Abstract:
The research work was undertaken to study the influence of.
grading on the strength of water-bound macadam (WBM). The study
includes the selection of a suitable aggregate grading for waterbound
macadam construction from the considerations of strength
and stability. Attempts are also made to study the properties of
brick-aggregate used for WBM construction.
The whole research work was carried out in three stages. In
the first stage, compaction type was selected from degradation of
brick aggregate due to different compactive efforts (i.e. 2.5 kg,
4.5 kg and vibrating hammer). Use of screenings was selected in
the second stage from bearing capacity of the mix for two
conditions -- one by mixing screenings with coarse aggregate and /
another by providing screenings on the top surface of coarse
aggregate. Finally. aggregate grading was selected from strength
and stability of the aggregate mix.
Four gradations were initially selected from the recommended
specified gradations .. Modified Bearing Ratio (MBR) tests were
then performed after compacting by a vibrating hammer at optimum
moisture contents as CBR test is not applicable to most of the
gradings used.
The study reveals that "Picked Jhama" brick-aggregate-sandsoil
mixes are good for use in WBM construction, from the"
standpoint of strength and stability. WBM mixes with picked jhama
brick aggregates give satisfactory results when they are
constructed using dense grading compacting by vibrating hammer at
optimum moisture content.
