15 March 2001
3.1. Description and Composition. Concrete
is made from portland cement, water, fine
aggregate (sand), and coarse aggregate (gravel or crushed rock), with or without additives (air
entraining, fly ash, etc.), developed to achieve the strength and durability of natural stone.
Concrete generally achieves its initial set within 1 hour after water is added and will become fairly
hard within 6 hours of placement. Concrete will continue to gain strength at an ever decreasing
rate for many years as long as moisture is retained within the consolidated mass and there is no
adverse chemical reaction either internally or due to external action.
3.2. Properties and Behavior.
3.2.1. Performance. A concrete pavement has a relatively long economic life when properly
designed, constructed, and maintained. In general, the economic life of a pavement ends when,
under the effects of traffic, weather, and/or lack of proper maintenance, it breaks into small
unstable sections; surface problems develop; and costly, extensive maintenance is required.
Durability is improved by surface maintenance, especially at joints and cracks. Maintaining the
joints to minimize the infiltration of water and to prevent the entrance of incompressible material is
essential under most conditions for long life. Frequent loadings greater than those for which the
pavements were designed will cause early failure of the pavement.
3.2.2. Rigidity. PCC is classified as a rigid pavement. Because of its beam action or resistance
to bending, it can bridge small, soft, or settled areas of a subgrade. Overloading of concrete
pavements can result from applied loads being greater than the design load, more passes than
assumed in the design, or the foundation support being reduced as a result of pumping,