30 June 2001
not to exceed 45 meters (150 feet). A grouting pumping will be used to inject the grout. The grouting will
commence at an end vent and continue until grout is forced out of the first interior vent along the conduit.
The end vent will then be sealed, and grout will be injected through the first interior vent until it is
extruded from the second interior vent. This procedure will be continued until the entire length of conduit
has been grouted.
a. Joint Spacing. Experience has shown that from a practical standpoint, the maximum length of
prestressed concrete slabs should be 150 meters (500 feet), although lengths of 180 and 215 meters
(600 and 700 feet) have been constructed. The width of the slab will vary depending upon the capability
of the construction equipment but will generally be a minimum of 7.6 meters (25 feet).
b. Joint Types.
(1) Longitudinal joint. Runway and taxiway pavements will be prestressed for their full width,
and the longitudinal joints will be the butt type with the prestressed tendons carried through the joint.
The transverse prestressing operation will be carried out after all paving lanes have been completed.
For areas wider than 150 meters (500 feet) (such as aprons), the pavement must be constructed in
widths not to exceed 150 meters (500 feet); therefore, longitudinal fill-in lanes will be required to permit
access for applying the transverse prestressing.
(2) Transverse joint. Because of the length of prestressed slabs and the low subgrade restraint,
large movements will occur at the transverse joints. The transverse joint must be designed to
accommodate these movements that are a function of the temperature change, slab length, and
moisture conditions. The anticipated movements can be determined by
)LT = change in length of slab due to temperature change )T, inches
L = slab length, feet
)T = change in temperature in degrees (either daily or seasonally)
)LM = maximum change in length of slab due to seasonable moisture change
,M = coefficient of moisture expansion of concrete (assumed to be 1 10-4 inch per inch