UFC 3-260-02
30 June 2001
75 millimeters (3 inches) for pavements 300 to 450 millimeters (12 to 18 inches) in thickness, and
one-sixth of the slab thickness for pavements greater than 450 millimeters (18 inches) in thickness. In
no case will the depth of the groove be less than the maximum nominal size of aggregate used.
Concrete placement conditions may influence the fracturing of the concrete and dictate the depth of
groove required. For example, concrete placed early in the day, when the air temperature is rising, may
experience expansion rather than contraction during the early life of the concrete with subsequent
contraction occurring several hours later as the air temperature drops. The concrete may have attained
sufficient strength before the contraction occurs so that each successive weakened plane does not result
in fracturing of the concrete. As a result, excessive opening may result where fracturing does occur. If
this situation occurs, increase the depth of the initial groove by 25 percent to assure the fracturing and
proper functioning of each of the scheduled joints.
(3) Width and depth of sealant reservoir. The width and depth of the sealant reservoir for the
weakened plane groove will conform to dimensions shown in Figure 12-31. The dimensions of the
sealant reservoir are critical to satisfactory performance of the joint sealing materials.
(4) Spacing of transverse contraction joints. Transverse contraction joints will be constructed
across each paving lane, perpendicular to the centerline, at intervals of not less than 3.8 meters
(12.5 feet) and generally not more than 6 meters (20 feet) for the Navy and 6 meters (20 feet) for the
Army and Air Force. The joint spacing will be uniform throughout any major paved area, and each joint
will be straight and continuous from edge to edge of the paving lane and across all paving lanes for the
full width of the paved area. Staggering of joints in adjacent paving lanes can lead to sympathetic
cracking and will not be permitted unless reinforcement is used. The maximum spacing of transverse
joints that will effectively control cracking will vary appreciably depending on pavement thickness,
thermal coefficient and other characteristics of the aggregate and concrete, climatic conditions, and
foundation restraint. It is impractical to establish limits on joint spacing that are suitable for all conditions
without making them unduly restrictive. The joint spacings in Table 12-7 have given satisfactory control
of transverse cracking in most instances and may be used as a guide, subject to modification based on
available information regarding the performance of existing pavements in the vicinity or unusual
properties of the concrete. For the best pavement performance, the number of joints should be kept to a
minimum by using the greatest allowable joint spacing that will control cracking. Experience has shown,
however, that oblong slabs, especially in thin pavements, tend to crack into smaller slabs of nearly equal
dimensions under traffic. Therefore, it is desirable, insofar as practicable, to keep the length and width
dimensions as nearly equal as possible. In no case should either dimension exceed the other dimension
by more than 25 percent. Under certain climatic conditions, joint spacings different from those in
Table 12-7 may be satisfactory. Where it is desired to change the joint spacing, a request will be
submitted to the Transportation System Mandatory Center of Expertise, TSMCX (CENWO-ED-TX) for
Army projects, or the appropriate Air Force Major Command for Air Force projects, regardless of who
performs the design.
12-20
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