Technology news in clay and construction industries

Clay Technology magazine
11 May 2016

A round-up of the latest research in clay

Clay-based geopolymer could halt pathogens

Researchers at the Universidad Michoacana de San Nicolás de Hidaldo (UMSNH), Mexico, have developed an inorganic polymer resin that can be used as a cement and inhibits the growth, reproduction and transfer of yeast and fungi. 

Consisting of clay and sea sand dissolved in an aqueous solution, using microscopic glass particles as a biocidal agent to inhibit bacterial growth, the antibacterial geopolymer, named Antibac, can set in less than 24 hours. Dr José Carlos Rubio, the lead researcher, claims it can adhere to metal, ceramic and glass surfaces, and has a duration of around 100 years, resisting acids and water. 

It is also intended for use as an antibacterial coating, particularly for surfaces in hospitals, restaurants and the food processing industry. Once solidified, the resin encloses antibacterial microcrystals in its microstructure. When pathogens come into contact with the surface, they get stuck because of their high affinity with the microcrystals, preventing contact transference. The pathogens can then be removed by existing diffusion or a cleaning product. 

‘If someone sneezes on the table, the bacteria remain on the surface and can transfer to anything that touches it. In this sense the [traditional polymer] surface is a vector for the pathogens’, Rubio explains. 

The new geopolymer, which is estimated to cost around US$10 per square metre, has been patented and UMSNH is now looking for investors to begin its production. 

It follows recent news of the discovery of potent antibacterial properties in a rare mineral clay found in Canada’s British Columbia province. Microbiologists at the University of British Columbia (UBC) studied the unique clay found in Kisameet Bay, which has been used for centuries by First Nations people as a therapeutic medicine. 

In the first ever scientific study of the clay, the UBC team found that, when suspended in water, it killed 16 strains of ESKAPE pathogens – the class responsible for the majority of hospital infections in the USA. ESKAPE pathogens have contributed to increased mortality rates in hospitals, and are highly resistant to antibacterial drugs.

Buildings mapped in minutes

A new piece of software can create a 3D model of a building in 10 minutes using a tablet computer, even down to the detail of the arrangement of bricks in a façade. Computer scientists at ETH Zurich, Switzerland developed the software, which compares multiple images taken on a tablet with a fisheye lens and maps them based on the known location of the camera. The research is part of Google’s Project Tango, which aims to create a mobile device with advanced spatial perception. 

Clay swelling simulated

Tipped for use as a barrier for nuclear waste canisters buried in deep geological disposal sites, a full understanding of bentonite clay is essential. Now, University of Eastern Finland scientists have developed
a method to simulate the potential swelling pressure of sodium and calcium bentonites.

As a buffer between the canister and underground water and corrosive agents, the clays’ plasticity would help the canister to survive mechanical forces such as earthquakes or rock movements. But the swelling behaviour of the material is also crucial to the safety of disposal.  

The combination of environmental and interrelated structural factors that influence the swelling behaviour is difficult to measure experimentally. Instead, the researchers took a computational approach to examine atomic-level interactions among components of a clay-water system. 

They found that an increase in water salinity decreased swelling pressure, more evident in calcium chloride than sodium chloride solutions. Calcium clays were found to lose their swelling pressure as soon as swelling initiates, while sodium clays developed substantial swelling pressure after hydration. The computational model will be extended to measure the pressures of other potential barrier clays.