Scientists develop method to produce concrete without cement

Using industrial waste, such as flyash, the scientists have found that the final product is as strong as traditional concrete, more resilient to the damaging effects of acid, and more stable when exposed to extreme heat and cold.

Portland cement is a basic ingredient of concrete and the most commonly used type of cement around the world. However, up to 1 t of CO₂ is released for every 1 metric t of portland cement that is produced. In fact, the global cement industry is thought to be responsible for 7% CO₂ emissions each year.

KTU researchers are aiming to reduce the concrete industry’s negative impact on the environment and are investigating methods for substituting portland cement with different materials.

It has been found that great amounts of industrial waste can be used in the production of concrete, as it contains active forms of silicon and aluminium compounds. It has been suggested that, in theory, any material that contains silicon or aluminium compounds could be used to produce concrete. This includes blastfurnace slag and metakaolin (material derived from the modification of clay mineral kaolitine).

It has been found that, once treated with an alkaline solution, these waste materials will start to melt and bind in a similar way to traditional cement. The final product can be either geopolymer or alkali-activated material, depending on the composition. The researchers also found that alkali-activated concrete is much more resilient to the effects of fire and acid, as well as protecting against corrosion, due to its higher pH level.

The KTU researchers have suggested that alkali-activated concrete could be used in place of traditional concrete in many fields. Indeed, they have suggested that it is becoming a globally popular alternative to traditional concrete. The proper preparation of raw materials and the activating solution also means that the alkali-activated concrete can solidify at the usual temperature. Still, the researchers recommended that, in order to produce this type of cement in a cost efficient way, local materials should be used.

“At first, the idea that concrete could be produced without using cement seemed radical,” said Vytautas Bocullo, Researcher in the Civil Engineering and Architecture department at KTU. “Now, after several years of intensive work, we succeeded in developing alkali-activated concrete, the compressive strength of which is the same as usual concrete. Instead of portland cement, we are using alkali-activated industrial waste products – flyash, biofuel bottom ash, AIF3 production waste – and silicagel etc. We are trying to use waste materials from local industry, such as aluminium fluoride production waste – silicagel and biofuel ash. The preparation of the substance depends on the material itself. For example, flyash from coal can be used instantly, where biofuel ash must be ground to the fineness of the cement. In order to improve the quality 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 concrete.”

The researchers in the Faculty of Civil Engineering and Architecture at KTU are continuing to experiment and develop other types of concrete mixtures. This includes ultra high performance concrete, which is being used for safe production, self-renewing concrete, and others.

KTU is a leading Lithuanian university, providing a range of studies and closely cooperating with business.

Read the article online at: https://www.worldcement.com/europe-cis/05112018/scientists-develop-method-to-produce-cement-without-concrete/