Center for By-Products Utilization

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1 Center for By-Products Utilization FREEZING AND THAWING DURABILITY OF CONCRETE INCORPORATING CLASS C FLY ASH By Tarun R. Naik, Shiw S. Singh, and Mohammad M. Hossain Report No. REP-199 July 1993 Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN - MILWAUKEE

2 FREEZING AND THAWING DURABILITY OF CONCRETE INCORPORATING CLASS C FLY ASH Prepared By Center for By-Products Utilization University of Wisconsin-Milwaukee College of Engineering and Applied Science Department of Civil Engineering and Mechanics 3200 N. Cramer Street, Milwaukee, WI Ph: (414) FAX: (414) Tarun R. Naik, Ph.D., P.E. Director, Center for By-Products Utilization Shiw S. Singh, Ph.D., P.E. Post-Doctoral Fellow, Center for By-Products Utilization and Mohammad M. Hossain Research Associate, Center for By-Products Utilization Prepared for Electric Power Research Institute 3412 Hillview Avenue

3 Palo Alto, California 94304

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5 ABSTRACT This research was undertaken to evaluate the freezing and thawing durability of concrete made with or without Class C fly ash. Two series of tests were planned. For the first series of tests (Series A) concrete mixes were proportioned to have cement replacement with one source of Class C fly ash in the range of 0-70% by weight, whereas for the second series (Series B) of tests concrete mixtures were made with several fly ashes for replacing cement in the range of 35 to 55% by weight. This report includes extensive review of the previous investigations and the experimental results for the first series of tests only. Air entrained reference concrete mixtures without fly ash was proportioned to have the 28-day compressive strength of 6000 psi (41 MPa). For each concrete mixture compressive strength, flexural strength, air-void characteristics of hardened concrete, and freezing and thawing durability were determined. Concrete resistance to freezing and thawing actions were evaluated in accordance with ASTM C 666, Procedure A. In general, concrete mixtures up to 50% cement replacement showed satisfactory performance with respect to strength properties as well as freezing and thawing resistance. The 30% fly ash mixture showed the best results. All the concrete mixtures with adequate air contents up to 70% cement replacement with fly passed the freezing and thawing requirements per ASTM C 666, Procedure A. i

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7 Section 1 INTRODUCTION Concrete structures are subject to freezing and thawing actions in cold climate regions. These structures experience tensile stresses resulting due to expansion resultin from freezing of moisture present in the concrete. These stresses are high enough to cause damage to structures such as pavements, bridge decks, retaining walls, parking structures, structures in marine environment, etc. This results in large expenditures in repair and maintenance of the structures. Powers (1) described freezing and thawing mechanism in concrete. Water present in a capillary cavity freezes when temperature drops below freezing point. This is accompanied with increase in volume resulting in development of generation of hydraulic pressure developed in the cavities. This causes expansion in concrete. The amount of expansion can be decreased by introducing entrained air in concrete as they provide escape boundaries for the relieve of the hydraulic pressure generated. Verbeck and Klieger (2) determined the amounts of water frozen in hardened concrete paste at various temperatures. They, based on test results, concluded that the amount of frozen water in concrete depends greatly upon the temperature and the water-to-cement ratio. Experimental evidence revealed that if concrete contained an appropriate entrained air void system with a spacing factor less than about in. (0.20 mm), freezing does not produce destructive stresses (3). Several parameters can effect freezing and thawing durability of concrete. These include properties of aggregate, water-to-cementitious material ratio, air-void parameters, the degree of saturation, strength of the 1

8 material, and environmental conditions. In accordance with ACI Building Code (4), the following requirements should be met to avoid damage due to freezing and thawing actions. (1) The specified compressive strength f'c greater than 5000 psi (34.5 MPa) with adequate air content (Table 1-1), (2) Low permeability concrete, and (3) The minimum cement content of concrete mixtures when exposed to freezing and thawing in the presence of chemicals shall be 520 lb/cu.yd. (308 kg/m 3 ) of concrete. Table 1-1 Total Air Content for Frost-Resistant of Concrete (4) Nominal Maximum Aggregate Size (in) 3/8 1/2 3/ /2 2 3 Air Content, percent Severe exposure 7½ ½ 5 4½ Moderate exposure 6 5½ 5 4½ 4½ 4 3½ Note: 1 in. = 25.4 mm It is now well established that addition of fly ash improves concrete structure due to pore filling as well as grain refinements, resulting in a denser structure. The improved structure results in decreased permeability to water which can result in improved resistance to freezing 2

9 and thawing deteriorations. Concrete structure improves with increase in fly ash content up to certain levels of cement replacement, beyond which performance can be deteriorated. This research wwas primarily carried our to investigate the effects of fly ash addition on concrete resistance to freezing and thawing actions. 3

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11 Section 2 LITERATURE REVIEW Air-entrainment is one of the most important variables that affect concrete resistance to freezing and thawing actions. A number of researchers (5-12) have indicated that inclusion of fly ash in concrete increases dosage of the air entraining admixtures (AEA) compared to concrete without fly ash. The increased dosage of AEA in fly ash, concrete is primarily attributed to the carbon content of fly ash and absorption capabilities of the carbon. Minnick (10) indicated that the organic compounds of the AEA were absorbed by the carbon present in fly ash. Larson (11) reported that fly ash did not have adverse effects on the air voids in hardened concrete. The requirements of AEA in concrete can depend upon the chemical composition of fly ash, fineness of fly ash, type and amount of fly ash used in the mixture. Gebler and Kleiger (12) investigated the effects of fly ash on the air-void stability, and air-entraining admixture requirement in concrete using 10 different fly ashes. Their results led to the following main conclusions. (1) Concretes containing Class C fly ash demands less AEA compared to concretes with Class F fly ash. (2) Class C fly ash concretes showed better air-void stability than concretes with Class F fly ash. (3) Spacing factors on concrete specimens made with the fly ashes 1

