Volcanic ash vs radiation, nuclear waste

February 16, 2025 | 12:00am

MANILA, Philippines — Magma is now coming out as ash from Kanlaon Volcano.

The large amounts of volcanic ash the volcano scattered across Negros might just be useful.

All that ash need not go to waste, it can be used to shield against harmful radiation, even from radioactive nuclear waste.

It is a practical way to manage and dispose of volcanic waste, according to a new study conducted at the National University and the Ateneo de Manila.

The study, to be published on April 1 in the Journal of Building Engineering, is the first to look at the radiation shielding properties of geopolymer mortar based on volcanic ash from Taal Volcano in Batangas.

The geopolymer, a natural cement-like binder, is an eco-friendly alternative to Portland cement, says the study’s lead author, Floyd Rey Plando, a professor at the National University in Manila.

Plando and co-researchers Myris Supnad and Joel Maquiling are also connected with the Ateneo Geophysics Research Laboratory, Physics Department.

They used volcanic ash from Taal as an aluminosilicate, a mineral compound made of aluminum and silicate commonly known as feldspar.

The volcanic ash was obtained from Taal Volcano in Batangas during its eruption in January 2020. It was mixed with silica-rich fine sand from Pampanga rivers.

Taal Volcano is the second most frequently erupting active volcano in the Philippines. Its 2020 eruption produced an ashfall deposit covering an area of 6.2 million square meters.

Cleaning up a large amount of ashfall debris has ended up in various disposal pits which, in the long run, is unsafe especially in a tropical country like the Philippines, as it is possible for the wetted ash to “cement” or solidify over time, says Plando.

Currently, efforts to make use of this waste as a supplementary cement-like binder mix the volcanic ash with plastic, sand and cement to make “eco-bricks”.

The primary purpose of current efforts to convert volcanic ash into useful materials is to lessen the carbon dioxide emissions produced in making cement.

Using volcanic ash in geopolymers, or three-dimensional inorganic materials, is an alternative to cement to lessen carbon dioxide emisAsions, Plando says.

Making geopolymer is an eco-friendly way to manage volcanic waste and lessen the harmful effects of volcanic ash in soil, water, atmosphere and even human inhalation, he adds.

There is also a growing interest in applying geopolymer in radiation shielding. Marble stones, barite, basalt and magnetite have been utilized due to their high density, durability and natural properties to reduce the intensity of radiation passing through them.

Radiation shielding is essential for hospitals, industrial sites and nuclear research facilities.

These places use ionizing radiation for beneficial purposes such as helping doctors treat sick organs and broken bones, aiding engineers looking for structural weaknesses in buildings, or helping nutritionists sterilize food for longer shelf life.

Using volcanic ash for protection against radiation exposure lessens disposal issues after eruptions and turns the waste material into something useful.

“One of the potential industrial applications of this geopolymer mortar is the encapsulation of radioactive waste materials,” Plando says. “Using it as landfill liners due to its high density would prevent leachate contamination while providing a stronger and more stable matrix for long-term storage.”

Another application is reinforcing existing structures.

“Retrofitting buildings with this geopolymer mortar would enhance radiation shielding properties, especially in facilities that use radioactive materials, such as medical and nuclear facilities,” says Plando.

The study showed that incorporating Taal volcanic ash into geopolymer mortar significantly improves its microstructure, thermal resistance and radiation shielding capabilities — providing a shield to reduce radiation exposure. This improvement is largely due to the distinct chemical properties of volcanic ash, including its natural iron-rich mineral content.

“Iron has greater shielding capability because it contains more electrons. In addition, it is a dense metal due to its heavy and tightly packed structure. Materials with high electron density, such as Taal volcanic ash, are more efficient in blocking hazardous X-rays and gamma rays,” says Plando.