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Poly-Triplex® Liner System Product Descriptions |
| Evaluation and Comparison of Manhole Rehabilitation Products by Ronald A. McNeil, President and Founder of Poly-Triplex® Technologies (a SunCoast Environmental International, Inc. Company) |
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| Are manhole rehabilitation products equal? Is there a way to bid them in comparative ways? How important is the low bid product to the utility?
Does it make sense to compare the cost of maintaining a structure with each product over the next 25-50 years? Are manufacturers' product
specifications written to sell abundant quantities of product, or to actually solve rehabilitation problems?
The answers to the questions may be about as varied as the opinions of the people calling the shots. The manufacturer has one perspective, the engineer another, and the utility still another - and what happens? The consumer foots the bill through the years for whatever decisions were made. As a practical environmentalist trying for many years to solve problems in a lasting yet cost effective manner, I have my own observations and conclusions. No, products are not even remotely equal in the manhole rehabilitation market. Yes, there is a fair way to bid them comparatively through request for proposal style bidding with products bid as "alternatives" rather than "equal" and bid in schedules, thus allowing the bid winner to be selected on overall value rather than lowest price. Yes, it makes sense to compare long-term costs - low bids should be of little value compared to long-term values of time and money spent to keep the problems solved. If there are no requirements to assure that rehabilitation work will have an excellent probability of lasting 25-50 years, there should be a reasonable explanation of why a temporary fix is justified. Yes, because of the great proportion of rehabilitation failures, it certainly appears that specifications marketed by manufacturers are often written to sell their materials. The focus must be on an application process for those products that will provide permanent rehabilitation. One has to wonder - if some existing companies were to develop a quality system, would they admit that the products they have formerly applied do not actually work satisfactorily over time? It's one thing to make a product pass a final inspection of the project; it's quite another for the product to perform effectively for decades under varying environmental factors such as severe weather, traffic, sewer gas, and hydrostatic head pressure. Utility districts, municipalities, and environmental engineers must step forward and insist on "value engineering" to provide permanent solutions to problems. Sewage collection systems have already had too much inadequate planning and product failure problems caused by lack of technology, lack of awareness, and the drive for corporate profits. It is time to get our utility infrastructure ready to meet the needs of the next century. Requests for Proposals should be written for annual and renewable contracts for manhole and pump station rehabilitation and should allow for schedules A, B, and C. Each schedule should contain varying degrees of rehabilitation requirements. For example: Schedule "A" should be methods of serious structural rehabilitation for high infiltration and/or gas deteriorated structures. Schedule "B" should be for rehabilitation methods where less serious problems exist because of infiltration or gas deterioration, but where rehab is definitely needed. Schedule "C" should be primarily for preventive maintenance and minor rehabilitation requirements. This will allow the utility to analyze each structure and determine which schedule of rehabilitation to use to adequately solve the problem with the most economical method that will last for a satisfactory number of years. Schedule "A" products receiving consideration should be chosen from the following: (1) Pre-formed fiberglass inserts that are lowered into place after removing the chimney and corbel of the manhole and then back filled with concrete; (2) Poured-in-place concrete rehab using inside-the-manhole forming with synthetic liners inserted to provide a gas resistant interior surface; and (3) Cured-in-place fiberglass inserts (Poly-Triplex Liner System, PTLS-6800 series) molded into place with a non-porous membrane bonded between the layers of structural fiberglass, forming a permanent barrier to stop future infiltration or gas deterioration to the existing structure. Schedule "B" products receiving consideration should be chosen from the following: (1) Calcium aluminate concrete mixed with ½ lb. of synthetic reinforcing fibers per cubic ft. of material applied one inch thick, plus a top coat of epoxy 120 mils thick applied after the concrete properly cures; (2) Polyurethane coating applied in layers thick enough to offset the possible hydrostatic head of future infiltration - ¼ inch thick for the first five feet, and an increase of ¼ inch in thickness for each five feet of manhole depth or portion thereafter; and (3) Cured-in-place fiberglass liner (Poly-Triplex Liner System, PTLS-5600 series) molded into place with a non-porous membrane bonded between the layers of structural fiberglass, forming a permanent barrier to stop future infiltration or gas deterioration to the existing structure. Schedule "C" products receiving consideration should be chosen from the following: (1) Epoxy coating - 120 mils thick, spray applied in layers no more than 40 mils thick per application; (2) Polyurea coating - 180 mils thick, spray applied in layers no more than 90 mils thick per application; (3) Polyurethane coating - 150 mils thick, spray applied in layers no more than 75 mils thick per application; (4) Calcium aluminate concrete with epoxy top coat - three-fourths inch thick layer of calcium aluminate concrete applied with ½ lb. per cubic ft. of synthetic reinforcing fibers, applied in layers not more than 3/8 inch thick per application, and top coated with 60 mils of epoxy, spray applied in 30 mil coats per application of material; and (5) Cured-in-place structural epoxy/fiberglass coating - (Poly-Glass Structural Coating, PGSC-2700 series) with 27 oz. per sq. yd. of woven and stitched fiberglass and felt saturated in epoxy, pressurized in place, and heat cured.