12 remained unchanged over a period of 90 minutes. (4) In general, AEA requirements tend to increase with increasing fly ash content. The air-entraining admixture requirement increases with organic matter content, carbon content, and loss of ignition of fly ashes. (5) An increase in total alkalies in fly ash reduces the air entraining admixture requirements. (6) An increase in specific gravity of a fly ash improves the air retention capability of concrete. The same effect was also observed for the SO 3 content of fly ash. Rodway (13) evaluated the influence of air-entraining agent on air-void parameters of concrete made with low and high calcium fly ashes. Concrete mixture were proportioned to have cement replacement by 25% fly ash with total cementitious materials of 573 lb/cu.yd. (340 kg/m 3 ). The lime contents of the fly ash samples varied from 0.7 to 24.3%. The spacing factor for air-void system in hardened concrete for all the test mixtures ranged from to in. (0.14 to 0.05 mm). The values of the spacing factor were found to be satisfactory in order to attain adequate freezing and thawing resistance of the concrete systems used. The resistance to freezing and thawing was relatively independent of lime content of fly ash. Several studies (14-46) have been directed toward evaluations of freezing and thawing durability of fly ash concretes. 2

13 Yuan and Cook (16) studied freezing and thawing durability of air-entrained and non-air-entrained fly ash concretes. In their study an ASTM Class C fly ash was used to replace cement in the range of 0-50% by weight. Total cementitious material content of 652 lb/cu.yd. (387 kg/m 3 ) was used in all the mixtures at a water-to-cementitious materials ratio of The freezing and thawing test was performed in accordance with ASTM C 666, procedure A. Test results showed a very poor performance for the non-air entrained concretes when subjected to freezing and thawing cycles. Whereas the air-entrained concrete with a 6.3 to 6.9 % air content did not experience any damage even after 800 freezing and thawing cycles. The freezing and thawing durability test results are illustrated in Figures 2-1 and 2-2. The authors presented the following conclusions. (1) The air-entrained concrete with or without fly ash did not show any appreciable amount of damage up to 400 cycles of freezing and thawing. (2) The 50% fly ash mixture exhibited significant scaling damage after about 400 cycles of freezing and thawing, and (3) The concrete containing 20 percent fly ash showed the best performance at 1200 cycles of freezing and thawing actions. Haque et al. (17,18) determined freezing and thawing durability of high- volume fly ash concretes. Concrete mixtures were proportioned to contain various levels of an ASTM Class C fly ash up to 75 percent by weight of 3

14 the cementitious material. Three different series of concretes were made and tested. The slump values used were 1 to 2 in. (25 to 50 mm) for the first series, zero for the second series of concrete designated as "ns", and the third series mixes were made with 4

15 Figure 2-1. Weight Loss Vs. Number of Freeze-Thaw Cycles, Air Entrained Concrete With Indicated Percentage of Cement Replacements With Fly Ash After 14 Days of Curing (16) 5

16 Figure 2-2. Relative Dynamic Modulus Vs. Number of Freeze-Thaw Cycles for Air Entrained Concrete Specimens After 14 Days of Curing (16) 6

17 addition of a superplasticizer and were designated as "sp". The total cementitious material was maintained at about 490 ± 17 lb/cu.yd. (290 ± 10 kg/m 3 ). The air-entraining agent was used to obtain air contents between 4½ to 8 percent for all the mixtures. The freezing and thawing durability of the high-volume fly ash concretes was measured in accordance with ASTM C 666, Procedure A. The test results are presented in Table 2-1. The concrete mixtures from the first series, except the 40% fly ash mixture, and second series ("NS") showed poor freezing and thawing durability in accordance with ASTM C 666, Procedure A. The superplasticized high-volume fly ash concretes showed better results than unsuperplasticized concrete mixtures (Table 2-1). The results showed the highest durability factor of 95% for the 40% fly ash mixture (Table 2-1). Sturrup et al. (19) carried out an investigation to evaluate correlation between durability of Class F fly ash concrete systems and to evaluate the correlation between the freezing and thawing resistance and carbon content. The authors concluded that carbon content does not have an appreciable effect on the freezing and thawing resistance of concrete provided the adequate level of air entrainments are maintained. Gebler and Klieger (20) measured freezing and thawing resistance of air-entrained fly ash concrete systems. ASTM Class C and F fly ashes from ten different sources at 25% cement replacement were used in this investigation. Total amount of cementitious materials was maintained at 517 lb/cu.yd. (307 kg/m 3 ) for all concrete mixtures. An air-entraining agent was also used to maintain 6 ± 1% air content. Freezing and thawing tests were conducted in water and in a 4% NaCl 7

