(1). DESIGN OF LIGHTWEIGHT-AGGREGATE CONCRETE MIXES : Studies on Lightweight Concrete: Part 4

In this paper it is propored how to design lightweight-aggregate concrete mixes, satisfying given strength and consistency, by amending well-known method of mixing concrete of river sand and gravel aggregate, which are most commonly used in Japan. For this purpose several formulas are presented. In these formulas two kinds of factors, which are proper to each lightweight aggregate, are involved: (1) Workability factor or ratio of density; These factors are concerned with the shape and the grading of lightweight aggregate. It is known that the better the shape and the grading of aggregate, the larger its density. The author, therefore, uses the ratio of density for the purpose of distinguishing the shape and the grading of lightweight aggregate from those of normal river sand and gravel. Such ratio is referred to as "ratio of density". Workability factor is a certain function of the ratio of density. (2) Air void factor; This factor is used for indicating the grade of weakness of materials comporing aggregate, and is a ratio of the effect of void in aggregate to diminish the strength of concrete to the same effect of mixing water with equal volume in fresh concrete.