SECTION 517: PRECAST CONCRETE STRUCTURES
517.1 Description
This Work consists of fabricat ing and installing precast, non-s tressed components composed of PCC. The Department defines a concrete Structure or component that i s cast in a location that is not its final intended in-servi ce location to be precast con crete. The Department defines non-stressed components as precast concr ete members that are not subject to pre-tensi oning or post-tensioning.
517.2 Materials
Unless otherwise specified, the Contractor shall use concrete i n accordance with Section 509, “Portland Cement Concrete Mix Designs.” The Contractor shall provide PCC for precast concrete component s in accordance with Section 510, “Portland Cement Concrete,” unless otherwise speci fied in this section.
517.2.1 Design and Acceptability Requirements
Before casting, the Contractor shall obtain the State Materials Bureau’s approval of the concrete mix design. The Contr actor may only make changes to t he approved mix design in accordance with Section 509.2.8, “PCC Mixture Design and Approv al.”
517.2.2 Testing Requirements
The Contractor shall perform sampling and testing of coarse and fine aggregates for alkali-silica reactivi ty in accordance with Section 509.2.4, “A ggregate.” If specified in the Contract or directed by the Project Manager , the Contractor shall determine the required compressive strength in accordance with AASHTO T 22, at no additional cost to the Department. The Contractor shall make a nd cure, or obtain from the manufacturer four (4) inch × ei ght (8) inch compressive strengt h test cylinders in accordance with AASHTO T 23. If the Contractor places more than five (5) yd 3 of concrete in a Day, the Contractor shall make at least three (3) cylinders from the pla ced concrete. If the Contractor places less than five (5) yd3 of concrete in a single Day, the Contractor shall cast at leas t three (3) cylinders from a random sample for each 20 yd3 of placed concrete from consecutive pours. A compressive strength test is the average of two (2) or more c ompressive strength cylinder tests performed at the same age. The Department will determine Acceptance of the concrete in accordance with Sec tion 510.3.5.1.1, “Individual St rength Test.” The Contractor shall enter the actual batch weights used in each batch of conc rete and the measured moisture contents for each of the aggregates contained within e ach batch into the Field Report Form provided to the Contractor/Supplier at the same tim e the approved mix was provided. Insure that all test r esults for compressive strengt h and fresh concrete properties, including slump, air content and unit weight, are also entered into the Field Report. If compressive strength tests fail to comply with the Contract requirements, the Department will allow the manufacturer to perform in-place comp ressive strength testing on the members in question. The Department will evaluate these te sts in accordance with Section 510.3.5.4, “Investigation of Low Strength Cylinder Test Results.” The Contractor shall allow Department personnel access to obtai n test samples and to perform Independent Assurance testing at the Department’s discr etion.
517.2.3 Steel Products
517.2.3 1 Reinforcing Steel
The Contractor shall provide st eel reinforcement in accordance with Section 540, “Steel Reinforcement.”
517.2.3 2 Structural Steel
The Contractor shall provide Structural Steel items in accordan ce with Section 541, “Steel Structures.”
517.3 Construction Requirements
517.3.1 General
The Contractor shall manufacture precast components in one (1) of the following plants: 1. A Precast Concrete Institute (PCI), National Precast Concret e Association (NPCA) or American Concrete Pipe Associ ation (ACPA) certified plant re gularly engaged in design, fabrication and construc tion of precast concrete compon ents, or 2. An on-site Project specific facility inspected and approved by the Project Manager.
517.3.2 Quality Control
The Contractor shall ensure that precast concrete manufacturing facilities have a current Quality Control Plan on record that describes the procedures in detail. The Plan shall include an organization chart of the overall casting operation, a list of responsible people and a detailed description of their job duties, and the telephone num ber of the responsible party for contact 24 h per Day during fabr ication and placement of precas t Structures. The Contractor shall obtain all batch weights used for each Day ’s production directly from the computer generated production record for each batch, a nd record each batch weight on the same Field Report form as the test results referenced in Section 517.2.2, “Testing Requirements.” Electronic copies of the report form for each D ay’s production will be kept available for review by the D epartment Precast Concrete Inspect or upon request. In addition to the electronic copy, a printed copy of the summary page and all original computer generated production records will be kept on file for each Day’ s production. The Contractor shall make these copies availabl e to the Precast Concrete Inspe ctor upon his request. For a facility that has no computer or computerized capability, actua l batch weights of each ingredient will be recorded before the load is discharged. Any Precast items cast from concrete batches that cannot be ver ified or with non- complying test results or batch weights cannot be used on Depar tment Projects, and will be disposed of at no cost to the Department. The Contractor shall submit certificates of compliance for ceme nt, reinforcing steel, anchor bolts, supplemental cementit ious Materials and liquid ad mixtures.
