(5) Effect uniform movements in subgrade areas subject to frost heaving.
(6) Provide operating surfaces for construction equipment, especially
during unfavorable weather.
b. Materials. Processed or stabilized, well-graded materials that are not
frost susceptible usually are suitable base materials under concrete
pavements; see Section 6. The plasticity index shall not exceed 5.
c. Compaction. Bases shall be constructed in layers. Design layers with
maximum compacted thicknesses of 6 inches and minimum compacted densities of
95 percent of modified Proctor maximum density.
Provide surface drainage for water collection and removal from
road surfaces, and for interception and collection of water flowing from adja-
cent areas. Provide subsurface drainage to intercept, collect, and remove
ground water flow: (a) into subgrade, (b) to lower high water tables, (c) to
drain perched water tables, and (d) to prevent frost action. For design
criteria for surface drainage, see NAVFAC DM-5.3. For subsurface drainage, see
subgrades in Section 4 and bases in Section 6.
5. DESIGN FOR FROST EFFECTS. In areas having freezing temperatures, determine
the need for designing for frost effects from state, county, or city highway
or street departments. Also, determine depths of frost penetration from high-
way departments and from local utilities. Where design for frost is necessary,
use results of local experiences. For more complete discussion of frost
design, see NAVFAC DM-21.
6. JOINTS. Use expansion and contraction and construction joints in pavements
to prevent uncontrolled cracking caused by shrinkage and by contraction and
expansion induced by temperature changes. Also provide joints to control
random cracking results from uneven subgrade support and construction joints,
as required. Use the kinds of joints and sealing compounds specified in
Joints, Reinforcement, and Mooring Eyes Concrete Pavement, NAVFAC TS-02614.
7. DESIGN OF DISTRIBUTED REINFORCING STEEL. Distributed reinforcing steel
(wire mesh and bar mat) is used to control cracking and to prevent cracks from
enlarging. Provide in accordance with NAVFAC TS-02614.
Section 10. DESIGN OF PORTLAND CEMENT CONCRETE
1. MIX DESIGN. Concrete mixes for rigid pavements should be designed in accor-
dance with Portland Cement Concrete Pavement for Roads and Airfields. NAVFAC
2. AIR ENTRAINMENT. Use air entraining admixture wherever available. Air
entrainment usually causes moderate flexural strength decreases; consider this
when selecting design flexural strength.
3. LOW ALKALI CEMENT. As a precaution against alkali aggregate reactions, use
low alkali cement containing not more than 0.6 percent total alkalies.
Section 11. LOW-COST ROADS
1. BASIC FACTORS. Low-cost roads are suitable for low traffic volumes only and
result in excessive maintenance costs and unsatisfactory service if used
improperly. Where roads are upgraded in stages, plan the work in phases that
will permit existing roads to be incorporated in upgraded phases with a
minimum loss of existing construction.
a. Progressive Improvement of Roads. Stage construction of roads can be
accomplished readily where a flexible type of construction is suitable and
economical, as for normal pavement areas.