Product Evaluations and Application Methods SCHEDULE A PRODUCTS Pre-formed Fiberglass Inserts: Potential Schedule A product - Pre-formed fiberglass inserts are very effective in situations where manhole collapse is probable. The only weak point besides cost is that it is extremely hard to stop infiltration around pipes or where the insert stops at the bench area with a pre-formed, ridged insert. This type of rehabilitation requires the chimney and corbel areas of the manhole to be removed, and all infiltration in the bench area, around pipes, and the lower cylinder area of the manhole stopped; then the insert may be lowered into position, back poured with concrete, and completed at the surface area. Poured-in-place Concrete Rehab: Potential Schedule A product - Poured-in-place concrete rehab is very effective where manhole collapse is probable. Like the pre-formed fiberglass insert, it is susceptible to infiltration around pipes, the lower cylinder and bench areas. Therefore, infiltration around these areas should be stopped prior to installation of the formed and poured-in-place concrete application. The use of this process should be in conjunction with a synthetic liner material placed to the inside area of the manhole in the form, in order to provide interior surface that is resistant to sewer gases and chemicals. Cured-In-Place Fiberglass Inserts: Potential Schedule A, B, & C product - Cured-in-place fiberglass inserts (Poly-Triplex Liner System, PTLS-6800 series, US Patent # 5,265,981 & 5,490,744) are very effective at stopping all future infiltration and gas deterioration, as well as structural enhancement of the existing manhole. Prior to installing the insert, infiltration located within six inches of the edges of the liner should be controlled - such as around pipes or where the bench area meets the invert channel.This system requires custom manufacturing a multiple layered liner and its inflation bladder that will provide a molded-in-place, laminated, epoxy/fiberglass insert that is bonded under steam injection and pressure to the existing surface. This patented, laminated liner contains a non-porous membrane bonded between the structural layers of fiberglass. This system provides excellent freeze/thaw qualities that help significantly in the northern areas of the US and in Canada. The cured-in-place fiberglass insert (Poly-Triplex Liner) carries a five-year, non-prorated warranty to stop infiltration and further deterioration of the manhole. SCHEDULE B PRODUCTS Calcium Aluminate Concrete: Potential B & C schedule product - General evaluation of effectiveness - calcium aluminate blends and other cementitious products are among the least favorable products for manhole rehab. The reasons are simple. Whatever deteriorated the existing structure will sooner or later deteriorate these materials. Whatever pressures and conditions cracked the existing structure, which was 4" to 8" thick, will most certainly reopen cracks in these materials. The new material will not be bonded to the old materials as well as either is bonded to itself; therefore, stresses will likely separate the new rehab materials from the old structure, allowing deterioration and infiltration to resume. Stop infiltration prior to applying calcium aluminate concrete or Portland mixtures with chemical injection grouting or straight hydraulic cement. Remember, if cementitious products are cured while infiltration is seeping through the material, they will continue to leak during wet times, and will allow sewer gases to penetrate through microscopic openings during dry times - severely affecting the life of the product and the effectiveness of the rehabilitation program. Reinforce the cementitious product by attaching reinforcing wire to surfaces that are being rehabilitated prior to applying the product, or add one-half pound of solid core, synthetic reinforcing fibers to every cubic foot of material that is being used. This is not a four-inch thick sidewalk being poured on stable ground, but rather plastering a relatively thin coating on a physically and chemically unstable surface, especially where old brick structures are concerned. Please realize that most of the cost in applying cementitious rehabilitation is labor and time related, not necessarily the quality of the materials being applied. Future cracking must be eliminated as much as possible. Product should be applied at least one inch thick, and applied in layers of approximately 1/4" inch during each application in order to minimize hair line cracks in the material as it cures. Topcoat the structure with epoxy to provide a moisture barrier and the reduction of future gas