2521Walks

2521.1DESCRIPTION

This Work consists of constructing concrete or bituminous walks. Concrete walks include concrete median walk and concrete truck aprons.

2521.2MATERIALS

A.1 Concrete Walk ........................................................................................... Mix No. 3F52 A.2 Concrete Walk, Exposed Aggregate Finish ............................................. Mix No. 3F57EX A.3 Concrete Walk, Colored ......................................................................... Mix No. 3F52CO A.4 Concrete Truck Aprons ............................................................................... Mix No. 3F52 C.1 Bituminous Walk ............................................................................ Mix No. SPWEA230B D Curing Materials

2521.3CONSTRUCTION REQUIREMENTS

A Foundation Preparations Excavate, shape, and compact the foundation to a firm, uniform bearing surface to the dimensions and grade as shown on the Plans and in accordance with 2106, “Excavation and Embankment – Compacted Volume Method,” 2112, “Subgrade Preparation,” and 2211, “Aggregate Base.” B Sawing Concrete Walk Saw existing concrete walk to produce a neat line for the new Work. C Forms Provide forms made of non-reactive metal or wood, or other Material in accordance with 1805, “Methods and Equipment,” capable of maintaining the concrete until the concrete can retain the molded shape. Provide forms with a height at least equal to the walk thickness of the formed concrete shown on the Plans. Support the forms on the foundation to maintain the line and grade shown on the P lans. Before placing the concrete, coat the contact surfaces of the forms with an approved form treating Material in accordance with 3902, “Form Coating Material.” Leave forms in place for at least 12 hours after placing the concrete unless otherwise approved by the Engineer. D Placing and Finishing Concrete The concrete Contractor, or Subcontractor, shall have at least two people with a current ACI concrete flatwork associate, concrete flatwork finisher, or advanced concrete flatwork finisher certification, and at least one of them must be onsite for every concrete pour. Wet the foundation and forms before placing the concrete. Prevent segregation of the concrete during placement. Consolidate the concrete to fill voids using internal vibration. Strike-off the concrete to the grade shown on the Plans, and float the surface smooth. After the water sheen disappears, edge the joints and lightly brush the surface to a uniform texture. D.1 Specialty Concrete Walk D.1.a Exposed Aggregate Finish Provide concrete mix No. 3F57EX with multi-colored rounded stone, modified for exposed Aggregate construction. Use surface retardation, meeting the Type B requirements in 3113, “Admixtures for Concrete,” to produce a medium to deep exposure on the Aggregate finish making the Aggregate the dominant surface feature. Do not embed or top seed the Aggregate.

Apply retardant coating immediately after completion of the concrete surface screeding, edging, and jointing. Apply retardant as recommended by the manufacturer to produce a 1/4 inch ± 1/8 inch etch of mortar removal after final concrete set. Use pressurized water to remove surface mortar. Do not loosen individual Aggregate particles with the pressurized water. After the Engineer approves the exposed Aggregate finish, apply a 10 percent muriatic acid solution to the exposed Aggregate surfaces. Allow the acid solution to interact with the exposed Aggregate surface for 5 minutes to 10 minutes before flushing the surface with water. Cover the concrete with white polyethylene sheeting to continue curing . Before applying sealer, remove staining or streaking from the exposed A ggregate surface resulting from the moist curing. Seal the exposed Aggregate finish with 2 coats of a clear acrylic based compound with at least 18 percent solids meeting the requirements of ASTM C309, Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete. D.1.b Colored Concrete Provide concrete mix No. 3F52CO with approved color additive for colored concrete walk construction. For color verification, provide sample chip(s) of specified color(s) indicating color additive number(s) and required dosage rate(s). Samples indicate general color and may slightly vary from concrete finished in the field. One week before first placement of the colored concrete on the Project, hold a preconstruction meeting with the Department, prime Contractor, concrete Contractor, ready-mix concrete representative, testing Department, and colored admixture manufacturer representative to discuss the proposed colored concrete placement and application Materials. D.1.b(1) Colored Concrete Contractor/Installer Qualifications Pre-qualified colored concrete Contractors/installers shall meet the following requirements:

scope and quality.

in the last 5 years by Contractor/installer.

Contractor/Installers List available from the Department website. D.1.b(2) Test Panels Before placing any colored concrete, demonstrate workmanship by constructing test panels of the colored concrete in accordance with the following:

Materials, concrete supplier, and concrete plant

intended for use on permanent Work, including stamping and curing/sealing procedures.

