426 SECTION 610 CURBS, COMBINATION CURBS AND GUTTERS , AND MEDIANS
610.1 -DESCRIPTION : This work shall consist of the construction or resetting of curbs, combination curbs and gutters, and medians in accordance with these Specifications and in reasonably close conf ormity with the lines , grades, dimensions, and locations shown on the Plans or established by the Engineer. The types of curbing, combination curbs and gutters, or medians are as follows:
610.2 -MATERIALS : Except as provided below, materials shall meet the requirements of the following Subsections of Division 700:
MATERIAL SUBSECTION Asphalt Emulsion for Paint Coat 705.4 or 705.11 Asphalt for Tack Coat 705.4 or 705.11 Expansion Joint Filler Preformed 708.1 Joint Sealing Material 708.3 or 708.4 Joint Tie Bolt Assembly 709.7 PG Binder for Asphalt Curb 705.5* Reinforcing Steel 709.1, 709.4
* Standard grade specified for local area unless indicated otherwise on the Plans.
Concrete shall meet the requirements of Section 601, Class B, or 501. Concrete, asphalt mixes, and manufactured curbing materials will be subject to inspection and tests at the plants for compliance with quality requirements. All materials will be subject to inspection for acceptance as to condition at the latest practicable time the Engineer has the opportunity to check for compliance prior to or during incorporation of materials in the work. Asphalt curbing component materials shall meet the appl icable requirements of Section 401 and the composition of the mix shall meet the following Table 610.2:
427 TABLE 610.2 (MASTER RANGE CRITERIA) ½ inch (12.5 mm) 100 3/8 inch (9.5 mm) 80 – 100 # 4 (75 mm) 50 – 80 # 8 (2.36 mm) 30 – 60 # 16 (1.18 mm) 20 – 50 # 30 (600 mm) 12 - 36 # 50 (300 mm) 5- 25 # 200 (75 mm) 3- 9 % Asphalt 4 – 10
No mix design approval will be required for asphalt curbing, however, the Contractor shall establish a Plant Mix Formula (PMF) for asphalt content and gradation which meets the above requirements and submit it to the District for approval. The District sh all review the design and submit a completed T -400 form to the Materials Control, Soil, and Test Division. The Materials Division will assign a laboratory number to the design. This PMF shall also include the percentage of any additive that may be used a s a stiffener for the curbing mix. If lime or other similar granular additive is used, then this material should be included in the PMF gradation. The mix shall be produced within the allowable tolerances of the following table.
Plant Mix Formula Plant Mix Tolerance Range Percentage Passing Sieve Sizes 3/8 inch (9.5 mm), # 4 (4.75 mm) ± 7 Percentage Points Percentage Passing Sieve # 8 (2.36 mm) ± 6 Percentage Points Percentage Passing Sieve Sizes # 16 (1.18 mm), # 30(600 m) ± 5 Percentage Points Percentage Passing Sieve Size # 50 (300m) ± 4 Percentage Points Percentage Passing Sieve Size # 200 (75m) ± 3 Percentage Points Percentage of Asphalt ± 0.5 Percentage Points
The Contractor shall perform quality control sampling and testing of the asphalt curbing mix by taking a random sample once per day of production and testing for asphalt content and gradation to verify the materials composition. If testing indicates that the plant mix formula tolerances are not bein g met, then production shall halt until the reason for any deficiencies are determined and adjustments are made to correct these deficiencies and documented in the plant diary.
428 CONSTRUCTION METHODS
610.3 -PLAIN CONCRETE CURBING, INTEGRAL CONCRETE CURBING, AND COMBINATION CONCRETE CURB AND GUTTER : 610.3.1 -Excavation: Excavation shall be made to the required depth, and the base upon material shall be removed and replaced with suitable material which shall be thoroughly compacted. When called for on the Plans, the base upon which the curb is to be set shall be constru cted of bed course material in accordance with Section 609.
610.3.2 -Form: Forms shall be of wood or metal, straight, free from warp, and of such construction that there will be no interference with the inspection of grade or alignment. All form shall extend for the entire depth of the curb and shall be braced and secured sufficiently so that no deflection from alignment or grade will occur during the placing of the concrete. Forms shall be cleaned and oiled just prior to placing the concrete.
610.3 .3-Mixing, Placing, and Finishing: Concrete shall be proportioned, mixed, and placed in accordance with the requirements for the class of concrete specified. Concrete shall not be transported in nonagitating trucks. Compaction of concrete placed in forms shall be by vibration or other acceptable methods. Drainage openings shall be made through the curb, where indicated, or as directed by the Engineer, at the elevation and of the size required. Forms shall be left in place for 24 hours unless the concre te has set sufficiently prior to that time to permit their removal without injury to the curbing. Upon removal of the forms, the exposed curbing face shall be immediately rubbed to a uniform surface. Rubbing shall be accomplished by the use of water and a wood block or carborundum brick. For the purpose of matching adjacent concrete finishes or for other reasons, the Engineer may permit other methods of finishing. No plastering will be permitted. All damaged and rejected curb shall be removed and repla ced.
610.3.4 -Sections: All concrete curbing shall be constructed in sections having an approximate length of ten (10) feet unless otherwise indicated on the Plans or directed. In the construction of integral concrete curb or combination concrete curb and gutter abutting concrete pavement, the sections shall be such that the contraction and expansion joints are located opposite the contraction and expansion joints respectively in the pavement. Sections shall be separated by joints ⅛ inch wide except at expansion joints. All joints shall be filled with joint sealing material conforming to the requirements of subsection 708.3.
610.3.5 -Expansion Joints: Expansion joints shall be formed at the intervals shown on the Plans using a preformed expansion jo int filler having a thickness of ¾ inch. When the curb is constructed adjacent to or on concrete pavement, expansion joints shall be located opposite or at expansion joint in the pavement.
610.3.6 -Curing: Immediately upon completion of the rubbing, th e curbing shall be moistened and kept moist for three days, or the curbing shall be cured by the use of membrane forming material. The methods and details of curing will be subject to the approval of the Engineer.
610.3.7 -Backfilling: After the concre te has set sufficiently, the spaces in front and back of the curb shall be refilled to the required elevation with suitable materials, which shall be thoroughly tamped in loose layers of not more than six (6) inches.