What are Montana Concrete Barrier Rail Specifications?

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The Montana Department of Transportation outlines specifications regarding the proper dimensions for concrete barrier rails, including general notes, plan view details, elevation details, section details and loop fabrication requirements.

Montana Concrete Barrier Rail General Notes

The Montana Department of Transportation’s general instructions are as follows:

  1. Use class deck concrete or equivalent.

  2. Reinforcing steel consists of deformed bars conforming to AASHTO M 31 Grade 60.

  3. Connect each 10” section with connecting pins as details and conforming to AASHTO M 270, Grade 36 or better. Connecting pins need not be painted.

  4. Cutouts on edges of each section are shown with slight taper to facilitate form removal. Rectangular cutouts are acceptable.

  5. The contractor is responsible for the proper fit up of the precast concrete barrier rail. Assemble and pin sufficient number of precast sections in the fabrications plant to determine that proper fit up can be maintained on all roadway alignment curves as well as on tangent. This is to be determined early in the fabrication.

  6. Attach reflectors to the rail every 30’. Use aluminum alloy meeting the aluminum association alloy AA5052-H32. Follow the manufacturer’s specifications for adhesive mounting. In narrow pave median applications, reflectorize both sides.

  7. Do not install unanchored concrete barrier rail for obstacles within 6.5’ of the base (traffic side) of the rail.

  8. The optional tapered end shown in an acceptable alternate to the vertical end for all concrete barrier rail ends.

  9. Galvanize or epoxy coat loops and connecting pins after fabrication/bending. Galvanize in accordance with ASTM A153, B695 (Class 50) or other applicable ASTM galvanizing standards.

Montana Concrete Barrier Rail Loop Fabrication Requirements

Loop fabrications in Montana should conform to the following specifications according to the Montana Department of Transportation:

Requirements

  1. Use reinforcing steel conforming to ASTM A 706, Grade 60 for rebar being welded to loops.

  2. Loop ends consist of smooth round bars conforming to AASHTO M 270, Grade 36.

  3. Cold bend the loops by using a jog that will produce an accurate radius without marring the bar. Do not heat the bar to facilitate bending.

  4. Weld rebar to loops meeting section 624 requirements using 1/8” diameter E8018 rod. Do not tack weld the pieces together prior to welding.

  5. No additional welding is permitted on the smooth round bars r reinforcing steel.

Optional Loop Details

  1. Use continuous smooth round bars conforming to AASHTO M 270, Grade 36 to fabricate the optional loops.

  2. Cold bend the loops by using a jig that will produce an accurate radius without marring the bar. Do not heat the bar to facilitate bending.

  3. No welding is permitted on the smooth round bars or reinforcing steel.

Montana Concrete Barrier Rail Specifications

Concrete barrier rails in Montana should include the following features, according to the Montana Department of Transportation specifications.

Elevation View

Barriers should include a reflector and may have an optional tapered end. Barriers also have a lifting slot that is 3’-10” in length.

On the left hand side of the barrier, the top loop is spaced 9-7/8” from the top of the barrier; the middle loop is spaced 7-1/2” from the top lop; and the bottom loop is spaced 7-1/2” from the middle loop.

On the right hand side of the barrier, the top loop is spaced 8-1/8” from the top of the barrier; the middle loop is spaced 7-1/2” from the top lop; and the bottom loop is spaced 7-1/2” from the middle loop.

Plan View

Barriers include 16 #5s (typ.) spaces spaced 7” apart, with a 4” gap on either side.

End View

A barrier break point occurs 1’-1” from the ground line. There is a 10” R at the break point and a 1” R at the vertical reveal. The Upper slope should measure 5” wide from the center of the barrier and the bottom slope should measure 7” wide from the center of the barrier.

This blog post is an interpretation of specifications by the Montana Department of Transportation. Please consult with Montana DOT's most recent requirements for definitive information.

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