Center for By-Products Utilization Effects of Temperature and Fly Ash on Compressive Strength and Permeability of High-Performance Concrete* By Tarun R. Naik, William A. Olson, Jr., and Shiw S. Singh Report No. REP-245 October 1994 Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN MILWAUKEE
EFFECTS OF TEMPERATURE AND FLY ASH ON COMPRESSIVE STRENGTH AND PERMEABILITY OF HIGH-PERFORMANCE CONCRETE* By Tarun R. Naik, Ph.D, P.E. Director, Center for By-Products Utilization William A. Olson, Jr., P.E. Research Associate, Center for By-Products Utilization and Shiw S. Singh, Ph.D., P.E. Post-Doctoral Fellow, Center for By-Products Utilization Department of Civil Engineering and Mechanics, College of Engineering and Applied Science, University of Wisconsin-Milwaukee P.O. Box 784, Milwaukee, WI 53201 Telephone: (414) 229-6696 FAX: (414) 229-6958
*For presentation at the ACI 1994 International Conference on High-Performance Concrete, November 15-18, 1994, Singapore. OBJECTIVE The major objective of this study was to investigate the effects of curing environments on performance of high-performance of (HPC). The performance factors considered were : (1) Strength, (2) Permeability, (3) Workability, and (4) Cost. Two different curing environments, namely moist curing and Variable Temperature Curing Environments (VTCE) were used.
EXPERIMENTAL PROGRAM Mixture Proportions Two concrete mixtures (12.5P and 12.5E) were proportioned to have a 28-day design strength of 85 MPa (12,500 psi). The 12.5P mixture was proportioned to contain 20% Class C fly ash, and 5% silica fume. The 12.5E mixture was composed of approximately 30% Class C fly ash and 20% Class F fly ashes. The details of mixture proportions are given in Tables 1 and 2.
CONCRETE PROPERTIES TESTED Slump Air Content Density (Fresh and Hardened) Compressive Strength Chloride Ion Permeability Air Permeability Water Permeability
CONCLUSIONS COMPRESSIVE STRENGTH (1) Mixture 12.5P, with 20% Class C fly ash and 5% silica fume, achieved higher strength than the Economical Mixture 12.5E at all ages for specimens cured in the moist room and VTCE. The economical concrete mixture contained approximately 30% Class C and approximately 20% Class F fly ashes.
(2) The 12.5P mixture, achieved higher rates of strength gain at early ages when cured in the VTCE compared to moist curing. (3) Beyond the 28-day age, the compressive strength of the 12.5E mixture was relatively unaffected by the types of curing environments used in this work.
PERMEABILITY (1) In general, the chloride ion permeability/diffusion decreased with an increase in the amount of pozzolanic additives. (2) The Variable Temperature Curing Environment (VTCE) improved on the ability of the concrete to resist chloride ions pentration. (3) Generally, as the concrete compressive strength increased the chloride ion permeability decreased for specimens cured in both the environments.
(4) The Variable Temperature Curing Environment (VTCE), with a range of temperatures similar to the range of temperatures used in this investigation, improved the ability of the high-performance concretes to resist chloride ions penetration. (5) The Figg method was found to be inadequate to measure air and water permeability of the HPCs used in this work.
