Page 53 - Unit 2: Pavement Material

Civil Engineering Department | DCC3113 : Highway & Traffic Engineering

AC Mix

i. After the completion of the stability and flow test, specific gravity and voids analysis shall
be carried out for each test specimen to determine the percentage air voids in the
compacted aggregate filled with bitumen (VFB) and that percentage air voids in the
compacted mix (VIM).
ii. The average values of bulk specific gravity, stability, flow, VFB and VIM obtained above
shall be plotted separately against the bitumen content and smooth curve drawn
through the plotted value.

Density Stability Flow VIM VFB

% Bitumen Content % Bitumen Content % Bitumen Content % Bitumen Content % Bitumen Content
Figure 3.1 : Five different types of graphs in Marshall Design
iii. The mean optimum bitumen content shall be determined by averaging five optimum
bitumen contents so determined as follows;

a) Peak of curve taken from the stability graph
b) Flow equals to 3 mm from the flow graph
c) Peak of curve taken from the bulk specific gravity graph

d) VFB equals to 75% for wearing course and 70% for binder course from the VFB graph
e) VIM equals to 4.0% for wearing course and 5.0% for binder course from the VIM
graph.

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Prepared by : SITI ZURAIFA BINTI MD SAH, zuraifa@pmu.edu.my