9-118 Section 913. Masonry Units
913.01 General Requirements
Clay brick, concrete brick, concrete block, salvaged paving brick, precast reinforced concrete units, and structural tile for masonry structures must meet the requirements of this section.
913.02 Testing
Testing will be in accordance with the specified ASTM or AASHTO method as modified by this section.
913.03 Brick
A.Brick Dimensions. Brick must meet the following nominal size limitations:
1.Depth – 2 to 2½ inches ;
2.Width – 3½ to 3¾ inches; and
3.Length – 7½ to 8 inches. Brick for a single structure must b e of one nominal size and must not vary from the manufacturer ’s specified standard dimensions by more than ±⅛ inch in any dimension. However, clay brick may vary in length by ±¼ inch, and up to 2% of the contract ’s clay brick quantity may exceed the dimens ional tolerances.
B.Clay Brick . Clay brick to construct manholes, catch basins, and similar structures must meet the requirements of ASTM C32 for Grade MS. Recessed or cored brick is acceptable. Salvaged paving brick meeting the requirements of this section is acceptable.
C.Concrete Brick. Concrete brick must meet the requirements of ASTM C55 for concrete building brick. Recessed or cored brick is acceptable.
D.Sand -Lime Brick . Sand- lime brick for masonry structures must meet the requirements of ASTM C73 for Grade SW and the following 5-hour boiling test water absorption requirements:
1.Average of five bricks – 18% maximum; and
2.Individual brick – 20% maximum. MDOT Standard Specifications for Construction Section 913 9-119 913.04. Concrete Masonry Units for Structures Other than Drainage Structures
A.Load -Bearing Units . Hollow, load- bearing, concrete masonry units must meet the requirements of ASTM C90, Normal Weight.
B.Non-Load -Bearing Units . Hollow, non-load bearing, concrete masonry units must meet the requirements of ASTM C129, Normal Weight.
913.05 Concrete Block for Drainage Struct ures
Concrete blocks for manholes, catch basins, and inlets must meet the requirements of ASTM C139 except as modified by this subsection.
A.Shape . Block must be solid with parallel inside and outside surfaces, curved to the required radii , and must have a groove or other Department -approved joint at the ends.
B.Size. The block manufacturer will select the nominal block dimensions for length and height . Blocks must have a nominal width of 6, 8, or 12 inches, ±3%, as shown on the plans. Where standard plans call for 12-inch-thick drainage structure walls, the Contractor may use two 6-inch-wide blocks to meet the required width. Blocks must be designed for length so that only full or half -length blocks are required to l ay the circular wall of any one course. The shape of blocks for use in the cones or tops of manholes or other structures must allow for constructing the structure as shown on the plans with inside and outside joints not to exceed ¼ inch in thickness.
913.06 Precast Reinforced Concrete Units for Drainage Structures
Circular precast concrete units with circular reinforcement for tops, risers, and sump bases for manholes, catch basins, and inlets must meet the requirements of AASHTO M199 and the following additions and exceptions:
A.Units must have the internal diameter shown on the plans and must accept standard covers.
B.The joint with the vertical wall of the structure must be the same design as the joints in the circular pipe sections to allow a uniform bearing on the full wall thickness of the pipe.
C.Construct openings for pipe inlets or outlets in the riser sections of drainage structures by blocking out the openings when casting the sections by scribing the openings in the green concrete and removing the green concrete from the openings or by drilling out the openings from cured concrete with a water -cooled diamond bit. MDOT Standard Specifications for Construction Section 913 9-120 D. Openings in the riser sections must be 3 inches larger than the OD of the inlet or outlet pipe. The interior spacing between openings in a riser section must be at least 12 inches.
E.Obtain the Engineer ’s approval for the design of units for structure tops and for the design of sump risers with base units . Request approval for sump riser and base units used together.
913.07 Precast Concrete Bases for Drainage St ructures
Precast concrete bases for drainage structures for sewers less than 48 inches in diameter must be cast with Grade 3000 or Grade 4000 concrete.
913.08 Structural Tile
A.Load -Bearing Units . Structural clay load- bearing tile must meet the requirements of ASTM C34 for Grade LBX.
B.Non-Load -Bearing Units . Structural clay non-load-bearing tile must meet the requirements of ASTM C56.
913.09 Precast Concrete Slope Paving Blocks
Blocks must have a compressive strength of at least 2, 500 psi for an average of three units with no individual block having a compressive strength of less than 2, 000 psi . The average water absorption of three units must be no greater than 10 pounds per cubic foot. The Department will sample and test precast concrete slope paving blocks in accordance with ASTM C140/C140M with the following exceptions:
A.Test 4 by 4 inch compression test specimens sawn from precast concrete slope paving block units . The specimens will be tested with the load applied in the direction of the thickness of the unit.
B.Determine water absorption using half of the unit used for the compression test specimen.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 928–930 of 1,146.