1. © INFLUENCE OF CEMENT COMPOSITION ON CONCRETE DURABILITY RASHEEDUZZAFAR AMER CONCRETE INST, ACI MATERIALS JOURNAL; pp: 574-586; Vol: 89 King Fahd University of Petroleum & Minerals http://www.kfupm.edu.sa Summary Cement composition significantly affects the durability performance of concrete. Pore fluid studies and x-ray diffractograms shaw that C3A partially removes dissolvable corrosion-inducing chlorides from the pore solution by forming Friedel's salt. Accelerated corrosion tests and exposure site data on concrete specimens show the practical significance of chloride binding by the C3A phase of cement. Corrosion initiation time, time-to-cracking of cover concrete, and chloride threshold values were found to increase systematically, whereas metal loss from reinforcement decreased as the C3A content of the cement increased. The data also show that, for given C3A and chloride contents, more chlorides are bound if they are present initially in the mix at the time of making concrete (called internal or primary chlorides), compared to chlorides that penetrate into concrete from external sources later during the service life of a structure (called external or secondary chlorides). Also, with increasing levels of chloride addition to concrete, the quantity of bound chloride increases, and the rate of chloride binding decreases. Although cement alkalies have an inhibiting effect on chloride binding, they also significantly and concomitantly increase the OH- concentration of the pore solution resulting in a lowering of the Cl-/OH- ratio, which is a measure of corrosion risk. The latter effect dominates and overshadows the inhibiting effect of cement alkalies on chloride binding, thereby reducing the corrosion risk. Cement alkalies also cause concrete durability problems due to alkali- silica reaction in conjunction with aggregates containing reactive siliceous constituents. In addition to the C3A phase, cements with high C3S/C2S ratios also are prone to sulfate attack of a softening type caused by gypsum formation. Tests show Copyright: King Fahd University of Petroleum & Minerals; http://www.kfupm.edu.sa

2. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. © that such an attack may also occur in low C3A cements in which the composition is characterized by high C3S and low C2S contents to achieve high early age strengths. C3A and C3S phases of cement influence temperature rise and thermal cracking in concrete; whereas gypsum content influences shrinkage cracking. Blended cements formulated by partial replacement of ordinary Type I high C3A portland cement by 10 percent silica fume, 20 percent fly ash, or 70 percent blast furnace slag concomitantly show a significantly superior performance in terms of corrosion-initiation time and resistance to sulfate attack.These cements also show lower chloride permeability, only one-tenth to one-half of the allowable expansion due to alkali-silica reaction, and lesser risk of cracking due to heat of hydration gradients. Composition of modem cements usually is characterized by markedly higher C3S/C2S ratios than in older cements. Concretes made with these cements and specified in terms of 28-day strength only usually would satisfy these specification at higher water-cement ratios than concretes made with older cements. In general, this would lead to a more permeable, and hence less durable, concrete. References: ANDRADE C, 1986, BRIT CORROS J, V21, P49 ARYA C, 1990, CEMENT CONCRETE RES, V20, P291 BAKKER RFM, 1983, SP79 AM CONCR I, P589 BAMFORTH PB, 1980, P I CIVIL ENG PT 2, V180, P777 BAUMEL A, 1960, BETON HERSTELLUNG VE, V10, P256 BELLPORT BP, 1968, PERFORMANCE CONCRETE, P77 BENTUR A, 1976, J AM CERAM SOC, V59, P210 BLUNDELL R, 1973, SEP P S LARG POURS R, P66 BLUNDELL R, 1975, NEW CIVIL ENG BYFORS K, 1986, CEMENT CONCRETE RES, V16, P760 CARLSON RW, ACI J, V76, P821 COPELAND LE, 1969, 5TH P INT S CHEM CEM, V2, P387 DIAMOND S, 1986, CEMENT CONCRETE AGGR, V8, P97 GUNKEL P, 1983, CHLORIDGEHALTE AUSGE HANSEN WC, 1968, PERFORMANCE CONCRETE, P18 HOLDEN WR, 1983, CORROSION REINFORCEM, P144 LAMBERT P, 1985, CEMENT CONCRETE RES, V15, P675 LEA FM, 1935, CMEENT CHEM IND LOND, V54, P22 LERCH WL, 1946, P ASTM, V46, P1252 MATHER B, 1968, PERFORMANCE CONCRETE, P66 MEHTA PK, 1973, CEMENT CONCRETE RES, V3, P1 MEHTA PK, 1977, STP629 ASTM, P12 Copyright: King Fahd University of Petroleum & Minerals; http://www.kfupm.edu.sa

3. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. © MEHTA PK, 1979, CEMENT CONCRETE RES, V9, P439 MEHTA PK, 1983, CEMENT CONCRETE RES, V13, P401 MILLER DG, 1939, TECHNICAL B USDA, V358 MONFORE GE, 1960, ACI J P, V57, P491 PAGE CL, 1983, MATERIALS STRUCTURES, V16, P19 PICKETT G, 1956, ACI J P, V52, P581 RAMACHANDRAN VS, 1971, MATERIAUX CONSTRUCTI, V4, P3 RAMACHANDRAN VS, 1984, MAT CONSTRUCTIONS, V17, P285 RASHEEDUZZAFAR SS, 1990, CEMENT CONCRETE RES, V20, P723 RASHEEDUZZAFAR, AR6138 KACST ABD CIT RASHEEDUZZAFAR, 1989, ARAB J SCI ENG, V14, P235 RASHEEDUZZAFAR, 1990, ACI MATER J, V87, P114 RASHEEDUZZAFAR, 1990, CORROSION REINFORCEM, P213 RASHEEDUZZAFAR, 1991, CEMENT CONCRETE RES, V21, P779 RASHEEDUZZAFAR, 1992, ACI MATER J, V89, P3 RASHEEDUZZAFAR, 1992, ACI MATER J, V89, P337 ROBERTS MH, 1962, MAGAZINE CONCRETE RE, V14, P143 SWENSON EG, 1971, CANADIAN BUILDIN APR THEISSING EM, 1978, CEMENT CONCRETE RES, V8, P683 TRITTHART J, 1989, CEMENT CONCRETE RES, V19, P683 VERBECK GJ, 1968, PERFORMANCE CONCRETE, P113 For pre-prints please write to: abstracts@kfupm.edu.sa Copyright: King Fahd University of Petroleum & Minerals; http://www.kfupm.edu.sa