2
Introduction
In consideration of increased traffic loads and in order to improve pavement performance, rubber modified
asphalts have been developed during the last few decades. The added rubber can strongly enhance the binder
properties and permit the building of safer roads and the reduction of maintenance costs (Polacco
et al
., 2005).
Asphalt has numerous applications and one of its major uses is as a binder for aggregate materials in the construction
of highways and runways (Krishnan
et al
., 2005). However, this material has poor mechanical properties because it is
hard, fatigue cracking and brittle in cold weather (low temperature), soft, rutting and fluid in hot environment (high
temperature) and it has a low elastic recovery. The brittle character of the asphalt makes it easy to fracture when it is
subjected to stress. For these reasons asphalt is usually reinforced by rubber to improve its mechanical properties
(Estevez, 2009).
The main objective of this work has been to study on the compression properties of natural rubber - asphalt -
aggregate blends. The effects of aggregate size and the speed of the compression. Cauchy’s equation, compression
modulus and true stress were used in order to characterize the linear and non-linear behavior of polymer blends.
Material and Methods
Materials
STR 5L Grade Rubber (Chana Rubber Company Limited), Penetration Grade liquid asphalt (AC 60/70)
(Pattani Highway District) and aggregate diameter of 4.75 - 9.50 mm, 9.50 - 12.50 mm and 12.50 - 19.00 mm. were
used for preparation of samples.
Sample preparation
The polymer blends were prepared using a high shear mixer. Firstly, asphalt was heated until it became fluid
in a small iron container, then upon reaching about 110° C, the rubber (based on 100 parts asphalt) and aggregate were
added. The stirring time was 2 hours at the stirring speed of 320 rpm. Finally, the sample was poured into a PVC tube,
2.6 cm in diameter and 5 cm in height.
Compression property test
The compression properties of polymer blends were tested by the speed of compression at 50, 150 and 250
mm/min (25°C). Cauchy’s equation, compression modulus and true stress were used in order to characterize the linear
and non-linear behavior of polymer blends, which can be calculated by the following equation:
True stress =
)(
)(
)(
tA
tF
t
where F (t) is the force and A (t) is the cross-sectional area at time t.