6 feet by 4 inches unless otherwise directed by the Engineer.

visual standard for the Work of this section and quality standard for permanent Work. D.1.b(3) Placing, Finishing, and Curing Colored Concrete Construct colored concrete in accordance with products processes and techniques used on approved test panel(s). Do not add water at any time to the slab surface while finishing. Do not over finish the concrete edges. After completing final finishing operations, cure and seal exposed concrete surfaces meeting the following requirements and methods:

3752, “Membrane Curing/Sealing Compound for Colored Concrete.”

concrete placement/form removal or once the bleed water has dissipated, unless the Engineer directs otherwise in accordance with 2521.3E.1.a, “Membrane Curing Method.”

homogeneously to provide a uniform coverage on exposed colored concrete surfaces including the edges.

compound a minimum of 30 Calendar Days after placement of the colored concrete. Cover adjacent finished surfaces to protect from splatters and excess Materials during colored concrete installation and curing/sealing. D.2 Joint Construction For 4-inch walk thickness, divide the walk into square panels of uniform size no greater than 36 square feet. For 6-inch walk thicknesses, divide the walk into square panels of uniform size no greater than 81 square feet. For concrete truck aprons, construct joints according to 2301.3N, “Joint Construction Operations,” and Standard Plan 5-297.221. Provide vertical and straight joints parallel with or at right angles to the walk centerline . Align the joints with joints in adjoining work unless isolated by a 1/2 inch preformed joint filler. Sawcut all concrete curb ramp, concrete walk, and concrete truck aprons. To reduce the risk of random cracking, the Engineer will allow tooling joints on long sidewalk placements. Sawing of tooled joints is required. The Engineer will allow tooling or sawing joints in the concrete median walk located outside of the pedestrian circulation path. If tooling, round joints with a 1/4 inch radius grooving tool and round edges with an edging tool having a radius no greater than 1/2 inch.

Extend contraction joints to a depth of at least 30 percent of the walk thickness. If saw cutting, provide 1/8 inch wide contraction joints. Provide joint filler in accordance with 3702, “Preformed Joint Fillers,” that is 1/2 inch wide and equal in depth to the full thickness of the walk. Modify joint construction if a fixed object or Structure extends through the walk, as directed by the Engineer. Place preformed joint filler material 1/2 inch thick adjacent to fixed objects to separate the object from the abutting concrete edges. D.3 Workmanship and Quality The Engineer will use a 10 foot straightedge to measure surface tolerance. The Department considers vertical deviations in the surface greater than 3/16 inch and line deviations greater than 1/2 inch from the required location as unacceptable Work. Remove and replace unacceptable Work as directed by the Engineer. E Concrete Curing and Protection After completing final finishing operations, cure exposed concrete surfaces . Use one of the following curing methods:

membrane curing compound conforming to 3754, “Poly-Alpha Methyl Styrene (AMS) Membrane Curing Compound,” or 3755, “Linseed Oil Membrane Curing Compound,” within 30 minutes of concrete placement or once the bleed water has dissipated, unless the Engineer directs otherwise. Place the membrane curing compound on the edges within 30 minutes after permanent removal of the forms or curing blankets, unless the Contract requires otherwise.

practical without marring the surface in accordance with 2521.3E.1.b , “Walks, Curing Blanket Method.”

Exposed Aggregate Finish.”

Concrete.” Whenever weather conditions are such as to cause unusual or adverse placing and finishing conditions, expedite the application of a curing method or temporarily suspend the mixing and placing operations, as the conditions require. If necessary to remove the coverings to saw joints or perform other required W ork, and if the Engineer approves, remove the covering for the minimum time required to complete that W ork. E.1 Curing Methods E.1.a Membrane Curing Method Before application, agitate the curing compound as received in the shipping container to obtain a homogenous mixture. Protect membrane curing compounds from freezing before application. Handle and apply the membrane curing compound in accordance with the manufacturer’s recommendations. The Engineer will only approve airless spraying machines equipped with a recirculating bypass system that provides for continuous agitation of the reservoir Material, separate filters for the hose and nozzle, and multiple or adjustable nozzle system that provides for variable spray patterns.

Apply the curing compound with an Engineer approved airless spraying machine in accordance with the following:

area.

coverage on exposed concrete surfaces (equal to a white sheet of copy paper) at the time of application. Some Department-approved curing compounds may have a base color (i.e. yellow) that cannot comply with the above requirement. In this case, provide a uniform, solid, opaque consistency meeting the intent of the above requirement.

immediately repair the damaged area by respraying. If the Engineer determines that the initial or corrective spraying may result in unsatisfactory curing, the Engineer may require the Contractor to use the blanket curing method, at no additional cost to the Department. E.1.b Curing Blanket Method After completion of the finishing operations and without marring the concrete, cover the concrete with curing blankets. Install in a manner that envelops the exposed concrete and prevents loss of water vapor. After the concrete has cured, apply membrane curing compound to the concrete surfaces that will remain exposed in the completed Work. E.2 Protection Against Rain Protect the concrete from damage due to rain. Have available at the site of the Work, Materials for protection of the edges and surface of concrete. Should any damage result, the Engineer will suspend operations until the Contractor takes corrective action, and may subject the rain-damaged concrete to 1503, “Conformity with Contract Documents,” and 1512, “Unacceptable and Unauthorized Work.” E.3 Protection Against Cold Weather If the National Weather Service forecast for the construction area predicts air temperatures of 36°F or less within the next 24 hours and the Contractor wishes to place concrete, submit a cold weather protection Plan. Protect the concrete from damage, including freezing due to cold weather . Should any damage result, the Engineer will suspend operations until the Contractor takes corrective action, and may subject the damaged concrete to 1503, “Conformity with Contract Documents,” and 1512, “Unacceptable and Unauthorized Work.” E.3.a Cold Weather Protection Plan Submit a proposed time schedule and Plans for cold weather protection of concrete in writing to the Engineer for acceptance that provides provisions for adequately protecting the concrete during placement and curing. Do not place concrete until the Engineer accepts the cold weather protection Plan. F Bituminous Place the bituminous mixture in accordance with 2360, “Plant Mixed Asphalt Pavement.”

