Abstract
This paper presents the experimental investigation of the proper grading of aggregates for the proportioning of concrete which should be selected to produce economical concrete of the required strength and workability.
For this purpose, the authors examined the effects of various gradings, especially gap grading, of aggregates on the bulk density, compressive strength and workability of concrete. The aggregates used are river gravel and sand, and the particle shape may practically be considered as constant.
The experimental results are as follows;
(a) The proper gap grading of aggregate gives the weighty bulk density and the concentrated grading gives the minimum value.
(b) Two fineness modulus of aggregates having the same property give the same bulk density.
(c) Relationship between the thickness of cement paste film and consistency of concrete, is approximately linear. Consistency of concrete is decreased as the cement paste film is reduced, if other factors are equal.
(d) Compressive strength of concrete which is made of the proper gap grading of aggregate is higher than that of concrete made of the continuous grading of aggregate.
(e) When cement content and consistency of conrete are constant, the compressive strength of concrete is decreased, as the void ratio or specific surface of aggregates is increased.
Herewith, the authors propose to take the specific surface and the voids of aggergates as parameters for designing the proportion of concrete.
