement ratio (0.6) concrete Moderate water-cement ratio (0.4-0.5) concrete Low water-cement ratio (0.4) concrete Latex-modified concrete Polymer concrete
LOW
Very !ow Negligible
scaling after 4 weeks of moist curing followed by 3 weeks of air curing in the laboratory. The deicer used was 4% CaCl, solution, as prescribed by the ASTM test method.
Test results and discussions Compressive strength The compressive strength test results for all the six mixtures are illustrated in Figure I. The compressive strengths were measured at the ages of 1, 3, 7, 28, 91 and 365 days. At early ages up to 3 days, all the fly ash concrete mixtures showed lower strength compared to the reference mixture without fly ash; and it decreased with increasing fly ash content (Figure I). The 30% fly ash mixture showed peak compressive strengths at all ages beyond 3 days. Above 30% cement replacement, the compressive strength of concrete generally decreased with increasing amounts of fly ash up to 70% cement replacement. At 28 days, the 30% mixture showed in excess of 48 MPa. The 40 and 50% fly ash mixtures attained 2%day strengths in excess of 30 MPa. As compared with the reference concrete, the fly ash concrete mixtures showed high rates of strength gain due to the contributions from pouolanic reactions of the fly ash. As a result, the compressive strength of the fly ash mixtures increased substantially compared to their strengths at 28 days (Figure I). Splitting tensile strength The splitting tensile strength test data are presented in Figure 2. The tensile strength increased with age. The early age tensile strength decreased with increasing fly Construction
cl
20
40 c-t
Figure
80
80
Replmmemt, racnt
1 Compressive strength versus cement replacement with fly
ash
0
Figure 2 Splitting tensile strength versus cement replacement with fly ash
ash content, but the tensile strength obtained for the concrete mixtures having O-30% cement replacement showed identical results at 7 days. The 15% mixture produced peak tensile strength at 7 days. At 28 days, and Building Materials 1995 Volume 9 Number 4
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Properties of high performance
concrete:
T. R. Naik et al.
the tensile strength results were similar up to 30% cement replacements. The difference between tensile strength of the control and the fly ash concrete mixtures diminished greatly, especially at later ages. This occurred because of grain and pore refinements of the concretes resulting from pozzolanic reactions of the fly ash. At 91 and 365 days, peak tensile strengths were achieved at 30% cement replacement level. Flexurul strength
Test data observed at the ages of 3, 7, 28, 56 and 365 days are given in Figure 3. The flexural strength of concrete increased substantially with age. At a 3-day age, the fly ash concretes showed lower flexural strength compared to the reference concrete. At 7 days, flexural strengths of the mixtures were nearly identical up to 30% cement replacement. When the concretes were cured for 28 days, the 30% mixture exhibited the maximum flexural strength of all the mixtures evaluated (Figure 3). The same trend was noticed at 56 days. At 365 days, the fly ash mixtures up to 30% cement identical flexural nearly replacements produced strengths. The values of the flexural strength for the 30% mixture varied from 5.6 MPa at 28 days to 7.0 MPa at 365 days. Modulus oj’ elusticity
The secant modulus of elasticity data (measured according to the ASTM test procedure) of the test mixtures are illustrated in Figure 4. The modulus of elasticity increased substantially with age up to 365 days. The very early-age modulus of elasticity of concrete
Figure 3 Flexural
strengthversus cement replacement with fly ash
Figure 4 Modulus of elasticity versus cement replacement with fly ash
200
Construction
decreased with increasing fly ash content. The modulus of elasticity values of the mixtures varied from 2.0 x lo4 MPa to 2.6 X IO4 MPa at 28 days. The modulus of elasticity of all the mixtures varied from 2.7 X lo4 MPa to 3.4 X lo4 MPa at 91 days, and from 3.3 X lo4 MPa to 4.6 x lo4 MPa at 365 days. The modulus values for up to 30% cement replacements were very satisfactory for high strength applications. The modulus of elasticity of concrete at high cement replacement levels (40, 50 and 70%) was similar to the values shown by structural grade concretes. Shrinkage
The shrinkage strain test results for all the concrete mixtures are presented in Figure 5. The results show that the shrinkage strain generally increased with increasing ages for all the mixtures irrespective of fly ash addition. In general, beyond 7 days, the shrinkage strain of test specimens decreased as fly ash content increased. However, the shrinkage strains experienced by all the test specimens were small. Abrasion resistance
The abrasion tests were performed at ages of 28, 91 and 365 days. The average depth of wear for test specimens for all the mixtures are presented in Figure 6. The results indicated that the concrete mixtures up to 30% cement replacement by fly ash had abrasion resistance similar to that for concrete without fly ash. Beyond 30% cement replacements, abrasion resistance decreased slightly up to 50% cement replacement. The 70% Class C fly ash mixture attained the lowest abra-
Figure 5 Shrinkage strain versus cement replacement with fly ash
Figure 6 Abrasion resistance versus cement
and Building Materials 1995 Volume 9 Number 4
replacement
with fly ash
Properties
of high performance
concrete:
T. R. Naik et al.
Table 7 Air void parameters of hardened concrete* Air void parameters*
Mixture no. c-3 P4-6 P4-2 P4-3 P4-I P4-8
Fly ash (%)
Air in plastic concrete (“/)
Air in hardened concrete (“A)
Specific surface (mm mm-‘)
Number of air-void per cm
Spacing factor (mm)
0 15 30 40 50 70
6.3 6.7 5.2 6.4 7.0 6.4
4.0 4.8 5.6 4.8 4.9 5.8
2.2 16 19 42 39 59
2.2 2.3 2.6 5.0 4.8 6.9
0.23 0.25 0.23 0.13 0.13 0.08
* The data presented are averages of three observations Table 8 Summary of test results of concrete prisms after 300 cycles of freezing and thawing Mixture no.
Percent change at the end of 300 freezing and thawing cycles
Fly ash (“h) Weight
Length
Resonant frequency
c-3 P4-6 P4-2 P4-3 P4-I P4-8
0 I5 30 40 50 70
-0.56 -0.52 Al.36 -1.14 -0.91 -1.07
0.03 0.08 0.04 0.07 0.06 0.05
-0.02 -0.09 -0.03 -0.15 -0.12 -0.15
Relative dynamic modulus of Pulse velocity
elasticity
-2.20 -8.07 -1.18 -11.22 -6.72 -9.46
95.8 83.4 94.3 72.4 71.7 12.3
Durability factor
w 96 83 94 12 78 12
Table 9 Deicer salts scaling test results Mixture no.
