February 7, 1973 washing with water. Such fillings shall be kept moist under wet burlap for at least 48 hours or steam cured as required in Subparagraph e. (4) (a) for a minimum of 12 hours. All other repairs shall be made in accordance with the procedures of Chapter VII of the Sixth Edition of the Bureau of Reclamation Concrete Manual. o. Hauling and handling.-Pipe shall not be stored in the manufacturer's yard or at the jobsite for an extended period of time under conditions which would cause injurious drying out of the concrete. Whenever necessary, in order to prevent cracking of the concrete or other objectionable effect of drying, of drying, stored pipe shall be adequately protected by means of shelter and application of water. The pipe shall not be dropped or subjected to any unnecessary jar, impact, or other treatment that might crack the shell or otherwise damage the pipe. No pipe shall be hauled to the site of the work until it has attained the strength after full curing specified in Subparagraph e. (4) unless otherwise approved by the contracting ferent from repair of structural concrete, is discussed separately for convenient reference to detail procedures for such work. If followed closely, these procedures will result in substantial repairs, and pipe not repaired in accordance with these procedures should not be accepted. Most imperfections in and damage to precast concrete pipe, such as inadvertent or occasional imperfections or damage that occurs during normal operations, can be repaired and the pipe made acceptable. But repairs should not be permitted when the imperfections or damage are the result of continuing failure to take known corrective action to eliminate the cause of the imperfections or damage. Imperfections and damage that can normally be repaired are: (1) Rock pockets. (2) Exposed steel on the outside of any size pipe and on the inside. of pipe 36 inches or larger in diameter. (3) Roughness due to form-joint leakage. (4) Broken bells containing circumferential reinforcement. (5) Impact damage over less than 45° of circumference except for spigots. (6) Fractures or cracks passing through the shell. (7) Out-of-round bells, if not so far out of round that reinforcement steel will be exposed after the repair. (8) Spalled shoulders on spigots for support of rubber gaskets. (9) Air holes and roughness in the gasket bearing surfaces of bells and spigots. Imperfections and damage that cannot normally be repaired are: (1) Spigots or bells that are out of round or are off center to the extent that reinforcement would be exposed after the repair. (2) Spun pipe out of limits for diameter because of an excess or deficiency of concrete having been placed in the form. (3) Porous, unconsolidated spigots in dry-tamped pipe. (4) Exposed steel inside of pipe smaller than 36 inches in diameter. Repairs should not be permitted on pipe damaged by impact when the damaged area covers more than 45° of the pipe circumference. Also, repairs should not be permitted on gasketed spigots if the break is entirely through the shell and into or beyond the area of gasket bearing and extends more than 4 inches around the circumference under the gasket. Pipe that is imperfect or damaged beyond repair on one end can frequently be cut and the good end used at structure connections. (b) Methods of Repair.-Repair of imperfections in or damage to precast concrete pipe may be made. with hand-placed mortar, pneumatically applied mortar, or concrete, depending upon the severity and location of the imperfection. Before preparations are started for the repair of any pipe, except very minor repairs, the method of repair should be approved by a Government inspector. Hand-placed mortar should be used only for making superficial repairs on the outside of pipe, or for making minor repairs on the inside of pipe that is too small to permit application of pneumatically applied mortar (usually pipe smaller than 36 inches in diameter). Pneumatically applied mortar should be used for the repair of all other shallow surface imperfections, such as to cover exposed reinforcement steel on the outside of any size pipe and on the interior of pipe 36 inches or more in diameter, and to build up spalled shoulders on spigots for support of rubber gaskets. Pneu matically applied mortar should not be used where more than one-half square foot of the area to be repaired extends back of reinforcement steel. Preshrunk concrete should be used for the repair of all other imperfections including area where more than one-half square foot of the area extends back of reinforcement steel. (c) Preparation of Imperfections for Repair.-All visibly unsound or imperfect concrete should be removed before any type of replacement is made. Where pneumatically applied mortar is to be used for the replacement, unsound materials should be removed to any shape with beveled edges that will not entrap rebound. Where hand-applied mortar is to be used for the replacement, the area requiring repair should be chipped to a depth of not less than three-fourths of an inch; the edges of the area should be sharp and squared with the surface, leaving no featheredges. Where concrete February 7, 1973 is to be used for the replacement, the old concrete should be removed to a depth of at least 1 inch back of the first layer of reinforcement steel, even though this involves removal of good concrete. The edges should be sharp and squared with the surface, leaving no featheredges. Keys are not necessary. As soon as the chipping is completed and the area is acceptably shaped for the selected repair method, the surface of old concrete should be given a preliminary washing to remove all loose material and stone dust. Surfaces within the trimmed holes should be kept wet for several hours, preferably overnight, before the repair replacement is made. This is best done by packing the holes or covering the area with several layers of wet burlap as shown in figures 144, 145, and 146. Immediately before new material is applied, all surfaces of the trimmed holes or areas to be filled should be thoroughly cleaned with wet sandblasting, followed by washing with an air-water jet to remove all foreign material, dried grout, and any material crushed and embedded in the surfaces by chisels or other tools during trimming. Some equipment for placing pneumatically applied mortar is effective for wet sandblasting. Other devices such as the air-suction gun shown in figure 105 may be used if they will produce acceptable results. Surfaces to which the replacement is to bond should be damp but not wet when new material is applied. The prepared surfaces should be inspected before the repair is made. (d) Hand-Placed Mortar Replacement.