UNIT 17: ROADS AND PAVEMENTS
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INTRODUCTION
Engineers do not only build buildings. They also build roads, highways, and parking lots. Roads must be strong, smooth, and safe. They must handle heavy trucks and rain.
STORY 1: Layers of a Road
A road is made of several layers. The bottom layer is the subgrade. This is the natural soil, compacted. On top of that is the sub-base. This is crushed stone. Next is the base course, made of larger stone. The top layer is the pavement. This is wh