PRE CAST CONCRETE

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

Elsewhere

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.

The installers must not have less than
two years successful experience in

erecting similar items to those required in this work.

5.2 Submittals

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 .

5.2.2 Samples

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.

b.    Storing and delivering of the units shall be in a manner to prevent cracking , distortion , warping, staining, and other physical damages,

and in a manner to keep all marking visible.

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.

5.5 Products

5.5.1      General

a.       Concreting materials as referred to in section ( 4_2). " Concrete

Work ".

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.

5.5.2 Design

a. Provide  complete  design,  calculations,  and  drawings  prepared  and signed by an engineer properly licensed to perform such services.

b. Make all necessary provision in the design to accomodate all stresses to be encountered.

Design in accordance with all pertinent recommendations contained in:

1.    ACI 301

2.    ACI 304

3.    ACI 311

4.    ACI 310

5.    ACI 347

6.  Concrete  Reinforcing  Steel  Institute  "  Manual  of  standard

Practice" .

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.

They shall have sufficient strength to withstand high frequency vibration and to prevent deformation under applied loads. The form's surfaces shall be coated with a bond breaking compound before reinforcement is placed.

The coat shall not adversely affect concrete properties of appearance.

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

5.7.1 General

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 .

5.7.2 Curing

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

a.        Finish of formed surfaces Normal plant_run finish produced by forms that impart a  smooth finish to the concrete. Small surfaces holes caused by air bubbles, normal form joint marks, and minor chips and spalls will be tolerated, but no major unsightly imperfections,  honeycomb, or structural defects will be

permitted.

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 .

5.8 Execution

5.8.1 Inspection

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.

d. Pack spaces with stiff grout materials, tamping voids completely full. place the grout in a  manner to finish smooth} plumb and leved with adjacent concrete surfaces,

e. Keep grouted surfaces damp for not less than 24 hours after grout has taken its initial set .

Promplly remove all grout material from exposed surfaces before it hardens.

5.9 Cleaning

Upon completion of installation and patching ,  all exposed work of this section shall be washed clean with clean water. All excess materials shall be removed and the site left in a clean and acceptable condition.

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.