The markets: Utility infrastructure (2019)

Corroded metal infrastructure continues to be a problem, and composite materials, including new advancements in graphene nanotubes, are providing solutions. 

As noted in the introduction, the repair and replacement of corroded metal infrastructure is a pressing need. Corrosion is currently the major cost driver in the maintenance of communication towers throughout the US Air Force inventory, for example. The Air Force’s desire to address corrosion led to an innovative composite solution. The result was a 118-ft communications tower completely constructed from pultruded composites and installed by the Air Force at Hanscom AFB in Massachusetts. The prototype tower uses fastener-less joining technology where individual components, such as the lattice cross members, “snap” together during the assembly process without the need for metallic bolts. The tower was fabricated by Composite Support & Solutions (CSSI, San Pedro, CA, US) using Ashland (Dublin, OH, US) Derakane vinyl ester resin designed for pultrusion. The effort earned a Tibbett’s award from the Small Business Admin. for CSSI. The snap-fit system not only eliminates possible fastener corrosion but also enables tower erection in about one-eighth the time required for a comparable metal tower, tallying commensurate cost savings.

Another pressing need is underground pipe. The US Environmental Protection Agency’s (EPA, Washington, DC, US) report, titled State of Technology for Rehabilitation of Water Distribution Systems, says, “The impact that the lack of investment in potable water infrastructure will have on the performance of aging underground infrastructure over time is well documented, and the needed funding estimates range as high as US$325 billion in the coming 20 years.” Composites can play an important role by providing corrosion-resistant, durable and long-lasting solutions. One recent example of composites put to use for piping was a water project in the Middle East. The selected pipe for the project was Amiantit Europe’s (Mochau, Germany) pipe product, Flowtite Grey, which was intended for water, sewage, waste and raw material management. Flowtite Grey is more resistant to rough installation and transport practices than previous generations of composite pipe, but it comes at a comparable or lower price point than traditional (metal or concrete) materials. The large-diameter pipe was produced on Flowtite’s continuous filament winding machinery, a technology developed for cost-effective pipe production. 

The 20th Annual Underground Construction Municipal Sewer and Water Survey, conducted by Underground Construction magazine (Oildom Publishing Co., Houston, TX, US) reported in February 2017 that, although 2015 and 2016 had, for the first time in many years, given municipal sewer and water personnel some reason to be optimistic about spending plans for refurbishment of decaying underground pipe systems, 2016 ended as a disappointment. Nationwide, sewer and water spending fell 4.2% in 2016 from an anticipated US$19 billion to US$18 billion. Survey information reports that cities hoped to spend about US$11 billion in 2017 on new and replacement construction for underground pipes, with sewer comprising US$5.2 billion, water US$3.8 billion and stormwater US$2.0 billion of that total. About $8.2 billion was anticipated to be spent on pipe rehabilitation including US$4.7 billion on sewer, US$2.1 billion for water and US$1.4 billion for stormwater.

The survey also measured impacts from trenchless construction and rehabilitation methods, in which composite materials are used to reline existing pipes (cured in-place pipe, or CIPP). During budget-crunching times, trenchless rehabilitation gained ground as a cost-effective and successful stop-gap measure to stretch dollars. As a result, trenchless work has gained a foothold in all aspects of construction and rehabilitation in the US and abroad. The survey revealed that 52% of cities prefer to use trenchless CIPP for rehab, and for new construction, trenchless is used in about 25% of projects.

In early August of 2018, the American Composites Manufacturers Assn. (ACMA) announced that both chambers of the US Congress have introduced new legislation to encourage research and deployment of innovative construction techniques and materials, including composites, in infrastructure projects nationwide. According to Senator Sheldon Whitehouse’s (D-RI) Web site, investing in these new techniques and materials would help to extend the life of critical public works that draw increasingly poor ratings for condition and performance. The legislation, known as the Innovative Materials for America's Growth and Infrastructure Newly Expanded (or IMAGINE), was introduced in the Senate by Whitehouse, Lamar Alexander (R-TN), Mike Rounds (R-SD) and Cory Booker (D-NJ), and in the House of Representatives by Reps. Barbara Comstock (R-Va.), Elizabeth Esty (D-Conn.) and David Cicilline (D-R.I.). It is designed to promote the increased use of innovative materials like composites, as well as new manufacturing methods to speed up the deployment and extend the life of infrastructure projects. The ACMA is lobbying for passage of the bill.  

Filament wound fiberglass/polyester composites have recently found broad application in several stages of seawater reverse osmosis (SWRO) desalination. SWRO plants around the world use many miles of corrosion-resistant fiberglass-reinforced polymer (FRP) low-pressure piping as a distribution network, primarily over land, to carry seawater to the plant, to distribute the potable water that is produced, to carry the brine (salt and impurities) back to the ocean, and for internal plant treatment piping and energy-recovery devices. Fiber-reinforced plastic also forms storage tanks and piping used in desalination plants to contain sodium hypochlorite (NaOCl) used in chlorination of desalination process water, and for sulfuric acid — very difficult to store in metal but readily handled in fiberglass/epoxy vinyl ester tanks and piping at ambient temperatures and concentrations below 50%, according to corrosion industry resin producer Ashland

Improvements to composite materials are benefiting those fighting corrosion. One case in point is the use of nanocomposites to combat a hazardous situation involving fiberglass tanks. An electrostatic charge can be generated when filling or emptying tanks, particularly those containing petroleum-based liquids, because the product movement can create a static charge between the liquid and the tank wall. Because fiberglass acts as an insulator, static charges tend to accumulate in the liquid, and a stray spark can lead to an explosion. To address this risk, fiberglass tank manufacturers have historically used anti-static fillers in the resin, typically carbon black or conductive mica, to dissipate any static charge. But, filler ratios up to 30% are often necessary, which makes wetout of the fiberglass more difficult and slows the resin cure rate. Use of TUBALL graphene single-wall carbon nanotubes supplied by OCSiAl (Leudelange, Luxembourg and Columbus, OH, US) can provide electrostatic discharge (ESD) protection by dissipating electrostatic charge inside and outside a storage tank. One OCSiAl partner customer previously used conductive carbon black at a loading of 15%, but has replaced it with just 0.5% of TUBALL MATRIX 204, a pre-dispersed graphene nanotube concentrate. 

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