deterioration. Epoxy coating should be applied 120 mils thick and have synthetic reinforcing fibers blended into the mixture to prevent the epoxy coating from cracking. The epoxy coating should be a 100% solids material that will not shrink when it cures. Polyurethane Coating: Potential Schedule B & C product - Polyurethane is a good product for gas deterioration, but is questionable for infiltration problems. In either case it must be applied properly and in multiple layers of thin coats because it shrinks as it cures and pulls itself off the surface. Another problem is that it is expensive under these conditions. First, all infiltration must be stopped. The surface needs to be completely dry if even minimal adhesion is to be expected. Actually, if you spray an entire new manhole with polyurethane, it will pull itself off the wall as it cures and will be slightly separated from the structure. The reason is that its power to shrink as it cures is greater than its ability to bond. The problem this causes with structures that have infiltration is obvious, but rather hidden from sight. The product separates itself from the surface as it cures and allows future infiltration to sheet down behind the material and come out wherever the coating stops at the pipes or invert channel. Even after a good installation with the product completely cured, there is a need to drill and pump chemical foam grout behind the Polyurethane coating in the lower walls, bench areas, and around pipes. The structure may look fine but not be functional during times when hydrostatic head and infiltration are present. Because of this lack of bonding, the material must be applied thick enough to offset the possible future hydrostatic head of infiltration. Stage the product thickness to reduce the material cost of rehabilitating manholes. A good rule would be a quarter inch thick for use up to five feet deep in the manhole, and add an additional ¼ inch in thickness for each additional five feet of depth, or portion thereof. Example: ¼" first five feet; ½" the next five feet; ¾" the next five feet, etc. In this method a 15 ft. deep structure could start off with ¼" of material in the first five feet, yet have a ¾" material thickness in the lower section. As the depth and potential hydrostatic head increases, so does the need for increased material thickness - because the material will not adequately bond to the structure. Use multiple applications of material for proper curing. Polyurethane should be applied in layers no more than 75 mils thick per application, because of running, curing, and shrinkage factors. The structure should be dry for applying polyurethane. All infiltration leaks should be stopped using chemical grout injections and/or hydraulic cement prior to application of the product. Cured-In-Place Fiberglass Liner: Potential Schedule B & C product. Cured-in-place fiberglass liners (Poly-Triplex Liner System, PTLS-5600 series, US Patent # 5,265,981 & 5,490,744) are very effective at stopping all future infiltration and sewer gas deterioration, as well as adding significant structural support to manholes. This is the same product as Cured-in-Place Fiberglass Inserts listed above in Schedule A except with slightly less structural fiberglass and resin. Both are pressurized with an inflation bladder. Both are molded and bonded under steam injection to the existing structure to form a laminated, monolithic liner from the ring and cover to the invert channel. The Schedule A product contains 68 oz. per sq. yd. of pre-saturated fabrics, and the Schedule B product contains 56 oz. per sq. yd. of pre-saturated fabrics. Both contain the same felt impregnated non-porous membrane bonded between the structural layers of fiberglass. This schedule B product also carries a five-year, non-prorated warranty to stop infiltration and further deterioration. The liners are custom manufactured for each structure and when installed, form a monolithic structure from the ring and cover to the invert channel. This product provides excellent freeze/thaw qualities that help in the northern areas of the US and in Canada. With this process infiltration needs to be controlled that is within six inches of the edges of the liner around pipes or the invert channel prior to installing the liner. SCHEDULE C PRODUCTSEpoxy Coating: Potential Schedule C product. Epoxy coating is rather brittle and may tend to crack except when applied with structural synthetic fibers. Use one ounce of ¼ inch solid core, synthetic reinforcing fibers per gallon of epoxy resin. The strengths of epoxy are in its bonding ability and resistance to sewer gases and chemicals. Applied correctly and because of