18 Solution. Test specimens were moist cured at 73 F (23 C) and 40 F (4.4 C). Freezing 8

19 Table 2-1 Freezing and Thawing Durability Test Results for High-Volume Fly Ash Concretes (17,18) Mix No. Fly Ash, Percent Air Content, Percent No. of Cycles Durability Factor, Percent * NS NS NS NS SP * SP * SP SP * 85 * Specimens did not fail after 300 cycles 1 = No slump concrete 2 = Superplasticized concrete and thawing durability of the test specimens were measured in accordance with ASTM C 666, Procedure A. Test results are presented in Table 2-2 and 2-3. The authors used durability factor as an indication of internal condition of the concrete specimens. All the concrete mixture showed excellent freezing and thawing durability as their relative durability factors were either equal or greater than 95. However, weight loss for some of the Class F fly ash mixtures was high, greater than 10%. However, in general, durability factor of the fly ash concretes were comparable to those obtained for the concrete without fly ash during 9

20 Table 2-2 Freezing and Thawing in Water (20) Fly Ash Mixture Air Content Results at 300 cycles Cured at 73 F (23 C) 1 Cured at 40 F (4.4 C) 2 Identification Clas s of fly ash Mean freshly mixed concrete, % Hardene d concrete, % Expansion, % Weigh t loss, % Durability factor Relative durabilit y factor (3) Expansion, % Weigh t loss, % Durability factor Relative durability factor (3) A B C D E F G H I J C F F F F C C F C F Average of Class C Class F Control mixtures 517 lb/cu.yd lb/cu.yd Following storage in molds for one day at 73 F (23 C), prisms were moist cured at 73 F (23 C) for 13 days followed by storage in laboratory air at 73 F (23 C) and 50% relative humidity for 14 days. Following storage in molds for one day at 40 F (4.4 C), prisms were moist cured at 40 F (4.4 C) for 13 days followed by storage in laboratory air at 40 F (4.4 C) and 95% relative humidity for 14 days. Relative to the 474 lb/cu.yd. (281 kg/m 3 ) control concrete. 1 lb/cu.yd. = kg/m 3 10

21 Table 2-3 Freezing and Thawing in 4% NaCl Solution (20) Fly Ash Mixture Air Content Results at 300 cycles Cured at 73 F (23 C) 1 Cured at 40 F (4.4 C) 2 Identification Clas s of fly ash Mean freshly mixed concrete, % Hardene d concrete, % Expansion, % Weigh t loss, % Durability factor Relative durabilit y factor (3) Expansion, % Weigh t loss, % Durability factor Relative durability factor (3) A B C D E F G H I J C F F F F C C F C F Average of Class C Class F Control mixtures 517 lb/cu.yd lb/cu.yd Following storage in molds for one day at 73 F (23 C), prisms were moist cured at 73 F (23 C) for 13 days followed by storage in laboratory air at 73 F (23 C) and 50% relative humidity for 14 days. Following storage in molds for one day at 40 F (4.4 C), prisms were moist cured at 40 F (4.4 C) for 13 days followed by storage in laboratory air at 40 F (4.4 C) and 95% relative humidity for 14 days. Relative to the 474 lb/cu.yd. (281 kg/m 3 ) control concrete. 1 lb/cu.yd. = kg/m 3 11

22 freezing and thawing tests carried out in water as well as in 4% NaCl solution. Archuleta et al. (21) investigated resistance of fly ash concretes to freezing and thawing actions. ASTM Class C (Type B) and Class F (Type A) fly ashes were used in this study as a replacement for cement in the range of 0-35% by weight. Their test results revealed that an increase in the Class F fly ash content of concrete causes a decrease in the air content. Also, in the case of Class F fly ash mixtures, a decrease in the durability factor was observed when the cementitious content was increased from 564 lb/cu.yd. (334 kg/m 3 ) to 658 lb/cu.yd. (390 kg/m 3 ). In general, the concrete containing Class C fly ash exhibited satisfactory freezing and thawing durability regardless of the fly ash content used. The authors reported that for obtaining adequate freezing and thawing durability fly ash should have LOI of 0.26 percent or less. Many researchers (22,23,24) have also indicated the similar test results. Johnston et al. (25) studied the effects of microsilica and Class C fly ash on freezing and thawing durability of concrete. Mixture proportions used for the study had three different fly ash levels (16%, 27%, and 42%) as a cement replacement. The cement content was 526 lb/cu.yd. (318 kg/m 3 ) for no-fly ash concrete. Test results are presented in Table 2-4. The air bubble spacing factor in the hardened concrete was observed in the range of to in. (0.025 to 0.12 mm). Test results show that the durability factor for the control concrete and the mixtures with 16% and 27% of fly ash exceeded 80% (Figure 2-3). However, the mixture with 42% fly ash and the higher water-to-cementitious materials ratio passed the durability requirements per ASTM C 666, Procedure A. 12

23 Table 2-4 Freeze-Thaw Performance of Class C Fly Ash Concretes Made with Gravel Aggregate (25) Mixture Cement (kg/m 3 ) Fly Ash (kg/m 3 ) W/C+F ratio AEA 1 Air Content, % Air in Hardene d Concrete (%) L-mm DF RDF 3 Control 16% FA 27% FA 42% FA Note: 1 - Dosage of air-entraining admixture in ml/100 kg of cement plus fly ash 2 - Mean from four specimens after 300 cycles of procedure A of ASTM C Relative durability factor based on DF300 for the control as 100% 1 kg/m 3 = 1.69 lb/cu.yd., 1 mm = in. Johnston and Malhotra (26) evaluated freezing and thawing durability of high-strength semi-lightweight concrete made with up to 50% fly ash by weight of cement. Cement content ranged from 420 to 840 lb/cu.yd. (250 to 500 kg/m 3 ) with addition of a Class C fly ash (CaO = 10.7%) up to 50% by weight of cement. The dry rodded unit weight of lightweight aggregate was 61.7 lb/cu.ft. (988 kg/m 3 ) and a absorption of 12.8%. The freezing and thawing durability tests were carried out in accordance with ASTM C 666, Procedure A. In general, all the concretes with 5 ± 1% air performed poorly irrespective of addition of fly ash or superplasticizer. The authors reported that durability factor for air-entrained concrete observed with 14 days moist curing were less than 20% The durability factor exceeded 80% when a modified curing practice of 11 days of air-drying followed by 3 days of soaking was used. 13

