The following is an excerpt from a presentation at the 1990 Indiana Department of Transportation Annual Engineers Meeting:

Title: Polyethylene Liner Pipe

What I am going to share with you today is our experiences with polyethylene liner pipe. I am going to show when we use liner pipe: how we go about selecting locations and the criteria we use. I am going to show a private contractor installation and what IN DOT Maintenance in Vincennes has done. Finally, I will show how to size the polyethylene liner pipe and give a cost analysis of open cutting and replacing with fiber bonded or bituminous coated pipe versus the polyethylene liner pipe and give a cost analysis of open cutting and replacing with fiber bonded or bituminous coated pipe versus the polyethylene liner for various sizes of pipes and heights of fill sections. Then, I will open it up for questions. We have certain criteria we try to meet when using the polyethylene liner in lieu of fiber bounded or bituminous coated.

• Scouring: If we have heavy scouring in a location we may choose to use polyethylene liner: scouring by rock will cause the coating to be wore off exposing bare metal along with scouring the metal itself.
• Acid Conditions: Southwestern Indiana has extensive mining causing acidic conditions from sulfuric acid. A study done by the division of Research and Training conducted in 1982 showed that a pH of 5 or less was extremely detrimental to metal, aluminum, and galvanized steel pipe and that a fiber bonded or equivalent pipe would be required of longevity. Polyethylene pipe is not damaged by acids. It is highly acid resistant.
• Deep Fill Sections & High Traffic Volumes: In some locations, we have fill sections under the interstate as deep as 80 feet. Excavating these areas to replace the pipe would be not only be extremely costly, but almost impractical. Also the inconvenience to the public must be considered in any replacement that would cause a closure of the roadway.
• Resurfaced Roads: Although all bad pipes on a road are to be replaced prior to resurfacing, we are not infallible. And the motoring public looks unkindly toward having the road cut anytime soon after a resurface. Therefore, this may be a good location for polyethylene liner pipe on this merit alone.
• Cost of Polyethylene liner pipe can be competitive when compared to open cutting and replacing with bituminous coated or fiber bonded which I will show you later in my presentation.

We use these five criteria in selecting possible polyethylene liner locations. However, other criteria is used before final selection is made. The existing pipe must have retained its roundness and must be fairly straight, or the polyethylene liner pipe will not slide through. Also, the pipe must be clean or have the capability of being cleaned. If the pipe is not clean, the material will collect in front of the new pipe causing it to be shoved to the top against the existing pipe and becoming stuck. You must have a working area approximately 25 feet long at inlet or outlet, so the liner pipe may be laid in a trench so it can be pushed. Although the pipe can be manufactured in length from 2 to 45 feet we try to use 20 foot sections because the matching of each male and female ends to the price. This is the additional criteria you must consider in selecting polyethylene liner locations.

After establishing this criteria, we began looking for locations for the polyethylene liner to be used on contract. We found four locations, three were on US231 approximately 2.3, 2.4, and 2.8 miles North of the Ohio River in Spencer County. The first structure was 24 inches vitrified clay pipe 111 feet long. The next structure was a set of twin 24 inch clay pipe, each 111 feet long. The last one on US231 was again a 24 inch vitrified clay pipe, 72 feet long. All of these structures were under 25 feet fill sections. The joints were separated and this is a heavily traveled road. The detour in closing the road for pipe replacement would be approximately 60 miles. The fourth structure was on I 64 at the 66 mile marker. It was 48 inch bituminous coated metal pipe, 460 feet long under a 45 foot fill section. The pipe had numerous small holes in the flowline throughout the length of the pipe (probably caused by acid conditions from a hog farm operation). The pipes were to be pushed inside existing pipe and then grouted around for the full length of the pipe. The first section of the polyethylene liner is pushed in the old pipe leaving about 5 foot of the section sticking out. A trench may need to be dug to align the sections of the pipe. The next section is then placed in the trench and lined up. A choker chain is then wrapped around both sections of the pipe and then come-alongs are hooked up on both sides of the pipe to the chains. A lubricant, such as liquid soap is used on both the male and female ends. The sections of pipe are then snapped together and that new section is pushed in. This is repeated until the pipe is fully lined. The contractor had a problem with this procedure on US231, apparently the sections of vitrified clay pipe had separated to such an extent that the polyethylene liner pipe would not readily go through. This is not a recommended practice, however, it did work and there was no damage to the pipe with the exception of some minor distortion. The contractor then formed up both ends to pour grout. A hole was cut on top of both ends of the existing pipe and a foot stand pipe with a quick couple was placed over each hole. The grout was made by a mobile mixer and pumped into the pipe. The grout is used as a filler to fill the annular space between the existing structure and the polyethylene liner pipe.

