Figure 1:
British roads
 |
The British government also gave importance to road construction.
The British engineer John Macadam introduced what can be considered as the
first scientific road construction method.
Stone size was an important element of Macadam recipe.
By empirical observation of many roads,he came to realize that 250 mm layers of
well compacted broken angular stone would provide the same strength and
stiffness and a better running surface than an expensive pavement founded on
large stone blocks.
Thus he introduced an economical method of road construction.
The mechanical interlock between the individual stone pieces provided strength
and stiffness to the course.
But the inter particle friction abraded the sharp interlocking faces and partly
destroy the effectiveness of the course.
This effect was overcome by introducing good quality interstitial finer
material to produce a well-graded mix.
Such mixes also proved less permeable and easier to compact.
A typical cross section of British roads is given in
Figure 1.
|