24 Langan et al. (27) studied the effects of interrupted testing combined with prolonged freezing on the freezing and thawing resistance of fly 14

25 Figure 2-3. Effect of Class C Fly Ash on Freeze-Thaw Performance in 15

26 ASTM C 666, Procedure A (25) 16

27 ash concrete. Test specimens were evaluated for freezing and thawing resistance in accordance with ASTM C 666, Procedure A. Based on the test data, the authors offered the following conclusions. (1) Prolonged curing of a fly ash concrete specimen prior to the start of freezing and thawing testing has insignificant effect on freezing and thawing durability of concrete, (2) Interruptions in freezing and thawing testing of fly ash concretes did not show any marked effect on the results compared to those obtained from normal test procedures, and (3) Either prolonged freezing or interrupted testing showed acceptable results irrespective of the amounts of air content used. Malhotra and Painter (28,29) studied the early-age strength properties, and freezing and thawing resistance of high-volume concrete incorporating high volumes of ASTM Class F fly ash. Three different series of concrete mixtures were proportioned for this work. For the first series of tests, concrete mixtures were proportioned to have a constant cement content of 245 ± 8 lb/cu.yd. (145 ± 5 kg/m 3 ) and the fly ash content varied from 186 to 332 lb/cu.yd. (110 to 197 kg/m 3 ). The water-to-cementitious materials ratio varied from 0.32 to 0.42, at an air content of 9.5 ± 1%. The concrete mixtures for the second Series were identical to those of the first series but at a different air content about 5.5 ± 1.0%. The third series of mixtures were composed of fly ash varying from 309 to 480 lb/cu.yd. (183 to 275 kg/m 3 ). The water-to-cementitious materials ratio between 0.28 to 0.35, with an entrained air content of 4 ± 0.5%. The mixture proportions used are given in Table 2-5. The freezing and thawing test results are presented in Table 2-6. The freezing and thawing durability concrete Table 2-5 Mixture Proportions and Properties of Fresh Concrete (28,29) Mixture Series Mixture No. W (C+F) Cemen t Mixture Proportions, kg/m 3 Fly As h Fine Agg. (SSD ) Coars e Agg. (SSD) Superplasticiz er A.E.A. ml/m 3 Properties of Fresh Concrete Slum p (mm) Density (kg/m 3 ) Air Content (%) I

28 II III Note: 1 kg/m 3 = 1.69 lb/cu. yd. 1 mm = in. 1 m 2 = 1 ml = oz Table 2-6 Relative Dynamic Modulus of Elasticity and Durability Factors (28,29) Mixture Series Mixture No. W (C+F) Fly Ash, (kg/m 3 ) Air Content, % No. of Freezing and Thawing Cycles Completed Relative Dynamic Modulus, % Durability Factor* I II III * Calculated according to ASTM C 666 Note: 1 kg/m 3 = 1.69 lb/cu.yd. 18

29 of specimens were determined according to ASTM C 666, Procedure A. The results showed that all the concrete mixtures attained durability factors in excess of 87. However, some specimens experienced moderate to considerable surface scaling. Gifford et al. (30) studied freezing and thawing durability of fly ash concretes. The concrete mixture proportions were proportioned to have compressive strength of 4000 psi (27.6 MPa) at 28 days. A reference mixture had cement content of 556 lb/cu.yd. (330 kg/m 3 ). Additionally, other concrete mixtures containing Class C fly ash (CaO = 11.6%) were proportioned to have cement replacements of 10%, 20%, and 30% by weight. Fly ash to cement ratio was varied from 1.50 to Water-to-cementitious materials ratio was ranged from 0.31 to Test data showed that for an adequate air-void system fly ash concrete attained freezing and thawing resistance comparable to reference concrete without fly ash. Giaccio and Malhotra (31) evaluated freezing and thawing resistance of high-volume Class F fly ash concretes made with ASTM Types I and III cements. The water-to-cementitious materials ratio for all mixtures were maintained at 0.32 ± 0.01 with a fly ash-to-(fly ash + cement) ratio of The cement content of the mixture was 260 lb./cu.yd. (154 kg/m 3 ). All the mixtures were air-entrained and superplasticized. Concrete specimens were also tested for determination of air-void parameters. The values of the specific surface ranged from 0.66 to 0.98 in -1 (16.8 to 24.0 mm -1 ) and the values of the spacing factor (L) ranged from to 0.01 in. (0.176 to mm). Their test data are presented in Table 2-7. The freezing and thawing durability were performed according to 19

