Testing Procedure

GENERAL

This covers methods for carrying out the following tests on reinforced concrete pipes to evaluate the properties stipulated in the relevant Indian Standards.

  1. Three-edge bearing test,
  2. Absorption test,
  3. Hydrostatic test,
  4. Permeability test, and
  5. Straightness test.

INSPECTION

The quality of all materials, process of manufacture and the finished pipes shall be subject to inspection and approval by the purchaser. If the pipe is tested for three-edge bearing or absorptions, inspection of the reinforcement shall be made on the Pipe sections used for those tests.

GENERAL PRECAUTIONS

The test specimens shall not have been exposed to a temperature below 4 o C for 24 hours immediately preceding the test and shall be free from all visible moisture. The specimens shall be inspected and any specimen with visible flaws shall be discarded.

If any test specimen fails because of mechanical reasons, such as failure of testing equipment or improper specimen preparation, it shall be discarded and anotrer specimen taken.

SELECTION OF TEST SPCIMENS

In addition to the requirements specified in this standard, the number of test specimens and the method of their selection shall be in accordance with the specification for the type of pipe being tested.

THREE-EDGE BEARING TEST

1. GENERAL

Three-edge beanng test shall be performed by the method grven in 5.2 the pipe, shall be surface dry when tested. The test specimen shall be tested in machine so designed that a crushing force may be exerted in a true vertical plane through one diameter and extending the full length of the barrel of the pipe but excluding the sockets, if any.

2. THREE-EDGE BEARING METHOD

2.1. Apparatus
2.1.1. Testing machine

Any mechanical or hand-powered device may be used in which the head that applies the load moves at such a speed as to increase the load at a uniform rate of approximately 20 percent of the expected crushing load per linear meter per minute. The loading device shall be calibrated within an accuracy of +2 percent. The testing machine used for the load tests should produce a uniform deflection throughout the full length of the pipe and shall be so substantial and rigid throughout, that the distribution of the test load along the length of the barrel of the pipe will not be appreciably affected by the deformation or yielding of any part of the machine during the application of the load.

2.1.2. Lower bearing block

The lower bearing block (see Fig. 1) shall consist of two hardwood or hard rubber strips fastened to a wooden of steel beam or direct to a concrete base, which shall provide sufficient rigidity to permit application of maximum load without appreciable deflection. Wooden or rubber strips shall be straight, have a cross-section of not less than 50 mm in width and not less than 25 mm nor more than 40 mm in height and shall have the top inside corners roundedto a radius of approximately 15 mm. The interior vettical sides of the the strips shall be parallel and spaced apart a distance of not more than 1/12 th of the specimen diameter but in no case less than 25 mm. the bearing faces of the bottom strips shall not vary from a straight line vertically or horizontally by more thanl 1mm in 375mrn of the length under load.

About 6mm thick hard rubber or felt should be placed / fixed at the lower face of the upper wooden block which shall come in contact with the surface of the pipe.

2.1.3. Upper bearing block

The upper bearing shall be a rigid hardwood block or a block with hard rubber facing at least 150 mm x 150 mm in cross-section. The wood block shall be free of knots and shall be straight and true from end to end. It shall be fastened to steel or wood faced steel beam of such dimensions that defletions under maximum load will not be appreciable. The beanng face of the upper beanng block shall not deviate from a straight line by more than 1 mm in 375 mm of length under load.

2.1.4. Application of Load

The equipment shall be so designed that the load will be distributed about the center of overall length of the pipe. The load may be applied either at a single point or at multiple points dependent on the length of the pipe being tested and the rigidity of the test frame.

NOTE - Multiple points of load applicable to the top bearing will permit use of lighter beams without appreciable deflection.

2.1.5. Crack measuring gauge

The crack measuring gauge shall be made from 0.25 mm thick strip and shall be of a shape.

2.2. Procedure
2.2.1. Preparation of Specimen

The specimen shall be placed on the two bottom bearing strips in such a manner that the pipe test firmly and with the most uniform possible bearing on each strip for the full length of the pipes less the socket portion, if any.

If mutually agreed upon by the manufacturer and the purchaser prior to the test, a fillet of plaster of paris not exceeding 25 mm in thickness may be cast on the surface of the upper and lower bearing before the pipe is placed. The width of the fillet cap, top or bottom, shall be not more than 25 mm per 300 mm diameter, but in no case less than 25 mm.

2.2.2. Placement & Load on Specimen

Each end of the pipe at a point mid-way between the lower bearing strips shall be marked and then diametrically opposite points thereof shall be established. The top bearing block shall be so placed that it contacts the two ends of the pipe at this marks. After placing the specimen in the machine on the bottom strips, the top beatring shall be symmetrically aligned in the testing machine. Load shall be applied at the rate indicated in 2.1.1 until either the formation of a 0.25 mm wide crack or ultimate strength load, as may be specified, has been reached. If both the 0.25 mm crack and ultimate load are required, the specified rate of loading need not be maintained after the load at 0.25 mm crack has been determined.

2.2.3. Observation during Loading

The O.25 mm crack load is the maximum load applied to the pipe before a crack having a width of 0.25 mm measured at close intervals occurs throughout a length of, 300 mm or more. The crack shall be considered 0.25 mm in width when the Point of the measuring gauge described in 2.1.5 penetrates 1.5 mm at close intervals throughout the specified distance of 300 mm. The ultimate load will be reached when tre pipe will sustain no greater load.