c-3 P4-6 P4-2 P4-3 P4-I P4-8
Fly ash (“h)
Air content (“A)
Final visual rating*
Total scaled off residue (kg m-3
0 15 30 40 50 IO
6.3 6.7 5.2 6.4 7.0 6.4
0 0 0 0 2 5
0.323 0.355 0.323 0.388 0.840 2.32
* ASTM C 672 visual rating scale Rating 0
Surface Condition No scaling
I 2 3 4
Very slight scaling (3.2 mm depth, max no coarse aggregate visible) Slight to moderate scaling Moderate scaling (some coarse aggregate visible) Moderate to severe scaling Severe scaling (coarse aggregate visible over the entire surface)
5
sion resistance value. In this work, the abrasion was found to be strongly affected by compressive strength regardless of inclusion of fly ash. Air and water permeability
The air and water permeability test results are presented in Figures 7 and 8. In general, concrete air permeability decreased with age (Figure 7). Both at 14 and 28 days, air permeability of the concrete increased somewhat with addition of fly ash. But at 28 days, the concrete mixtures up to 40% cement replacements were rated ‘good’ as regards to resistance to air permeability as per the classification given in Table 4. At 91 days of age, air permeability of the fly ash concretes generally decreased to a great extent. The concrete mixture having 50% cement replacement showed the minimum permeability at 91 days. When fly ash inclusion was increased to
70%, the air permeability
increased substantially. The water permeability test results are presented in Figure 8. The mixture with 30% cement replacement showed the best results with respect to water permeability at all test ages. In general, the fly ash concretes up to 40% cement replacement showed better results than the reference concrete without fly ash at all test ages. The mixtures with 30, 40 and 50% replacements showed excellent resistance to water permeability at 91 days, whereas the other mixtures including the reference mixture showed good resistance to water permeability at this age. Chloride ion permeability
The chloride ion permeability test results are presented in Figure 9. In this study all the concrete mixtures except the 70% fly ash mixture at 2-month age exhibited ‘moderate permeability’ in accordance with ASTM C
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Properties of high perfotmance concrete: T. R. Naik et al. Air-void parameters
0
30
15 C.men,
40 R.pl.c.mmt.
50
70
P.m.“,
Figure 7 Air permeability of concrete having various levels of cement replacement with fly ash
of hardened concrete
The test results for air-void parameters of hardened concrete are presented in Table 7. The air-void variables such as air content, air bubble spacing, and specific surface affect freezing and thawing resistance of concrete to a large extent. In general, for adequate freezing and thawing resistance, concrete should have 4 to 7% air content, an air bubble spacing factor of less than 0.2 mm, and a specific surface greater than 24 mm mm-3. As can be expected, the measured air content of the hardened concrete specimens was lower than that for the fresh concrete. This probably is due to loss of air that occurs during casting of the specimen and mechanical vibration. In this investigation, the values of bubble spacing factor were around 0.20 mm and varied from 0.08 to 0.25 mm for the mixtures tested. The specific surface values for the mixtures ranged from 19 to 59 mm mm-3. Freezing and thawing
Figure 8 Water permeability of concrete having various levels of cement replacement with fly ash
Bwo
1
Figure 8 Chloride permeability of concrete having various levels of cement replacement with fly ash
A summary of test results regarding freezing and thawing durability of all the mixtures is presented in Table 8. The reference mixture and the 30% fly ash mixture exhibited similar durability factor values up to 300 cycles of freezing and thawing. However, other fly ash mixtures showed lower durability factor values compared to the reference mixture, though higher than 60 which is normally considered satisfactory. In general, the freezing and thawing durability factor decreased with an increase in fly ash content, particularly beyond the 30% replacement level. The 70% fly ash mixture experienced severe surface scaling when subjected to 300 cycles of freezing and thawing. The values of bubble spacing and specific surface were 0.23 mm and 22 mm mm-3 for the reference mixture, and 0.23 mm and 19 mm mm-3 for the 30% mixtures, respectively. The 15% mixture showed similar values of these parameters. The 50% and 70% mixtures showed lower values of bubble spacing and higher values of specific surface area (Table 7). The results of this work confirmed that bubble spacing should be in the range of 0.2 ? 0.08 mm to obtain adequate freezing and thawing durability of concrete systems.
1202 criteria, Table 6. However, the fly ash mixtures up
Deicer salt scaling resistance
to 50% cement replacement attained higher resistance to chloride permeability compared to the mixtures containing no fly and 70% fly ash up to 3-month of age. The 50% fly ash concrete mixture showed higher resistance to chloride penetration relative to the reference concrete at all test ages. The chloride permeability values observed were 1170 coulombs for the reference concrete without fly ash, 390 coulombs for the 15% mixture, 605 coulombs for the 30% mixture, 650 coulombs for the 40% mixture, 430 coulombs for the 50% mixture, and 230 coulombs for the 70% fly ash at one year age. Thus all the fly ash mixtures attained ‘very low’ chloride permeability, except the reference mixture which exhibited ‘low’ chloride permeability at one year age.
Test results determined in accordance with ASTM C 672 are presented in Table 9. According to ASTM C 672, concrete resistance to surface scaling is rated between zero and five, zero being the highest and five being the lowest resistance to salt scaling. The results indicated that concrete containing fly ash for up to 40% cement replacements exhibited no scaling after 50 cycles of freezing and thawing in the presence of deicing salt. The 50% fly ash concrete mixture achieved a rating of two, representing ‘slight to moderate’ scaling according to ASTM C 672. However, the 70% fly ash concrete showed severe surface scaling. The mass of the scale residue after 50 cycles of freezing and thawing was low for the fly ash concretes up to 50% cement replace-
202
Construction and Building Materials 1995 Volume 9 Number 4
Properties of high performance concrete: T. R. Naik et al. ments, ranging from 0.194 to 0.840 kg m-2. Concrete specimens made from the 70% fly ash mixture exhibited a high amount of scale-off residue with a value of 2.32 kg m-2 at the end of 50 cycles.
Conclusions Based on test data, the following primary conclusions can be drawn. In general, at the ages of one day strength properties of the fly ash concretes were lower than the reference concrete. However, due to substantial pozzolanic reactions of the fly ash, the fly ash mixtures showed rapid gains in strength with age. With respect to compressive strength, tensile strength, flexural strength, and modulus of elasticity, the 30% mixture showed the best results. This mixture produced high values of these parameters at 28 days which are comparable to those exhibited by high-strength concretes. Shrinkage of concrete decreased slightly with increasing amounts of fly ash. Air permeability of the concrete mixtures having between 0 and 40% cement replacements was rated to be good at 28 days, but the no-fly ash mixture showed the lowest permeability value. At 91 days, all the mixtures up to 50% cement replacements showed good resistance to air permeability and the 50% fly ash mixture showed the lowest permeability value. The fly ash concrete mixtures up to 40% cement replacements showed better results than the reference mixture at 28 days with respect to the water permeability. At 91 days, the 30, 40 and 50% mixtures showed excellent resistance to water permeability, while the remaining mixtures including the reference concrete showed good resistance to water permeability. Abrasion resistance of the fly ash concrete mixtures up to 30% cement replacements was essentially the same. Beyond 30%, up to 70% cement replacement with the fly ash, abrasion resistance of concrete decreased. At about two months of age, all the mixtures up to 50% cement replacements exhibited moderate chloride ion permeability. At three months, all the fly ash mixtures up to 50% cement replacements showed low permeability, while the reference mixture and the 70% mixture showed moderate chloride permeability. At one year, all the mixtures except the reference mixture attained very low permeabilities, ranging from 230 to 605 coulombs. The reference mixture showed a chloride permeability of 1170 coulombs at the one year age. Both the reference mixture and the 30% mixture showed excellent resistance to freezing and thawing all the mixtures with and actions. However, without fly ash passed the freezing and thawing resistance in accordance with ASTM C666. Construction
9
The concrete mixtures up to 40% cement replacements with the Class C fly ash showed excellent salt scaling resistance according to ASTM C 672 criteria. The 50% fly ash mixture exhibited slight to moderate surface scaling. However, the 70% fly ash mixture performed poorly in the salt scaling tests. 10 Test data revealed that up to 30% cement replacement (F/(C+FA) ratio of 35% mixtures) can be used in production of high performance concretes. However, all the mixtures, up to 50% cement replacements with the fly ash, can be used for structural applications.
