Laserfiche WebLink
mechanical spraying equipment, in the opinion of the Engineer, will be permitted. When the ambient air temperature is <br /> above 15°C, the Contractor shall fog the surface of the concrete with a fine spray of water as specified in Section 90-7.O1A, <br /> "Water Method." The surface of the pavement shall be kept moist between the hours of 10:00 a.m.and 4:30 p.m. on the day <br /> the concrete is placed. However, the fogging done after the curing compound has been applied shall not begin until the <br /> compound has set sufficiently,to prevent displacement. Fogging shall be discontinued if ordered in writing by the Engineer. <br /> 90-7.03 CURING STRUCTURES <br /> • Newly placed concrete for cast-in-place structures, other than highway bridge decks, shall be cured by the water <br /> method, the forms-in-place method, or, as permitted herein, by the curing compound method, in conformance with the <br /> provisions in Section 90-7.01, "Methods of Curing." <br /> • The curing compound method using a pigmented curing compound may be used on concrete surfaces of <br /> construction joints, surfaces that are to be buried underground, and surfaces where only ordinary surface finish is to be <br /> applied and on which a uniform color is not required and that will not be visible from a public traveled way. If the <br /> Contractor elects to use the curing compound method on the bottom slab of box girder spans,the curing compound shall be <br /> curing compound(1). <br /> • The top surface of highway bridge decks shall be cured by both the curing compound method and the water method. <br /> The curing compound shall be curing compound(1). <br /> • Concrete surfaces of minor structures,as defined in Section 51-1.02, "Minor Structures," shall be cured by the water <br /> method,the forms-in-place method or the curing compound method. <br /> • When deemed necessary by the Engineer during periods of hot weather,water shall be applied to concrete surfaces <br /> being cured by the curing compound method or by the forms-in-place method, until the Engineer determines that a cooling <br /> effect is no longer required. Application of water for this purpose will be paid for as extra work as provided in <br /> Section 4-1.03D,"Extra Work:." <br /> 90-7.04 CURING PRECAST CONCRETE MEMBERS <br /> • Precast concrete members shall be cured in conformance with any of the methods specified in Section 90-7.01, <br /> "Methods of Curing." Curing shall be provided for the minimum time specified for each method or until the concrete reaches <br /> its design strength,whichever is less. Steam curing may also be used for precast members and shall conform to the following <br /> provisions: <br /> A. After placement of the concrete, members shall be held for a minimum 4-hour presteaming period. If the ambient <br /> air temperature is below 10°C, steam shall be applied during the presteaming period to hold the air surrounding the <br /> member at a temperature between 10°C and 32°C. <br /> B. To prevent moisture loss on exposed surfaces during the presteaming period, members shall be covered as soon as <br /> possible after casting or the exposed surfaces shall be kept wet by fog spray or wet blankets. <br /> C. Enclosures for steam curing shall allow free circulation of steam about the member and shall be constructed to <br /> contain the live steam with a minimum moisture loss. The use of tarpaulins or similar flexible covers will be <br /> permitted, provided they are kept in good repair and secured in such a manner as to prevent the loss of steam and <br /> moisture. <br /> D. Steam at the jets shall be at low pressure and in a saturated condition. Steam jets shall not impinge directly on the <br /> concrete, test cylinders, or forms. During application of the steam, the temperature rise within the enclosure shall <br /> not exceed 22°C per hour. The curing temperature throughout the enclosure shall not exceed 65°C and shall be <br /> maintained at a constant level for a sufficient time necessary to develop the required transfer strength. Control <br /> cylinders shall be covered to prevent moisture loss and shall be placed in a location where temperature is <br /> representative of the average temperature of the enclosure. <br /> E. Temperature recording devices that will provide an accurate, continuous, permanent record of the curing <br /> temperature shall be provided. A minimum of one temperature recording device per 60 in of continuous bed length <br /> will be required for checking temperature. <br /> F. Members in pretension beds shall be detensioned immediately after the termination of steam curing while the <br /> concrete and forms are still warm, or the temperature under the enclosure shall be maintained above 15°C until the <br /> stress is transferred to the concrete. <br /> G. Curing of precast concrete will be considered completed after termination of the steam curing cycle. <br /> 90-7.05 CURING PRECAST PRESTRESSED CONCRETE PILES <br /> • Newly placed concrete for precast prestressed concrete piles shall be cured in conformance with the provisions in <br /> Section 90-7.04, "Curing Precast Concrete Members,"except that piles in a corrosive environment shall be cured as follows: <br /> Contract No. 10-OM7104 <br /> 87 <br />