2.3. Calculation

The crushing strength in Newton per linear metre of pipe shall be calculated by dividing the total load on the specimen by the nominal laying length. Effective length of the pipe shall be taken as the nominal laying length of the specimen. In case of spigot and socket ended pipes, the effective length shall be equal to the overall length minus the depth of socket and in case of collar and flush jointed pipes, the effective length shall be equal to the overall length.

NOTE - In most machines the total load will include the dead weight of the top bearing plus the load applied by the loading apparatus.

ABSORPTION TEST

1. Test Specimen

Each specimen selected at random shall have a square area of 100cm 2 + 10 % of the length of the pipe as measured on surface or the pipe, and a thickness equal to the full depth of the pipe thickness and shall be free from visible cracks.

2. Procedure

2.1 Drying Specimens

Specimens shall be dried in a mechanical convection oven at a temperature of 105oC to 115oC until two successive weightings at intervals of not less than 8 h show an increment of loss not greater than 0.1 percent of the mass of the specimen. The drying time shall be not less than 36h. The dry mass of the specimen shall be the mass after the firial drying determined at ambient temperature.

2.2 After drying and weighting

as specified in 2.1, the specimens shall be immersed in clean water at room temperature for the specified period. The specimens shall then be removed from the water and allowed to drain for not more than one minute. The superficial water shall then be removed by absorbent cloth or paper and the specimens weighed immediately.

2.3 The least count/accuracy

of the weighing balance shall be 0.1 g which the test specimen shall be weighed.

2.4 Calculation and Report

The increase in mass of the specimen over its dry mass shall be taken as the absorption of the specimen and shall be expressed as a percentage of the dry mass. The results shall be reported separately for each specimen.

HYDROSTATIC TEST

1. Test Specimen

The specimens for determination of leakage under internal hydrostatic pressure shall be sound and full-size pipe. If the pipes are tested after storing in adverse weather condition, presoaking shall be permitted. For presoaking pipes shall be submerged in water or sprayed with water for a period not less than 6 hours prior to testing and excess water removed.

2. Procedure

2.1 The pipe shall be supported in such a way so that the longitudinal axis is approximately horizontal and the exterior surface excepting the supports can be examined readily.

2.2 The equipment for making the test shall be such that the specimen under test can be filled with water to the exclusion of air and subjected to the required hydrostatic pressure. Apply hydrostatic pressure to the whole pipe including the portion of socket and rebated joints, which is, subjected to pressure in the 'as laid' condition.

2.3 The specimen shall be filled with water and the air expelled. Pressure shall be applied at gradual rate until the specified test pressure is reached, or beads of water on the pipe surface is seen, whichever occurs first.

2.4 Pressure shall be maintained for 1 min + 30 s for each 10 mm of wall thickness, or for twice that entire period if the application of pressure resulted in the formation of beads of water on the pipe surface.

2.5 At the end of the holding period, the pressure shall be released immediately if the test pressure has been maintained. If the beads of· thewater have not grown or run the pressure shall be increased slowly until the test pressure is reached or the beads of water grow or run (whichever occurs first).

2.6 If the test pressure has been reached without the beads of water growing or running, the test pressure shall be maintained constant for 1 min + 30s for each 10 mm of wall thickness. At the end of the holding period the pressure shall be released imrhediately.

fter releasing the pressure, the test pipe shall be drained completely.

PERMEABILITY TEST

1. Priestessesd Concrete pipe

1.1 Procedure

The dry surface of the pipe shall be scrapped by wire brush and loose particles, if any, removed. Sealant shall then be applied to the lower portion of the cup ahd shall be pressed on the pipe. The water shall then be filled in the cup with wash bottle after hardening of the sealant. The glass tube with cork shall then be fixed in the cup as shown in FIg.4. Water in the tube shall then be filled using wash bottle and air shall be allowed to escape during filling. Precaution shall be taken so that water does not leak either from cup ends or from rubber stopper. Water shall be filled up to zero mark and reading taken at every half- hour interval up to 2 hours. On each pipe, simultaneously three tests shall be done immediately after curing of coating is completed.

1.2 Initial Absorption

The drop of water level in the stand pipe at the end of 2 h is initial absorption. The difference in any two readings shall not be more than 0.8 cm 3 .

1.3 Final Permeability

Fill the water in the stand pipe again up to the mark and take readings at half- hour interval up to 4 hours. Absorption in the fourth hour, that is, difference between fourth and third reading is the final permeability. The average reading of three teats conducted on a pipe shall be expressed in cm 3 and this shall not exceed 0.3 cm 3 .

STRAIGHTNESS TEST

1. Procedure

1.1 A rigid straight edge, made into a gauge of the form and dimension shown in Fig. 5 shall be placed in the bore or the pipe with edge x in contact with the pipe Internal surface and/or the line parallel to the pipe axis. Hold the plane of the gauge in radial plane.

1.2 If both ends of the gauge, when so placed are in contact with the internal surface of the pipe, the deviation from straightness is excessive. If this condition occurs at anyone of four different positions of the gauge, approximately equally spaced around the pipe circumference the pipe does not comply with the particular requirement.

1.3 If both ends of the gauge, when used as described in 1.1 are not in contact with the internal surface of the pipe at both ends, the gauge shall be reversed so that edge Y, placed as in 1.1 is adjusted to the internal surface of the pipe. If the two studs in edge Y cannot be made to touch the surface of the pipe simultaneously, the deviation from the straightness is excessive.

If this condition occurs at any four position of the gauge the pipe does not conform to these particular requirements.