ARCHITECTURAL PRECAST CONCRETE
Has been made precast concrete shop drawings for an education center.
ARCHITECTURAL PRECAST CONCRETE
PRECAST MEMBERS
The work includes the provision of precast non-prestressed concrete herein referred to as precast members. Precast members shall be the product of a manufacturer specialized in the production of precast concrete members.
SUBMITTALS
Manufacturer's Catalog Data.
a. Anchorage and lifting inserts and devices
b. Bearing Pad
Drawings
a. Drawings of precast members
Drawing Information
Submit drawings indicating complete information for the fabrication, handling, and erection of the precast members. Drawings shall not be reproductions of contract drawings. Design calculations and drawings of precast members (including connections) shall be prepared and sealed by a registered professional engineer, and submitted for approval prior to fabrication. The drawings shall indicate, as a minimum, the following information:
a. Marking of members for erection
b. Connections for work of other trades
c. Connections between members, and connections between members and other construction
d. Joints between members, and joints between members and other construction
e. Reinforcing details
f. Material properties of steel and concrete used
g. Lifting and erection inserts
h. Dimensions and surface finishes of each member: Sill, lintel, jambs, arched sections, coping at landscape walls and bench supports.
i. Erection sequence and handling requirements
j. All loads used in design (such as live, dead, handling, and erection)
k. Bracing/shoring required
Design Data
a. Precast concrete member design calculations
b. Concrete mix design
Design Calculations
Submit calculations reflecting design conforming to requirements of paragraph entitled "Precast Concrete Member Design". Design calculations and drawings of precast members (including connections) shall be prepared and sealed by a registered professional engineer, and submitted for approval prior to fabrication.
Concrete Mix Design
Thirty (30) days minimum prior to concrete placement, submit a mix design. Include a complete list of materials including type; brand; source and amount of cement, pozzolan, and admixtures; and cladding applicable reference specifications.
Statements
a. Fabrication
Submit quality control procedures established in accordance with UNI EN 206-1by the precast manufacturer.
Factory Test Reports
a. Contractor-furnished mix design Submit copies of test reports showing that the mix has been successfully tested to produce concrete with the properties specified and will be suitable for the job conditions. Obtain approval prior to fabrication.
Samples
Submit for approval samples of each type of precast member as indicated showing finish and color:
a. Arch
b. Arch jamb
c. Recessed mullion
d. Lower head
e. Lower sills
f. Upper head
g. Upper sills
h. Bench support
i. Wall coping
Records
a. Concrete batch ticket information
QUALITY ASSURANCE
Precast Concrete Member Design
Design precast members (including connections) for the design load conditions and spans indicated, and for additional loads imposed by openings and supports of the work of other trades. Design precast members for handling without cracking. Factory Fabrication, Sampling and Testing at the precast manufacturer's option, in lieu of core samples, full scale load tests may be performed. Perform on randomly selected members, as directed by the Contracting Officer.
DELIVERY AND STORAGE
Lift and support precast members at the lifting and supporting points indicated on the shop drawings. Store precast members off the ground. Separate stacked precast members by battens across the full width of each bearing point. Protect from weather, marring, damage, and overload.
FACTORY INSPECTION
The Contracting Officer shall inspect precast units prior to being transported to the job site, at Contracting Officer’s option. The Contractor shall give notice 14 days prior to the time the units will be available for plant inspection. Neither the exercise nor waiver of inspection at the plant will affect the Government's right to enforce contractual provisions after units are transported or erected.
PART 2 - PRODUCTS
CONTRACTOR-FURNISHED MIX DESIGN
Compressive Strength
The minimum compressive strength at 28 days shall be Rck = 300 (300 kg/sq. cm) as determined in accordance with Italian Law No. 1086 and Ministerial Decree 9 January 1996.
Chloride Content
Maximum allowable shall not exceed 0.4 percent per UNI EN 206-1.
Maximum Water Cement Ratio: 0.45.
Minimum Cement Content kg/cubic meter: 300 per UNI EN 206-1.
Minimum Air Content: 6 percent per UNI EN 206-1.
Exposure Class: 3 per UNI EN 206-1.
Resistance to Water Penetration. The mix shall not exceed the minimums set by ISO 7031, with maximum values of penetration less than 50 mm and mean average values of penetration less than 20 mm.
MATERIALS
Cement
Portland cement Type 325 or high strength Portland cement Type 425.
Water
Water shall be fresh, clean and potable.
Aggregate
8 mm nominal, normal-weight per ISO 5783. Aggregate shall not contain harmful constituents in such quantities as may be detrimental to the durability of the concrete or cause corrosion of the reinforcement. Aggregates are required to be frost resistant.
Grout
Non-shrink Grout. Cementitious Grout. Shall be a mixture of Portland cement, sand, and water. Proportion one part cement to approximately 2.5 parts sand, with the amount of water based on placement method. Provide air entrainment for grout exposed to the weather.
Admixtures
Air-Entrained Agents
All concrete shall be air entrained. Air-entraining agents shall conform to UNI EN 934-2. The agent and the cement proposed for use shall be selected well in advance of concrete placing, and the Contractor shall provide satisfactory facilities for ready procurement of adequate test samples. Concrete mixtures shall have air content, by volume of concrete, minimum 6 percent.
Air content shall be based on measurements made on concrete mixture at point of discharge of mixer. Air-entraining shall be produced by adding an air-entraining agent at the mixer. When necessary to increase the air content within the specified range, additional air-entraining admixture compatible with that already in the mixture shall be added in the mixer. Retarder for Exposed Aggregate on Exterior Benches Retarder must not weaken finished precast item. No more than 3 mm of aggregate exposure will be permitted. Other admixtures shall be used only on written approval and shall conform to UNI EN 934-2.