517.3.3 Notice of Beginning Work
Section 517: Precast Concrete Structures Page 394 The Contractor shall give the Project Manager and the Precast I nspector adequate notice before starting Work in the plant as follows: 1. Plants in the State of New Mexico: seven (7) Calendar Days; 2. Plants in the Contiguous United States: 21 Calendar Days; a nd 3. Plants outside the Contiguous United States: 60 Calendar Da ys. The Contractor shall not perform Work before the Project Manage r and the Precast Inspector give written authorization for fabrication. The Contractor shall request ins pections at least three (3) Cal endar Days in advance.
517.3.4 Approval of Plants and Equipment
The Contractor shall obtain approval of the Precast Inspector f or plants and Equipment used in manufacturing precast conc rete members before Work begi ns. The Precast Inspector may forbid the use of machinery, Equipment, or appurtenances th at prove unacceptable. In the event that the Contractor fabricates Materials on site, the Project Manager shall then approve on site plants and Equipment.
517.3.5 Shop Drawings
The Contractor shall fabricate pr ecast concrete Structures in a ccordance with the Department’s Standard Drawings . For modified or Project specific precast concrete Structures, the Contractor shall submit shop drawings stamped b y a professional Engineer licensed in the State of New Mexico to the State Bridge Enginee r for review and Acceptance. The Contractor shall provide shop drawings that show sizes, sha pes, dimensions, and concrete cover for the reinforcing steel and other items embedd ed in the concrete. The Contractor shall provide shop drawings in accordance with ACI D etailing Manual and Section
541.3 1, “Applicable Codes and Documents.”
The Contractor shall allow 30 Days for review and Acceptance of the modified or Project specific drawings. The Contractor shall allow 14 Calendar Days for review and Acceptance of Standard Drawings . Any re-submittals will require an additional 14 Days for rev iew.
517.3.5 1 Calculations
The Contractor shall submit design calculations to the State Br idge Engineer for modified or unique precast concrete Structures not previously reviewed a nd approved by the Department. The Contractor shall ensure that a professional En gineer licensed in the State of New Mexico performs and stamps the calculations. The Contracto r shall submit the design and calculations at least 30 Calendar Days for review and Accep tance before the start of fabrication.
517.3.6 Precast Concrete Member Assembly
517.3.6 1 Beds and Forms
The Contractor shall use forms that are smooth, mortar tight, a nd capable of withstanding forces caused by placement and consolidation of co ncrete. The Contractor shall accurately fabricate and secure forms in position so that the p recast member has true, smooth, and even surfaces. The Contractor shall provide suppor t for casting beds on unyielding foundations. The D epartment will not allow internal bracing and holding devices in forms if they remain in the finished member. Section 517: Precast Concrete Structures Page 395 The Contractor shall provide co rners with a chamfer or radius i n accordance with the Plans. The Contractor shall check the grade and alignment of forms eac h time they are set, and maintain them during concrete placement. The Contractor shall ensure forms are reasonably free of rust, grease, or other Deleterious Materials. The Contractor shall thoroughly clean b eds and forms after each use and before each casting operation. The Contractor shall not al low coatings used for release of members to build up. The Contractor shall maintain beds and forms to produce an Acceptable product. The Contractor shall construct t he forms to facilitate removal without damage to the concrete. The Contractor shall use care in removing forms to n ot deface or damage the member. The Contractor shall not use methods of removal that c ause overstressing of the concrete.