its bonding ability, epoxy coating can provide substantial help in preventing future infiltration in existing Schedule C type manholes. Apply in coatings of not more than 40 mils thick, because of running problems. It takes several hours for epoxy coatings to solidify on the surface of the structure. Apply the epoxy in layers that become at least 120 mils thick for the final surface. The surface should be free of all infiltration prior to applying an epoxy coating. Stop all infiltration with chemical grout or hydraulic cement prior to applying the product. Polyurea Coating: Potential Schedule C product. Polyurea coating is resistant to sewer gases and chemicals, but adds practically no additional strength to the structure. It does not need to be used where there is potential for future infiltration problems, because the product remains more flexible than the other coatings listed in Schedule C, and it does not bond well to the existing structure. The surface should be dry prior to applying the product. Material applications should provide a finish coat of 180 mils, and should be applied in coats of a maximum of 90 mils per application. Stop all infiltration with chemical grout or hydraulic cement prior to applying the product. Polyurethane Coating: Potential Schedule C product. Polyurethane coating is resistant to sewer gases and chemicals, but adds insignificant strength to the structure. It actually shrinks as it cures; therefore, it does not remain bonded well to the existing structure. The surface should be dry prior to applying the product. Material applications should provide a finish coat of 150 mils, and should be applied in coats of a maximum of 75 mils per application. Because of its lack of bonding ability, it should not be used as a Schedule C coating product where there is potential for future infiltration problems. Stop all infiltration with chemical grout or hydraulic cement prior to applying the product. Calcium Aluminate Coating With Epoxy Finish: Potential Schedule C Product. With the epoxy finish coat, calcium aluminate concrete can provide a viable Schedule C product that adds structural and bonding qualities as well as good resistance to sewer gases and chemicals. Apply the calcium aluminate concrete in two separate layers totaling ¾ inch thick, and then apply a 60 mil coating of epoxy that is applied in two 30 mil coats. Make certain the calcium aluminate concrete is blended with one half pound of solid core, synthetic reinforcing fibers per cubic yard of material. The epoxy top coat should be blended with one ounce of ¼ inch synthetic reinforcing fibers per gallon of material in order to inhibit future cracks. Stop all infiltration with chemical grout or hydraulic cement prior to applying the product. Epoxy/Fiberglass, Structural Coating: Potential Schedule C product. Epoxy/Fiberglass coating (Poly-Glass Structural Coating, PGSC-2700 series, US Patent #5,490,744) is very resistant to sewer gases and chemicals. It is cured-in-place under heat and pressure, and provides a structural coating that is bonded to the manhole. If applied to a relatively dry structure, it provides excellent protection against future infiltration problems in Schedule C type conditions. The structural coating should contain 27 oz. per sq. yard of laminated structural fiberglass and felt, stitched together and saturated with epoxy resin that will bond to wet or dry surfaces. Stop all infiltration with chemical grout or hydraulic cement prior to installing the product. Conclusion As you can readily see, manhole rehabilitation programs have many options available to solve problems in a quality manner. We must require that preparation work is accomplished properly, and that products are applied or installed in ways that come as close as possible to providing permanent rehabilitation to the structures. Products and processes have come a long way from the days in the not too distant past of grouting manholes with concrete that would crack again in a short period of time. Anything that cracked the structure to begin with would certainly re-crack a plaster of cement grout. Solutions are plentiful. Some of the products like the pressurized system of the cured-in-place Poly-Triplex Liner System and the Poly-Glass Structural Coating are equally suited for rehabilitation of sewage pump stations. If you have any questions or comments, or if you would like samples of bid documentation that can implement this type of rehabilitation program, please contact us. Poly-Triplex® Technologies can help you successfully accomplish the rehabilitation of your utility's infrastructure. |
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