-For the application of hand-placed mortar, the pipe should be turned so that the area to be repaired will be upward and the new material will rest on concrete of the pipe. The mortar used for the replacement should have the same proportions and air entrainment as the mortar used in the mix of which the pipe was made. The repair mortar should be preshrunk by mixing it to a plastic consistency as long in advance of its use as the cement will permit. Depending on mix, cement, and temperature, the time for preshrinking should range from 1 to 2 hours. Trial mixes should be made and aged to determine the longest period of delay that the mortar, after reworking, will have sufficient plasticity to permit application. The mortar should be stiff as possible and yet permit good workmanship. It is not intended or expected that this relalatively stiff, preshrunk mortar should be applied as readily as ordinary plaster. Immediately prior to application of mortar, the damp surface to which the new mortar is to bond should be scrubbed thoroughly with a small quantity of mortar, using a wire brush. Remaining loose sand particles should be swept away immediately before application of the mortar. The mortar should be compacted into the surface, taking care to secure tight filling around the edges, and shaped and finished to correspond with the undamaged surface of the pipe. (e) Pneumatically Applied Mortar Replacement.-For pneumatic application of mortar, the pipe should be turned so that the area requiring repair is in a near vertical position so that rebound will fall free and will not be included in the replacement. When pneumatically applied mortar is used to cover exposed steel on the outside surface of a pipe, the coating should be at least three-fourths of an inch thick. A similar coating on the inside surface should be between one-half and three-fourths of an inch thick. The mortar coating should extend 1 foot in each direction beyond the limits of the exposed steel. Pneumatically applied mortar on the outside surface of a pipe should not be finished other than to sweep off any rebound that would interfere with a good membrane coat of white-pigmented sealing compound. After repair of pipe interior, bells, and spigots by means of pneumatically applied mortar, the surfaces should be trimmed to correct shape, care being taken to avoid damage to hond. Interior surfaces should be finished only by rubbing lightly with a damp rag. Bell-and-spigot surfaces should be tooled and finished to conform to requirements for the joint. Standard commercial equipment of a small size commensurate with the small areas to be treated is available from several manufacturers. Also, the equipment shown in figure 105 is adaptable for such work. (f) Concrete Replacement.-For replacement repairs made with concrete, the pipe should be turned so that the area where concrete is to be placed will be on the top of the pipe for an outside repair or on the bottom of the pipe for an inside repair. The pipe should be in the latter position for repair of holes completely through the pipe shell, with the pipe lying in a segment of an outside form. Concrete replacement repairs to bells and spigots should be cast with the pipe in a vertical position with the area to be repaired at the top end of the pipe. Proportions of concrete used for replacement should be the same as used in the original concrete, including the size and amount of sand and gravel and the amount of cement and air-entraining agent. The slump of the concrete as mixed should be between 2 and 3 inches, but the concrete should not be placed until the slump has dropped to zero. The delay for preshrinking concrete should be as long as the concrete will still respond to vibration and a running vibrator will sink into the concrete of its own weight. Such preshrunk, stiff concrete can be molded by ample vibration into an open. unformed horizontal area with little difficulty and will be much less subjeet to shrinkage than ordinary concrete. Immediately prior to placing preshrunk concrete, the prewetted, clean, damp surfaces of old concrete to which the new work is to be bonded should be coated with a thin layer of plastic mortar similar in February 12, 1973 mix to that in the concrete. The mortar should be worked thoroughly into the old concrete surface by means of shooting with one of the air guns, by brushing, or by rubbing with the hand encased in a rubber glove. (g) Curing of Repairs.-New repairs should be covered with 4-ply wet burlap as soon as the burlap can be applied without damage to the surface. The wet burlap should be held in position with boards or forms, as shown in figure 146. leakage at 50-foot head other than sweating, the pipe may be accepted for heads of less than 50 feet. Repairs should be aged for at least 1 month after the specified water curing, then inspected to determine the adequacy of bond before the pipe is tested. BISH CONTRACTING COMPANY, INC. IBCA-951-1-72 Decided February 12, 1973 Contract No. 14-10-7-971-254 Repairs at joints should be cured for 7 days under continually wet burlap in close contact with the repaired surface. On other repairs, Walks, Business Center, South Rim, the wet burlap may be removed at the end of the first 24 hours and the surface coated with membrane coating of an approved white-pigmented sealing compound. If the surface of the repair is not moist when the burlap is removed, moist curing should be continued for an additional 24 hours before the sealing compound is applied. (h) Testing Repaired Pipe.Each pipe on which major repairs have been made, such as repairs extending through the shell thickness or large repairs to bells, should be tested at the service head in order to assure that the repair is competent. Occasional pipe having lesser repairs capable of affecting performance of the pipe if the repairs are not sound should be tested to assure the security of such typical lesser repairs. Representative units of cracked but unshattered pipe should be tested and, if there is no 497-456-73-11 Construction of Roads, Parking and Grand Canyon National Park, Arizona, National Park Service. Denied. Contracts: Construction and Operation: Modification of Contracts-Contracts: Disputes and Remedies: Burden of Proof-Rules of Practice: Appeals: Burden of Proof A construction contractor's claim for an equitable adjustment is denied where the evidence shows that payment for the overlay work involved in repairing eroded pavement was provided for in an accepted change order and the appellant failed to sustain its burden of showing that the straitened financial circumstances in which the contractor was in at the time of the change order was the result of wrongful action by the contracting officer or other Government personnel administering the contract |