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February 7, 1973 washing with water. Such fillings ferent from repair of structural conshall be kept moist under wet burlap crete, is discussed separately for for at least 48 hours or steam cured convenient reference to detail proceas required in Subparagraph e.(4) dures for such work. If followed (a) for a minimum of 12 hours. All closely, these procedures will result other repairs shall be made in ac- in substantial repairs, and pipe not cordance with the procedures of repaired in accordance with these Chapter VII of the Sixth Edition of procedures should not be accepted. the Bureau of Reclamation Concrete

Most imperfections in and damManual.

age to precast concrete pipe, such

as inadvertent or occasional imper0. Hauling and handling.–Pipe fections or damage that occurs durshall not be stored in the manufac- ing normal operations, can be turer's yard or at the jobsite for an repaired and the pipe made acceptextended period of time under con- able. But repairs should not be perditions which would cause injurious mitted when the imperfections or drying out of the concrete. When- damage are the result of continuing erer necessary, in order to prevent failure to take known corrective cracking of the concrete or other action to eliminate the cause of the objectionable effect of drying, imperfections or damage. Imperstored pipe shall be adequately pro- fections and damage that can nortected by means of shelter and ap- mally be repaired are: plication of water. The pipe shall (1) Rock pockets. not be dropped or subjected to any (2) Exposed steel on the outside unnecessary jar, impact, or other of any size pipe and on the inside treatment that might crack the shell

of pipe 36 inches or larger in diamor otherwise damage the pipe. No eter. pipe shall be hauled to the site of

(3) Roughness due to form-joint the work until it has attained the

leakage. strength after full curing specified

(4) Broken bells containing cirin Subparagraph e.(4) unless other

cumferential reinforcement. wise approved by the contracting

(5) Impact damage over less officer.

than 45° of circumference except

for spigots. APPENDIX B

(6) Fractures or cracks passing

through the shell. Chapter VII, Section 137 Bureau of Reclamation, Concrete (7) Out-of-round bells, if not so

Manual, Sixth Edition far out of round that reinforcement 137. Procedure for Repair of

steel will be exposed after the rePrecast Concrete Pipe.-(a) Gen

pair. eral.—Repair of precast concrete (8) Spalled shoulders on spigots pipe, although not basically dif- for support of rubber gaskets.

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(9) Air holes and roughness in Hand-placed mortar should be the gasket bearing surfaces of bells used only for making superficial reand spigots.

pairs on the outside of pipe, or for Imperfections and damage that making minor repairs on the inside cannot normally be repaired are: of pipe that is too small to permit

(1) Spigots or bells that are out application of pneumatically apof round or are off center to the ex- plied mortar (usually pipe smaller tent that reinforcement would be ex- than 36 inches in diameter). Pneuposed after the repair.

matically applied mortar should be (2) Spun pipe out of limits for used for the repair of all other shaldiameter because of an excess or

low surface imperfections, such as deficiency of concrete having been

to cover exposed reinforcement steel placed in the form.

on the outside of any size pipe and

on the interior of pipe 36 inches or (3) Porous, unconsolidated spig. ots in dry-tamped pipe.

more in diameter, and to build up (4) Exposed steel inside of pipe support of rubber gaskets. Pneu

spalled shoulders on spigots for smaller than 36 inches in diameter.

matically applied mortar should not Repairs should not be permitted be used where more than one-half on pipe damaged by impact when

square foot of the area to be rethe damaged area covers more than

paired extends back of reinforce45° of the pipe circumference. Also,

ment steel. Preshrunk concrete repairs should not be permitted on

should be used for the repair of all gasketed spigots if the break is en

other imperfections including area tirely through the shell and into or

where more than one-half square beyond the area of gasket bearing foot of the area extends back of reand extends more than 4 inches

inforcement steel. around the circumference under the

(c) Preparation of Imperfections gasket. Pipe that is imperfect or

for Repair.-All visibly unsound or damaged beyond repair on one end imperfect concrete should be recan frequently be cut and the good moved before any type of replaceend used at structure connections.

