Displaying items by tag: Fly Ash

UK: A study by the University of Dundee has dispelled the myths of substantial performance differences between concretes made with cement containing dry or wet-stored fly ash, with comparable reinforcement corrosion between the two.

Vertical News has reported that the research, whose backers included the Department for Environment, Food & Rural Affairs and Heathrow Airport Holdings, was aimed at “quantifying moisture effects, which indicate agglomeration of fly ash and a tendency for this to increase with free lime content, storage period and temperature.”

Researchers tested five moistened fly ashes and samples from two power station stockpiles, and further investigated different material and storage variables, comparing the concretes at 75mm slump and 28 day strength. Air permeability and water absorption of moistened fly ash proved greater with high free lime (up to 0.9%) and lower with low free lime (to under 0.1%). What benefits there were improved with longer storage. The moistening of low-free-lime fly ash generally yielded similar, or slightly higher, carbonation and chlorine diffusion. The moisture caused little change in high-free-lime ash’s carbonation, while increasing chloride diffusion. Furthermore, high storage temperature equated to greater carbonation.

In spite of these intriguing chemical differences, the study concluded, "these didn't seem to have a noticeable effect on concrete resistance.”

Charah Solutions has been steadily building up its fly ash distribution business in recent years with an eye on the supplementary cementitious materials (SCM) market. This week it opened the third of its new series of SCM grinding plants, at Oxnard in California, US. The unit sticks out because it is focusing on grinding natural pozzolans. The plant will receive natural pozzolan by truck and rail and then use Charah’s patented grinding technology to produce pozzolan marketed under its MultiPozz brand. The previous plants in this series mentioned natural pozzolans but this is the first to promote it explicitly.

The change is potentially telling because global demand for granulated blast furnace slag (GBFS) outstrips supply. Both performance benefits and environmental regulations are pushing this. It’s a similar situation for fly ash, also driven by trends to close coal-fired power stations in some countries. As Charles Zeynel of SCM trading firm ZAG International explained in the March 2019 issue of Global Cement Magazine, “...volcanic pozzolans are a potential SCM of the future. This is gaining traction, but it’s slow progress at the moment. This will be the answer for some users in some locations.”

The problem though is that natural pozzolans are down the list of preferred SCMs for their chemical properties after silica fume, GBFS and fly ash. The first is expensive but the latter two were traditionally cheap and easy to obtain if a cement or concrete producer had access to a source or a distribution network. Natural pozzolans are very much subject to variations in availability.

It’s no surprise then that Charah is promoting natural pozzolans in a Californian plant given that state’s environmental stance. It’s unclear where Charah is sourcing their pozzolan from but they are not the only company thinking about this in the US. Sunrise Resources, for example, is working on the environmental permits for a natural pozzolan mine near Tonopah in Nevada. As it described in its company presentation, California and Nevada are the most affected states in the fly ash supply crisis because they are, “...at the end of the line when it comes to rail deliveries from power stations in central and eastern USA.” It also estimated that California used 0.9Mt of pozzolan in its cement production of which about 90% is fly ash. The state produced 9.6Mt in 2015. Other companies are also mining and distributing natural pozzolans in the US as the website for the National Pozzolan Association (NPA) lists. Although, if this line-up is comprehensive, then the field is still fairly select. Most of these companies are based in the west of the country.

One last thing to consider is that various groups are tackling a potential future lack of SCMs for the cement industry by making their own pozzolanic materials through the use of calcined clay. These groups include the Swiss-government backed LC3 project and Cementir’s Futurecem products. Using clay should bypass the supply issues with natural pozzolans but the cost of calcining it requires at the very least an investment to get started.

As concrete enthusiasts often point out, a variant of pozzolanic concrete was used by the Romans to build many of their iconic structures, some of which survive to the present day. To give the last word to the NPA, “What is old is new again: natural pozzolan is back!” If environmental trends continue and steel and coal plants continue to be shut then it might just be right.

UK: Aggregate Industries has launched its Lafarge Endure SR, a CEM II blended cement product that uses fly ash. It says that the product has a lower embodied CO₂, has improved plastic and hardened properties when used in concrete and has enhanced suitability for all ground types. Lafarge Endure SR is resistant to sulphates, allowing contractors and suppliers to scope a wider variety of projects. It also uses 10% less water than CEM I products to reach a workable consistency and offers improved pumpability and mixing efficiency.

“As its name suggests, Lafarge Endure SR is designed to dramatically increase the longevity of the concrete it forms a part of. It is a great solution for contractors that want to reduce the environmental impact of their build while simultaneously improving its life span,” said Steve Curley, Commercial Director at Aggregate Industries.

