Cement-Treated Base (CTB) is a strong, frost-resistant base for a concrete or asphalt pavement wearing surface. CTB is made up of native soils, gravels/manufactured aggregates blended with engineered quantities of cement and water. Pavements with CTB are much stronger and more rigid than a non-stabilized granular base. Cement-Treated Base is engineered so the thickness of the base is less that required for granular bases carrying the same weight and traffic. Properly engineered CTB can distribute loads over a wider area reducing the stresses on the sub-grade and acting as the load-carrying element of a flexible pavement or a sub base for concrete.
When mixed with a high-intensity, high-output, twin-shaft continuous mixing plant, its slab-like characteristics and beam strength are unmatched compared to granular bases that can fail when aggregate interlock is lost. This happens when wet sub-grade 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. Cement-Treated Base continues to gain strength with age even under traffic. This reserve strength accounts in part for CTB’s excellent performance.
The rigidity of Cement-Treated Base reduces deflection, rutting in the base and other asphalt strains. The versatility of cement is critical to the success in this pavement solution because site conditions and soil types (from gravel to clay's) can easily change during or between projects and cement acts as a "universal stabilizer."
Cement-Treated Base, as described above, is a mixture of aggregate material, granular soils combined with prescribed amounts of cement and water that hardens after compaction and curing to form a durable paving material. A 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 cement and sufficient water to permit maximum compaction. The CTB must be adequately cured to both let the cement hydrate and to harden the cement-aggregate mixture.
The fundamental control factors for quality Cement-Treated Base are: