Highway Engineering

222 Highway Engineering

Warping joints are required in plain unreinforced concrete slabs only. They

permit small angular movements to occur between adjacent concrete slabs.

Warping stresses are very likely to occur in long narrow slabs. They are required

in unreinforced slabs only, as in reinforced slabs the warping is kept in check by

the reinforcing bars. They are simply a sealed break or discontinuity in the con-

crete slab itself, with tie-bars used to restrict any widening and hold the sides

together.

Construction is normally organised so that work on any given day ends at the

location of an intended contraction or expansion joint. Where this proves not

to be possible, a construction joint can be used. No relative movement is per-

mitted across the joint.

The four transverse joints are shown diagrammatically in Figs 7.15 to 7.18.

(It should be noted that, in all cases, reinforcement is required to support

dowels/tie-bars during construction.)

SLAB SLAB

Dowel bar (one half

debonded)

Reinforcement

Seal

Crack inducer

h/ 2

h

SUBBASE

Figure 7.15Contraction joint detail.

SLAB SLAB

Compressible

filler

Dowel bar

Reinforcement

Seal

SUBBASE

Figure 7.16Expansion joint detail.