Canada: Lafarge Canada plans to develop and demonstrate a full-cycle solution to capture and reuse CO₂ from a cement plant. Project CO₂MENT will demonstrate and evaluate Inventys' CO₂ capture system and a selection of CO₂ utilisation technologies at Lafarge's Richmond cement plant in British Colombia over the next four years. This project is being led by Inventys in partnership with Lafarge Canada and Total. It also received financial support from CCP (CO₂ Capture Project), the Province of British Colombia and Canada's federal government through the National Research Council of Canada Industrial Research Assistance Program (NRC IRAP).

"At Inventys, we see a real opportunity to build a CO₂ marketplace where tonnes of CO₂ are traded between emitters and users," said Inventys president and chief executive officer (CEO) Claude Letourneau.

Phase I of Project CO₂MENT, the Contaminant Program, will attempt to reduce harmful organic and inorganic substances, such as sulphur dioxide, dust and soot, as well as nitrogen oxides, from cement flue gas. Phase II, the CO₂ Capture Program, will separate the CO₂ from flue gas using a customised-for-cement version of Inventys' carbon capture technology at pilot scale. Phase III, the CO₂ Reuse Program, will prepare post-combustion CO₂ for reuse and support the economical assessment and demonstration of CO₂ conversion technologies onsite, such as CO₂-injected concrete and fly ash.

Funding for the first two phases is complete and development of Phase I is underway. Phase I will begin operation in 2019 followed by Phase II and III in 2020.

US: Charah Solutions has opened a terminal for fly ash in Hopedale, Massachusetts. The unit has railway access and is connected to local road networks. It is intended to serve customers in New England.

Charah Solutions says that the terminal will increase the availability of fly ash from its MultiSource materials network locations in the South, New England, the Midwest, the Rocky Mountains and California. These locations supply Class C and Class F fly ash for ready mix concrete producers and other customers.

Bangladesh: The Bangladesh Cement Manufacturers Association (BCMA) has asked for import tariffs on clinker to be reduced. In a letter to the National Board of Revenue (NBR) it requested that the duty be cut to either US$2.40/t or a fixed rate of 5%, according to the Dhaka Tribune newspaper. Importers pay around US$6.00/t at present. The BCMA argues that the cement industry is paying more than other industries for its imports.

The association has also called for value added tax (VAT) on raw materials to be cut to 5% from 15%, reducing advance income tax to 2.5% from 5% and exempting regulatory duties for fly ash and import duties for cement bulk carriers.

Serbia: Elektroprivreda Srbije, a government-owned power company, has completed a Euro14m terminal on the River Danube for its Kostolac B coal-fired power plant. The unit will be use to transport 105,000t/yr of synthetic gypsum and 157,000/yr of fly ash. It will also process limestone. The terminal was built as part of the first phase of a credit arrangement between Serbia and China.

Spain: Endesa sold 0.3Mt of fly-ash from its Carboneras power plant in Almeria to cement companies in the UK and North America in 2018. The energy company also sold fly-ash to the nearby LafargeHolcim Carboneras cement plant, according to La Voz de Almería newspaper. The company has also sold 30,00t of slag and 60,000t of gypsum from its limestone plant.

US: Charah Solutions has installed its MP618 thermal beneficiation technology at its terminal in Sulphur, Louisiana. The upgrade is intended to improve the quality of fly ash and to increase its supply of marketable fly ash to concrete producers. The proprietary process reduces loss on ignition, ammonia, activated carbon and moisture in fly ash.

The company hopes to provides concrete product producers and builders with a source of Class F fly ash to support a growing number of construction projects in the greater Lake Charles and Sulphur region. The Sulphur terminal is Charah Solutions’ second barge-supplied location in southern Louisiana. Its LaPlace, Louisiana terminal currently serves customers in Louisiana, Mississippi and Alabama.

China: Anhui Conch has continued a cement sale and purchase agreement with Jiangsu Conch Building Materials by entering into a new contract worth US$364m. Subsidiaries of Anhui Conch based in east China will sell a total of 7.5Mt of cement products to Jiangsu Conch, a non-wholly owned subsidiary of Anhui Conch, in 2019. Additionally, three of Anhui Conch’s subsidiaries in Shanghai region will procure 0.13Mt of fly ash and 70,000t of flue gas desulphurisation gypsum from Jiangsu Conch Building Materials in 2019 for a value of around US$3m. The deals follow a similar arrangement for Anhui Conch to sell cement to Jiangsu Conch in 2018.