Base (CTB) is an intimate mixture of aggregate material and/or granular
soils combined with measured amounts of portland cement and water
that hardens after compaction and curing to form a durable paving
material. A bituminous or portland cement concrete wearing course
is placed on the CTB to complete the pavement structure. CTB is
widely used as a pavement base for highways, roads, streets, parking
areas, airports, and materials handling and storage areas.
In CTB construction the objective is to obtain a thorough mixture of an aggregate/granular material with the correct quantity of portland cement and enough water to permit maximum compaction. The completed CTB must be adequately cured to both let the cement hydrate and to harden the cement-aggregate mixture. The fundamental control factors for quality CTB are:
- Proper cement content
- Adequate moisture content
- Thorough mixing
- Adequate compaction
- Proper curing
aggregate/granular material, cement, and water are typically mixed
in a central mixing plant. Central plants can either be continuous-flow
or batch-type pugmill mixers. CTB can also be mixed-in-place using
transverse-shaft pulvermixers or traveling mixing machines.
thicknesses are less than those required for granular bases carrying
the same traffic because CTB is a cemented, rigid material that
distributes the load over a large area. Its slab-like characteristics
and beam strength are unmatched by granular bases that can fail
when interlock is lost. This happens when wet subgrade soil is forced
up into the base by traffic loads. Hard, rigid CTB is practically
impervious. It resists cyclic freezing, rain, and spring-weather
damage. CTB continues to gain strength with age even under traffic.
This reserve strength accounts in part for CTB's excellent performance.
More About CTB:
CTB Case Studies
CTB Research In Progress
Other SC Sites: