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Study identifies top reasons for sewer line failure

Concrete sewer pipes around the world are most likely to fail either because their concrete is not strong enough or because they can’t handle the weight of trucks that drive over them, a new study indicates.

The study used a statistical analysis to show that those two factors were the most likely to trigger a problem among 16 common causes of sewer pipe failure they examined.

The study was published online earlier this year in the journal Structure and Infrastructure Engineering.

“There is a vast array of pipes underground that is working every day and if there is disruption — leakage or collapsing in a pipe, for example — not only will there be discomfort for the residents, but also economic, health and environmental consequences,” said Abdollah Shafieezadeh, senior author on the study and an associate professor of civil, environmental and geodetic engineering at The Ohio State University. “The losses can be significant.”

And so can the cost of repairs and maintenance: In 2017, the American Society of Civil Engineers estimated the cost to fix and maintain the U.S. sewer system at $150 billion.

For this study, researchers gathered data and analyzed buried sewer pipes, which, in the United States, are commonly made of concrete. Then, they identified the most likely causes of sewer pipe failure. Those causes included things like the density of soil surrounding sewer pipes, the elasticity and strength of the concrete materials and the weight of trucks that regularly drive over them.

They then built a statistical model that could evaluate the stress caused to the pipes by each variable individually and in combinations, and conducted several statistical analyses using the Ohio Supercomputer Center.

The analyses showed that, statistically, cracks that will eventually influence the structural integrity of sewer pipes are most likely to form when the concrete is made from weak components and not maintained properly, or when heavy trucks regularly drive on roads above the pipes. Cracks that influence structural integrity, the researchers say, are the first signs that a sewer pipe is on its way to collapse.

“It’s a worldwide problem, and part of the issue is that, for many cities around the world, these sewer systems have been installed long ago, and the challenge now is to maintain these old systems,” Shafieezadeh said.

Systems can be complex and expensive to maintain. Cities often have tens of thousands of miles of sewer pipes running beneath them. And, because they are underground, spotting issues is not as simple as finding issues with above-ground infrastructure like roads or power lines, said Soroush Zamanian, a graduate research associate in civil, environmental and geodetic engineering at Ohio State and lead author of the paper.

“In 2017, the American Society of Civil Engineers gave the United States’ overall sewer system a D+ rating,” Zamanian said. “And that’s part of why we are looking at this question and seeing if we could help predict where lines might fail.”

The researchers said future studies should examine the way aging and corrosion of pipes affects the way in which system operators can repair them. And, they said, future studies could analyze other pipe configurations, or analyze more details about the types of soil that surround those pipes.

“The big picture is if we want to design sewer pipes for the future, or if we want to assess the current condition and predict future conditions of these pipes, one key element is to know the important factors contributing to their failures — and how do those factors play out in the real world,” Zamanian said.

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Materials provided by Ohio State University. Original written by Laura Arenschield. Note: Content may be edited for style and length.

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ScienceDaily

A bio-inspired addition to concrete stops the damage caused by freezing and thawing

Concrete is one of the most abundant and durable building materials used in modern-day infrastructures, but it has a weakness — ice — which can cause it to crumble and spall. Now, inspired by organisms that survive in sub-zero environments, researchers in Colorado are introducing polymer molecules with anti-freezing abilities into concrete. The method, which tests if the new concrete can stop the damage caused by freezing and thawing, appears in the journal Cell Reports Physical Science on May 27.

Concrete is a porous material with capillary pores that allow water to permeate into the material. For places that experience large temperature swings, concrete roads and buildings go through “freeze-thaw cycles.” The water freezes and expands inside of the material, building up pressure as the ice crystals grow, eventually popping the surface of the concrete off. The polyethylene glycol-graft-polyvinyl alcohol (PEG-PVA) molecules that the researchers have identified appear to keep the ice crystals small and prevent them from coalescing into larger crystals.

“We’re particularly excited because this represents a departure away from more than 70 years of conventional concrete technology,” says senior author Wil Srubar, who heads the Living Materials Laboratory at the University of Colorado Boulder. “In our view, it’s a quantum leap in the right direction and opens the door for brand new admixture technologies.”

For over 70 years, the primary way to mitigate freeze-thaw damage was to put in tiny air bubbles that act as pressure release valves inside of the concrete, known as air-entraining admixtures. But putting tiny air bubbles into the concrete not only lowers the strength of the material but also makes it more porous, acting like a superhighway for more water and other harmful substances, like salts, to enter. Instead of tackling the symptoms of ice expansions, the team decided to target the source: ice crystal growth.

Found in organisms that survive in sub-zero environments, anti-freeze proteins bind to ice crystals to inhibit their growth that would otherwise be fatal to the organisms. Inspired by the protein, the team introduced polymer molecules that mimicked the protein’s properties to the concrete mix. The molecules effectively reduced the size of ice crystals by 90 percent. The new concrete mix also withstood 300 freeze-thaw cycles and maintained its strength.

Although the new concrete passed industry-standard tests, there are still questions about the true long-term resilience of the material in a real-world application and its economic viability. The next step for the team is to optimize their method by identifying new molecules that are more cost-effective and testing the compatibility of the molecule with different recipes of concrete. “Making concrete is a lot like baking a cake,” says Srubar, hoping that concrete recipes can benefit from the new additive.

“For the next 30 years, the world will be building a New York City every 35 days, which is astounding,” says Srubar. “What that means is that we’re going to be building a lot of buildings and roads, and we’re going to be using a lot of concrete. Because it has significant impacts on the environment, the concrete that we do make really does have to be as sustainable as possible and as durable as it can be.”

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Materials provided by Cell Press. Note: Content may be edited for style and length.

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3D Printing Industry

The Delta WASP 3MT CONCRETE 3D printer – technical specifications and pricing

WASP has launched its new Delta WASP 3MT CONCRETE 3D printer. The large-scale concrete 3D printer is aimed at construction professionals, educational institutes, and architects, boasting a “new standard in the additive manufacturing of concrete mortars”. According to WASP, the printer is productive, versatile, safe, and characterized by the expertise of its manufacturer. The option […]

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Author: Kubi Sertoglu

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3D Printing Industry

QUIKRETE and Contour Crafting partner up to fight homelessness with concrete 3D printing

U.S.-based concrete specialists QUIKRETE and Contour Crafting Corporation (CC Corp) have announced a collaboration to develop a proprietary concrete to be used with CC Corp’s concrete 3D printing technology. The partnership will see the automated construction of residential, commercial, industrial, and government buildings around the U.S. starting with the City of Angels, Los Angeles. Dr. […]

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Author: Kubi Sertoglu

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3D Printing Industry

Messina researchers develop high-strength lightweight cement mix for concrete 3D printing

Researchers from the University of Messina have formulated a lightweight foamed concrete to more effectively 3D print building structures without the need for any formwork. Unlike traditional lightweight foamed concrete, the novel material (3DPC) is able to retain its shape in its ‘molten’ or ‘fresh’ state due to a very high viscosity. Upon extensive testing, […]

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Author: Kubi Sertoglu

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3D Printing Industry

Purdue University engineers set to 3D print concrete wind turbines

Engineers from Purdue University have begun working on a method of 3D printing concrete wind turbine parts for offshore use. According to the U.S. Department of Energy, harnessing wind energy off the coast of the U.S. could generate more than double the total electricity output of all the country’s electric power plants. The main issue […]

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Author: Kubi Sertoglu

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3D Printing Industry

Twente AM unveils large-scale concrete 3D printer in Dubai

Twente AM, a Dutch start-up focused on architectural 3D printing, has unveiled its latest large-scale concrete 3D printer. The machine was developed and assembled at the company’s research and development center in Nelson, Canada days before being showcased on screens at the 40th annual Big 5 International Building & Construction Show in Dubai. Ian Comishin, […]

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Author: Kubi Sertoglu

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3D Printing Industry

3D Printing Industry News Sliced: Essentium, Tommy Hilfiger, Prodways, Arkema, Smart International

In this week’s edition of Sliced, the 3D Printing Industry news digest, concrete 3D printing is looked as at a solution for rebuilding a village; fashion brands are integrating 3D printing for a “sizeless” solution, and generative design is used for architectural planning. We also cover news from Essentium, Ricoh, Smart International, Arkema, Prodways, Endurance Lasers and […]

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Author: Tia Vialva

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IEEE Spectrum

Ampacity Calculations of High-Voltage Cables Using Multiphysics Simulation

Get an introduction to modeling thermal performance of high-voltage cables in COMSOL Multiphysics® in this webinar. High-voltage power cables are major assets and are expected to work reliably for many years. One of the factors affecting reliability is thermal performance of the cables. This has to be determined at the early stage of the design and is achieved by calculations of the thermal rating (often called ampacity).

Ampacity calculations usually involve two different physics: heat transfer (in solids and gases/liquids) and electromagnetics (Joule losses in the conductor, dielectric losses, and electromagnetic induction). Some models of cable installations are relatively easy to solve, while others require in-depth knowledge of the physics and experience in building FEM models. For example, the heat transfer from directly buried cables involves only conduction, while for cables installed in air, radiation and convection must be taken into consideration.

This webinar will demonstrate how to build finite element models of underground cables using COMSOL Multiphysics®. The presentation concludes with a Q&A session.

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3D Printing Industry

RCAM Technologies and Accucode target 3D printing for offshore wind turbines

3D printed concrete startup RCAM Technologies has inked a partnership with IT service provider Accucode, Inc. Together, the partners will work to develop large-scale, 3D printed concrete structures supporting offshore wind turbines. Part of the project will be done at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). After initial testing, RCAM concrete 3D printing […]

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Author: Beau Jackson