References 1 Gillott, M. A., Naik, T. R. and Singh, S. S. Microstructure of fly ash containing concrete with emphasis on the aggregate-past boundary. In Proc. 51~ Annual Meeting of the Microscopy Society of America, August 1993
2
3
4 5
6
7
8
Naik, T. R. and Ramme, B. W. Low cement content high strength structural grade concrete with fly ash. Presented at the 1986 Fall Convention, ACI, Baltimore, Maryland, November 9-14, 1986; and In!. J. Cement Concr. Res. 1989, 17, 283-294 Naik, T. R., Ramme, B. W. and Tews, J. H. Pavement construction with high-volume class C and class F fly ash concrete. Presented at the Fourth International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Istanbul, Turkey, 49 May 1992 Naik, T. R. and Ramme, B. W. High strength concrete containing large quantities of fly ash. AU Mater. J. 1989,86 (2) 11l-1 17 Naik, T. R. and Singh, S. S. Superplasticized structural concrete containing high volumes of class C fly ash. ASCE J. Energy Eng. 1991, 117 (2) 87-95 Giaccio, G. M. and Malhotra, V. M. Concrete incorporating high volumes of ASTM class F fly ash. ASTM J. Cement, Concr. Aggreg. 1988, 10 (2) 88-95 Malhotra, V. M. and Painter, K. E. Early-age strength properties and freezing and thawing resistance of concrete incorporating high volumes of ASTM class F fly ash. Int. J. Cement Compos. Lightw. Aggreg. 1989, 11 (1) 3746 Langley, W. S., Carette, G. G. and Malhotra, V. M. Structural concrete incorporating high volumes of ASTM class F fly ash. ACZMater.
J. 1989, 86 (5) 507-514
9
Naik, T. R., Singh, S. S. and Hu, W. Y. High-volume fly ash concrete technology. EPRI Report No. TR 100473, March 1992 10 Bilodeau, A. and Malhotra, V. M. Concrete incorporating high volumes of ASTM class F fly ashes: mechanical properties and resistance to deicing salt scaling and to chloride-ion penetration. In Proc. Fourth International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Istanbul, Turkey, ed. V. M. Malhotra, Vol. 1, AC1 Special Publication No. SP-132, 1992, pp. 319-349
11 Garette, G. G., Bilodeau, A., Cheurier, R. and Malhotra, V. M. Mechanical properties of concrete incorporating high volumes of fly ash from sources in the USA. AC1 Mater. J. I994,90 (6) 535-544 12 Gebler, S. H. and Kheger, P. Effect of fly ash on physical properties of concrete. In Proc. CANMET/ACI Second International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Madrid, Spain, ed. V. M. Malhotra, Vol.
1, AC1 Special Publication No. SP-91, 1986, pp l-50 13 Tikalsky, P. J., Carrasquillo, P. M. and Carrasquillo, R. L. Strength and durability considerations affecting mix proportioning of concrete containing fly ash. ACI Mater. J. 1988, 85 (6) 505-511
14 Hadchti, K. M. and Carrasquillo, R. L. Abrasion resistance and scaling resistance of concrete containing fly ash. Center for Transportation Research, Bureau of Engineering Research, University of Texas at Austin, Research Report No. 481-3, August 1988, p 185 15 Ellis, W. E., Jr., Riggs, E. H. and Butler, W. B. Comparative results of utilization of fly ash, silica fume, and GGBFS in reducing the chloride permeability of concrete. In Proc. Second CANMET/ACI International Conference on Durability of Concrete, Montreal, Canada, ed. V. M. Malhotra. AC1 Special
Publication No. 126, 1991, pp 443458
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I7 I8
IY
20 21
concrete:
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Naik. T. R.. Pat&, V. M. and Brand. L. E. Performance of highstrength concrete incorporating mmerals by-products. Presented at the Research in Progress Seminar at the AC1 National Convention. Washington, DC. IS-19 March 1992 Thomas, M. D. A. and Matthews, J. C. The permeability of Ay ash concrete. Muter. Sfruct. 1992, 25 (151) 38%396 Bilodeau. A.. Sivasundaram, V.. Painter. K. E. and Malhotra. V M. Durability of concrete incorporating high volumes of tly ash from sources in the USA. ACI Ma!rr. J 1994. 91 (I) 3.-17 Rodway, E. L. Effect of air-entraining agent on air-void parameters of low and high-calcium Hy ash concretes. AST,%I .I Cemenr Concr. Aggreg. 1988. 10 (I) 35.~38 Larson. T. D. Air entrainment and durability aspects of f! a5.h concrete. In Proc. Amer. Conc,r. Insf. 1964. 64. 866.-886 Gebler, S. and Klieger, P. Effect of tlv ash on the air void stabiltty of concrete. In Proc. First Internui>onul Co+wtw on the lJw qf F1.v A.\h, Silica Fume, Slug und Olhzr Nuturul ByProcluc~~ in Concrete, Monrehellow. Cunadu. ed V M. Malhotra. Vol I. AC1
22
204
Special Publication No. SP-79, 1983. pp 103-142 Johnston, C. Effects of microsilica and class C fly ash on resistance of concrete to rapid freezing and thawing and scaling in the presence of deicing agents. Concrete Dtrrohilit_v Proceedings of the
Kothurine and Bryant Mother Internationul Conference. Atlanta, Georgiu, AC1 Special Publication No. SP-100, April-May 1987,
23
pp 1183-1204 Nasser, K. W. and Lai. P S. H. Resistance of By ash concrete freezing and thawing. In Proc. Fourth International Conference the ll.w of F1.v Ash. Silicu Cotwere, Lytunhul. Turky,
24
Fume.
Slug, und Nuturul
ed V. M. Malhotra, Vol. 1, AC1 Special Publication No. SP-132. 1992, pp 205-226 Naik. T. R. and Ramme. B. W. Freezing and thawing durabtlity of high-lime content class C fly ash concrete. In Proc. Srwnd CANMET/ACI In~ernuiionul Conference Concrete, Montreul, Quebec, Cunudu, August
25
76 27
to
on Pozzoluns in
on
Duruhilit.v
qf
199 I, pp 6 15-64 1 Naik, T. R. and Singh, S. S. Use of high-lime fly ash in cementbased construction materials. Approved for Publication and Presentation at the Fifth International Conference on the Use of Fly Ash, Silica Fume. Slag, and Natural Pozzolans in Concrete, Milwaukee, Wisconsin, USA, 4-9 June 1995 Figg, J. W. Methods of measuring the air and water permeability of concrete. MUK. Concr. Res 1973. 25 (251 213-219 Cather. R. B., Figg. J. W.. Marsdon. A. 6. and O’Brien. T. P. Improvement to the Figg method for determining the air permeability of concrete. Mug. Concr. Rex 1984, 36 (129) 241.-245
Construction and Building Materials 1995 Volume 9 Number 4
8 1995 Elsevier Science Limited Printed in Great Britain. AI1 rights reserved 0950-0618/95 $10.00+0.00
o95o-o618(95)oooO!L7
Properties of high performance concrete systems incorporating large amounts of high-lime fly ash Tarun R. Naik, Shiw S. Singh and Mohammad
M. Hossain
Department of Civil Engineering and Mechanics, College of Engineering and Applied Science, The University of Wisconsin - Milwaukee, PO Box 784, Milwaukee, WI 53201, USA Received
1 September
1993; revised 30 November
1994; accepted
16 January
1995
This research was undertaken to evaluate the engineering propenies of high-lime (ASTM Class C) fly ash concretes. An air-entrained reference concrete mixture without fly ash was proportioned to have 28-day compressive strength of 41 MPa. Additionally, concrete mixtures were also proportioned to have cement replacement with Class C fly ash in the range of O-70% by weight. For each concrete mixture, specimens were made to evaluate compressive strength, tensile strength, flexural strength, modulus of elasticity, shrinkage, abrasion resistance, air permeability, water permeability, chloride ion permeability, air-void parameters, freezing and thawing durability, and salt scaling resistance, of hardened concrete. The results of this study established that high-performance concrete incorporating Class C fly ash at 30% cement replacement can be proportioned for high-strength applications. In general, concrete mixtures up to 50% cement replacement with fly ash showed satisfactory performance with respect to strength and physical durability properties appropriate for structural applications. Keywords:
abrasion; air entertainment;
air permeability
