What are the Massachusetts Concrete Barrier Wall Specifications?

The Massachusetts Department of Transportation outlines specifications regarding concrete barriers and their parts, including slipform barriers, conventionally formed barriers, median barrier caps, delineators, and more.

Massachusetts Precast Barrier Specifications

According to the Massachusetts Department of Transportation, precast concrete barriers and transition pieces should be in lengths of 10’ and are subject to the approval of the Engineer for method of casting, handling and setting of the sections.

The reinforcing steel should be in conformance with 901.62: Reinforcement and M8.01.7: Epoxy Coated Reinforcing Bars, as modified to conform to ASTM Designation A615, Grade 60.

The 1” plain dowel bars should conform to ASTM A36 and should be galvanized according to AASHTO M 111M/M 111. The units should be manufactured in a plant approved by the Engineer and subject to their inspection and control.

Forms

The forms should be constructed of steel or other approved material. They should conform to the design shown on the plans. Wood forms will not be allowed, and reuse of old, worn or misshapen forms will also not be allowed.
The form release material should be applied to the forms in an approved manner and of a type that will not reduce the adhesive and or penetrating qualities of the protective coating to the concrete.

The dowel bars should be accurately set true to a plane at right angles to the plane of the end of the unit.

Lifting holes or devices should be as indicated on Construction Standards so that no undue stresses are transmitted to the units.
The units should be cast with the forms in a 180° inverted position and compacted with an approved vibrator. Air holes are to be filled immediately after form removal to the satisfaction of the Engineer.

Massachusetts Cast In Place Barrier Specifications

Conventionally Formed Barriers

According to the Massachusetts Department of Transportation, conventionally formed barriers should be accurately set to the required line and grade, secured by a method not detrimental to the roadway pavement and maintained in a true position during concrete placement. Forms may be removed no sooner than 24 hours after placement of concrete.

Slipform Barriers

Concrete traffic barriers may be constructed by the use of slipform equipment provided that the finished barrier is true to the specified line and grade within a tolerance of ±¼” in 10’. The barrier should present a smooth, uniform appearance in its final position, and should conform to the horizontal and vertical lines shown on the plans or as directed by the Engineer. Any unsatisfactory section of the barrier should be removed and replaced at the Contractor's expense.

The concrete should be vibrated and worked until adequately consolidated and free of honeycomb. The concrete should be of such consistency after slipforming that it will maintain the shape of the barrier without support. Prior to the beginning of operations, the Contractor should ensure that a continuous supply of concrete is available to the slipform machine to minimize starting and stopping. The slump of concrete should not exceed 1.5” unless directed otherwise by the Engineer.

The slipform machine should be guided by vertical and horizontal sensors that ride along a wire line. A grade line gauge or pointer should be attached to the machine in such a manner that a continual comparison can be made between the barrier being placed and the established grade line. The slipform machine should not exceed the speed recommended by the manufacturer. In lieu of sensor controls, the slipform machine may be operated on rails or supports set at the required grade.

Concrete Median Barrier Caps

The work consists of constructing a 4”-thick cast-in-place cap between the single face median barriers as shown on the plans. The cap should be cast in place on a gravel foundation with the length of each section being 30’. A ½” premolded joint filler will be placed between these 30” sections. A ½” premolded joint filler will be placed around bridge pier columns and along the joints between the barrier and the cap where required.

Placement of Barriers

Precast concrete barrier units should be placed on a previously compacted gravel foundation utilizing 24” by 8” by 24” concrete leveling blocks set flush with the top of the gravel to control setting of the unit to the proper grade.

The Contractor should schedule their operation and sequence of installation of the barriers so that a minimum amount of closure pieces will be required.

Expansion and construction joints should be as shown on the Construction Standards.

Any units showing cracks or other damages due to curing, transportation, installation or other acts of the Contractor should be removed and replaced by the Contractor at no additional compensation.

Concrete Penetrant/Sealer

Concrete Penetrant/Sealer should be applied to the exposed faces of the cement concrete barriers and concrete median barrier cap by the method described below and as directed by the Engineer.

The compound should conform to the provisions of M9.15.0: Liquid Penetrant/Sealant and should not be applied sooner than 28 days after the concrete has been poured and finished. The compound should not be applied when the air temperature is below 50°F. unless otherwise directed; the compound is not to be heated.

All of the surfaces that are to be treated should be dry and cleaned of all dust, dirt, form oil, and debris by sweeping, sand blasting or air blasting.

All joints that are to be filled with a joint sealer are to be shielded from contact with the concrete penetrant/sealer with tape or other suitable protective measures approved by the Engineer.

The compound is to be applied in accordance with the manufacturer’s specifications.

Delineators

Delineators should be installed in conformance with manufacturer's recommendations at beginnings and ends of each continuous run of barrier with intermediate placement at 80” intervals.

Two sided amber reflectors should be mounted on top of double-faced median barriers. Single faced barriers should have side mounted installation with amber color delineating left edge, white color delineating right edge and red color backing on each. Delineators should be mounted at appropriate angles which provide maximum reflectorization.

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

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