Sidewalk Construction

12.01 GENERAL

The work included in this specification requires furnishing all labor, materials, and equipment necessary for the construction of concrete sidewalks.

12.02 MATERIALS A) Sand

Sand for base material shall meet the Michigan Department of Transportation Standard Specifications for Construction, Section 902, Class I granular materials for fill and sub-base.

B) Concrete

Concrete shall be a Michigan Department of Transportation (MDOT) grade 35S or 35P. The cement may be a Type 1 with add mixture provided or Type 1A.

Course aggregate shall be limestone meeting MDOT Standards for 6A aggregate, and fine aggregate shall meet MDOT Standards for natural sand designation 2NS. The concrete shall contain 5.5 sacks of cement per cubic yard and shall have six percent (6%) air-entrainment. The maximum allowable slump shall be four inches (4"), and the compressive strength at twenty-eight (28) days shall be 3,500 lbs. per square inch. Delivery shall be in accordance with MDOT Standard Specifications for Construction.

C) Joint Filler

Expansion joint filler shall be pre-formed, non-extruding, fiber-type, conforming to ASTM D-1751. Expansion joint material shall be one-half inch (1/2") thick with a width equal to the sidewalk thickness plus one-half inch (1/2") and a length equal to the width of the walk. Two (2) pieces shall be used to achieve a one inch (1") expansion joint where specified on the Plans.

D) Curing Compound

Membrane curing compound shall be white membrane type, conforming to the MDOT Standard Specification 8.24.06.

12.03 TESTING

A) Slump Tests

ASTM C-153. Contractor shall be prepared to make slump tests during any hour at Engineer's request.

B) Air Entrainment Tests

ASTM C-231, C-173, or C-138. Contractor shall make test at Engineer's request.

C) Cylinder Tests

During the progress of the work and for each different mix of concrete, a set of three (3) standard six-inch (6") concrete cylinders shall be made and tested if from 25 to 100 cubic yards of concrete are placed during each day's operation.

Make an additional set of tests for each 100 cubic yards. When less than 25 cubic yards of concrete are placed per day, requirements for test cylinders by the Contractor shall be at the discretion of the Engineer. Mold cylinders of each set from the same sample of concrete. One (1) cylinder shall be tested seven (7) days and two (2) tested at twenty-eight (28) days at the direction of the Engineer.

ASTM C-31 shall govern. Testing shall be done per ASTM C-39. Laboratory for testing cylinders must have approval of the engineer before testing is begun.

Mail or deliver all reports of concrete tests directly from the testing laboratory to the Engineer.

D) Laboratory Tests

All tests are to be conducted by an independent laboratory approved by the Engineer. Tests shall be made at the Contractor's expense. Designated laboratory shall provide a concrete design mix.

12.04 PREPARATION FOR PLACING CONCRETE

A) Removal

In removing sidewalk, curb, gutter, and curb and gutter, removal shall be to existing joints or to a sawed joint as specified. The concrete shall be cut full depth with a concrete saw unless otherwise provided. Adjacent to structures that are to remain in place, the removal procedures used shall be such that no damage occurs to the structure or to the sidewalk that is to remain. Sufficient removal shall be made to provide for proper grade and connections in the new work. All roots beneath or abutting designated sections shall be removed to a depth of four inches (4") beneath the bottom of the finished grade of the new concrete sections and within three inches (3") along the sides of the sections. Earth which may be removed when removing concrete shall be replaced with a similar material at the Contractor's expense. The concrete sidewalk and all other debris shall be disposed of by the Contractor immediately after removal and shall not be allowed to accumulate at the work site. The Contractor shall furnish, erect, and maintain suitable barriers and flashers at all places where sidewalk has been removed until such time as the sidewalk is replaced and ready for use.

Sidewalk, curb, gutter, and curb and gutter removal shall be to existing construction joints. Unbroken joints must be sawcut. If a sawcut can be made where the remaining section of undisturbed, unbroken and unjointed concrete is five feet (5') long (or equal to the width of a sidewalk), then removal shall be to that point.

B) Preparation of Base

Excavation shall be made to the required depth and width that will permit forming.

All soft and yielding material shall be removed and replaced with acceptable granular material. The base shall be a minimum of four inches (4") of compacted sand, shaped and compacted to a firm, even surface conforming to the sections shown on the plan. Base preparation shall provide for transverse slope of 1/4-inch-per-foot towards the center line of the street unless existing grades of abutting sidewalks will not allow for this. Any continuous section of sidewalk shall be graded to drain laterally to a driveway or perpendicular sidewalk connecting to the street, as well as transversely toward the street where possible. Where the proposed sidewalk elevation is above the existing ground level, the sidewalk shall be placed on compacted sand fill.

C) Forms

Fixed forms shall be used and shall be straight, free from warp and have sufficient strength to resist springing during the process of depositing concrete against them. The forms shall be the full depth of the concrete. Fixed forms shall be firmly staked to the required line and grade.