30 ASTM C 666, procedure A. All the concrete mixture exhibited durability factor greater than 95 percent after

31 Table 2-7 Summary of Test Results on Concrete Prisms after 300 Cycles of Freezing and Thawing* (31) Mix No. H 20 (C+F+S) Air Content, % 70 by 102 by 390 mm Test Prisms Weight, kg Length, mm, m/s Change in Resonant Frequency, H W 0 W 300 Change, % L 0 L 300 Change, % V 0 V 300 Change, % N 0 N 300 Change, % Relative Dynamic Modulus of Elasticity, % Durab-il ity Factor, % * Each result represents the average of two sets. Note: 1 mm = in.; 1 m = ft 21

32 cycles, but significant surface scaling was observed. Sajadi and Head (32) evaluated freezing and thawing durability of highvolume Class F fly ash concretes using three different sources. The fly ashes used were A (CaO = 1.3%, carbon content = 3.8%), B (CaO = 1.5, carbon content = 5.13%) and C (CaO = 1.1%, carbon content = 15.34%). A reference concrete without fly ash was propostioned to have a cement content of 564 lb/cu.yd. (335 kg/m 3 ). Besides, fly ash concrete mixtures were also proportioned to have five levels of cement replacement (25%, 40%, 50%, 60%, and 75%). The fly ash concrete mixtures were designated as A25, B25, C25, A40, B40, C40, A50, B50, C50, A60, B60, C60, A75, B75, and C75. The concrete mixtures were made with or without a superplasticizer. The air-void characteristics of the mixtures are presented in Tables 2-8 and 2-9. The results showed the spacing factor (L) ranging from to in. (0.078 to 0.15 mm) unsuperplasticized fly ash concrete and from to in. (0.094 to 0.14 mm) for superplasticized concrete. The freezing and thawing durability test results are presented in Figure 2-4. The authors concluded that: (1) Both amount and properties of fly ash influence the amount of air-entraining admixture required for maintaining a particular entrained air content in concrete, (2) All the concrete mixture with or without fly ash showed very good freezing and thawing durability. (3) The superplasticized fly ash concrete, mixtures experienced smaller weight losses when compared to the unsuperplasticized fly ash concretes. 22

33 Table 2-8 Characteristics of Air-Void Systems for the Control and Unsuperplasticized Fly Ash Concrete Mixtures (32) Specimen Designation* Fly Ash Content (%) Air in Plastic Concrete (%) Air-Void Parameters in Hardened Concrete Air in Hardened Concrete (%) Number of Voids (per inch) Specific Surface (in. 2 /in. 3 ) Spacin g Factor (in.) A A A A A A B B B B B C C C C * The first letter refers to fly ash type (A, B, or C) and the following number refers to cement replacement with fly ash. 23

34 Note: 1 in. = 25.4 mm 24

35 Table 2-9 Characteristics of Air-Void Systems for Fly Ash Concrete Mixtures Containing a High-Range Water Reducing Admixture (32) Specimen Designation* Fly Ash Content (%) Air in Plastic Concrete (%) Air-Void Parameters in Hardened Concrete Air in Hardened Concrete (%) Number of Voids (per inch) Specific Surface (in 2 /in 3 ) Spacin g Factor (in) A25SP A40SP A50SP A60SP A75SP B25SP B40SP B50SP B60SP B75SP C25SP C40SP C50SP C60SP C75SP * The first letter refers to fly ash type (A, B, or C) and the following number refers to cement replacement with fly ash. Note: 1 in. = 25.4 mm 25

36 Figure 2-4. Durability Factor After 300 Freeze-thaw Cycles as Affected 26

37 by Amount of Cement Replaced by Fly Ash (32) 27

38 (4) The fly ash concrete made with the high-range water reducing admixture produced bubbles with larger diameter compared to the mixtures without superplasticizer. Sivasundaram et al. (33) studied the durability of concrete containing high-volume of low-calcium fly ash. Concrete mixtures were made with fly ash at 58% cement replacement at a water-to-cementitious material ratio of The freezing and thawing durability was determined according to ASTM C 666, Procedure A. The freezing and thawing durability data are given in Table The fly ash concrete mixture C4 (CaO 12.3%) were tested for freezing and thawing durability after 14 days of moist curing. Whereas mixture B8 having a fly ash (CaO = 1.21%) was tested after 14, 21, and 28 days of moisture curing. The results indicated that all the specimens showed excellent durability against freezing and thawing as their durability factors remained about 99 after 300 cycles. However, the specimens experienced substantial surface scaling. Langely et al. (34) evaluated freezing and thawing resistance of ASTM Class F fly ash concretes. The fly ash was substituted for cement at 56% of the total cementitious materials were used. High-range water-reducing admixtures were added to the concrete mixture to obtain the desired level of workability. Concrete mixtures were made by incorporating 320 lb/cu.yd. (190 kg/m 3 ) of fly ash and 253 lb/cu.yd. (150 kg/m 3 ) ASTM Type I and Type III portland cement at a water-to-cementitious materials ratio of 0.30 and The tests were conducted in accordance with ASTM C 666, Procedure A. Air-void parameters of the concrete specimens containing 253 lb/cu.yd. (150 kg/m 3 ) of ASTM Type I cement and 320 lb/cu.yd. (190 kg/m 3 ) of fly ash were determined. The spacing factors 28

39 were 0.01 and in. (0.25 and 0.30 mm). Test data 29

40 Table 2-10 Test Results on Concrete Prisms after 300 Cycles of Freezing and Thawing (33) 76 x 102 x 390 mm Test Prisms Mix. No. W/(C+F) Initial Moist-C Air uring Content % Period W 0 W 300 Change % Weight, kg Length, mm, m/sec L 0 L 300 Change % V 0 V 300 Change % Resonant Frequency, Hz N 0 N 300 Change % Relative Dynamic Modulus of Elasticity % Durability Factor B d B d B d C d Note: 1 kg = lb 1 mm = in. 30

