Environmentally friendly concrete from industrial waste is as strong as traditional

November 1, 2018, Kaunas University of Technology
After several years of intensive work KTU scientists succeeded to develop alkali activated concrete, which compressive strength is 55 MPa (the same as in usual concrete). Credit: KTU

Scientists at Kaunas University of Technology (KTU), Lithuania are developing methods for producing concrete without cement, using fly ash, an industrial waste product. The final product is as strong as traditional concrete, is more resilient to damaging effects of acid, and more stable in cases of exposure to extreme heat and cold.

In order to produce one metric ton of Portland , a basic ingredient of concrete and the most commonly used type of cement around the world, up to one ton of carbon dioxide (CO2) is released. It is estimated that the global cement industry is responsible for 7 percent of yearly emissions into the atmosphere. Aiming to reduce the concrete industry's negative impact on the environment, KTU researchers have been investigating methods of substituting Portland cement with other materials.

"At first, the idea that concrete can be produced without using cement seemed radical. Now, after several years of intensive work, we successfully developed alkali-activated concrete, with compressive strength of 55 MPa (the same as in conventional concrete). Instead of Portland cement, we are using alkali-activated industrial products—fly ash, biofuel bottom ash, AlF3 production waste—silica gel etc.," says Vytautas Bocullo, researcher at KTU Faculty of Civil Engineering and Architecture.

According to the researcher, the biggest advantage of this type of binder is that in its production, a great amount of containing an active form of silicon and aluminum compounds can be used. Theoretically, any material containing silicon and aluminum compounds could be used, such as blast furnace slag or metakaolin, material derived from modification of clay mineral kaolinite.

Aiming to reduce the negative concrete industry's impact on the environment, KTU researchers have been investigating methods of substituting Portland cement with other materials. Credit: KTU

Treated with a special alkaline solution, these materials start melting and binding similarly to traditional cement. Depending on the composition, the final product can be either geopolymer or alkali-activated material. Alkali-activated concrete is much more resilient to the effects of fire and acid. Also, due to its higher pH, this concrete protects armature against corrosion.

Bocullo maintains that alkali-activated concrete can be used instead of traditional concrete in many fields, and is becoming a globally popular alternative to traditional concrete. By properly preparing raw materials and the activating solution, such concrete solidifies at the usual temperature. However, in order to produce this type of concrete in a cost-efficient manner, local materials are best.

"We are trying to use waste from local industry, such as aluminum fluoride production waste—silica gel and biofuel ash. The preparation of the substance depends on the material itself. For example, fly ash of coal can be used immediately, but the biofuel ash need to be ground up to the fineness of the cement. In order to improve the qualities of the final product, several substances can be mixed, but before that, their chemical composition and additives need to be investigated for their impact on the environment and on the compressive strength of the concrete," says Bocullo.

Explore further: Making cement sustainable

Related Stories

Making cement sustainable

October 17, 2018

Cement production accounts for up to nine percent of global anthropogenic carbon dioxide emissions, according to the World Business Council for Sustainable Development. Sabbie Miller, assistant professor in the Department ...

Researcher tests fly ash for stronger concrete

March 15, 2017

Portland cement has been around for more than 250 years as the binding material for concrete, mortar and stucco, but a Missouri University of Science and Technology researcher is studying ways to make concrete without the ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

EPA adviser is promoting harmful ideas, scientists say

March 22, 2019

The Trump administration's reliance on industry-funded environmental specialists is again coming under fire, this time by researchers who say that Louis Anthony "Tony" Cox Jr., who leads a key Environmental Protection Agency ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.