388 surface. Shotcrete shall be cured by (a) covering with burlap mats and keeping them wet for at least seven days after placing, (b) flooding for a period of at least seven days or, (c) applyin g liquid membrane curing compound, conforming to 707.9, at a minimum rate of one gallon per 150 per feet of shotcrete surface for each application. Shotcrete cured by membrane forming compound shall receive two applications; the second application shall b e made after the first application has set. Other methods of curing may be used if approved by the Engineer. After the completion of the fill over the pipe, any gaps which develop between the plates and the concrete or shotcrete paving shall be filled by pouring heated asphalt material complying with requirements of subsection 713.3. Prior to using Portland cement concrete or shotcrete for paving culverts with coatings containing aluminum, the aluminum -concrete contact area shall be coated with commercia lly- available paint.
604.10 Remove and Relay Pipe :
When specified, the Contractor shall remove, salvage, clean, safely store, and relay existing culverts. The construction requirements in this Section shall apply equally in the case of remove and relay pipe. The Contractor shall restore or replace, any pipe designated for reuse that incurs damage or destruction through faulty handling or storage. All pipes salvaged for relaying shall be cleane d of all foreign material prior to reinstallation.
604.11 Jacking Pipe :
Jacking or tunneling may be designated on the Plans or may be permitted if written approval is obtained. Culverts to be jacked shall be rei nforced concrete pipe. The strength of pipe designated in the Contract will be designated as required for vertical load only. Additional reinforcement or strength of pipe required to withstand jacking pressure shall be determined and furnished by the Con tractor without additional cost to the Division. Variation from theoretical alignment and grade at the time of completion of jacking placement shall not exceed 0.2 feet for each twenty ( 20) feet of pipe so placed. An approach trench shall be constructed on the side from which jacking operations shall take place. The end of the approach trench away from the jacking face shall be cut perpendicular to the axis of the jacking operation to provide bearing surface for the back stop and the jack blocking. The length of the approach trench shall be such that the distance between the jack blocking and the face of the bore shall be equal to five ( 5) feet plus the length of the individual pipe sections. The jacking face shall be a minimum of three ( 3) feet above t he top of the pipe; the face shall be cut vertically and shall be shored to prevent raveling and slipping. A sump shall be constructed in one corner of the trench to provide drainage. The back stop shall be constructed of heavy timbers or steel rails cap able of withstanding the jacking force. In the event the site of jacking operations is such that an approach trench cannot be constructed, the jack blocking shall be constructed to carry the reaction of the jack to the ground. This may be accomplished by means of timber, steel, or concrete vertical back stops set into the ground with the tops supported by diagonal members bearing against an embedded anchorage. Directly opposite the approach trench, an exit trench shall be constructed to line and grade. The exit trench shall be constructed in the same manner as the approach trench except that no back wall is necessary. Jacks shall be of sufficient capacity to overcome soil resistance to the jacking operation and shall be operated in pairs. As a guide, c apacity of jacks for concrete pipe shall be a minimum of 50 tons each. For large pipe, more than one pair of jacks may be required. Small track jacks may be used to start the pipe.