41 are shown in Figure 2-5. The fly ash concrete exhibited slightly better results than the concrete without fly ash (Figure 2-5). However, slight surface scaling occurred on fly ash concrete prisms after about 50 cycles of freezing and thawing. Tikalsky et al. (35) evaluated resistance to freezing and thawing durability of concrete containing both Class C and Class F fly ashes. Fly ash was substituted for cement at the rates ranging from 0 to 35 percent of total cement by weight. The freezing and thawing resistance tests were conducted on 3x4x16 in. (75x100x400 mm) specimens having cementitious content ranging from 517 to 658 lb/cu.yd. (306 to 390 kg/m 3 ). The results revealed that all the mixtures containing greater than 3.5 percent air passed the freezing and thawing durability requirement in accordance with ASTM C 666, Procedure A. The durability of the Class C fly ash mixture having air contents between 4.5 and 5.5 percent are shown in Figure 2-6. The author reported that adequate freezing and thawing resistance for the concrete mixtures were obtained when adequate air content was introduced in the concretes. Naik and Ramme (36) evaluated freezing and thawing durability of Class C fly ash concretes. Concrete mixture proportions were developed for producing concrete on a 1.25 to 1 fly ash replacement for cement weight basis, at 45% cement replacement level. Both non-air and air-entrained concretes of 4000 psi (27.6 MPa) compressive strength at 28-day were produced and tested. Test results are presented in Table As expected the non-air entraining concrete failed after a low number of cycles of rapid freezing and thawing. The air entrained concrete did not indicate failure even after 300 cycles of rapid freezing and thawing according to ASTM C 666, Procedure A. The author concluded that properly 31

42 air entrained concrete having 45% cement 32

43 Figure 2-5 Durability Factors of Control and Fly Ash Concretes Subjected to Repeated Cycles of Freezing and Thawing Using 33

44 ASTM C 666, Procedure A. (34) 34

45 Figure 2-6 Freeze-Thaw Durability of Concrete With or Without Fly 35

46 Ash. (35) 36

47 Table 2-11 Freeze-Thaw Tests* on Air Entrained Concrete (36) Percent Expansion at Freeze-Thaw Cycle Indicated Mix No P4-39A B C AV Percent Weight Loss at Freeze-Thaw Cycle Indicated Mix No P4-39A B C AV Mix No. Relative Dynamic Modulus of Elasticity at Freeze-Thaw Cycle Indicated P4-39A B C AV Mix No. Durability Factor P4-39A 83 B 92 C 96 AV. 90 * Tested in accordance with ASTM Designation C Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing (Procedure A). 37

48 replacement with fly ash attained high durability against freezing and thawing. In another study (37) they also evaluated the freezing and thawing resistance of three different concretes. Freezing and thawing tests were performed in accordance with the ASTM C 666, Procedure A and B. Test data are summarized in Table It shows that relative durability factor for the concrete containing 140 lb (64 kg) of fly ash and concrete without fly ash were essentially the same. On the other hand, the concrete containing 110 lb (50 kg) of fly ash had a lower relative durability factor. A relative durability factor of 60 is considered to be "passing" (37). Therefore, the no-fly ash and the 140 lb (64 kg) fly ash content concretes passed the freezing and thawing test. Table 2-11 also shows the freezing and thawing testing in accordance with the Procedure B. These results also show that the relative durability factor for the concrete without fly ash and the concrete containing 140 lb (64 kg) of fly ash were almost the same. The concrete containing 110 lb (50 kg) of fly ash showed the lowest durability factor when tested according to ASTM C 666, Procedure B. Malhotra et al. (38) evaluated freezing and thawing durability of high- volume Class F fly ash concretes. Concrete mixture were proportioned to contain about 253 lb/cu.yd. (150 kg/m 3 ) and fly ash of about 56% by weight of total cementitious materials. The water-to-cementitious materials ratio was kept at about The freezing and thawing tests were conducted according to ASTM C 666, Procedure A. Their test results are presented in Table In general, the entrained high-volume fly ash concretes showed excellent performance in freezing and thawing environment. Their durability factors ranged from 95 to 97. The bubble spacing parameters (L) for the concretes were and 0.01 in. (

49 mm and mm) for concrete made with fly ash as received and 39

50 Table 2-12 Relative Durability Factor ASTM C 666 (36) Procedure A Specimen Fly Ash, lbs. % Air Relative Durability Factor 1A A A Act Ave Procedure B Specimen Fly Ash, lbs. % Air Relative Durability Factor 1B B B Act. * Ave * Unable to determine - specimen broke 40

51 Table 2-13 Summary of Test Results on Concrete Prisms After 300 Cycles of Freezing and Thawing (38) 76 x 102 x 390 mm Test Prisms * Mixture No. W/ (C+F+S) Air Conte nt (%) Weight (kg) W 0 W 300 Change (%) Length (mm) L 0 L 300 Change (%) (m/s) V 0 V 300 Change (%) Resonant Frequency (Hz) N 0 N 300 Change (%) Relative Dynamic Modulus of Elasticity, % Residual Flexural Strength (%) 1 (Fly Ash as Received) (Beneficiated Fly Ash) Note: 1 mm = in, 1 m = 3.28 ft. 1 kg = lb * Each result represents the average of two tests 41

