Frequently Asked RCC Questions
Are sawed contraction joints needed for roller-compacted
Sawed contraction joints for controlling random cracking are not
required in RCC pavements due to the fact that RCC has lower water
and cement contents than conventional concrete, and thus shrinkage
is reduced. Random shrinkage cracks typically occur at 20- to 60-ft
intervals, depending on the RCC properties and pavement thickness.
The primary reason for sawing joints in RCC pavements is to reduce
or prevent random cracking. On certain projects where efficiency
of aggregate interlock or increased load transfer at the joints
is critical, joints are sawed to minimize crack openings through
reduced saw joint spacing, compared to longer spacing of random
cracks. Widely spaced random cracks can have wider then desired
crack width. The improved aggregate interlock increases load transfer
across the joint. Furthermore, reducing random cracking is sometimes
desired for aesthetic reasons.
When used, transverse sawed joints are typically spaced at intervals
of 15 to 20 ft for pavements less than 8 in. thick, and 3 to 4 times
(in ft) the pavement thickness (in in.) for pavements 8 in. thick
|Cutting joint with early-entry saw
Because the longitudinal loading of RCC pavements is different
than the transverse loading and causes more of a hinge action, the
spacing of longitudinal joints is typically smaller than the spacing
of transverse joints. For large paved surfaces, such as industrial
sites, a square jointing pattern is preferred. The spacing is normally
15 to 20 ft for pavements less than 8 in. and 2.5 times the pavement
thickness (in ft) for pavements 8 in thick or greater.
As with conventional concrete, the timing of saw cuts is based
on the prevention of raveling and random cracking. Sawing should
begin as soon as the concrete is hard enough to withstand spalling
damage caused by sawing operations. For increased load transfer
through aggregate interlock, the depth of the saw cuts should not
exceed 1/4 of the pavement depth. Thin early-entry saws are being
used more frequently because of the speed and convenience they offer.
Sawing can begin within one to four hours after final compaction.
The sawcut depth for early-entry sawing ranges from 1 to 1.25 in.
regardless of the pavement thickness.