Using Coal Waste to Create Sustainable Concrete

New Coal Concrete Reduces Energy Demand, Greenhouse Emissions

Date: July 12, 2018
Source: Washington State University
Summary: Researchers have created a sustainable alternative to traditional concrete using coal fly ash, a waste product of coal-based electricity generation.

Chemical engineering student Ka Fung Wong looks at the data log, which is used to gather data from sensors buried under the concrete test plot.
Credit: WSU

Washington State University researchers have created a sustainable alternative to traditional concrete using coal fly ash, a waste product of coal-based electricity generation.

The advance tackles two major environmental problems at once by making use of coal production waste and by significantly reducing the environmental impact of concrete production.

Xianming Shi, associate professor in WSU's Department of Civil and Environmental Engineering, and graduate student Gang Xu, have developed a strong, durable concrete that uses fly ash as a binder and eliminates the use of environmentally intensive cement. They report on their work in the August issue of the journal, Fuel.

Reduces Energy Demand, Greenhouse Emissions

Production of traditional concrete, which is made by combining cement with sand and gravel, contributes between five and eight percent of greenhouse gas emissions worldwide. That's because cement, the key ingredient in concrete, requires high temperatures and a tremendous amount of energy to produce.

Fly ash, the material that remains after coal dust is burned, meanwhile has become a significant waste management issue in the United States. More than 50 percent of fly ash ends up in landfills, where it can easily leach into the nearby environment.

While some researchers have used fly ash in concrete, they haven't been able to eliminate the intense heating methods that are traditionally needed to make a strong material.

"Our production method does not require heating or the use of any cement," said Xu.

Molecular Engineering

This work is also significant because the researchers are using nano-sized materials to engineer concrete at the molecular level.

"To sustainably advance the construction industry, we need to utilize the 'bottom-up' capability of nanomaterials," said Shi.

The team used graphene oxide, a recently discovered nanomaterial, to manipulate the reaction of fly ash with water and turn the activated fly ash into a strong cement-like material. The graphene oxide rearranges atoms and molecules in a solution of fly ash and chemical activators like sodium silicate and calcium oxide. The process creates a calcium-aluminate-silicate-hydrate molecule chain with strongly bonded atoms that form an inorganic polymer network more durable than (hydrated) cement.

Aids Groundwater, Mitigates Flooding

The team designed the fly ash concrete to be pervious, which means water can pass through it to replenish groundwater and to mitigate flooding potential.

Researchers have demonstrated the strength and behavior of the material in test plots on the WSU campus under a variety of load and temperature conditions. They are still conducting infiltration tests and gathering data using sensors buried under the concrete. They eventually hope to commercialize the patented technology.

"After further testing, we would like to build some structures with this concrete to serve as a proof of concept," said Xu.

The research was funded by the U.S. Department of Transportation's University Transportation Centers and the WSU Office of Commercialization.

Story Source: Washington State University. "Using coal waste to create sustainable concrete: New coal concrete reduces energy demand, greenhouse emissions." ScienceDaily. ScienceDaily, 12 July 2018. https://www.sciencedaily.com/releases/2018/07/180712100513.htm.

Water Efficiency in Rural Areas is Getting Worse, Even as it Improves in Urban Centers

Date: May 18, 2017
Source: North Carolina State University
Summary: A nationwide analysis of water use over the past 30 years finds that there is a disconnect between rural and urban areas, with most urban areas becoming more water efficient and most rural areas becoming less and less efficient over time.

This map shows spatio-temporal patterns of water-use efficiency (per-capita consumption) across the continental United States. Colors indicate the change in per-capita consumption, in gallons per day per person, computed as the difference between 2010 and 1985 estimates. The numbers shown in each state indicate the number of 5-year periods each state reduced its per-capita withdrawals from 1985 to 2010.
Credit: Sankar Arumugam

A nationwide analysis of water use over the past 30 years finds that there is a disconnect between rural and urban areas, with most urban areas becoming more water efficient and most rural areas becoming less and less efficient over time.

"Understanding water use is becoming increasingly important, given that climate change is likely to have a profound impact on the availability of water supplies," says Sankar Arumugam, lead author of a paper on the work. "This research helps us identify those areas that need the most help, and highlights the types of action that may be best suited to helping those areas." Arumugam is a University Faculty Scholar and professor of civil, construction and environmental engineering at North Carolina State University.

The new paper stems from a National Science Foundation-funded, interuniversity research project which focuses on understanding how water sustainability in the United States has changed over the past 30 years as a result of climate change and population growth.

For this paper, researchers evaluated water use data at the state and county level for the 48 contiguous states. Specifically, the researchers looked at water-use efficiency, measured as per capita consumption, in 5-year increments, from 1985 to 2010.

"This is the first systematic evaluation of water use across the continental U.S.," Arumugam says. "And we found that some states -- including Washington, Pennsylvania and Wyoming -- were becoming more efficient every five years. Meanwhile, other states -- such as South Carolina, Oklahoma and Mississippi -- have gotten worse every five years."

But a look at the county-level data reveals what may be the most important finding: most rural counties are getting less efficient, while most urban counties are getting more efficient.

"In other words, as we are facing a more uncertain future regarding water resources, rural counties are being left behind," Arumugam says.

The researchers found that investment in new water-efficiency technologies, and retrofitting existing water infrastructure, are big reasons for the improvement in urban areas.

"Rural counties appear to lack the resources, the political will, or both, to keep pace," Arumugam says.

Another important finding is that technologies and strategies focused on efficiency -- as opposed to large-scale projects, such as building new reservoirs -- have been extremely successful. These efforts have allowed urban areas to avoid sharp increases in water use, even as their populations have grown significantly.

"There may be a role for huge infrastructure projects at some point, but these findings underscore the value of focusing on efficiency measures -- and the need to pursue those measures in rural counties," Arumugam says.

Story Source: North Carolina State University. "Water efficiency in rural areas is getting worse, even as it improves in urban centers." ScienceDaily. ScienceDaily, 18 May 2017. http://www.sciencedaily.com/releases/2017/05/170518140246.htm

National Academies – Report on Sustainable Reuse and Recycling

Energy and Water Considerations for the Sustainable Reuse and Recycling of Materials

In September 2013, the STS Program convened a meeting of research leaders and technical experts in private industry as well as representatives from government and academia to examine the energy-water considerations of material reuse and recycling. The meeting examined the data and research needs for assessing the energy-water linkages with the reuse and recycling of waste streams and materials; the technologies and approaches needed to further recycling and reuse strategies; and how the public and private sectors can leverage the efforts of key stakeholders to further technological development, innovation, data collection, and research. This meeting summary synthesizes the discussions held during the event.

Source: For more information, go to http://sites.nationalacademies.org/PGA/sustainability/PGA_084717.

Click here to download the meeting summary