It is now well established that inclusion of fly ash is not only desirable for deriving economic, energy conservation and ecological benefits, but it is also highly effective in modifying concrete properties for numerous applications1-25. The use of Class C and F fly ashes as an admixture is desirable in the production of very dense and durable concretes. This is achieved because the presence of fly ash generally reduces heat of hydration and thus helps reduce the adverse effects of rapid hydration reaction resulting from the use of rich mixtures. Additionally, both grain and pore refinements occur due to the fly ash addition’ resulting in increased resistance to permeability of water, CO, and other aggressive agents. This, in turn, improves durability of concrete. More recently, attempts have been made to develop high-performance concrete containing significant amounts of mineral admixtures. In this work, highperformance concrete has been defined as a concrete which exhibits excellent strength and durability properties that are required for a particular application. This research was carried out to establish fly ash concrete mixtures for high-performance and structural applications. To accomplish this, concrete mixtures with and without Class C fly ash were manufactured and their strength and durability properties were determined. Highperformance concrete requires: (1) low-heat cement; (2) high-quality aggregates; (3) supplementary cementing Construction
materials; (4) low water-to-cementitious materials ratio; and (5) chemical additives. These requirements were satisfied for the concrete used for this project by low-cement factor with use of fly ash, addition of high-range water reducers and use of high-quality aggregates. Review of literature For more than half a century fly ash has been used in concrete. Since the late 194Os, significant amounts of Class F fly ash has been used in mass concrete to reduce the heat of hydration and early age cracking. Currently fly ash is being employed in a wide variety of concrete construction projects29 3. Up to a certain level of cement replacement with Class C fly ash, strength properties of concrete are either better than or comparable to concrete without fly ash. More recent investigations have shown adequate strength and durability characteristics of high-volume fly ash systems for structural and other applications2-g. Pioneering work for production of structural concrete with low-lime (ASTM Class F) fly ash was done by Malhotra and his associates. Research work pertaining to the use of large quantities of Class C fly ash in structural and paving concretes started at the University of Wisconsin-Milwaukee, in 19842,4. Shrinkage of concrete containing fly ash has been investigated by a number of and Building
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Properties
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T. R. Naik et al.
researchers3j8-“. In general, shrinkage of fly ash concrete is either lower than or comparable to no-fly ash concrete. Gebler and Klieger’? proportioned concrete mixtures at 25% cement replacement with Class F and Class C fly ashes. The authors reported that the abrasion resistance of Class C fly ash concrete was generally superior to Class F fly ash concrete. Tikalsky et al.” observed the same trend but up to 35% cement replacement with fly ash. Hadchti et ~1.‘~ reported that at equal strengths, concrete with fly ash is as resistant to abrasion as no-fly ash concrete. Naik et cd.3 reported that concrete made with 50% Class C fly ash attained higher abrasion resistance than concrete with 40% Class F fly ash. Bilodeau and Malhotra’O studied abrasion resistance of concrete incorporating 55 to 60% Class F fly ash of total cementitious materials. Their test results showed lower abrasion for the fly ash concretes compared to a reference concrete without fly ash. Ellis et ~1.‘~showed that concrete made with Class F fly ash was more effective in reducing concrete permeability than concrete incorporating Class C fly ash. Naik et (11.‘~ reported chloride permeability of 918 coulombs for the reference concrete with 20% Class C fly ash, 391 coulombs for 50% Class C fly ash mixture, and 188 coulombs for 40% Class F fly ash at one year age. Other researchers “3 i* also found very low chloride permeability results for fly ash concrete systems. Studiesi9-** have established that inclusion of fly ash in concrete increases the dosage of air-entaining admixtures (AEA) compared to concrete without fly ash. The dosage rate for AEA depends upon the loss-on-ignition (LOI) and chemical composition of fly ash, fineness of fly ash, type and amount of fiy ash used in the mixture, etc. Larson20 reported that fly ash does not have adverse effects on the air void system in hardened concrete. Gebler and Klieger2’ reported that concrete containing Class C fly ash demands less AEA compared to concrete with Class F fly ash. Several studies&*xii, ‘Z 18,?‘-24have shown that properly air entrained fly ash concretes exhibit freezing and thawing resistance similar to no-fly ash concretes. A number of studies33lo, Is, 22 have shown low salt scaling resistance of concrete containing fly ash. More research is needed to establish salt scaling characteristics/resistance of concrete as a function of fly ash inclusion. Some researchers25 have found reduction in sulphate resistance of concrete due to addition of Class C fly ashes. However, other researchers25 did not observe this trend. Additional research is needed to establish sulphate resistance of concrete containing Class C fly ash. In the presence of amorphous silica containing aggregates, addition of Class C fly ash having large amounts of water soluble alkali sulphates can participate in the alkali-silica reactions in concrete. The reaction can produce significant expansion if the value of total amounts of water soluble alkalies in concrete from all sources is greater than 2.5 kg m-3. 196
Construction
Experimental program An experimental program was designed to develop fly ash concrete mixture proportions for high-performance and structural applications. Each concrete mixture was evaluated with respect to compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, shrinkage, air permeability, water permeability, chloride ion permeability, abrasion resistance, air-void system parameters, freezing and thawing resistance, and salt scaling resistance of hardened concrete.
Materials A Type I portland cement conforming to ASTM C 150 requirements was used. The test results are shown in Table 1. An ASTM Class C fly ash obtained from the Pleasant Prairie Power Plant, Kenosha, Wisconsin was used throughout this investigation. The chemical and physical properties of the fly ash were determined in accordance with applicable ASTM test methods (Tuble I). A natural sand with a 6.35 mm maximum size was used as a fine aggregate. A coarse aggregate used in this study was 25 mm nominal maximum size of crushed limestone obtained from one source. Physical properties of the aggregates are given in Table 2. Both the fine and coarse aggregates met the ASTM C 33 gradation requirements. A commercially available melaminebased superplasticizer and a resin type air-entraining admixture were used.
Mixture proportions A total of six different mixtures were produced. One of them was the reference mixture containing no fly ash, and the other five mixtures contained the Class C fly ash. The mixture proportions were developed for producing concrete on a 1.25 to 1, fly ash inclusion to cement replaced, weight basis. The levels of cement replacement ranged from 15-70%. The mixture proportions are given in Table 3. The control mixture without fly ash was proportioned to have 28-day compressive strength of 41 MPa. The water-to-cementitious materials ratio (W/(C+FA)) was maintained at about 0.35 + 0.02 and air content was kept at 6 ?Y1%. Each test batch of 0.76 m3 was mixed in a power-driven revolvingpaddle mixer according to ASTM C 192.
