5. PRE CAST CONCRETE
5. 1 General
5.1.1 Scope of Work
Provide precast concrete panels, materials equipments, and , labors, complete, in place, as shown on the drawings, specified herein, and as evidently required for a complete and proper installation of precast concrete work .
5.1.2 Related work Described
a. Cast in place concrete b. Concrete reinforcement
5.1.3 Quality Assurance
The manufacture should demonstrate the ability to provide the required quality as specified on the drawings or as directed by the Engineer.
5. 2.1 Manufacturing Data
The Contractor, prior to any work " shall submit to the Engineer the following items :
a. Complete material list with their specifications of all items proposed to be furnished and installed for this work.
b. Specifications and instructions for all manufactured materials and products going to be used in this work.
c. Laboratory test reports as required by the Engineer.
d. Shop Drawings showing complete information for the fabrication and installation of all required work, which is also suppose to include the following information:
i. Member dimensions and cross section, location, size, and type of reinforcement and lifting devices use for handling and erection.
ii. Details inserts, connections, and joints, including all accessories.
iii. Location and details of anchorage devices that are to be embedded in other construction,
iv. Gelded connections by AWS standards,
v. Erection procedure, sequence of erection, and method for temporary bracing and staging .
a. Precast samples approximately 300x300x50mm. cast from the mix specified illustrating equality color and texture of the proposed surface finish.
b. Submit samples of east_in gaskets, anchorages, and other attachments and accessories if required by the Engineer.
c. Prior to start of installation, one full-size sample of each required precast concrete unit shall be submit to the job site for approval by the Engineer, Acceptable samples may be incorporated in the construction,
d. The Engineer inspect color, texture, and general condition only .
Compliance with all other requirements is the exclusive responsibility of the contractor.
5. 3 Delivery and Storage
a. Deliver the work of this section to the job site in such quantities and at such times as to assure the continuity of the installation.
c. Lift and support the units at the designed lift points as shown on the approved shop Drawings.
d. At no time shall units be permitted to rest on earth or other staining materials.
e. Units shall be seperated one from another with non-staining wood strips.
f. Thin or flat elements shall be maintained in avertical position.
5. 4 Protection and Replacements
Use all means necessary to protect", the units from damages and staining before, during, and after installation. In the events of damage to the units or any materials of all other trades, immediately make all repairs necessary to the satisfaction of the Engineer. Where corrective measures are considered un-practicable or unsatisfactory, the faulty work shall be replaced by new units at no additional cost to the Employer.
a. Concreting materials as referred to in section ( 4_2). " Concrete
b. Provide all reinforcement, necessary, and connection materials required in accordance with the final design as approved "by the Engineer,
c. All anchors, bolts, dowels, fittings and attachment members shall be of types indicated on the drawings and as approved by the Engineer.
d. All the materials provided under this Article shall meet or exceed the cfuality specified for similar materials tinker other sections of these specifications*
e. Those materials not specified tinder those sections, but requried for a complete and proper installation, shall be new, first quality of their respective kinds, and selected by the contractor subject to the approval of the Engineer.
a. Provide complete design, calculations, and drawings prepared and signed by an engineer properly licensed to perform such services.
1. ACI 301
2. ACI 304
3. ACI 311
4. ACI 310
5. ACI 347
6. Concrete Reinforcing Steel Institute " Manual of standard
7. Prestressed Concrete Institute MILL116 " Manual for Plants and Production of precast concrete products.
Comply with building code requirements which are more stringent than above. In the event of conflict, the morn stringent provisional shall be govern.
c. Engineer's review of calculation dees not relieve the manufacturer of design responsibility .
d. Design modifications may be made as necessary to meet field conditions and to ensure proper fitting of work.
Maintain the general design concept as shown without increasing sizes of members or altering profile and alignments, and as acceptable to the Engineer.
5.5.4 Concrete mixes
a. Preinre design mixes for each type of concrete required, and secure the Engineer's approval of the proposed design. Design mixes may be prepared by an independent plant, at precast naiiufacturers option.
b. Design the mix and proportion of the concrete to attain a minimum compressive strength of 201 Kg / cm2 when cured and. tested at 20 days in accordance with ASTM C39 with minimum cement content of305Kg/m3
c. Submit written reports to the Engineer of proposed mix at least Relays prior to start of precast unit production.
d. Mix designed adjustments may be requested when characteristics od materials, job conditions weather, test , results, or other circumstances .
warrant laboratory test data for revised mix designs and strength results must be submitted to and accepted by the Engineer before using in the work.
