- 737 - SECTION 908 -- CONCRETE SLOPE PROTECTION, DITCH LINING, FLUMES AND DISCHARGE STRUCTURES
908.01 Description
1.The Contractor shall furnish all materials, prepare the subgrade, and construct the following as described in the contract:
a.Concrete slope protection.
b.Concrete ditch lining. c. Concrete flumes. d. Concrete discharge structures.
908.02 Material Requirements
1.Concrete shall be Class "47B-3000" (47B-20).
2.All materials shall conform to the requirements in Table 908.01. Table 908.01 Material Requirements Applicable Materials Section Concrete ........................................... 1002 Preformed Jo int Filler .............................. 1015 Reinforcin g Steel ..................................... 1020, 1022, 1023
908.03 Construction Methods
1.a. The Contractor shall pre pare the subgrade by trenching or filling to the required elevation.
b.The subgrade shall be thoroughly tamped. c. In cuts, the excavation shall be made sufficiently wide to allow placing of forms and performing the required placing and finishing work.
d.In fills, the su bgrade shall be made at least 1 foot (300 mm) wider on each side than required by the flumes or discharge structures. The subgrade shall be compacted to a minimum of Class I embankment or as shown in the contract.
e.The subgrade shall be excavated carefully in order that the finished grades conform to the neat lines of the bottom and slopes of the structure as shown in the contract.
f.No raised places or bumps will be allowed. Depressions left in the surface of the subgrade s hall be filled with concrete.
g.If necessary, water shall be added by sprinkling to facilitate compaction.
h.At the time concrete is deposited, the subgrade shall be thoroughly moistened. Water ponding on the surface will not be allowed.
i.Sand-fill, when required, shall be uniformly compacted. The moisture content shall be sufficient to allow sa tisfactory compaction.
2.Tie bars shall be placed at the locations shown in the contract. Tie bars shall be used in all concrete di scharge structures that are placed adjacent to the concrete pavement.
3.The forming requirements of Section 607 shall apply to this work. Concrete Slope Protection, Ditch Lining,
908.03 Flumes and Discharge Structures
- 738 - 4. The Contractor shall place join ts and reinforcing steel as described in the contract.
5.The backfill shall be graded and co mpacted to the elevation of the top of the concrete structur e as shown in the contract.
6.a. The concrete shall be placed the full thickness of the slab in one operation and shall be consolidated by tamping and the excess concrete screeded off flush with the forms.
b.The edges adjacent to all forms, expansion joints, curbs, or fixtures in the surface shall be thoroughly spaded for the full depth.
c.After consolidation, the surface shall be alternately tamped and struck off with a strike board until all voids are removed and the surface has the required grade and cross section.
7.The Contractor shall finish t he edges with a suitable edging tool after the concrete has been floated.
8.The concrete shall be cured by one of the methods described in Section 603.
9.a. Concrete ditch liners shall hav e joints cut through them at least 25% of their slab thickness with an approved tool at intervals of not more than 8 feet (2.4 m).
b.The concrete shall be edged on both sides of the cuts. c. Each cut shall be vertical and normal to the forms. 10. a. The concrete ditch lining footings and structure turndowns shown in the contract do not need to be formed if concrete is placed directly into excavated trenches that have smooth walls and level bases.
b.Footings and turndowns shall be placed monolithic with the ditch lining.
11.If the trenches are excavated larg er than shown in the contract, the entire trench volume is still filled with concrete.
12.The Contractor shall dispose of all excess soil.
908.04 Method of Measurement
1.Concrete slope protection will be measured by the square yard (square meters) of finished surface area, including turndowns.
2.Concrete ditch lining will be measured by the Square Yard (SY) [Square Meter (m 2)] or Linear Foot (LF) [Meter (meter)] along the center of the flow line and will be continuous through the end sections.
3.Concrete flumes and discharge structures shall be measured by the each. Concrete Slope Protection, Ditch Lining, Flumes and Discharge Structures 908.05 - 739 - 908.05 -- Basis of Payment
1.P a y I t e m P a y U n i t Concrete Flume, Type _____ Each (ea) Concrete Flume Each (ea) Concrete Discharge Structure Each (ea) Concrete Ditch Lining _____ Linear Foot (LF) [Meter (m)] Concrete Ditch Lining _____ Square Yard (SY) [Square Meter (m 2)] Concrete Slope Protection Square Yard (SY) [Square Meter (m2)]
2.In the event that more than one type of discharge structure is shown in the contract, an appropriate designation will be added to the pay item to differentiate as to t he type or dimensions required.
3.a. The 28-day compressive stre ngth of each day's production will be determined from cyli nder strength tests.
b.Payment shall be reduced by the amount described in Table 603.03.
4.Payment is full compensation for all work described in this Section. - 740 - SECTION 909 -- INSTALLING TIE BARS
909.01 Description
1.The Contractor shall furnish and install transverse deformed steel tie bars in existing concrete slabs adjacent to new concrete pavement as described in the contract.
909.02 Material Requirements
1.Steel bars used shall be of the size and length specified in the contract and in conformance with Section 1020.
2.Grout shall be listed on the Department’s Approved Products List.
909.03 Construction Methods
1.a. The Contractor shall drill ti e bar holes to the depth shown in the contract. The diameter of the hole shall be at least 1/8-inch (3-mm) but not more than 3/8-inch (9-mm) larger than the bar diameter.
b.Wet or dry drilling operations may be employed.
c.Drilled holes shall be normal to the edge of the slab and level.
d.Dry-drilled holes shall be brushed with a stiff bristle brush and blown clean with oil-free, compressed air.
e.Wet-drilled holes shall be thoroughly washed after drilling to remove any residue.
2.Grout shall be placed in the holes so all of the embedded portion of the bar is bonded.
909.04 Method of Measurement
1.Tie bars are measured by the each.
909.05 Basis of Payment
1.P a y I t e m P a y U n i t T i e B a r s E a c h ( e a ) 2. Payment is full compensation for all work described in this Section.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 771–773 of 1,048.