Casting and curing of test specimens Cylinders (150 X 300 mm) were cast from each mixture to evaluate compressive strength, modulus of elasticity and splitting tensile strength. Prism specimens of 75 x 100 X 400 mm were cast for flexural strength and shrinkage measurements. Cylinders (100 X 200 mm) were cast for measurement of chloride ion permeability. Prism specimens (75 X 100 X 400 mm) were cast to evaluate freezing and thawing durability. Slab specimens (300 X 300 X 100 mm) were cast for air permeability, water permeability, abrasion resistance and
and Building Materials 1995 Volume 9 Number 4
Properties of high performance concrete: T. R. Naik et al. Table 1 Properties of cement and fly ash used
Cement (“/)
Chemical composition
Silicon dioxide, SiO, Aluminium oxide, Al,O, Ferric oxide, Fe,O, Total, SiO, + Al,O, + Fe,O, Sulphur trioxide, SO, Calcium oxide, CaO Magnesium oxide, MgO Titanium dioxide, TiO, Potassium oxide, K,O Sodium oxide, NarO Moisture content Loss on ignition
ASTM C 150, Type 1
Fly Ash (“~)
ASTM C 618, Class C
_
30.5 17.2 5.5 53.2 _ 28.6 4.7 1.6 0.4 2.0 0.1 0.3
_
20.2 4.7 0.3 25.2 _ 64.1 0.9 0.3 0.1 0.1
_ _ _ 3 max. _ 6 max. _ _ _ 3.0 max.
_
50.0 min 5.0 max. _ 5.0 max. _ _ 1.5 max. 3.0 max. 6.0 max.
Physical properties of cement 7.1 395.8 0.03 3.16
Air content (%) Fineness (m2 kg-‘) Autoclave expansion (%) Specific gravity Compressive strength, (MPa) 1-day 3-day 7-day 28-day Vicat time of initial set (min)
_ _ _
12 max. 280 min. 0.8 max.
_
16.2 25.7 31.5 37.9 145
12.4 min. 19.3 min. _ 45 min., 375 max.
Physical properties of fly ash Fineness retained on No. 325 sieve (%) Pozzolanic activity index with cement 28-day (% of control) Water requirement (% of control) Autoclave expansion (%) Specific gravity
_ _
_ _
18.6 105
34 max. 75 min.
_ _ _
_ _ _
90.4 0.02 2.78
105 max. 0.8 max.
Table 2 Physical properties of aggregates Fine aggregates Sieve size
#4 #8 #16 #30 #50 #loo
Coarse aggregates
% Passing
ASTM C 33, % Passing
Sieve size
% Passing
ASTM c33, % Passing
100 91 74 49 17 4
95-100 80-100 50-85 2560 lo-30 2-10
25 mm 19 mm 13 mm 9.5 mm #4 #8
99 96 43 15 3 2
95 to 100 _ 25 to 60 _ oto 10 0 to 5
Physical properties Aggregates
Fine Coarse
Bulk specific gravity
Bulk specific gravity (SSD)
Apparent specific gravity
2.54 2.76
2.57 2.78
2.62 2.84
deicer salt scaling resistance. All the test specimens were cast according to ASTM C 192. Immediately after casting, all the specimens were covered with plastic to minimize their moisture loss. These specimens were stored at temperatures of about 23°C in the casting room area of a precast concrete plant. After 24 h, the specimens were demoulded. They were then put into a moist curing room at 23°C with 100% relative humidity until the time of test. The 70%
SSD absorption (%) 1.30 1.10
Dry rodded unit weight (kg m-r)
Percent voids
1764 1756
30.5 36.4
fly ash mixture specimens were demoulded after 11 days of curing under room conditions at 23°C due to their slow setting. Testing of specimens Fresh concrete properties
Slump, unit weight, temperature, and air content for each batch were determined according to applicable ASTM test methods. The results are presented in Table 3.
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Table3 Mixture proportions using ASTM class C fly ash - 41 MPa specified strength Mixture no.
c-3
P4-2
P4-3
P4-6
P4-7
P4-8
Cement (kg m-9 Fly ash (kg mm’) Water (kg m-3)
315 0 136 0.36 682
259 139 133 0.34 677
220 182 150 0.37 659
320 71 129 0.33 693
180 226 135 0.33 655
110 316 155 0.36 607
1183 120 6.3 2.9 270 21 23
1173 159 5.2 2.x 348 21 23
1153 121 6.4 2.7 514 21 26
1181 146 6.7 2.8 416 19 21
1138 114 7.0 2.7 886 22 26
1146 121 6.4 2.6 1380 21 25
2381
2393
2360
2400
2337
2365
2470
2432
2416
2440
2342
2326
W/(C+FA)I Sand, SSD (kg mm3) 25 mm aggregates, SSD (kg mm3) Slump (mm) Air content (%) Superplasticizer (1 m-‘) Air entraining agent (ml m 3, Air temperature (“C) Concrete temperature (“C) Fresh concrete destiny (kg m-‘) Hardened concrete density, SSD (kg mm3)
Hurdened concrete properties
Compressive strength tests of test specimens were performed according to ASTM C 39. The static modulus of elasticity of concrete was determined in accordance with ASTM C 469. The tensile strength test was carried out in accordance with ASTM C 496. Flexural strength measurements were made using the third-point loading according to ASTM C 78. The water storage test method was used to evaluate the shrinkage characteristics of concrete specimens in accordance with ASTM C 157. Three specimens were tested for each experimental condition for evaluation of the above properties. Air and water permeabilities of the test specimens were evaluated by using the Figg method. A detailed description of this test technique is presented elsewhere26*27.This method involved drilling a hole typically 40 mm deep by 10 mm in diameter from the top of concrete surface. These holes were plugged with a polyethylene foam pad and the head sealed with a silicone sealant. A hypodermic needle was then pushed into the plug. For the air permeability testing the hypodermic needle was subjected to a vacuum pressure of about minus 55 kPa by a hand vacuum pump. The time taken for the pressure change from minus 55 kPa to minus 50 kPa was taken as a measure of air permeability of concrete. For water permeability testing a water head of 100 mm was applied to the concrete through the needle. Then the time taken to absorb 0.02 ml of water was recorded as a measure of water permeability. Typical air and water permeability qualitative interpretations normally used26 are given in Tables 4 and 5. Chloride ion permeability of concrete was determined in accordance with ASTM C 1202. Three 100 X 200 mm cylinders were cast for each experimental condition. From each cylinder, three 100 mm diameter X 50 mm thick slices were cut from the middle portion using a diamond tipped saw. Each mixture was evaluated for resistance to chloride permeability according to criteria presented in Table 6. Abrasion tests were conducted on the moulded surface of the slab specimens to maintain uniform 198
surface of the specimens. All the specimens were tested in a dry condition by the ASTM C 994 test method. Three separate areas were tested on the same face of the specimen. The rotating cutter consisted of 24 grinding dressing wheels. The rotating cutter, having washers with a diameter equal to that of the dressing wheels, produced depths of abrasion of about 1 mm after about 60 min of exposure to the abrasive force. This was considered too slow. Therefore, it was decided to develop an accelerated technique, especially for concretes having high resistance to abrasion similar to the ones used in this investigation. The developed method was equipped with washers having a smaller diameter relative to the dressing wheels. Furthermore, approximately one teaspoon of silica sand (‘Ottawa Sand’) was added to the concrete surface subjected to abrasion at an interval of one minute. At each wear location (circle of wear), for each wear time, readings were taken at two points in the circle. At each point, three readings were recorded, and the average of these six readings was reported as one data point for each wear circle at the measured time of wear. The parameters of the air-void system in hardened concrete were measured in accordance with ASTM C 457. The linear traverse method was employed in this work. Test specimens (75 X 100 X 19 mm) were obtained from the prism specimens used for flexural strength tests. Each sample was polished to obtain a surface suitable for microscopic examination as required by the ASTM procedure. Freezing and thawing resistance of concrete was evaluated according to ASTM 666, Procedure A. Each mixture was evaluated for freezing and thawing durability at different testing ages. This was done to test them at an equivalent strength/maturity level with a minimum specified strength of 28 MPa. Mixture Nos C-3 and P4-2 were tested after 14 days of moist curing. Mixture No. P4-3 was tested at a 56-day age, and the other mixtures (P4-6, P4-7 and P4-8) were tested at 66 days of age. Specimens (300 X 300 X 100 mm) were tested for deicer salt scaling resistance in accordance with ASTM C 672. The specimens were subjected to the deicer salt
Construction and Building Materials 1995 Volume 9 Number 4
Properties of high petfotmance concrete: T. R. Naik et al. Table 4 Classification of air permeability of concrete (specimens conditioned to constant weight and temperature)% Quality category
0
I 2 3 4
Time for pressure change (s)
Interpretation
Typica material
< 30 30-100 100-300 300-1000 > 1000
Poor Moderate Fair Good Excellent
Porous mortar 21 MPa concrete 41 MPa concrete 62 MPa concrete Polymer-modified concrete
Table 5 Typical water permeability qualitative classification26 Time for absorption (s)
Concrete category
Protective quality
Typical material
Poor Moderate Fair Good Excellent
Mortar 21 MPa concrete 41 MPa concrete 62 MPa concrete Polymer-modified concrete
4zO 100-200 200-1000 > 1000
Table 6 Chloride permeability based on the charge passed in accordance with ASTM C 1201 Charge passed (Coulombs) >4000 2OOO4000 1000-2000 100-1000 c 100
Chloride permeability
Typical material
High Moderate
High water-cement ratio (0.6) concrete Moderate water-cement ratio (0.4-0.5) concrete Low water-cement ratio (0.4) concrete Latex-modified concrete Polymer concrete
LOW
Very !ow Negligible
scaling after 4 weeks of moist curing followed by 3 weeks of air curing in the laboratory. The deicer used was 4% CaCl, solution, as prescribed by the ASTM test method.