5. 6. Equipments
a. forms shall be constructed of steel, with smooth contact surfaces and free from any staining effect confirming the exact design dimension and shapes.
b. Vibrating table shall be of design and. Construction to provide frequency vibration as required to produce units of the strength, aggregate distribution, and, finish specified and defined by the approved samples and test specimens.
c. Mixers shall be of type to maintain even distribution of fine and coarse aggregate, d. Lifting of precast units shall be done using power equipment of a type approved
by the Engineer.
5. 7 Fabrication
a. mix Materials for concrete in an acceptable drum type batch machine mixer and as explained in section(4_6) provide a batch ticket for each batch discharge and used in work, indicating project ; Identification name and number, date, mix type, mix time, quantity, and amount of water introduced .
b. Ready mix concrete shall be comply with requirements of ASTM C94, and as herein specified.
i. Addition of water to batch will not be permitted.
ii. During hot weather, or under conditions contributing to rapid setting of concrete, a shorter mixing and delivery time than that specified in ASTM C94 may be required.
c. Place and secure all anchors , clips, inserts, reglets, lifting devices, stud bolts , shear ties, and other devices required for handling and isntalling the precast units, and for attachment of subsequent items as indicated or specified.
d. Finish units shall be straight , true to size and shape and within the specified casting tolerances. Exposed edges shall be sharp, straight , and Square.
e. Dimensional tolerances shall be + ;- 3rnand for lintels shall be + ;- 6mm. Variation from position in plan + ;- 13mm maximum at any locations. Offsets in ftllgaaent of adjacent members at any joint shall be 1,5 in any 3000mm run and 6mm maximum .
Form cure for a minimum of 20 hours. Keep Wet continuously for not less than seven days after being removed from the forms. Following this curing period, allowing this curing period, allow the units to air dry for at least four days before being erected.
5. 7. 3 Surface Finish
Appearance of the precast units is of primary importance and special attention shall be paid to uniformity color, and texture
b. Finish of unformed surfaces .
Apply trowel finish to unformed surfaces unless otherwise indicated , consolidate concrete, bring to proper level with a straightedge, floot and trowel to a smooth, uniform finish. Apply scratch finish to precast units which will recieve concrete topping after installation .
Examine the areas and conditions under which work of this section will be installed. Correct conditions detrimental to proper and timely completion of the work. Bo not
proceed until unsatisfactory condition have been corrected.
5. 3. 2 Installations
5. 8. 2. 1 General
Install the work of this section in strict accordance with the approved shop Drawings, and all partinent codes and regulations. All cutting, drilling and welding required for installation shall be provided.
5. 3. 2. 2 Bracing
Bracing shall be adequate to resist any dimensional changes and resist wind load. They shall be left in place until final connections to the structural frames have been made.
5. 8. 2. 3 Bearing Pads
Install flexible bearing pads where indicated on the approved shop Drawing, set pads on level and uniform bearing surface, maintain in correct position until precast units are in place.
5. 8. 2. 4 Welding
Perform all welding in compliance with the approved drawings. All unsatisfactory connections shall be replaced or corrected according to the instructions of the Engineer,
5. 8. 2. 5 Grouting
a. After precast units have been placed and secured, grout open spaces at connections and joints.
Atlall times excerise extreme care to prevent staining of exposed panel surfaces.
b. Use only grout systems recommended by the manufacturer of the precast units and approved by the Engineer.
c. Provide any acceptable method to retain the grout in place until it is sufficiently hard to support itself.
Promplly remove all grout material from exposed surfaces before it hardens.
5.10 Plant Quality control Evaluations
a, The manufacturer shall provide samples of materials and concrete mixes as may be requested for additional testing and evaluation.
b . The strength of precast concrete units will be consider potentially deficient if they fail to comply with any of the requirements which may affect the strength including the following conditions:
1. Failure to meet compressive strength tests requirements.
2. Reinforcement not conforming to specified fabrication requirements.
3. Precast units damaged during handling erection. When there is evidence that the strength of precast concrete units does not meet specification requirements, cores shall be drilled for compressive strength determination complying with ASTM G42.
c. Where core test results are satisfactory and precast units are acceptable for use, fill core holes solid with patching mortar, and finish to match adjacent concrete surfaces.
d. Defective units which do not conform to the specified requirements shall be replaced with suitable units and corrections shall also be made for any other work affected by this correction without any additional cost.