Table 1 Concrete Batch Proportions for Mixture 12.5P 12,500 psi Proven Mix Batch Proportions Mix Number 12.5P1 12.5P2 12.5P3 12.5P4 Design Strength, psi 12500 12500 12500 12500 Cement, lbs/cu yd 713 766 757 746 Fly Ash ("C"), lbs/cu yd 178 192 190 187 Fly Ash ("F"), lbs/cu yd 0 0 0 0 Silica Fume, lbs/cu yd 45 48 47 47 Water, lbs/cu yd 253 287 281 281 Sand (SSD), lbs/cu yd 1025 1100 1087 1070 3/4" Aggregate (SSD), lbs/cu yd 1606 1724 1702 1676 Water-to-Cementitious Materials Ratio 0.27 0.28 0.28 0.29 HRWRA, liq-oz/cu yd 122 131 129 127 Retarder, liq-oz/cu yd 27 29 28 28 Slump, inches 4½ 3½ 6¾ 7 Air Content, % 1.0 2.4 2.3 2.3 Air Temperature, F 67 68 68 68 Concrete Temperature, F 58 65 66 63 Concrete Density, pcf 150.2 151.3 151.4 150.0
Table 2 Concrete Batch Proportions for Mixture 12.5E 12,500 psi Economical Mix Batch Proportions Mix Number 12.5E1 12.5E2 12.5E3 12.5E4 Design Strength, psi 12500 12500 12500 12500 Cement, lbs/cu yd 545 592 575 597 Fly Ash ("C"), lbs/cu yd 314 346 336 349 Fly Ash ("F"), lbs/cu yd 174 189 184 191 Silica Fume, lbs/cu yd 0 0 0 0 Water, lbs/cu yd 273 298 290 300 Sand (SSD), lbs/cu yd 927 1006 978 1014 3/4" Aggregate (SSD), lbs/cu yd 1429 1552 1508 1564 Water-to-Cementitious Materials Ratio 0.26 0.26 0.27 0.26 HRWRA, liq-oz/cu yd 89 97 94 98 Retarder, liq-oz/cu yd 31 34 33 34 Slump, inches 9½ 9½ 10 9¼ Air Content, % 2.5 2.3 2.6 2.2 Air Temperature, F 68 68 68 68 Concrete Temperature, F 58 58 56 58 Concrete Density, pcf 145.7 146.7 145.3 147.2
Table 3 Compressive Strength Test Results for Mixture 12.5 P and Mixture 12.5E Subjected to Moist Room and Variable Temperature Curing Environments Test Moist Room Lab Cured Variable Temperature Cured Age, 12.5P Mixture 12.5E Mixture 12.5P Mixture 12.5E Mixture Days Actual Average Actual Average Actual Average Actual Average 3 8040 5410 9210 5760 3 8370 8250 5370 5340 9220 8390 5980 5830 3 8330 5220 6760 5740 7 10770 7540 10990 7960 7 9800 10010 7380 7490 10470 10850 7580 7550 7 9460 7560 11090 7100 28 12600 10170 12250 9230 28 12240 12560 9100 9440 12190 12800 9850 9750 28 12830 9050 13960 10180 56 13401 11410 12650 11420 56 13460 13470 12020 11710 13320 13270 11870 11620 56 13550 11710 13840 11570 91 13750 12600 14750 13580 91 14810 14380 12620 12570 13990 14500 12340 13100 91 14570 12480 14760 13370
Table 4 Rapid Chloride Ion Test Results For Mixture 12.5P and 12.5E Specimens Cured in the Moist Room Mix No. Age (days) Specimen No. Total Charge Passed, Coulombs 1 650 Average Charge Passed, Coulombs 12.5P2 28 2 723 690 3 692 1 296 12.5P2 56 2 335 330 3 353 1 288 12.5P2 91 2 298 300 3 303 1 4343 12.5E2 28 2 4321 4440 3 4648 1 2001 12.5E2 56 2 1652 1850 3 1887 1 1199 12.5E2 91 2 1190 1180 3 1147
Table 5 Rapid Chloride Ion Test Results for Mixture 12.5P and 12.5E Specimens Subjected to a Variable Temperature Curing Environment Mix No. Age (days) Specimen No. Total Charge Passed, Coulombs 1 192 Average Charge Passed, Coulombs 12.5P2 29 2 194 190 3 183 1 162 12.5P2 62 2 199 170 3 147 1 175 12.5P2 91 2 254 215 3 209 1 2502 12.5E2 28 2 3443 2990 3 3017 1 882 12.5E2 56 2 950 1040 3 1296 1 963 12.5E2 91 2 880 1070 3 1376
MOIST CURING ENVIRONMENT IN THE CBU LABORATORY
VARIABLE TEMPERATURE CURING ENVIRONMENT
COMPRESSION TESTING MACHINE
RAPID CHLORIDE ION PERMEABILITY TESTING MACHINE
FIGG AIR PERMEABILITY TEST
FIGG WATER PERMEABILITY TEST