ment is made. Where pneumatically (b) Methods of Repair.—Repair applied mortar is to be used for the of imperfections in or damage to replacement, unsound materials precast concrete pipe may be made should be removed to any shape with with hand-placed mortar, pneu- beveled edges that will not entrap matically applied mortar, or con- rebound. Where hand-applied morcrete, depending upon the severity tar is to be used for the replaceand location of the imperfection. ment, the area requiring repair Before preparations are started for should be chipped to a depth of not the repair of any pipe, except very less than three-fourths of an inch; minor repairs, the method of repair the edges of the area should be sharp should be approved by a Govern- and squared with the surface, leavment inspector.

ing no featheredges. Where concrete

February 7, 1973 is to be used for the replacement. The prepared surfaces should be inthe old concrete should be removed spected before the repair is made. to a depth of at least 1 inch back of (d) Hand-Placed Mortar Rethe first layer of reinforcement placement.--For the application of steel, even though this involves re- hand-placed mortar, the pipe moral of good concrete. The edges should be turned so that the area should be sharp and squared with to be repaired will be upward and the surface, leaving no feather- the new material will rest on conedges. Keys are not necessary. crete of the pipe. The mortar used As soon as the chipping is com

for the replacement should have the pleted and the area is acceptably same proportions and air entrainshaped for the selected repair meth

ment as the mortar used in the mix od, the surface of old concrete

of which the pipe was made. The reshould be given a preliminary pair mortar should be preshrunk washing to remove all loose material by mixing it to a plastic consistency and stone dust. Surfaces within the as long in advance of its use as the trimmed holes should be kept wet

cement will permit. Depending on for several hours, preferably over

mix, cement, and temperature, the night, before the repair replace- time for preshrinking should range ment is made. This is best done by

from 1 to 2 hours. Trial mixes packing the holes or covering the

should be made and aged to deterarea with several layers of wet bur

mine the longest period of delay lap as shown in figures 144, 145,

that the mortar, after reworkand 146. Immediately before new

ing, will have sufficient plasticity to material is applied, all surfaces of permit application. The mortar the trimmed holes or areas to be

should be stiff as possible and yet filled should be thoroughly cleaned

permit good workmanship. It is not with wet sandblasting, followed by

intended or expected that this relawashing with an air-water jet to latively stiff, preshrunk mortar

should be applied as readily as orremove all foreign material, dried

dinary plaster. grout, and any material crushed

Immediately prior to application and embedded in the surfaces by

of mortar, the damp surface to chisels or other tools during trim

which the new mortar is to bond ming. Some equipment for placing should be serubbed thoroughly with pneumatically applied mortar is ef

a small quantity of mortar, using a fective for wet sandblasting. Other

wire brush. Remaining loose sand devices such as the air-suction gun particles should be swept away imshown in figure 105 may be used if mediately before application of the they will produce acceptable results. mortar. The mortar should be comSurfaces to which the replacement pacted into the surface, taking care is to bond should be damp but not to secure tight filling around the wet when new material is applied. edges, and shaped and finished to correspond with the undamaged (f) Concrete Replacement.–For surface of the pipe.

replacement repairs made with con(e) Pneumatically Applied Mor- crete, the pipe should be turned so tar Replacement. For pneumatic that the area where concrete is to be

application of mortar, the pipe placed will be on the top of the pipe should be turned so that the area for an outside repair or on the botrequiring repair is in a near vertical tom of the pipe for an inside repair. position so that rebound will fall The pipe should be in the latter pofree and will not be included in the sition for repair of holes completely replacement. When pneumatically through the pipe shell, with the applied mortar is used to cover ex- pipe lying in a segment of an outposed steel on the outside surface of side form. Concrete replacement rea pipe, the coating should be at least pairs to bells and spigots should be

