To reduce pollution, ITS doctor strengthens concrete with fly ash

Wiwik Dwi Pratiwi, “Cement with high fly ash content is suitable for marine environments. (Photo: Prive. Doc)

IO, Surabaya – Solid waste from coal combustion, also known as fly ash, is still commonly found piled up in some regions in Indonesia. Concerned about these conditions, Wiwik Dwi Pratiwi, from the doctoral program of the Department of Civil Engineering Sepuluh November Institute of Technology (ITS), conducted a study using high levels of fly ash for cement mixes to further strengthen concrete.

The dissertation titled Very-High Volume Fly Ash (VHVFA) Cement with the Combined Alkaline Activator was successfully presented in an open doctoral session at the ITS Department of Civil Engineering. Discarding fly ash can pollute the surrounding environment. Therefore, in her research, Wiwik seeks to reduce the existing buildup by utilizing fly ash from various Steam Power Plants (PLTU) in Indonesia. Among them is Paiton Power Plant, Tanjung Jati Power Plant and Bayah Power Plant.

Not only from PLTU but Wiwik also obtained samples from Petrochemicals. “I was assisted by my promoter in getting fly ash samples,” she said in a release received by Independent Observer, Tuesday (3/3/2020).

The woman who works as a lecturer at Surabaya State Shipbuilding Polytechnic (PPNS) uses 80 percent of fly ash in the cement mixture, in contrast to other studies that only use fly ash at levels of 0-70 percent. This is one of Wiwik’s focuses on her dissertation. “I want to use fly ash with high levels in this study,” she said.

This Chemical Engineering alumnus of Gadjah Mada University (UGM) explained that she had several aims and objectives. In addition to reducing fly ash buildup in Indonesia, high levels of fly ash are also considered to be able to strengthen the cement mixture to be used. “The addition of fly ash is already known to increase the strength of cement.”

Wiwik stated that fly ash has a low reactivity, so that it needs additional activators. The finding of the composition of activators for fly ash is the next focus. She has discovered were Precipitated Calcium Carbonate (PCC) and NaOH solution: this activator is considered to be able to increase the compressive strength of cement with very high levels of fly ash.

Another focus in her research was to identify the very diverse nature of fly ash. The nature and characteristics of the fly ash also determine the strength of the cement. “I did this so that the characteristics of good quality fly ash would be clearer.”

After conducting her research, Wiwik revealed the characteristics of good quality fly ash. The nature and characteristics of fly ash in terms of morphane, levels of CaO, silicon (Si) dissolved in NaOH solution, and grain size. “The finer the better, the more amorphous the better, and the more dissolved Si, the better,” she said.

Admittedly, there are still a few more problems she wants to solve related to fly ash and Wiwik hopes that her research will continue. Cement with very high levels of fly ash can be utilized, for buildings in the sea. “Cement with very high levels of fly ash is well suited for marine areas,” she mentioned. (*/est)