Eco-friendly is not only about plastic

PHOTO 2020 03 30 16 32 23

Kazakhstani leading educational institution’s innovational research project on ground improvements

The term “being eco-friendly” is getting popular day by day not only because the hype around of it with “eco-friendly” products but because it is one of global the challenges the world faces today. Many experts have predicted that so called “climate change” which caused by human efforts can lead to real catastrophes. In fact, it is true. There are million facts and proofs show that the way how people treat the environment today is not right! So, a logical question comes up, how does the world community react to the issue? Basically, it had led to be born so called “social and eco activism”. How about scientific communities around the world? Today, many educational institutions have been granted to conduct certain type of researches in order to prevent harnessing environment or to reduce the level of risks.

Currently, an assistant professor at Nazarbayev University, School of Engineering and Digital Science, Sung-Woo Moon is conducting research-based project in "Development of the sustainable and innovative ground improvement technique via environmentally friendly low-carbon rapid-hardening cements in Kazakhstan".

“Cementation, either by natural or artificial process, even in small amounts, tends to alter characteristics of soil behaviors and improve the strength of soil. Artificial cementation carried out by in-situ soil mixing can significantly improve the properties of the soft soil. For example, it has been applied for soil stabilization, column type reinforcement in soft soils, as gravity composite structures, liquefaction mitigation and in-place barriers for cutting off seepage. Cementation studies in laboratory are usually carried out to either understand the effect of natural cementation in field or to establish design criteria for cement stabilization. Hence, cementation effects need to be considered while designing foundation, analysis of the dynamic response of the subsurface, and evaluation of stability problems” says the assistant professor.

Assistant professor Sung explains that Ordinary Portland Cement (OPC) is the most commonly used binding material as extensive researches have been conducted to study the behavior of the cementing agent. OPC treated sand shows higher strength, improved liquefaction resistance, reduced permeability and compressibility. The mechanical properties of the soil are improved by the hydration of OPC with water available around and in the voids of geomaterial. The hydration of OPC involves converting calcium silicates to calcium silicate hydrates (CSH) and calcium hydroxide (Ca(OH)2), with CSH responsible for long term strength and also converting calcium aluminates to calcium aluminate hydrates (CAH), responsible for short term strength and dimensional stability (Taylor 1997). These cementitious materials bind the soil grains to improve shear strength, permeability and compressibility of soil mixtures. Carbon footprint of conventional OPC demands for discovering alternate binding admixture which has lesser impact on environment. To meet its obligations under the Kyoto Protocol Kazakhstan has agreed to reduce carbon emissions by 15% by 2020 and by 25% by 2050 compared to its 1992 level (National concept transition to green economy up to 2050, 2013). Calcium Sulfo aluminate (CSA) is a new alternative which has been studied with respect to concrete technology applications. The use of CSA for geotechnical soil improvement has never been explored yet. Compare to concrete technology applications, geotechnical applications such as ground improvement or land reclamation require generally much higher water to cement ratio. Apart from the eco-friendly characteristics, it is also expected that CSA-treated soil has higher initial strength gain than conventional OPC due to the compositional characteristic of CSA. In long term, the use of CSA in geotechnical projects would help us move towards a more sustainable approach in reducing carbon footprint.

Impact on science

Cement stabilization is one of the most common ground improvements works carried out in the world. For instance, Singapore has extensive coverage of soft clay, mainly marine clay deposit, which is characterized by low strength and high compressibility. Despite the unfavorable conditions, tunneling and underground space works are extensively practiced due to restricted space availability. Moreover, Kazakhstan has designed and constructed numerous underground space works which can lead to ground deformations, large settlements and foundation collapse especially in soft soils. Severe ground movements may not only impact the structure that it supports but will also affect surrounding buildings due to close proximity of construction. Therefore, binding admixtures are generally used to improve marine clay deposits. In addition, loose sand deposit can be also improved by artificial cementation, which is targeted to avoid any failure related to slope stability and soil liquefaction.

The goal of the research is to examine the effectiveness of Calcium Sulfoaluminate (CSA) in geotechnical applications, especially targeting cement-treated ground improvement. The carbon footprint of the widely used Ordinary Portland Cement (OPC) is much higher than CSA, which is examined as a new alternative with a lesser carbon footprint concerning global warming and climate change.