CHAPTER 5
EVALUATION OF GRDATION EFFECTS
Introduction
The packing of particulate matter into a confined volume has long been of interest
to mix designers. In the 1930's, Nijboer (1948) investigated the effects of particle size
distribution using aggregate particles. He found that a gradation plotted on a log-log
graph as a straight line with a slope of 0.45 produced the densest packing. He showed it
to be the case for both crushed and uncrushed aggregates. In 1962, Goode and Lufsey
(1962) published the results of studies they performed at the Bureau of Public Works.
They performed an experiment to confirm Nijboer's findings and then investigated
further to determine the packing of simulated gradations that might be actually used in
road construction. As a result of their studies, they developed a specialized graph in
which the vertical axis is the percent passing a sieve size and the horizontal axis is the
sieve opening raised to the 0.45 power. To reduce confusion, the horizontal axis does not
contain the actual calculated numbers, but instead has marks that indicate different size
sieves. This specialized graph became known as the 0.45 power chart. In 1992, Huber
and Shuler (1992) investigated the size distribution of particles that gives the densest
packing. They determined that a gradation drawn on a 0.45 power chart as a straight line
from the origin to the aggregate nominal maximum size produced the densest packing. In
2001, Vavrik et al. (2001) presented the Bailey method of gradation analysis. Bailey
method takes into consideration the packing and aggregate interlock characteristics of