517.3.6 2 Forms for Internal Voids
If constructing forms for inter nal voids, the Contractor shall use an approved watertight Material that is resistant to breakage and deformation during c oncrete placement. The Contractor shall provide stay-in-place internal forms that are as light in weight as practical. The Contractor shall securely anchor internal forms in position to prevent flotation or displacement during concrete placement. The Contractor shall vent and drain stay-in-place void forms th rough the base of the member. The Contractor shall seal splices and ends of stay-in- place void forms to prevent concrete from entering. The Contractor shall manufacture internal voids shaped by movin g mandrels in accordance with the same dimensional tolerances as formed voids . The timing and rate of mandrel movement will preclude fallout of inner surfaces, tensi le cracks, and the separation of concrete from reinforcing.
517.3.6 3 Placement of Reinforcing Bars
The Contractor shall accurately place and secure reinforcing ba rs in accordance with the Plans, and methods approved by the Project Manager and Precast Inspector. The Contractor shall pay particular attention to concrete cover requirements o ver reinforcing bars. The Contractor shall provide lap splices in accordance with the app roved drawings, and fasten them securely.
517.3.6 4 Placement and Consolidation of Concrete
The Contractor shall place concrete in accordance with Section 511, “Concrete Structures,” unless otherwise specified in this section. Before placing concrete, the Contractor shall correct deficienc ies found by the Inspector. To ensure that similar deficiencies do not recur, the Contracto r shall implement Quality Control procedures satisfactory to the Inspector. The Contractor shall use internal vibration to eliminate honeyc ombing. The Contractor shall attach a sufficient number o f external vibrators rigidly to the forms so that the vibrations extend throughout the entire length and volume of the member. Section 517: Precast Concrete Structures Page 396 The Department will not allow vibr ating methods that cause segr egation. The Department will reject members with voids or honeycombing that exposes reinforcement.
517.3.6 5 Tolerances
The maximum allowable deviations from the dimension and details shown in the Contract are listed in the Manual for Quality Control for Plants and Production of Precast and Prestressed Concrete Products , published by the PCI.
517.3.6 6 Curing
The Contractor shall cure precast members in accordance with Se ction 511, “Concrete Structures.” The Contractor may use steam, in accordance with Section 517.3.6.6.1, “Steam Curing.” Before placing concrete, the Contractor shall submit the propos ed curing methods and procedures to the Project Manage r or the Inspector for approval . The Contractor shall test elevated-temperature curing facilities for a minimum of 48 h be fore approval. The Contractor shall make curing Equipment and Materials for curing available before casting. The Project Manager or Inspector will suspend concrete placemen t if curing facilities are inadequate or the Contractor is not attending to the proper cur ing of the concrete. Placement may resume after the Contractor makes the appropriate correctio ns. The Contractor shall begin curing as soon as possible but not m ore than two (2) hours after casting. To prevent damage and discoloration of a concre te member, the Contractor shall not allow mats, sheets, or blankets to contact the concre te member. The Contractor may remove forms after the concrete has reached sufficient strength in accordance with the Specifications for the item being cast. Th e Contractor shall not interrupt the curing of members for more than 30 min when removing forms.
517.3.6 6.1 Steam Curing
If steam curing; the Contractor shall enclose the member entire ly within an approved and supported enclosure so that a clear space forms around the side s, ends, and top of the member. After placement and vibration of the concrete, the Contractor s hall allow it to attain its initial set before applying steam. The Contractor shall preven t surface drying during the period between placement of concrete and application of steam b y applying coatings, a membrane curing compound, moisture retention covers, or other e quivalent methods. The Contractor shall ensure that the rate of temperature rise a nd the maximum temperature, in combination with the cement used in the concret e mix, does not promote or initiate delayed ettringite formation. The Contractor shall equip each enclosure with accurate tempera ture recording devices spaced at no more than 100-foo t intervals to keep continuous ho urly records. If the air temperature is 40 °F or greater, the Contractor shal l not admit steam fog to the enclosure for a period of from two (2) h to six (6) h after fin al placement of concrete into the forms, to allow the initial set to take place. The Contractor shall maintain the steam fog surrounding the member at a temperature between 120 °F and 165 °F until the member attains the required strength. If the air temperature is less than 40 °F, the Contractor shall admit steam no hotter than 120 °F to the enclosure immediately. The Contractor shall allo w the two (2) to six (6) hour initial setting period to elapse before raising the steam tempe rature to the specified curing temperature range. The Contractor shall admit steam into the enclosure at a low pr essure and in a saturated condition. The Contractor shall position steam jets so they do not discharge directly onto the concrete, forms, or test cylinders. The Contractor shall caref ully check the housing to ensure uniform distribution of steam f og and uniform application of he at and moisture. When discontinuing the steam, the Contractor shall decrease the temperature of the air surrounding the member at a nearly constant rate not to exceed 70 °F per hour until it reaches a temperature 50 °F above the temperature of the surrounding ai r. At that time, the Contractor shall terminate the steam curing. The Contractor sh all maintain the temperature of the member above 35 °F for four (4) consecutive Days after comp letion of steam curing. The Contractor shall remove side forms from six (6) h to two (2 ) Days after completing the pour. The Contractor shall loosen or remove steel side for ms as early as practical to prevent damaging the concrete. The Contractor may interrupt cu ring briefly for this purpose as long as the surrounding air tem perature does not drop below 40 °F.
