Increasing numbers of new roads in developing countries are being built with
thick asphaltic concrete surfacings to accommodate increasing traffic volumes.
However, in areas of high traffic stresses, such as climbing lanes and junctions, the use of asphaltic concrete designed by the Marshall method is often not appropriate, particularly at high pavement temperatures. In these situations the commonly used 75-blow Marshall compaction method
underestimates the effect of secondary compaction under traffic and many of these surfacings suffer structural instability leading to severe plastic deformation.
This paper illustrates the importance of retaining sufficient voids in the mix after trafficking to prevent plastic deformation and discusses limitations associated with the Marshall design procedure. Many developing countries have limited facilities for bituminous mix design and an improved method of design is proposed which requires only commonly available or inexpensive equipment. The procedure uses a combination of the Marshall test method and determination of a 'reference refusal density' using a vibrating hammer
in accordance with the percentage refusal density test.
Proceedings of the Institution of Civil Engineers. Transport (1998) 129, Feb., 28-33. pp. 8
Bituminous surfacing for heavily trafficked roads in tropical climates.