G Concrete Protection from Backfilling and Loading For a minimum of 24 hours after placement of the concrete, do not perform vibration or backfilling operations adjacent to the concrete, drill into concrete, or operate construction equipment and public traffic loading on the concrete. Perform adjacent vibratory and backfilling operations or drilling into concrete at least 72 hours after placing the concrete or after the concrete reaches a compressive strength of at least 2,000 pounds per square inch. The Engineer will allow construction equipment and public traffic loading on newly placed concrete at least 72 hours after placing the concrete or after the concrete reaches a compressive strength of at least 3,000 pounds per square inch and the following: When moving on and off the concrete, construct a ramp to prevent damage to the concrete edges and joints. Protect the concrete surface and joints from damage due to heavy loads or Equipment in accordance with 1513, “Restrictions on Movement and Storage of Heavy Loads and Equipment.” Sweep the surface free of debris before placing the protective Material or tracked Equipment onto the slab. Operate Equipment on the concrete without causing damage. If damage results, suspend operations, and take corrective action as approved by the Engineer. Do not operate the Equipment wheels or tracks within 4 inches of the concrete edge. When hauling Aggregate and other Materials across newly constructed concrete, keep the concrete surface free of debris by sweeping or other method as approved by the Engineer to prevent spalling of the joints and edges. The Engineer will cast, cure, and test the concrete field control specimens in accordance with 2461.3G.5.c, “Field Control Strength Cylinders.” If damage results from any of these operations, the Engineer will suspend operations until the Contractor takes corrective action and obtains the Engineer’s approval of a new method. The Engineer may require removal and replacement of the damaged concrete in accordance with 1503, “Conformity with Contract Documents,” and 1512, “Unacceptable and Unauthorized Work.” The Contractor may use hand-operated concrete consolidation Equipment and walk behind vibratory plate compactors 24 hours after placing the concrete, and other Equipment as approved by the Engineer, in conjunction with the Concrete Engineer. After the curing is complete and without subjecting the concrete Work to damaging stresses, perform the backfill or embankment construction to the elevations shown on the P lans. Use suitable grading Materials from the excavation for backfill Material in accordance with 2106, “Excavation and Embankment – Compacted Volume Method,” unless otherwise required by the Contract. Place and compact the backfill Material in accordance with 2106, “Excavation and Embankment – Compacted Volume Method.” Dispose of surplus excavated Materials in accordance with 2106, “Excavation and Embankment – Compacted Volume Method.”

2521.4METHOD OF MEASUREMENT

The Engineer will measure each uniform thickness item separately by top surface area. In the case of transitions from one thickness or design to another, the Engineer will measure the entire transition for payment under the item with the higher Contract Unit Price.

2521.5BASIS OF PAYMENT

Payment for concrete walk (colored) at the Contract price per unit of measure is full compensation for cost to providing concrete walk and concrete truck aprons to the specified lines, grade and minimum thickness specified in the Plans, including but not limited to: forming, joint filler Material, colored concrete test panels, furnishing and placing the concrete, reinforcement bars, expansion joint material, concrete compaction by vibration, concrete curing, and protecting the completed Work from damage . The Engineer will measure and pay for concrete truck aprons (colored) as ___” Concrete Walk. The Contract Unit Price for concrete or bituminous construction includes furnishing the Materials and placement of the Work to the lines and grade of the Plan as specified. A Monetary Adjustments The Department must apply Incentives and Disincentives and may apply monetary deductions for Walks. The amounts of these adjustments are deemed reasonable. Failure to properly cure and protect the concrete in accordance with 2521.3E, “Concrete Curing and Protection,” will result in the Engineer applying a monetary deduction in accordance with 1503, “Conformity with Contract Documents,” and 1512, “Unacceptable and Unauthorized Work.” If the Contract does not contain a separate Contract Item for Structural concrete, the Department will apply a monetary deduction of $50.00 per cubic yard or 50 percent of the Contractor-provided invoice amount for the concrete in question, whichever is less. B Schedule The Department will pay for walk construction on the basis of the following schedule: Item No. Item Unit

2521.518 ___” Concrete Walk square foot

8 ___” Colored Concrete Walk square foot

8 ___” Bituminous Walk square foot