3240Precast Concrete Manufacturing

3240.1SCOPE

Provide precast concrete items manufactured off-site at a permanent manufacturing facility listed on the Department’s website, and manufacturing products such as box C ulverts, reinforced concrete pipe and manholes, Bridge beams, abutments, pier caps, and other Structures. After seasonal or other delays in production, provide a minimum of 14 Calendar Days of notice that production will begin. When a manufacturing facility has not produced items covered by this Specification in the current or previous calendar year, provide a minimum of sixty Calendar D ays’ notice of intent to manufacture. If a manufacturing facility is located outside of Department-specified coverage areas and has been given specific approval to manufacture products according to thisS pecification, all costs of providing that inspection will be deducted from monies paid under the Contract. A list of plants, locations, and products with regular Department inspection is on the APL.

3240.2REQUIREMENTS

A Fabrication Drawings If full construction details are not included in the Plans, or if modifications of the Plan drawings are necessary, provide shop drawings meeting the following requirements to the Engineer of Record for

review and approval by the Office of Bridges and Structures or other P roject representative as designated by the Materials Engineer, before fabricating the units:

Do not begin construction of the items until full approval of the shop drawings is attained. When shop drawings are transmitted electronically, the final, approved shop drawings should be sent from the approved Project representative directly to the Precast Inspection Engineer and/or the State’s Inspector(s) for the manufacturing facility. B Materials Provide concrete with mix designations as shown on the Plans for the specific items of Work. C Forms Provide forms capable of withstanding pressure from concrete, vibration, and impact without distorting. Set and maintain forms in a mortar tight condition, free of warp, and on a rigid foundation. If evidence of mortar leakage is apparent after a pour, take corrective action to prevent the leakage from recurring. Provide joints in the sectional forms without offset. Set forms to create dimensions of the precast unit as shown on the Plans. Repair or replace forms not meeting the dimensions shown on the P lans before casting additional sections. When recesses around lifting devices are required, use forming devices provided by the lifting device manufacturer. Clean forms before use. Treat the face of the forms in contact with the concrete with form coating Material in accordance with 3902, “Form Coating Material,” before setting the forms. D Concrete Curing D.1 General Begin curing operations immediately after concrete placement. Continue curing until reaching at least 45 percent of design strength or as required by the Plan or Special Provisions. D.2 Curing Methods Use any of the following to cure the precast items:

Curing” which will be considered to include any methods using an external heat source D.3 Steam Curing For all products except Bridge beams, delay the introduction of steam into the curing enclosure for curing purposes, until the concrete has taken its initial set and at least 3 hours after placing the concrete. During the delay period, the temperature inside the curing chamber may be

increased from the concrete temperature at the time of placement up to 10 °F per hour, to no higher than 90°F. Only use steam to maintain the curing enclosure temperature within these limits. For Bridge girder production, delay the introduction of steam into the curing enclosure, for curing purposes, until the concrete has taken its initial set and at least 3 hours after placing the concrete. During the delay period, maintain a temperature within the curing chamber of at least 50°F and no greater than 10°F higher than the temperature of the concrete at the time of placement. Use steam only to maintain the curing enclosure temperature within the limits. For all products, do not allow steam jets to impinge directly on the concrete or on the forms. Do not allow the rate of rise in temperature adjacent to the concrete to rise at rates greater than 30°F per hour (for Bridge beams and 40°F for all other products). Provide free circulation around the top, sides, and ends of the concrete units . Do not allow the temperatures adjacent to the concrete greater than 160°F. Use saturated steam within the curing enclosure. Maintain a temperature in the concrete unit of at least 50°F during the curing period. For Bridge items, do not allow a difference in temperature adjacent to the concrete within the enclosure to be greater than 10°F. After the expiration of the steam curing period, reduce the temperature inside the chamber at a rate no greater than 40°F per hour until the temperature inside and outside of the chamber equalizes. After removing items from the chamber, protect the items to avoid cooling at a rate greater than 40°F per hour until reaching the air temperature at the storage site. If removing forms before the completion of the steam curing cycle (including temperature taper off process), only remove and leave uncovered the minimum area of the curing enclosure at any one time needed to remove each individual form section. Close the open area in the enclosure immediately upon removing each form section or within 15 minutes of first uncovering the area. When removing the precast items from the casting bed during the cooling -off process, take appropriate measures to keep the items warm during the moving operations, and immediately resume the cooling-off process at the storage area. When control cylinders are cured in a chamber separate from the pieces represented, maintain the cylinder chamber at the same temperature as, or no more than 5 °F higher than, the curing chamber for the precast items represented at all times during the curing period. Provide a continuous recording thermometer for each curing enclosure that has an individual temperature control (at least 50 percent of the curing chambers for box Culvert production and at least 1 per 100 feet for Bridge girders). Variances from these requirements may be allowed with approval of the Materials Engineer. Locate thermometers in each curing enclosure as approved by the Materials Engineer. Submit complete temperature recording charts for all recording devices to the Materials Engineer upon request. Discontinue steam curing and use one of the other approved curing methods, if the records indicate noncompliance with temperature and time element specifications for steam curing. E Certified Plant Requirement Provide precast concrete items constructed in a precast concrete fabrication plant certified by the American Concrete Pipe Association, the National Precast Concrete Association, or another organization approved by the Materials Engineer. Provide Bridge beams constructed in a fabrication plant certified by the Precast/Prestressed Concrete Institute.