D) Transit Mixed Concrete

Transit mixed concrete shall meet the requirements stated above. Truck mixers shall be of the revolving drum or the pug mill revolving blade type and shall be water tight when closed. Each mixer shall be equipped with a tank for carrying the mixing water.

The size of the batch shall not exceed the maximum rated capacity of the mixer as stated by the manufacturer. Each batch of concrete shall be mixed not less than 50 or more than 150 revolutions, at the rate of rotation specified by the manufacturer as mixing speed. Delivery tickets for each batch shall show the amount of cement, fine aggregate, coarse aggregate, and water, and one (1) copy of each delivery ticket shall be given to the Engineer.

12.05 PLACING AND FINISHING CONCRETE A) Concrete Placement

No concrete shall be placed until the subgrade and forms have been approved by the Engineer. Prior to placing concrete, the subgrade shall be moistened with water and forms sprayed with water or oil. The concrete shall be thoroughly spaded along the faces of the forms and adjacent to the joints before finishing operations are started. After the concrete has been brought to the proper grade by means of the strike board, it shall be worked with a wooden float in the manner that will thoroughly compact it and provide a surface free from depressions or irregularities of any kind. The surface shall be steel troweled, but excessive working shall be avoided. In no case shall any cement or sand be sprinkled on the surface to absorb moisture or hasten hardening. After all joints are neatly made and all troweling is completed, the surface of the walk shall be transversely brushed. Brushing shall be accomplished before the initial set has taken place, but after the concrete has hardened sufficiently to retain the brush marks. Edging marks shall not be completely brushed out.

Sidewalk ramp slopes shall be uniform except as necessary for short grade changes. Where gutters are replaced in conjunction with sidewalk ramps, the gutters shall be constructed to the same dimensions and profiles and contain the same reinforcement as the existing gutter, unless otherwise shown on the Plans.

All valves and service boxes located in the proposed sidewalk shall have plastic sleeves.

B) Joints and Markings

Joints and markings shall be constructed true to line and shall not vary more than one-forth inch (1/4") from their designated position.

Transverse joints and markings shall be constructed at right angles to the center line of the sidewalk, and longitudinal joints shall be constructed parallel to the centerline.

The sidewalk shall be divided into squares, the transverse joints or markings being spaced equal to the width of the walk. The squares shall be produced by use of slab division forms, extending to the full depth of the concrete or by cutting joints into the concrete, after floating, to a depth of not less than one-forth the thickness of the sidewalk. The joints or markings shall not be less than one-eight inch (1/8") nor more than one-fourth inch (1/4") in width and shall be finished smooth and true to form. All expansion joints, joint markings, and outer edges shall be neatly rounded with a double edge having a one-fourth inch (1/4") radius.

C) Expansion Joints

Expansion joints shall be placed at least once every 50 feet in length of the walk.

The expansion joint shall be established by means of placing prepared strips of one-half inch (1/2") thick fiber matrix. The expansion joints shall extend the full depth of the sidewalk. One-half inch (1/2") expansion joints shall also be placed between walk and back of abutting parallel curbs, adjacent sidewalks or other rigid structures, or as directed by the Engineer.

D) Curing and Protection

After finishing operations have been completed and immediately after the free water has left the surface, the surface of the concrete shall be completely coated and sealed with a uniform layer of membranous curing compound. Curing compound shall meet the MDOT Standard Specifications for White Membrane Curing Compound. The compound shall be applied in a continuous uniform film by means of mechanical pressure sprayer equipment at the rate directed by the Engineer, but not less than one (1) gallon per 200 square feet of surface.

Contractor shall erect and maintain suitable barriers and flashers to protect the concrete from damage by pedestrians and animals for a minimum period of forty-eight (48) hours and shall protect the concrete from damage by rain with suitable covers. It shall be the Contractor's responsibility to protect concrete until accepted by the City. Any concrete damaged prior to acceptance by the city will be replaced at no cost to the city. No vehicular loads will be allowed for four (4) days.

E) Backfilling

After the concrete has set sufficiently, the side forms shall be removed, and the spaces on both sides shall be backfilled and restored. See Section 13 – Restoration and Cleanup.

12.06 MEASUREMENT AND PAYMENT A) Concrete Walk

(1) Description

The Contract Unit Price for this item shall include all work, materials, and equipment necessary to construct the concrete walk to these specifications.

(2) Method of Measurement and Basis of Payment

Four-inch (4") and six-inch (6") concrete sidewalk will be measured in place by area in square feet and paid for at the corresponding contract unit price per square foot for the square feet actually placed by the Contractor. This unit price shall include all materials, equipment, and labor to construct the concrete walk complete.

B) Handicap Ramp (1) Description

The Contract Unit Price for this item shall include all work, materials, and equipment necessary to construct the sidewalk ramp to these specifications.

Typically, a ramp will be considered to be ten feet (10’) in length, and no concrete walk payment will be made in that length.

(2) Method of Measurement and Basis of Payment

Handicap ramps shall be paid on a per each basis as actually installed by the Contractor.

T E C H N I C A L S P E C I F I C A T I O N S