Test results and discussions Compressive strength The compressive strength test results for all the six mixtures are illustrated in Figure I. The compressive strengths were measured at the ages of 1, 3, 7, 28, 91 and 365 days. At early ages up to 3 days, all the fly ash concrete mixtures showed lower strength compared to the reference mixture without fly ash; and it decreased with increasing fly ash content (Figure I). The 30% fly ash mixture showed peak compressive strengths at all ages beyond 3 days. Above 30% cement replacement, the compressive strength of concrete generally decreased with increasing amounts of fly ash up to 70% cement replacement. At 28 days, the 30% mixture showed in excess of 48 MPa. The 40 and 50% fly ash mixtures attained 2%day strengths in excess of 30 MPa. As compared with the reference concrete, the fly ash concrete mixtures showed high rates of strength gain due to the contributions from pouolanic reactions of the fly ash. As a result, the compressive strength of the fly ash mixtures increased substantially compared to their strengths at 28 days (Figure I). Splitting tensile strength The splitting tensile strength test data are presented in Figure 2. The tensile strength increased with age. The early age tensile strength decreased with increasing fly Construction
cl
20
40 c-t
Figure
80
80
Replmmemt, racnt
1 Compressive strength versus cement replacement with fly
ash
0
Figure 2 Splitting tensile strength versus cement replacement with fly ash
ash content, but the tensile strength obtained for the concrete mixtures having O-30% cement replacement showed identical results at 7 days. The 15% mixture produced peak tensile strength at 7 days. At 28 days, and Building Materials 1995 Volume 9 Number 4
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Properties of high performance
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T. R. Naik et al.
the tensile strength results were similar up to 30% cement replacements. The difference between tensile strength of the control and the fly ash concrete mixtures diminished greatly, especially at later ages. This occurred because of grain and pore refinements of the concretes resulting from pozzolanic reactions of the fly ash. At 91 and 365 days, peak tensile strengths were achieved at 30% cement replacement level. Flexurul strength
Test data observed at the ages of 3, 7, 28, 56 and 365 days are given in Figure 3. The flexural strength of concrete increased substantially with age. At a 3-day age, the fly ash concretes showed lower flexural strength compared to the reference concrete. At 7 days, flexural strengths of the mixtures were nearly identical up to 30% cement replacement. When the concretes were cured for 28 days, the 30% mixture exhibited the maximum flexural strength of all the mixtures evaluated (Figure 3). The same trend was noticed at 56 days. At 365 days, the fly ash mixtures up to 30% cement identical flexural nearly replacements produced strengths. The values of the flexural strength for the 30% mixture varied from 5.6 MPa at 28 days to 7.0 MPa at 365 days. Modulus oj’ elusticity
The secant modulus of elasticity data (measured according to the ASTM test procedure) of the test mixtures are illustrated in Figure 4. The modulus of elasticity increased substantially with age up to 365 days. The very early-age modulus of elasticity of concrete
Figure 3 Flexural
strengthversus cement replacement with fly ash
Figure 4 Modulus of elasticity versus cement replacement with fly ash
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Construction
decreased with increasing fly ash content. The modulus of elasticity values of the mixtures varied from 2.0 x lo4 MPa to 2.6 X IO4 MPa at 28 days. The modulus of elasticity of all the mixtures varied from 2.7 X lo4 MPa to 3.4 X lo4 MPa at 91 days, and from 3.3 X lo4 MPa to 4.6 x lo4 MPa at 365 days. The modulus values for up to 30% cement replacements were very satisfactory for high strength applications. The modulus of elasticity of concrete at high cement replacement levels (40, 50 and 70%) was similar to the values shown by structural grade concretes. Shrinkage
The shrinkage strain test results for all the concrete mixtures are presented in Figure 5. The results show that the shrinkage strain generally increased with increasing ages for all the mixtures irrespective of fly ash addition. In general, beyond 7 days, the shrinkage strain of test specimens decreased as fly ash content increased. However, the shrinkage strains experienced by all the test specimens were small. Abrasion resistance
The abrasion tests were performed at ages of 28, 91 and 365 days. The average depth of wear for test specimens for all the mixtures are presented in Figure 6. The results indicated that the concrete mixtures up to 30% cement replacement by fly ash had abrasion resistance similar to that for concrete without fly ash. Beyond 30% cement replacements, abrasion resistance decreased slightly up to 50% cement replacement. The 70% Class C fly ash mixture attained the lowest abra-
Figure 5 Shrinkage strain versus cement replacement with fly ash
Figure 6 Abrasion resistance versus cement
and Building Materials 1995 Volume 9 Number 4
replacement
with fly ash
Properties
of high performance
concrete:
T. R. Naik et al.
Table 7 Air void parameters of hardened concrete* Air void parameters*
Mixture no. c-3 P4-6 P4-2 P4-3 P4-I P4-8
Fly ash (%)
Air in plastic concrete (“/)
Air in hardened concrete (“A)
Specific surface (mm mm-‘)
Number of air-void per cm
Spacing factor (mm)
0 15 30 40 50 70
6.3 6.7 5.2 6.4 7.0 6.4
4.0 4.8 5.6 4.8 4.9 5.8
2.2 16 19 42 39 59
2.2 2.3 2.6 5.0 4.8 6.9
0.23 0.25 0.23 0.13 0.13 0.08
* The data presented are averages of three observations Table 8 Summary of test results of concrete prisms after 300 cycles of freezing and thawing Mixture no.