Reinforcement
Reinforcing Bars
Bars for reinforced concrete structures shall be high strength, high bond bars, Type FeB 44K and shall conform to the requirements of Ministerial Decree dated 9 January 1996 "Criteria for the Construction of Reinforced Concrete, Prestressed Concrete and Steel Structures", as indicated in Table A; bars with diameter greater than 26 mm shall be Type FeB 38K.
Metal Accessories
Hot dip galvanized after fabrication where practicable.
Structural Steel: Fe 360 Steel.
Bolts: UNI 3740.
Nuts and Washer: UNI 6602.
Bearing Pads
Bearing Pads
Multi-polymer plastic material with a minimum compressive strength of 560 kg/cm2, maximum coefficient of thermal expansion of 0.12m/cm/0C, maximum cold flow characteristic of 1 percent at 70 kg/cm2 and 22 degrees C for 10,000 hours.
FABRICATION
The units shall be in accordance with Law No. 1086 and Ministerial Decrees dated 9 January 1996 and 31 August 1972, unless differently specified.
Forms
Brace forms to prevent deformation. Forms shall produce a smooth, dense surface.
Reinforcement Placement
Reinforcement may be preassembled before placement in forms. Provide exposed connecting bars, or other approved connection methods, between precast and cast-in-place construction. Remove any excess mortar that adheres to the exposed connections.
Concrete
Concrete Mixing. UNI EN 197-1, and UNI EN 197-2. Mixing operations shall produce batchto- batch uniformity of strength, consistency, and appearance.
Concrete Curing. Commence curing immediately following the initial set and completion of surface finishing. Provide curing procedures to keep the temperature of the concrete between 10° and 87° C. When accelerated curing is used, apply heat at controlled date and uniformly along the casting beds. Monitor temperatures at various points in a product line in different casts.
Surface Finish
Repairs located in a bearing area shall be approved by the Contracting Officer prior to repairs. Precast members containing hairline cracks which are visible and are less than 0.50 mm in width, may be accepted, except that cracks larger than 0.12 mm in width for surfaces exposed to the weather shall be repaired. Prescast members which contain cracks greater than 0.50 mm in width shall be approved by the Contracting Officer, prior to being repaired. Any precast member that is structurally impaired or contain honeycombed section deep enough to expose reinforcing shall be rejected.
Finish Grade A
Forms do not produce a texture on the concrete. Fins are removed. Surface blemishes shall be filled and finished to provide a smooth surface without surface voids. Exposed surfaces shall be reasonably color matched. Standard Grade Finish. Forms do not produce a texture on the concrete. Fins are removed and large surface blemishes are filled. Sharp edges are ground down. Minor surface voids.
Formed Surface Finish Schedule. Unexposed Surfaces. Provide a standard grade surface finish. Exposed finish Grade A surface finish. The combined area of acceptable defective areas shall not exceed 0.2 percent of the exposed to view surface area, and the patches shall be indistinguishable from the surrounding surfaces when dry.
Exposed Aggregate Finish. To be used on exterior bench supports only. Exposure must create a uniform texture without extensive patching. Patches shall not be distinguishable for surrounding surfaces when dry.
PART 3 - EXECUTION
SURFACE REPAIR
Prior to erection, and again after installing, precast members shall be checked for damage, such as cracking, spalling, and honeycombing. As directed by the Contracting Officer, precast members that do not meet the surface finish requirements specified in Part 2 paragraph, titled "Surface Finish", shall be repaired, or removed and replaced with new precast members.
ERECTION
Precast members shall be erected after the concrete has attained the specified compressive strength, unless otherwise approved by the precast manufacturer. Erect in accordance with the approved shop drawings. Brace precast members, unless design calculations submitted with the shop drawings indicate bracing is not required. Follow the manufacturer's recommendations for maximum construction loads. Place precast members level, plumb, square, and true within tolerances. Align member ends.
BEARING SURFACES
Shall be flat, free of irregularities, and properly sized. Size bearing surfaces to provide for the indicated clearances between the precast member and adjacent precast members or adjoining field placed surfaces. Correct bearing surface irregularities with nonshrink grout. Provide bearing pads where indicated or required. Do not use hardboard bearing pads in exterior locations. Place precast members at right angles to the bearing surface, unless indicated otherwise, and draw-up tight without forcing or distortion, with sides plumb.
ANCHORAGE
Provide anchorage for fastening work in place. Conceal fasteners where practicable. Make threaded connections up tight and nick threads to prevent loosening.
Dowels
Provide a minimum of two stainless steel dowels for each section of wall coping.
Support Angles
Provide stainless steel support angles with continuously welded stainless steel bars. Grout connection at precast element and bar.
Strap Anchors
Grout strap anchors into slots where indicated.
WELDING
In accordance with UNI 4634. Protect the concrete and other reinforcing from heat during welding. Weld continuously along the entire area of contact except where tack welding is permitted. Do not tack weld exposed connections. Grind smooth visible welds in the finished installation.
OPENINGS
Holes or cuts requiring reinforcing to be cut, which are not indicated on the approved shop drawing, shall only be made with the approval of the Contracting Officer and the precast manufacturer. Drill holes less than 10 mm in diameter with a diamond tipped core drill.
GALVANIZING REPAIR
Repair damaged to galvanized coatings using zinc rich paint for galvanized surfaces damaged by handling, transporting, cutting, welding, bolting, or acid washing. Do not heat surfaces to which repair paint has been applied.
GROUTING
Clean and fill indicated keyways between precast members, and other indicated areas, solidly with nonshrink grout or cementitious grout. Provide reinforcing where indicated. Remove excess grout before hardening.
JOINTS BETWEEN PRECAST UNITS
Clean, clear all joints between members and provide backer rod and