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How are the properties of concrete affected by the fineness of the cement?
Here are the conclusions offered in a paper by E. C. Higginson on "The Effect of Cement Fineness on Concrete":
1. Increasing the fineness of cement reduces the amount of bleeding in concrete. This is more pronounced for concrete containing no entrained air.
2. Increasing the fineness of cement from 2700 to about 4000 cm2/g reduces the water requirement of concrete. Increasing the fineness of cement beyond an optimum limit increases the water requirement of concrete.
3. The workability of non air-entrained concrete is increased by increasing the cement fineness. In air-entrained concrete the effect of fineness of cement on workability is very much less pronounced.
4. The air-void system in air-entrained concrete or concrete containing no entrained air is not significantly affected by variations in the fineness of cement.
5. The 28-day compressive strength of concrete, with or without entrained air, increases with an increase in cement fineness. The difference in compressive strength due to difference in fineness of cement is considerably less at 1 year's age.
6. For concrete containing no entrained air, there is a slight decrease in the static modulus of elasticity at 28 days' age as the fineness is increased. The modulus of elasticity of concrete determined by sonic methods decreases as the fineness of the cement increases.
7. The fineness of cement influences the drying shrinkage of concrete. When the water content is increased because of fineness, the drying shrinkage is increased. However, if excessive bleeding due to coarseness of the cement takes place, a reduction in the drying shrinkage occurs.
8. The resistance of air-entrained concrete to deterioration caused by freezing and thawing decreases with an increase in cement fineness. The same trend is noted with non air-entrained concrete, but to a lesser degree.
9. Both air-entrained and non air-entrained concrete containing 100 percent reactive aggregate are detrimentally affected by increased expansion at all ages by increases in the fineness of a high-alkali cement.
10. A very coarse cement under some conditions can cause a serious bleeding problem on some construction projects.
11. When a cement is used that meets the present Federal specifications, it is doubtful that a field construction problem could be greatly influenced by changing the cement fineness.