Percent change at the end of 300 freezing and thawing cycles
Fly ash (“h) Weight
Length
Resonant frequency
c-3 P4-6 P4-2 P4-3 P4-I P4-8
0 I5 30 40 50 70
-0.56 -0.52 Al.36 -1.14 -0.91 -1.07
0.03 0.08 0.04 0.07 0.06 0.05
-0.02 -0.09 -0.03 -0.15 -0.12 -0.15
Relative dynamic modulus of Pulse velocity
elasticity
-2.20 -8.07 -1.18 -11.22 -6.72 -9.46
95.8 83.4 94.3 72.4 71.7 12.3
Durability factor
w 96 83 94 12 78 12
Table 9 Deicer salts scaling test results Mixture no.
c-3 P4-6 P4-2 P4-3 P4-I P4-8
Fly ash (“h)
Air content (“A)
Final visual rating*
Total scaled off residue (kg m-3
0 15 30 40 50 IO
6.3 6.7 5.2 6.4 7.0 6.4
0 0 0 0 2 5
0.323 0.355 0.323 0.388 0.840 2.32
* ASTM C 672 visual rating scale Rating 0
Surface Condition No scaling
I 2 3 4
Very slight scaling (3.2 mm depth, max no coarse aggregate visible) Slight to moderate scaling Moderate scaling (some coarse aggregate visible) Moderate to severe scaling Severe scaling (coarse aggregate visible over the entire surface)
5
sion resistance value. In this work, the abrasion was found to be strongly affected by compressive strength regardless of inclusion of fly ash. Air and water permeability
The air and water permeability test results are presented in Figures 7 and 8. In general, concrete air permeability decreased with age (Figure 7). Both at 14 and 28 days, air permeability of the concrete increased somewhat with addition of fly ash. But at 28 days, the concrete mixtures up to 40% cement replacements were rated ‘good’ as regards to resistance to air permeability as per the classification given in Table 4. At 91 days of age, air permeability of the fly ash concretes generally decreased to a great extent. The concrete mixture having 50% cement replacement showed the minimum permeability at 91 days. When fly ash inclusion was increased to
70%, the air permeability
increased substantially. The water permeability test results are presented in Figure 8. The mixture with 30% cement replacement showed the best results with respect to water permeability at all test ages. In general, the fly ash concretes up to 40% cement replacement showed better results than the reference concrete without fly ash at all test ages. The mixtures with 30, 40 and 50% replacements showed excellent resistance to water permeability at 91 days, whereas the other mixtures including the reference mixture showed good resistance to water permeability at this age. Chloride ion permeability
The chloride ion permeability test results are presented in Figure 9. In this study all the concrete mixtures except the 70% fly ash mixture at 2-month age exhibited ‘moderate permeability’ in accordance with ASTM C
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Properties of high perfotmance concrete: T. R. Naik et al. Air-void parameters
0
30
15 C.men,
40 R.pl.c.mmt.
50
70
P.m.“,
Figure 7 Air permeability of concrete having various levels of cement replacement with fly ash
of hardened concrete
The test results for air-void parameters of hardened concrete are presented in Table 7. The air-void variables such as air content, air bubble spacing, and specific surface affect freezing and thawing resistance of concrete to a large extent. In general, for adequate freezing and thawing resistance, concrete should have 4 to 7% air content, an air bubble spacing factor of less than 0.2 mm, and a specific surface greater than 24 mm mm-3. As can be expected, the measured air content of the hardened concrete specimens was lower than that for the fresh concrete. This probably is due to loss of air that occurs during casting of the specimen and mechanical vibration. In this investigation, the values of bubble spacing factor were around 0.20 mm and varied from 0.08 to 0.25 mm for the mixtures tested. The specific surface values for the mixtures ranged from 19 to 59 mm mm-3. Freezing and thawing
Figure 8 Water permeability of concrete having various levels of cement replacement with fly ash
Bwo
1
Figure 8 Chloride permeability of concrete having various levels of cement replacement with fly ash
A summary of test results regarding freezing and thawing durability of all the mixtures is presented in Table 8. The reference mixture and the 30% fly ash mixture exhibited similar durability factor values up to 300 cycles of freezing and thawing. However, other fly ash mixtures showed lower durability factor values compared to the reference mixture, though higher than 60 which is normally considered satisfactory. In general, the freezing and thawing durability factor decreased with an increase in fly ash content, particularly beyond the 30% replacement level. The 70% fly ash mixture experienced severe surface scaling when subjected to 300 cycles of freezing and thawing. The values of bubble spacing and specific surface were 0.23 mm and 22 mm mm-3 for the reference mixture, and 0.23 mm and 19 mm mm-3 for the 30% mixtures, respectively. The 15% mixture showed similar values of these parameters. The 50% and 70% mixtures showed lower values of bubble spacing and higher values of specific surface area (Table 7). The results of this work confirmed that bubble spacing should be in the range of 0.2 ? 0.08 mm to obtain adequate freezing and thawing durability of concrete systems.
1202 criteria, Table 6. However, the fly ash mixtures up
Deicer salt scaling resistance
to 50% cement replacement attained higher resistance to chloride permeability compared to the mixtures containing no fly and 70% fly ash up to 3-month of age. The 50% fly ash concrete mixture showed higher resistance to chloride penetration relative to the reference concrete at all test ages. The chloride permeability values observed were 1170 coulombs for the reference concrete without fly ash, 390 coulombs for the 15% mixture, 605 coulombs for the 30% mixture, 650 coulombs for the 40% mixture, 430 coulombs for the 50% mixture, and 230 coulombs for the 70% fly ash at one year age. Thus all the fly ash mixtures attained ‘very low’ chloride permeability, except the reference mixture which exhibited ‘low’ chloride permeability at one year age.
Test results determined in accordance with ASTM C 672 are presented in Table 9. According to ASTM C 672, concrete resistance to surface scaling is rated between zero and five, zero being the highest and five being the lowest resistance to salt scaling. The results indicated that concrete containing fly ash for up to 40% cement replacements exhibited no scaling after 50 cycles of freezing and thawing in the presence of deicing salt. The 50% fly ash concrete mixture achieved a rating of two, representing ‘slight to moderate’ scaling according to ASTM C 672. However, the 70% fly ash concrete showed severe surface scaling. The mass of the scale residue after 50 cycles of freezing and thawing was low for the fly ash concretes up to 50% cement replace-
202
Construction and Building Materials 1995 Volume 9 Number 4
Properties of high performance concrete: T. R. Naik et al. ments, ranging from 0.194 to 0.840 kg m-2. Concrete specimens made from the 70% fly ash mixture exhibited a high amount of scale-off residue with a value of 2.32 kg m-2 at the end of 50 cycles.
Conclusions Based on test data, the following primary conclusions can be drawn. In general, at the ages of one day strength properties of the fly ash concretes were lower than the reference concrete. However, due to substantial pozzolanic reactions of the fly ash, the fly ash mixtures showed rapid gains in strength with age. With respect to compressive strength, tensile strength, flexural strength, and modulus of elasticity, the 30% mixture showed the best results. This mixture produced high values of these parameters at 28 days which are comparable to those exhibited by high-strength concretes. Shrinkage of concrete decreased slightly with increasing amounts of fly ash. Air permeability of the concrete mixtures having between 0 and 40% cement replacements was rated to be good at 28 days, but the no-fly ash mixture showed the lowest permeability value. At 91 days, all the mixtures up to 50% cement replacements showed good resistance to air permeability and the 50% fly ash mixture showed the lowest permeability value. The fly ash concrete mixtures up to 40% cement replacements showed better results than the reference mixture at 28 days with respect to the water permeability. At 91 days, the 30, 40 and 50% mixtures showed excellent resistance to water permeability, while the remaining mixtures including the reference concrete showed good resistance to water permeability. Abrasion resistance of the fly ash concrete mixtures up to 30% cement replacements was essentially the same. Beyond 30%, up to 70% cement replacement with the fly ash, abrasion resistance of concrete decreased. At about two months of age, all the mixtures up to 50% cement replacements exhibited moderate chloride ion permeability. At three months, all the fly ash mixtures up to 50% cement replacements showed low permeability, while the reference mixture and the 70% mixture showed moderate chloride permeability. At one year, all the mixtures except the reference mixture attained very low permeabilities, ranging from 230 to 605 coulombs. The reference mixture showed a chloride permeability of 1170 coulombs at the one year age. Both the reference mixture and the 30% mixture showed excellent resistance to freezing and thawing all the mixtures with and actions. However, without fly ash passed the freezing and thawing resistance in accordance with ASTM C666. Construction
9
The concrete mixtures up to 40% cement replacements with the Class C fly ash showed excellent salt scaling resistance according to ASTM C 672 criteria. The 50% fly ash mixture exhibited slight to moderate surface scaling. However, the 70% fly ash mixture performed poorly in the salt scaling tests. 10 Test data revealed that up to 30% cement replacement (F/(C+FA) ratio of 35% mixtures) can be used in production of high performance concretes. However, all the mixtures, up to 50% cement replacements with the fly ash, can be used for structural applications.