, three-fourths of an inch thick. A cast with the pipe in a vertical posisimilar coating on the inside sur- tion with the area to be repaired face should be between one-half and at the top end of the pipe. three-fourths of an inch thick. The Proportions of concrete used for mortar coating should extend 1 foot replacement should be the same as in each direction beyond the limits used in the original concrete, inof the exposed steel.

cluding the size and amount of sand Pneumatically applied mortar on and gravel and the amount of cethe outside surface of a pipe should ment and air-entraining agent. The not be finished other than to sweep slump of the concrete as mixed off

' any rebound that would inter- should be between 2 and 3 inches, fere with a good membrane coat of but the concrete should not be placed white-pigmented sealing compound. imtil the slump has dropped to zero. After repair of pipe interior, bells. The delay for preshrinking concrete

, and spigots by means of pneumati- should be as long as the concrete will cally applied mortar, the surfaces still respond to vibration and a run

a should be trimmed to correct shape, ning vibrator will sink into the concare being taken to avoid damage to crete of its own weight. Such prehond. Interior surfaces should be shrunk, stiff concrete can be molded finished only by rubbing lightly by ample vibration into an open, with a damp raz. Bell-and-spigot informed horizontal area with little surfaces should be tooled and fin- clilliculty and will be much less subished to conform to requirements ject to shrinkage than ordinary for the joint.

concrete. Standard commercial equipment Immediately prior to placing preof a small size commensurate with shrunk concrete, the prewetted, the small areas to be treated is avail- clean, damp surfaces of old conable from several manufacturers. crete to which the new work is to be Also, the equipment shown in figure bonded should be coated with a thin 105 is adaptable for such work. layer of plastic mortar similar in

February 12, 1973

mix to that in the concrete. The mor- leakage at 50-foot head other than tar should be worked thoroughly sweating, the pipe may be accepted into the old concrete surface by for heads of less than 50 feet. Remeans of shooting with one of the pairs should be aged for at least 1 air guns, by brushing, or by rubbing month after the specified water curwith the hand encased in a rubber ing, then inspected to determine the glove.

adequacy of bond before the pipe is (g) Curing of Repairs.--New re- tested. pairs should be covered with 4-ply wet burlap as soon as the burlap can

BISH CONTRACTING COMPANY, be applied without damage to the

INC. surface. The wet burlap should be held in position with boards or IBCA-951-1-72 forms, as shown in figure 146.

Decided February 12, 1973 Repairs at joints should be cured for 7 days under continually wet

Contract No. 14-10-7-971-254 burlap in close contact with the re

Construction of Roads, Parking and paired surface. On other repairs, Walks, Business Center, South Rim, the wet burlap may be removed at

Grand Canyon National Park, Arizona, the end of the first 24 hours and the

National Park Service. surface coated with membrane coating of an approved white-pig- Denied. mented sealing compound. If the surface of the repair is not moist

Contracts: Construction and Operation: when the burlap is removed, moist

Modification of Contracts-Contracts: curing should be continued for an

Disputes and Remedies: Burden of additional 24 hours before the seal

Proof-Rules of Practice: Appeals: ing compound is applied.

Burden of Proof (h) Testing Repaired Pipe.- A construction contractor's claim Each pipe on which major repairs for an equitable adjustment is dehave been made, such as repairs ex- nied where the evidence shows that tending through the shell thickness payment for the overlay work inor large repairs to bells, should be volved in repairing eroded pavetested at the service head in order ment was provided for in an acto assure that the repair is compe- cepted change order and the appeltent. Occasional pipe having lesser lant failed to sustain its burden of repairs capable of affecting per- showing that the straitened finanformance of the pipe if the repairs cial circumstances in which the conare not sound should be tested to tractor was in at the time of the assure the security of such typical change order was the result of lesser repairs. Representative units wrongful action by the contracting of cracked but unshattered pipe officer or other Government personshould be tested and, if there is no nel administering the contract

497-456-73-11

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