517.3.7 Workmanship
The Precast Inspector will not reject Work because of fine crac ks on the surface of the member that do not extend to the plane of the nearest reinforce ment unless they are numerous and extensive. For members with diagonal cracks, whic h indicate damage from torsion, the Department will perform a structural review before Accepting. The Contractor shall repair cracks that extend into the plane o f the reinforcing steel (but are Acceptable otherwise) by sealing with an approved epoxy or other approved Material. The Contractor shall repair defective areas or surfaces needing patching using approved methods. The Contractor shall not plaster over defective areas . Unless otherwise noted, the Contractor shall provide finishes i n accordance with Section 511.3.8.2, “Class 1, Ordinary Surface Finish,” or Secti on 511.3.8.3, “Class 2, Rubbed Surface Finish,” except for temporary Structures which will req uire a Class 1 finish. The Contractor shall provide a Class 2 surface finish for visual su rface defects/pitting on Structures other than temporary Structures.
517.3.8 Lifting, Handling, Storing, and Shipping Precast Member s
The Contractor shall avoid chipping, cracking, fracturing, and excessive bending stresses when lifting, handling, storing, and shipping members. The Contractor shall support members on firm blocks. During handling and storage, the Contr actor shall keep the members vertical and the long axis approximately level. The Co ntractor shall make the points of support and direction of reactions with respect to the membe r approximately the same as when the member is in its final position in the completed Struc ture or application. The Contractor shall handle or support the items securely in an upr ight position. The Contractor shall use care during lifting, handling, hauling , storing, erecting, and driving to prevent cracking, spalling, or other damage to the m ember. The Contractor shall replace members damaged by improper handling methods. Section 517: Precast Concrete Structures Page 398 The Contractor shall verify lifting devices for capacity in lif ting and handling products, taking into account various positions during handling. The Con tractor shall not allow lifting devices to project above the surf ace of the member after placem ent unless the lifting devices will: 1. Be embedded in a subsequent concrete pour; 2. Have a concrete cover o f at least two (2) inches; and 3. Not interfere with the placement of reinforcing steel or con crete. The Contractor shall stack mem bers in storage only with approva l of the Project Manager or the Precast Inspector. The Contractor shall keep me mbers covered and protected until installed. The Contractor shall not subject members to heavy loads until t he members have attained the specified 28-Day strength.
517.3.9 Installation
The Contractor shall install pr ecast Structures in accordance w ith the Contract.
517.4 Method of Measurement
The Department will measure prec ast concrete members in accorda nce with the applicable sections of the Specifications.
517.5 Basis of Payment
The Department will pay for precast concrete members in accord ance with the applicable sections of the Specifications.
517.5.1 Work Included in Payment
The Department will consider as included in the payment for th e pay item(s) listed in this section and will not measure or pay separately for the followin g Work: 1. The development of the Contractor Quality Control Plan shall be included in the payment and is considered Incidental to the completion of this Bid Item. All references to Section 901.2, “Contractor Quality Control” are f or reference only and no separate measurement will be made. Section 518: Pre-Stressed Concrete Members Page 399