52 beneficiated fly ash, respectively. Several studies completed at CANMET (39,40,41) has revealed excellent durability of high-volume fly ash concrete against freezing and thawing, durability factor were in excess of 90. Langan et al. (42) studied strength and durability behavior of concretes using a number of replacement materials for cement. The replacement materials were composed of seven fly ashes (sub-bituminous, bituminous, and lignitic), limestone, and an inert material (silica flour). In this study, 50% cement was replaced by the total cementitious materials for the mixtures were kept at 506 lb/cu.yd. (300 kg/m 3 ) and a water-to-cementitious materials ratio of The freezing and thawing resistance of concrete was determined according to ASTM C 666, Procedure A. Test data are presented in Table As expected, non-air entrained concrete failed at a few cycles of freezing and thawing, normally before 50 cycles, whereas all mixtures containing proper air content passed the severe requirements of freezing and thawing. The authors further reported that addition of superplasticizing agent with air-entraining agent produced a decrease in the values of durability factor for the mixtures tested. Nasser and Lai (43) evaluated freezing and thawing resistance of high-volume Class C fly ash concrete. Freezing and thawing resistance of concrete, was determined according to ASTM C 666, Procedure A. Three different replacements of cement with fly ash 20, 35, and 50% were used in the work. Concrete mixture proportions are given in Table Two types of cement (Type I & V) were used in this investigation. cementitious materials content was 503 lb/cu.yd. (298 kg/m 3 ). Total The water-to-cementitious material ratio ranged from 0.51 to An

53 air-entraining agent was also used to maintain air content of about 6 ± 1.5%. Durability factors of the concretes are presented in Figure

54 Table 2-14 Summary of Freezing and Thawing Test Results (42) Mix No. Type of Fly Ash Air Content % Weight Change % Durabilit y Factor % Cycles at end of Test 2 No Fly Ash No Fly Ash Class F Class F Class C Class C Class C Class C Class C Class C Class C Class C Class C Class C Class F Class F Class C Class C Class F Class F Class C Class C

55 Figure 2-7 Effect of Fly Ash on the Durability Factor of Concrete (43). 45

56 Table 2-15 Summary of Test Results on Concrete Prisms after Repeated Cycles of Freezing and Thawing* (44) Specimen No. Source of Fly Ash Percent Replaceme nt No. of Freeze/Thaw Cycles Completed Percent change at the end of 300 freezing and thawing cycles Resonant Frequenc y Weight Relative Dynamic Modulus of Elasticity % Durability Factor % P F-25 F-26 F-27 P F-1 F-2 F-3 OCPP * Freezing and thawing cycles were carried out in accordance to ASTM C 666, Procedure A. The number of cycles completed at the termination test was 300. Analysis of the test results indicated that the control concrete and the concrete made with 20% fly ash exhibited adequate freezing and thawing durability. Other fly ash concrete mixture showed poor results (Figure 2-7). In general, an increase in fly ash content decreased the resistance of freezing and thawing durability factor. A similar trend was also observed from the average value of loss in mass. Naik et al. (44) investigated freezing and thawing resistance of high-volume Class C and Class F fly ash concretes for pavement construction. The concrete mixtures were composed of 20 and 50% Class C fly ash, and 40% Class F fly ash. In this work a control mixture selected was the standard 20% Class C fly ash concrete. Freezing and thawing resistance of test prisms are given in Tables 2-15 through As per ASTM criteria, all the concretes used in this investigation passed the 46

57 freezing and thawing durability resistance requirements. The 40% Class F fly ash concrete mixture exhibited the highest durability factor 47

58 Table 2-16 Changes in Fundamental Longitudinal Resonant Frequency of Test Prisms During Freeze-Thaw Cycling Per ASTM C 666 Procedure A (44) Specime n No. Sourc e of Fly Ash Percent Replacemen t Size of Specime n, in. Fundamental Longitudinal Resonant Frequency N, cps Reference Moist-Cured Prisms Initial At end of Freeze-Tha w Cycles time Percen t Chang e Freeze-Thaw Test Prisms N* N** N*** Percent Change P x4x12¼ F-28 F-29 F-30 P x4x12¼ F17 F21 F22 OCPP 40 3x3x11¼ P x4x12¼ [150] 6103[150] 6140[150] 5620[300] 5954[300] 5070[300] F-25 F-26 F-27 P x4x12¼ [150] 6030[150] 6092[150] 6194[300] 5891[300] 6101[300] F-1 F-2 F-3 OCPP 40 3x3x11¼ [150] 6805[150] 6770[150] 6890[300] 6780[300] 6780[300] * Average resonant frequency of prisms after moist curing at the commencement of the freezing and thawing cycling. ** Number in brackets represent the number of freezing and thawing cycles completed at the time of testing. *** Termination of freezing and thawing test. 1 in. = 25.4 mm 48

