Title: Pape Sand Grading Improves Mass Concrete
Author(s): Thomas B. Kennedy
Publication: Journal Proceedings
Appears on pages(s): 141-151
Keywords: no keywords
Two series of concrete mixtures were designed using 6-in. traprock coarse aggregate and eight separate gradings of natural sand ranging in fineness modulus from 3.60 to 1.35. Tests were made of the plastic concrete, and specimens were cast for tests of compressive strength, resistance to freezing and thawing, and drying shrinkage. Both series of concrete mixtures had a cement content of 2.5 bags per cu yd; one had a normal air content - 4 1/2 = 1 1/2 percent in the portion of the mixture passing the 1 1/2-in. sieve. Tests indicate that good durablity in freezing and thawing can be obtained within the normal air content range with fineness modulus between 2.50 and 2.90. With increased air content, however, the fineness modulus range can be increased to extend from 1.58 to 3.24. Compressive strength was generally affected adversely by increased air content, but not to a serious degree. Drying shrinkage was less with normalair content mixes than with high air content mixtures. It was least when a fineness model of 2.52 was used, little difference being apparent between the high and normal air content mixes with this fineness modulus. The air-entraining mixture requirement increased greatly as the fineness modulus of the sand decreased. The water ratio also intended to increase with decreeasing fineness modulus.