3622Sectional Concrete Manhole and Catch Basin Units

3622.1SCOPE

Provide precast, reinforced concrete manhole/catch basin units consisting of riser sections and appurtenances such as grade rings, base slabs, tops, and special sections to construct sewer or water works.

3622.2REQUIREMENTS

Provide reinforced concrete manhole/catch basin units meeting the requirements of AASHTO M 199 Standard Specification for Precast Reinforced Concrete Manhole Sections , 3236, “Reinforced Concrete Pipe,” manufactured in plants meeting the requirements of 3240, “Precast Concrete Manufacturing,” and the following. Notify the Materials Engineer according to the requirements of 3240, “Precast Concrete Manufacturing,” before the manufacturer starts production to arrange for inspection. A Physical Properties Provide sectional concrete manhole/catch basin units in the dimensions, shape, wall thickness, type, and quantity of reinforcement as shown on the Plans. The Contractor may use alternative spigot-up joint or alternative offset joint. Use the profile or pre-lubricated pipe seal system with the alternative offset joint. Ensure test results show a compressive strength of at least 4,200 psi at 28 Calendar Days and before shipping the product to the Project Site. B Manufacture Provide units true to shape and with smooth, dense surfaces uniform in appearance . As soon as the forms are removed, use mortar to fill minor surface cavities or irregularities not impairing the service value of the unit and capable of being corrected without marring the appearance . Remove forms without damaging the unit.

When the manufacturer provides manholes with block outs or holes, provide additional steel in the remaining unit to prevent cracking. If the unit is cracked, remove the cracked portion and repair with mortar in accordance with the approved repair procedure in the MnDOT QM Manual and notify the Department Inspector for acceptance. When manufacturing special design rectangular manholes, provide sections meeting the manufacturing requirements of 3238, “Precast Concrete Box Culverts.”