Item No. 430
Concrete Curb and Gutter
430.1 Description
This item shall govern Portland Cement (p.c.) concrete curb or p.c. curb and gutter with reinforcing steel as required, that is constructed in accordance with this specification on an approved subgrade and base in conformity with City of New Braunfels Standard Detail ST-010 and the lines, grades, section indicated on the Drawings or as established by the Engineer or designated representative.
430.2 Submittals
The submittal requirements of this specification item include:
A. Class A p.c. concrete mix design,
B. Type of Installation (i.e. P.C. Concrete Curb and Gutter or P.C. Concrete Curb) and construction details (i.e. base, reinforcing steel, joints, curing membrane),
C. Identification of the type, source, mixture, Pure Live Seed (PLS) and rate of application of the seeding.
430.3 Materials
A. Concrete
The Portland cement (p.c.) concrete shall conform to Class A Concrete, Section 403.7 (Table 4) of Standard Specification Item No. 403, "Concrete for Structures".
B. Reinforcing Steel
Reinforcing steel shall conform to Standard Specification Item No. 406, "Reinforcing Steel".
C. Expansion Joint Materials
Expansion joint materials shall conform to Standard Specification Item No. 408, "Expansion Joint Materials".
D. Membrane Curing Compound
Membrane curing compound shall conform to Standard Specification Item No. 409, "Membrane Curing".
E. Flexible Base
Aggregate shall conform to Standard Specification Item No. 210, "Flexible Base".
430.4 Construction Methods
A. Subgrade and Base Preparation
Subgrade for curb and gutter shall be excavated and prepared to depth and width requirements indicated on the Drawings, including a minimum of 12 inches behind the curb, unless a greater width is indicated on the Drawings. The subgrade shall be shaped to the line, grades, cross section and dimensions indicated on the Drawings. A minimum of 4 inches of flexible base shall be spread, wetted and thoroughly compacted under curb and gutter as specified in Standard Specification Item No. 210, "Flexible Base". If dry, the base shall be sprinkled lightly with water before p.c. concrete is deposited thereon.
B. C & G Forms
Forms shall be of metal, well-seasoned wood or other approved material. The length of the forms shall be a minimum of 10 feet. Flexible or curved forms shall be used for curves of 100-foot radius or less. Wood forms for straight sections shall be not less than 2 inches in thickness. Forms shall be a section, that is satisfactory to the Engineer or designated representative, of the depth required and clean, straight, free from warp and, if required, oiled with a light form oil. All forms shall be securely staked to line and grade and maintained in a true position during the placement of p.c. concrete.
C. Reinforcing Steel
The reinforcing steel, if required, shall be placed as shown on the typical section of the Drawings. Care shall be exercised to keep all steel in its proper location during p.c. concrete placement.
D. Joints
Joints shall be of the type and spacing shown on the Drawings. Expansion joint material, 3/4 inch in thickness, shall be provided at intervals not to exceed 40 feet and shall extend the full width and depth of the p.c. concrete. Weakened plane joints shall be made 3/4 inch deep at 10-foot intervals. All joint headers shall be braced perpendicular and at right angles to the curb.
Two round smooth dowel bars, 1/2 inch in diameter and 24 inches in length, shall be installed at each expansion joint. Sixteen inches of one end of each dowel shall be thoroughly coated with hot oil, asphalt or red lead, so that it will not bond to the concrete. The dowels shall be installed with a dowel sleeve on the coated end as indicated on the Drawings or equivalent method as directed by the Engineer or designated representative.
E. P.C. Concrete Placement and Form Removal
Concrete shall be placed in the forms and properly consolidated. Within 1 hour after p.c. concrete placement, a thin coating, that is no more than 1/2 inch nor less than 1/4 inch thick of finish mortar, composed of 1 part Portland Cement to 2 parts fine aggregate, shall be worked into the exposed faces of the curb and gutter by means of a "mule". After the p.c. concrete has become sufficiently set, the exposed edges shall be rounded by the use of an edging tool to the radii indicated on Standard Detail. The entire exposed surface of the curb and gutter shall be floated to a uniform smooth surface, and then finished with a camel hairbrush to a gritty texture. The forms shall remain in place a minimum of 24 hours unless approved otherwise by the Engineer or designated representative.
After removal of the forms, any minor honeycombed surfaces shall be plastered with a mortar mix as described above. Excessively honeycombed curb and gutter, as determined by the Engineer or designated representative, shall be completely removed and replaced when directed.
F. Curing
Immediately after finishing the curb, concrete shall be protected by a membrane curing conforming to Standard Specification Item No. 409, "Membrane Curing".
After a minimum of 3 days curing and before placement of the final lift of the base course, the curb shall be backfilled to the full height of the p.c. concrete, tamped and sloped as directed by the Engineer or designated representative. The upper 4 inches of backfill shall be of clean topsoil that conforms to Standard Specification Item No. 130, "Borrow" and is free of stones and debris.
G. Seeding in Turf Areas
When turf is to be established, preparation of the seedbed shall conform to Item No. 604, "Seeding for Erosion Control".
430.5 Measurement
Accepted work as prescribed by this item will be measured by the lineal foot of p.c. concrete curb and gutter and/or p.c. concrete curb, complete in place.
430.6 Payment
No direct measurement or payment will be made for the work to be done or the equipment to be furnished under this item, but shall be considered subsidiary to the particular items required by the bid.