References 1 Gillott, M. A., Naik, T. R. and Singh, S. S. Microstructure of fly ash containing concrete with emphasis on the aggregate-past boundary. In Proc. 51~ Annual Meeting of the Microscopy Society of America, August 1993
2
3
4 5
6
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Naik, T. R. and Ramme, B. W. Low cement content high strength structural grade concrete with fly ash. Presented at the 1986 Fall Convention, ACI, Baltimore, Maryland, November 9-14, 1986; and In!. J. Cement Concr. Res. 1989, 17, 283-294 Naik, T. R., Ramme, B. W. and Tews, J. H. Pavement construction with high-volume class C and class F fly ash concrete. Presented at the Fourth International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Istanbul, Turkey, 49 May 1992 Naik, T. R. and Ramme, B. W. High strength concrete containing large quantities of fly ash. AU Mater. J. 1989,86 (2) 11l-1 17 Naik, T. R. and Singh, S. S. Superplasticized structural concrete containing high volumes of class C fly ash. ASCE J. Energy Eng. 1991, 117 (2) 87-95 Giaccio, G. M. and Malhotra, V. M. Concrete incorporating high volumes of ASTM class F fly ash. ASTM J. Cement, Concr. Aggreg. 1988, 10 (2) 88-95 Malhotra, V. M. and Painter, K. E. Early-age strength properties and freezing and thawing resistance of concrete incorporating high volumes of ASTM class F fly ash. Int. J. Cement Compos. Lightw. Aggreg. 1989, 11 (1) 3746 Langley, W. S., Carette, G. G. and Malhotra, V. M. Structural concrete incorporating high volumes of ASTM class F fly ash. ACZMater.
J. 1989, 86 (5) 507-514
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Naik, T. R., Singh, S. S. and Hu, W. Y. High-volume fly ash concrete technology. EPRI Report No. TR 100473, March 1992 10 Bilodeau, A. and Malhotra, V. M. Concrete incorporating high volumes of ASTM class F fly ashes: mechanical properties and resistance to deicing salt scaling and to chloride-ion penetration. In Proc. Fourth International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Istanbul, Turkey, ed. V. M. Malhotra, Vol. 1, AC1 Special Publication No. SP-132, 1992, pp. 319-349
11 Garette, G. G., Bilodeau, A., Cheurier, R. and Malhotra, V. M. Mechanical properties of concrete incorporating high volumes of fly ash from sources in the USA. AC1 Mater. J. I994,90 (6) 535-544 12 Gebler, S. H. and Kheger, P. Effect of fly ash on physical properties of concrete. In Proc. CANMET/ACI Second International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Madrid, Spain, ed. V. M. Malhotra, Vol.
1, AC1 Special Publication No. SP-91, 1986, pp l-50 13 Tikalsky, P. J., Carrasquillo, P. M. and Carrasquillo, R. L. Strength and durability considerations affecting mix proportioning of concrete containing fly ash. ACI Mater. J. 1988, 85 (6) 505-511
14 Hadchti, K. M. and Carrasquillo, R. L. Abrasion resistance and scaling resistance of concrete containing fly ash. Center for Transportation Research, Bureau of Engineering Research, University of Texas at Austin, Research Report No. 481-3, August 1988, p 185 15 Ellis, W. E., Jr., Riggs, E. H. and Butler, W. B. Comparative results of utilization of fly ash, silica fume, and GGBFS in reducing the chloride permeability of concrete. In Proc. Second CANMET/ACI International Conference on Durability of Concrete, Montreal, Canada, ed. V. M. Malhotra. AC1 Special
Publication No. 126, 1991, pp 443458
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IY
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Naik. T. R.. Pat&, V. M. and Brand. L. E. Performance of highstrength concrete incorporating mmerals by-products. Presented at the Research in Progress Seminar at the AC1 National Convention. Washington, DC. IS-19 March 1992 Thomas, M. D. A. and Matthews, J. C. The permeability of Ay ash concrete. Muter. Sfruct. 1992, 25 (151) 38%396 Bilodeau. A.. Sivasundaram, V.. Painter. K. E. and Malhotra. V M. Durability of concrete incorporating high volumes of tly ash from sources in the USA. ACI Ma!rr. J 1994. 91 (I) 3.-17 Rodway, E. L. Effect of air-entraining agent on air-void parameters of low and high-calcium Hy ash concretes. AST,%I .I Cemenr Concr. Aggreg. 1988. 10 (I) 35.~38 Larson. T. D. Air entrainment and durability aspects of f! a5.h concrete. In Proc. Amer. Conc,r. Insf. 1964. 64. 866.-886 Gebler, S. and Klieger, P. Effect of tlv ash on the air void stabiltty of concrete. In Proc. First Internui>onul Co+wtw on the lJw qf F1.v A.\h, Silica Fume, Slug und Olhzr Nuturul ByProcluc~~ in Concrete, Monrehellow. Cunadu. ed V M. Malhotra. Vol I. AC1
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Special Publication No. SP-79, 1983. pp 103-142 Johnston, C. Effects of microsilica and class C fly ash on resistance of concrete to rapid freezing and thawing and scaling in the presence of deicing agents. Concrete Dtrrohilit_v Proceedings of the
Kothurine and Bryant Mother Internationul Conference. Atlanta, Georgiu, AC1 Special Publication No. SP-100, April-May 1987,
23
pp 1183-1204 Nasser, K. W. and Lai. P S. H. Resistance of By ash concrete freezing and thawing. In Proc. Fourth International Conference the ll.w of F1.v Ash. Silicu Cotwere, Lytunhul. Turky,
24
Fume.
Slug, und Nuturul
ed V. M. Malhotra, Vol. 1, AC1 Special Publication No. SP-132. 1992, pp 205-226 Naik. T. R. and Ramme. B. W. Freezing and thawing durabtlity of high-lime content class C fly ash concrete. In Proc. Srwnd CANMET/ACI In~ernuiionul Conference Concrete, Montreul, Quebec, Cunudu, August
25
76 27
to
on Pozzoluns in
on
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199 I, pp 6 15-64 1 Naik, T. R. and Singh, S. S. Use of high-lime fly ash in cementbased construction materials. Approved for Publication and Presentation at the Fifth International Conference on the Use of Fly Ash, Silica Fume. Slag, and Natural Pozzolans in Concrete, Milwaukee, Wisconsin, USA, 4-9 June 1995 Figg, J. W. Methods of measuring the air and water permeability of concrete. MUK. Concr. Res 1973. 25 (251 213-219 Cather. R. B., Figg. J. W.. Marsdon. A. 6. and O’Brien. T. P. Improvement to the Figg method for determining the air permeability of concrete. Mug. Concr. Rex 1984, 36 (129) 241.-245
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