59 amongst all the three mixtures tested. The average durability factor for the 50 percent Class C fly ash mixture was 90, which is comparable to the value observed for the 40% Class F fly ash mixture. However, the durability factor of the reference mixture with 20% Class C fly ash was significantly lower compared to the other mixtures. Drahushak-Crow and von Fay (45) studied freezing and thawing durability of concretes made with three different fly ashes. A Class F (CaO = 1.0%) from the Navajo Generating Station in Page, Arizona, a Class C fly ash (CaO = 21.4%) from the White Bluff Powerplant in Little Rock, Arkansas, and high lime content (CaO = 28.6%) Class C fly ash from the Pawnee Powerplant in Brush, Colorado were used for the study. The amount of fly ash used varied from 10 to 100 percent by weight of total cementitious materials. Concrete mixtures were proportioned at five different cement replacement levels (10, 30, 50, 75, 100 %) with the fly ashes. Two different levels of cementitious materials used were 424 lb/cu.yd. (251 kg/m 3 ) and 645 lb/cu.yd. (382 kg/m 3 ) for the investigation. Six 3 x 6 in. (75 x 150 mm) cylinders specimens were prepared from each mixture for freezing and thawing durability testing. Of these, three were cured for 28 days at 100% humidity, and the other three were cured for 14 days at 100% humidity and then they were kept at 50% relative humidity for 76 days. The cylinders were subjected to alternate cycles of freezing and thawing, consisting of freezing in water for 1-1/2 hours at 10 F (-12.2 C) and thawing in water for 1-1/2 hours at approximately 72 F (22.2 C). A specimen, after the treatment, was considered failed the freezing and thawing test when its weight loss exceeded 25% of the original weight. The test results are presented in Table The results revealed that specimens cured for 14 days with fog and 76 days with 50% 49

60 humidity attained higher durability factor values than those cured with 100% humidity for 28 days. In general, performance of the concretes improved with increasing cement content. 50

61 Table 2-17 Changes in Weight of Test Prisms During Freeze-Thaw Cycling Per ASTM C 666 Procedure A (44) Specime n No. Sourc e of Fly Ash Percent Replaceme nt Size of Specimen, in. Reference Moist-Cured Prisms Initial At end of Freeze-Tha w Cycles time Percent Change Weight W, kg Freeze-Thaw Test Prisms W* W** W*** Percent Change P x4x12¼ F-28 F-29 F-30 P x4x12¼ F17 F21 F22 OCP P 40 3x3x11¼ P x4x12¼ [150] 5.780[150] 5.785[150] 5.800[300] 5.763[300] 5.790[300] F-25 F-26 F-27 P x4x12¼ [150] 5.784[150] 5.759[150] 5.781[300] 5.773[300] 5.752[300] F-1 F-2 F-3 OCP P 40 3x3x11¼ [150] 3.856[150] 3.878[150] 3.827[300] 3.833[300] 3.858[300] * Average weight of prisms after moist curing at the commencement of the freezing and thawing cycling. ** Number in brackets represent the number of freezing and thawing cycles completed at the time of testing. *** Termination of freezing and thawing test. Note: 1 in. = 25.4 mm; 1 kg = lb 51

62 Table 2-18 Freezing and Thawing Durability of Control and Fly Ash Mixtures (45) Quantity of Cementitious Materials (lb/cu.yd.) Percent Fly Ash Cycles to Failure 28-day Fog Cure 14-day Fog Cure and 76-day 50% Humidity Control Mixes * * 3971* Navajo Fly Ash Mixes n/t 1550* 1658* 1345* 504 n/t White Bluff Fly Ash Mixes * * 1871* 2246* 835* 240 Pawnee Fly Ash Mixes 768* 849* * 1729* 1742* 1393* * 1000* 856* 410 n/t 3979* 3504* 1775* 686 n/t 1118* 1119* 841* * 3360* 2739* 823* * 1029* * 3194* 2852* * Good freezing and thawing durability 52

63 1 lb/cu.yd. = kg/m 3 53

64 The number of cycles to failure depended greatly upon type of fly ash, amount of cementitious content and type of curing (Table 2-18). In general, freezing and thawing resistance improved with increase in cementitious content. For the cured specimens at 424 lb/yd 3 cement content freezing and thawing durability of Class C fly ash mixtures were better than the Class F mixture or control concrete up to 50% cement replacement. Bilodeau et al. (46) studied freezing and thawing resistance of concrete incorporating high volumes of fly ash obtained from different sources. Concrete mixtures were proportioned to contain about 194 and 261 lb/cu.yd. (115 and 155 kg/m 3 ) of water and cement, respectively. The fly ash content was ranged from 55 to 60 percent of total cementitious materials. The concrete mixtures showed good air-void parameters with spacing factors ranging from to in. (0.111 to mm) and specific surfaces ranging from 653 to 1097 in. 2 /in. 3 (25.7 to 43.2 mm 2 /mm 3 ). The freezing and thawing resistance was measured in accordance with ASTM C 666 Procedure A. The freezing and thawing resistance test data are presented in Tables 2-19 and All the test specimens passed the ASTM freezing and thawing resistance requirements with a durability factor equal to or greater than

65 Table 2-19 Summary of Test Results of Concrete Prisms after 300 Cycles of Freezing and Thawing (46) Mixture No. Ceme nt Brand Fly Ash Source Percent change at the end of freeze-thaw cycling Weight Length Resonant Frequency Durability Factor C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 F1 F1 F2 F2 F3 F3 F4 F4 F5 F5 F6 F6 F7 F7 F8 F Table 2-20 Summary of Test Results of Concrete Prisms after 1000 Cycles of Freezing and Thawing (46) Mixture No. Cement Brand Fly Ash Source Percent change at the end of freeze-thaw cycling Durability Factor Weight Length Resonant Frequency C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 C1 C2 F1 F1 F2 F2 F3 F3 F4 F4 F5 F5 F6 F6 F7 F7 F8 F