4191.01 DESCRIPTION.
Metal keyway and expansion tubes shall meet the following requirements:

A. Metal Keyway.
Metal keyway shall be of coated or uncoated sheets of 24 gauge (nominal 0.6 mm thick) iron or steel formed to produce a trapezoidal offset in the face of the concrete of 1 inch (25 mm) plus 1/4 inch (6 mm) or minus 1/8 inch (3 mm). The dimension and installation details shall be as required in the contract documents. The keyway shall be punched along the center line of the face, to receive the bars and shall be furnished in lengths which are multiples of the bar spacing.

Keyways formed on the grade during the paving operation may be of coated or uncoated sheets of 26 gauge (nominal 0.4 mm thick) iron or steel.

C. Expansion Tubes.
Expansion tubes to be used as dowel caps on dowel bars through expansion joints shall be noncollapsable metal or plastic tubes with one end closed. They shall be formed with a positive bar stop, capable of withstanding a push of more than 20 pounds (90 N). The stop shall be located at least 2 3/4 inches (70 mm) from the open end of the tube. Each tube shall have an internal diameter not more than 1/16 inch (2 mm) larger than the nominal diameter of the bar. That part of the tube having this diameter shall extend beyond the stop a distance not less than the width of the expansion joint.