ITEM 435 ELASTOMERIC MATERIALS

Transcription

1 ITEM 4 ELASTOMERIC MATERIALS 4.1. Description. This Item shall govern for the furnishing and installation of elastomeric materials in accordance with the details shown on the plans and the requirements of this Item Materials. (1) Elastomeric Bearings. When shown on the plans, structural members shall be seated on elastomeric bearings. These bearings may be either "plain" (consisting of elastomer only) or "laminated" (consisting of alternating individual layers of elastomer and steel laminates) as shown on the plans. Elastomeric bearings will be designated by hardness (Durometer), size and configuration and, in the case of laminated bearings, by the thickness of the individual layers of elastomer and the size and position of special connection members, if any, required to be vulcanized with the bearing. (a) General. Unless otherwise shown on the plans, the elastomer for bearings shall be formulated from previously unvulcanized 100 percent virgin polychloroprene or 100 percent virgin polyisoprene rubber polymers. Rubber-like polymers employed in the elastomer formulation shall be exclusively of the polychloroprene or natural polyisoprene type. Bearings will not be acceptable if the elastomer employed contains previously vulcanized natural or synthetic rubber or other synthetic rubber-like polymers. Steel laminates shall be commercial grade steel strip or sheet with a thickness of three (3) millimeters ± 0.4 millimeter. Metal for special connections, including sole plates and bearing plates, shall conform to ASTM A 36, unless otherwise shown on the plans. (b) Physical Properties of the Elastomer. Elastomer formulated from polychloroprene and polyisoprene shall meet the requirements of AASHTO M251, Table 1. Certified test results showing actual test values obtained and the required values for the physical properties of the elastomer shall be furnished for each formulation. Material tests shall be made by the bearing manufacturer in accordance with the applicable test methods except that all tests shall be made on the finished product. Standard laboratory test slabs will not be utilized for this purpose. The apparatus employed in preparing test specimens from the finished product shall be in accordance with ASTM D 15, "Sample Preparation for Physical Testing of Rubber Products". (c) Formulation Prequalification and Certification. All bearings furnished by the Contractor shall be produced by a bearing manufacturer prequalified by the Materials and Tests Engineer. Each elastomer formulation produced by a manufacturer must be approved by the Materials and Tests Engineer prior to initial use on Department projects. To prequalify and obtain initial approval of a particular formulation, the bearing manufacturer shall submit to the Materials and Tests Engineer, in advance of anticipated use of his product, certified test results. The results must show actual test values obtained when the physical properties of the elastomer to be furnished were tested for compliance with the minimum requirements of AASHTO M251, including the Cold Temperature Shear Test. In addition, the manufacturer shall forward prequalification test samples, freight prepaid, to the Materials and Tests Engineer, Texas Department of Transportation, 3800 Jackson Ave., Building No. 5, Austin, Texas 78703, for testing and evaluation of compliance with prequalification requirements. The Department will test all laminated prequalification samples for adhesion in accordance with Texas Test Method Tex-601-J. Only elastomer of the type or types to be supplied shall be submitted (polychloroprene, polyisoprene). Prequalification samples shall consist of two (2) finished bearings typical of the formulation and workmanship intended for use on Departmental projects. When both laminated and plain bearings are required, two (2) samples of each type shall be submitted. Plain sample bearings shall measure 225 millimeters x 480 millimeters x 25 millimeters, 70 Durometer.