On the twin structure, we started pumping grout into one structure and the grout came out the other. Apparently there was void between the two, but the void should be filled by the grout. We realized a 20% overrun in the grout and it was suggested that we pay for grout on an actual basis instead of a theoretical basis. The contractor used a grout design that consists of:

1. 395 lbs. cement
2. 79 lb. fly ash
3. 1421 lb. dry sand
4. 229 lb. water (includes water in sand)
5. 11.9 cu. ft. preformed foam

Specifications require that the filler grout make a minimum of 150 psi at 28 days. The grout did not make the specified 150 psi and the contractor was penalized. This contract was in March, 1989 at a cost of just under $92,000.00. The estimated cost for open cutting and replacing the 48 inch pipe under the interstate only was $800,000.00. So far all polyethylene pipes are performing fine and we don't anticipate any problems for the next 50 years.

Vincennes District Maintenance thought that we may be able to use the polyethylene liner pipe for some of our maintenance replacements. So we selected some locations using the previously mentioned criteria. However, we decided to do smaller pipes only, since we do not readily have access to a track backhoe. Also we needed a new grout design since we do not have a pump and would have to gravity flow the grout. Our initial grout mix did not work well as it was found to have too much sand and the sand would settle out and pile up at the inlet causing the annular space between the liner and existing pipe to become stopped up. After a couple of changes, we came up with a grout design that would work. It consists of:

1. 300 lb. cement (type 1)
2. 1500 lb. fly ash (type C or F)
3. 156 oz super plasticizer (Rheobuild 1000) As needed for entraining admixture to obtain
4. 10% air content
5. 45 gal. water
6. 1200 lb. fine aggregate (SSD)

The grout was approximately $50.00 cu. yd. The compressive strength tested a 4000 psi. After pushing the pipe through we sealed both ends by placing a 6 inch thick duracal plug in the annular space between the liner and the existing pipe. We then proceeded to dump the grout in the upper end of the pipe through a stand pipe and watched for it to come up the stand pipe at the lower end. We also vibrated the mix with a portable vibrator to help the mix flow. The stand pipe consist of a piece of 6 inch PVC pipe. A hole, a little smaller than the diameter of the stand pipe is cut on each end of the existing pipe and duracal is poured to hold the pipe in place. They are then removed after grouting.

Vincennes District Maintenance has replaced approximately 10 pipes with polyethylene pipes in the Dale and Paoli Sub-districts since March of 1989. The local maintenance crews are very happy with this new procedure. We have replaced a polyethylene liner pipe and grouted in a 60 foot long 20 inch pipe and walked away in three hours. If we have several locations and then come back and grout all the locations at a later time. This makes for a more efficient operation and saves money on the hauling costs for grout.

The polyethylene liner pipe is sized by determining the flow of the pipe to be lined and then finding the flow of the polyethylene liner, the flow of the polyethylene should be at least equal to the flow of existing pipe.

A cost analysis comparing the cost of fiber bonded bituminous coated and the polyethylene pipe liner was done. If you look at the charts, you will see that the polyethylene liner pipe (list price) is more expensive than the bituminous coated pipe (actual cost) for all sizes. The savings come from reduced excavation cost, installation time, and inconvenience to the public. The cost comparisons indicate that liners are cost effective in many situations.

Richard Thomas
District Maintenance Field Engineer
Indiana Department of Transportation
P.O. Box 376
Vincennes, IN 47591

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