30 June 2001
e. Transverse Contraction Joints. For transverse contraction joints, the spacing should be the
same as the longitudinal construction joints, or close to the same. Again, it is usually not appropriate to
design the transverse joints all with the same spacing, unless this comes out with easily measured
spacing. Otherwise, make spacing an easily remembered and an easily measured distance, with any
take-up distance provided in one or two spaces. One main objective is to provide spacings that are easy
for the joint saw crew (usually working at night) to follow and not get confused (no fractional inches, or
odd metric units, and as little variation as possible).
f. Replacements and Additions. Much of the present airfield paving work consists of replacement
areas and additions to existing pavement. This often results in odd-shaped areas with irregular
boundaries, proving difficult to provide a really good jointing pattern. As much as possible, the
guidelines in the previous subparagraphs should be followed, modified as absolutely necessary. Care
should be taken to, as much as possible, prevent small slabs and odd-shaped slabs requiring
reinforcement. When working with areas having irregular boundaries, it becomes a process of trial and
error to provide the best fit to the area, following criteria and minimizing as much as possible the need
for odd-shaped reinforced slabs--an expense to be avoided. When abutting existing PCC pavement, an
attempt should be made to match the existing joint pattern, where possible. Older pavements will often
have 7.6-meters (25-foot) joint spacing, when now we are usually allowed a maximum of 6 meters
(20 feet). For jobs of moderate size, if it is possible to match the existing joint pattern, the new joint
spacing can be made 7.6 meters (25 feet), provided the existing has shown no distress because of the
7.6-meter (25-foot) spacing. Otherwise, use 3.8-meter (12.5-foot) spacing. Either is acceptable, but the
Using Service should be contacted to get their preference--some like one and some the other.
g. Expansion Joints and Slip Joints.
(1) New PCC to New PCC. Where pavements abut buildings and other fixed objects, an
expansion joint should be provided. Where two new PCC pavements meet a an angle, an expansion
joint is necessary. If they meet at a 90-degree angle, the intersection should be a, thickened-edge
expansion joint. If they meet at other than a 90-degree angle, it should be a thickened-edge joint, either
expansion joint or slip joint. If the joints on new-to-new construction do not match and no expansion or
slip joint is used, 900-millimeter (3-foot) wide strips of reinforcing should be installed along each side of
the joint to prevent sympathetic cracks from forming in line with mismatched joints. Normally, expansion
joints of any kind should not be doweled if load transfer can be provided in another way. There have
been projects where doweled expansion joints have been successfully used, but this should be used
only where no translation movements or stresses are expected.
(2) New PCC to Old PCC. Where new PCC pavement meets old (existing) PCC pavement at
an angle, an attempt should be made to provide load transfer. At a 90-degree intersection, an ordinary
thickened edge (one side) expansion joint can be used if no load transfer is necessary (existing
pavement so understrength that it will not match the new pavement). At a 90-degree intersection and at
an intersection other than 90 degrees, it usually will be best to put in a doweled construction joint at the
intersection, and then install a thickened-edge expansion joint far enough back on the new pavement
to totally clear any fillets and give the shortest unobstructed (straight) line across the pavement. .
(3) Slip Joints. Slip joints, 6-millimeter (1/4-inch) minimum thickness, can be used in lieu of
expansion joints in places where only translation is expected, and no movement perpendicular to the
joint is expected. At 6-millimeter (1/4-inch) thickness, they are sufficient to prevent sympathetic cracking
across the joint, and thus eliminate the need for the 900-millimeter (3-foot) strip of reinforcing on each
side of new-to-new construction.