2 Laminated sample bearings shall measure 225 millimeters x 5 millimeters x 38 millimeters with the following number of steel laminates: 50 durometer - three (3) steel laminates 60 durometer - two (2) steel laminates The bearing manufacturer shall certify that all of the samples submitted are of the same basic elastomer formulation and of equivalent cure to that used in the finished products to be furnished on Department projects. The bearing manufacturer shall perform the complete prequalification testing procedure during later production should the Engineer feel such action appropriate. (d) Manufacturing Requirements. All components of a "laminated" bearing shall be molded together to form an integral unit free of voids or separations in the elastomer or between the elastomer and the steel laminates or special connections unless otherwise shown on the plans. The elastomer between the laminates or special connections and on the outer surfaces of the bearing shall be well-vulcanized, uniform and integral such that the elastomer is incapable of being separated by any mechanical means into separate, definite, well-defined elastomeric layers. Evidence of this layered construction, either at the outer surfaces or within the bearing, shall be cause for rejection of such laminated bearing shipments. All edges of steel laminates shall be covered by a minimum of three (3) millimeters of elastomer except that exposure of the laminates will be permitted at approved laminate restraining devices and around holes that will be entirely enclosed in the finished structure. All laminates shall be properly positioned within three (3) millimeters of design (plan) location. Plain bearings may be molded individually, cut from previously molded strips or slabs molded to the full thickness of the finished bearings, or extruded and cut to length. The finished bearings shall have no voids or separations detectable either at the bearing surfaces or within the bearing. Plain elastomeric bearings shall be well-vulcanized, uniform and integral units of such construction that the bearing is incapable of being separated by any mechanical means into separate, definite and well-defined elastomeric layers. Evidence of layered construction either at the outer surfaces or within the bearing shall be cause for rejection of such bearing shipments. The finish of cut surfaces shall be ANSI 250, or smoother. The batch or lot number and the dimensions or piece mark shall be marked on the surface of each bearing. The markings shall remain legible until placement in the structure. In addition, all laminated bearings shall be permanently marked with: the Manufacturer's Name or Trademark, Lot Number, Date of Manufacture (Month-Year), and Direction of Slope. Unless otherwise shown on the plans, this marking shall be on a face which is visible after erection of the bridge. (e) Appearance and Dimensions. Flash tolerance, finish and appearance shall meet the requirements of the latest edition of the Rubber Handbook as published by the Rubber Manufacturers Association, Inc., RMA F3 and T.063 for molded bearings and RMA F2 for extruded bearings. For both plain and laminated bearings the permissible variation from the dimensions and configuration shown on the plans shall be as listed in AASHTO M251, Table 2. (f) Routine Inspection, Sampling and Testing. After prequalification approval, the inspection, sampling and testing of actual bearing production will be as outlined below: Plain Bearings. A minimum of one (1) plain bearing will be taken by a representative of the Materials and Tests Division from each batch or lot. Routine tests for compliance with the requirements of AASHTO M251 will be performed by the Materials and Tests Division. Samples will not be returned.

3 Laminated Bearings. Each laminated bearing shall be subjected, by the manufacturer, to an average compression of ten (10) megapascals or a stress approved by the Engineer. This compression test will be performed in the presence of a representative of the Materials and Tests Division who will perform visual inspection and accept or reject the bearings. The performance of each bearing will be considered satisfactory provided there is no visible evidence of bond failure or other damage to the bearing and provided the finished bearing meets all other pertinent portions of this specification. Samples of laminated bearings may be taken if the quality of the plant production becomes questionable. The manufacturer shall furnish certified laboratory test results on the elastomer properties of each batch or lot of compound used in the manufacture of bearings, both plain and laminated. Copies of Certified Mill Test Reports shall be required for all metal for special connections, including sole plates and bearing plates. (2) Waterstops. Waterstops shall be furnished and installed in accordance with the details shown on the plans. Except where otherwise shown on the plans, waterstops may be manufactured from either natural or synthetic rubber or from polyvinyl chloride (PVC) as specified below: (a) General. Natural rubber waterstops shall be manufactured from a stock composed of a highgrade compound made exclusively from new plantation rubber, reinforcing carbon black, zinc oxide, accelerators, anti-oxidants and softeners. This compound shall contain not less than 72 percent by volume of new plantation rubber. Synthetic rubber waterstops shall be manufactured from a compound made exclusively from neoprene or butadiene styrene rubber (GRS), reinforcing carbon black, zinc oxide, polymerization agents and softeners. This compound shall contain not less than 70 percent by volume of neoprene or GRS. Physical properties of natural or synthetic rubbers for waterstops shall be as shown in Table C below: TABLE C Physical Properties for Rubber for Waterstops Original Physical Properties: Hardness, ASTM D 676 (Durometer) Tensile Strength, Minimum MPa, ASTM D 412 Elongation at Break, Minimum percent Natural (Plain) Rubber 60 ± Synthetic (Neoprene or GRS) Rubber 55 ± Accelerated Tests to Determine Aging Characteristics (Alternate tests): (1) after 7 days in air at 70 C ± 1 C, ASTM D 573 or: (2) after 48 hours in oxygen at 70 C ± 1 C and 2 MPa pressure, ASTM D 572; Tensile Strength, % change, Maximum Maximum Elongation, % change, Maximum -- Unless otherwise shown on the plans, polyvinyl chloride (PVC) waterstop materials shall