If requested, provide quality control and plant certification records to the Materials Engineer. The quality control plans required by this Specification are subject to review and approval by the Materials Engineer. Failure to make any requested changes will result in removal of the plant from the APL. F Plant Quality Control The Materials Engineer will approve each precast concrete manufacturer and its individual plants to provide precast concrete products. The Materials Engineer will withdraw authorization or will not authorize precast concrete production if the manufacturer fails to abide by the terms, conditions, and requirements contained in this Specification. If the Materials Engineer finds manufacturer non-compliance with the Specification or evidence of non-conformance of precast products, the Engineer may perform any of the following:

F.1 Plant Quality Control In addition to the certified plant requirements of 3240.2E, Certified Plant Requirement,” establish and implement a Quality Control (QC) program, including the following elements for each plant: F.1.a Internal QC Program Ensure the manufacturer includes the following in the internal QC program:

Schedule of Materials Control or documentation of acceptability if Materials were previously inspected and tested, or received from a certified source

using an on-site cylinder strength testing machine, meeting the requirements of AASHTO T22 Standard Method of Test for Compressive Strength of Cylindrical Concrete Specimens, and capable of printing results.

F.1.b On-Site Quality Control Technicians Ensure the manufacturer employs and has on-site during production a QC technician trained and certified meeting the requirements of Department “Concrete Plant 1,” and either Department “Concrete Field 1” or ACI “Concrete Field 1” to perform the following:

quality products

pre-approved products

F.1.c System of Record Keeping Ensure the manufacturer maintains the following records:

authorized certification, or other evidence of inspection and satisfactory testing

F.2 Quality Assurance The Materials Engineer may visit each plant to perform tasks in accordance with this Specification and including the following:

precast products

stockpiling practices

The Engineer will perform a final inspection upon delivery to the P roject Site. F.3 Testing Rates F.3.a Concrete Ensure the manufacturer tests the slump/spread of concrete in each mix at least once per 25 cubic yards for each positive slump mix. Ensure the manufacturer tests the concrete according to the following: Cure wetcast and drycast control cylinders to be used for determining shipping strength in the same manner as the pieces they represent until they are tested. The testing of cylinders may or may not be witnessed by the Department Inspector, but the testing of cylinders with a specified strength of 5,000 psi or greater should be witnessed and documented by the Department Inspector.

Ensure control cylinders represent what is happening in the actual product. They must be exposed to the same conditions, at the same time. During the initial cure cylinders should be cured with the product. If cylinders are not cured with the product, the cylinder curing chamber must have the temperature controlled by what is happening to the product. Extra care must be taken to make sure the cylinders are not given a better cure than the product. Once the product has been moved out of the curing chamber, the cylinder should also be moved outside. If the cylinders do not stay with the product, they should go on a rack on the shady side of the building outside. They should not be in the sun all day, since the pieces represented are not entirely in the sun. Cores from individual pieces are used to verify proper placement of the reinforcing cages and to measure absorption of the concrete, which is an indicator of proper compaction of the drycast concrete. F.3.b Quality Control Testing Notify the Materials Engineer 2 full Business Days before three-edge bearing testing, shipping strength testing, or other acceptance testing, or1 full Business Day if inspectors are present on a daily basis. The Materials Engineer may select items or cylinders for testing and may direct the manufacturer to perform additional testing at no additional cost to the Department. Maintain documentation of all strength tests performed, including a signed, printed report from the cylinder testing machine that includes the following information:

date & time of the pour

F.4 Shipping Do not ship items that have not developed the specified compressive strength .

3240.3SAMPLING AND TESTING ................................................................................................... BLANK