4 conform to the Corps of Engineers Specification Number, CRD-C (b) Manufacturer's Certification. The manufacturer shall furnish certified test results, indicating compliance with this specification, for each batch or lot of waterstops furnished under this contract. (c) Manufacturing Requirements. Rubber waterstops shall be manufactured with an integral cross section which shall be uniform within plus or minus three (3) millimeters in width, and the web thickness or bulb diameter, within plus two (2) millimeters and minus three (3) millimeters. No splices will be permitted in straight strips. Strips and special connection pieces shall be well cured so that any cross section shall be dense, homogeneous and free from all porosity. All junctions in the special connection pieces shall be full-molded. Requirements for PVC waterstops shall be the same as for rubber waterstops except that splicing of PVC shall be done by heat sealing the adjacent surfaces in accordance with the manufacturer's recommendations. A thermostatically controlled electric source of heat shall be used to make all splices. The heat shall be sufficient to melt but not to char the plastic. (3) Nylon Reinforced Neoprene Sheet. Nylon reinforced neoprene sheet shall consist of weather resistant neoprene reinforced with one (1) layer of nylon fabric at mid-thickness and shall be of the thickness shown on the plans. The neoprene and neoprene sheet shall conform to the requirements shown below: Neoprene Minimum Tensile Strength, ASTM D 412 Minimum Tear Strength, ASTM D 624, Die B Minimum Elongation, ASTM D 412 Durometer Hardness, Shore A - ASTM D 2240 Change in Durometer Hardness, Shore A Heat aged C max - ASTM D 2240 Ozone - 1 ppm, 20% strain, 100 h - ASTM D 1149* 14 MPa 31, % 65 ± 5 ± 15 No Cracks Finished Sheet Thickness (2 or 3 millimeters) Breaking Strength, ASTM D 751, Grab Method, Minimum 2 mm sheet 3 mm sheet ± 10% 52,538 70,051 * Samples shall be wiped with solvent before testing to remove surface impurities. The manufacturer shall furnish the Engineer a certification indicating the actual test results obtained on the material furnished to the project. In addition, the manufacturer shall furnish representative samples of the finished sheet to the Materials and Tests Division for testing.

5 (4) Elastomeric Pads. When shown on the plans, rail posts, rail members, metal shoes or minor structural members shall be insulated, leveled, shimmed or otherwise protected by elastomeric pads, sheets or washers. Such pads may be any elastomeric material, plain, preformed fabric or laminated, having a hardness (durometer) between 70 and 100, unless otherwise shown on the plans or required by this Item. Acceptance testing will not be required. (5) Other Elastomeric Products. Other elastomeric products shall be in accordance with the requirements shown on the plans Construction Methods. (1) Elastomeric Bearings. Unless otherwise shown on the plans, concrete bearing seats shall be float finished to the required elevation. Variation from a level plane shall not exceed two (2) millimeters within the limits of the bearing. Welding in the vicinity of the bearings shall be done with care to avoid damage to the elastomer. Bearings damaged by field welding shall be replaced by the Contractor at his expense. (2) Waterstops. Field splices shall be either vulcanized; mechanical, using stainless steel parts; or made with a rubber splicing union of the same stock as the waterstop, at the option of the Contractor. All finished splices shall have a tensile strength not less than 50 percent of the unspliced material. (3) Nylon Reinforced Neoprene Sheet. Fabrication and installation of nylon reinforced neoprene sheet shall be as shown on the plans. Fabrication shall be such that there are no sharp reentrant cuts and all cuts shall be made to a circular punched hole. No splices shall be made in the material except as shown on the plans or approved by the Engineer. Any splices, approved by the Engineer, shall be made using a neoprene adhesive and reinforcing strips in accordance with the manufacturer's recommendations Measurement. Unless otherwise shown on the plans, elastomeric bearings used with prestressed (pretensioned) concrete units, elastomeric pads, waterstops and other miscellaneous elastomeric materials will not be measured for payment but will be considered subsidiary to the various pertinent bid items in the contract. Unless otherwise shown on the plans, elastomeric bearings used in conjunction with steel and post-tensioned concrete superstructures will be measured by each elastomeric bearing Payment. When this Item is specified as a pay item, the work performed and materials furnished in accordance with this Item and measured as provided under "Measurement" will be paid for at the unit price bid for "Elastomeric Bearing" of the type specified. This price shall be full compensation for all materials including anchor bolts and top plates, tools, equipment, labor, and incidentals necessary to complete the work.