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  • 1.
    Tole, Ilda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Mechanical activation of clay: a novel route to sustainable cementitious binders2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    EU Sustainable Development Strategy planned to achieve improvement of life-quality by promoting sustainable production and consumption of raw materials. On November 2018, EU Commission presented a long-term strategy, aiming among others a climate-neutral economy by 2050. Cement production is contributing to 6-10% of the anthropogenic CO2 emissions. Thus, several strategies for total or partial replacement of Portland cement in concrete production have been developed. The use of supplementary cementitious materials (SCM) and alkali-activated materials (AAM) is considered the most efficient countermeasure to diminish CO2 emissions. The broadening of knowledge with particular attention to the sustainable goals is the primary requirement to be fulfilled when novel materials are investigated. This study aims to develop a novel clay-based binder that can be used as a sustainable alternative to produce SCM as well as AAM. Clay is a commonly occurring material, with large deposits worldwide. However, natural clay has a low reactivity and various compositions, depending, e.g. on the weathering conditions. The present research aims exactly at enhancing the reactivity of natural clays occurring in Sweden subjecting them to mechanical activation in a planetary ball mill. Ball milling (BM) is considered a clean technology able to enhance the reactivity of crystalline materials without resorting to high processing temperatures or additional chemicals. BM was able to induce amorphization in clay minerals and to transform the layered platy morphology to spherical shape particles. The efficiency of the process was strictly related to the used process parameters. Higher ball to processed powder (B/P) ratio, longer time of grinding and higher grinding speeds increased the degree of the obtained amorphization. However, an undesired extensive caking and agglomeration occurred in certain setups. The potential of activated clay as a SCM was investigated in specific case studies. The measured compressive strength results showed a direct correlation between the enhanced amorphization degree of the mechanically activated clay and the increased strength values. The pozzolanic activity was induced and enhanced after the mechanical activation of the clay. The reactivity was assessed by the strength activity index (SAI). Furthermore, preliminary tests have shown that the alkali activation of the processed clays produced solidified matrixes with considerable strength.

  • 2.
    Tole, Ilda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders – review2019In: Mineralogy and Petrology, ISSN 0930-0708, E-ISSN 1438-1168, Vol. 113, no 4, p. 449-462Article in journal (Refereed)
    Abstract [en]

    Mechanochemical activation can be defined as a process able to induce structural disorder through intensive grinding. In certain conditions, it may increase the chemical reactivity of the processed material. The process is extensively utilized in extractive metallurgy, synthesis of nanocomposites or pharmacology. It is also considered an environmentally friendly alternative to activate kaolinitic clay avoiding high calcination temperature. This paper aims to give a comprehensive overview of the process, its evolution, process parameters and applications. The paper focuses on the mechanochemical treatment of natural clay minerals, aiming at their transformation into cementitious or pozzolanic materials. It provides a summarized review of the theories related to the mechanochemistry and discusses commonly used models. The paper also analyzes various key factors and parameters controlling the mechanochemical activation process. The optimization and control of the several factors, as the filling ratio, the grinding media, the velocity, the time of grinding, etc., can promote developments and new research opportunities on different fields of application. Examples of applications, with a special focus on mechanochemically activated clay minerals and their use as cementitious binders, are listed as well.

  • 3.
    Tole, Ilda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mechanochemically activated clay as asustainable cementitious binder2019Conference paper (Refereed)
    Abstract [en]

    High-temperature requirements, emission of hazardous substances from cement kilns and the significantCO2 footprint in the calcination step are factors requiring special attention in the cement industry. Local andcommonly occurring clays can be a sustainable alternative for producing cementitious binders. Structuraldisorder in natural clay minerals can be induced through mechanochemical activation (MCA), by whichthe material develops an enhanced reactivity. The treatment of a Swedish natural clay through intensivegrinding is carried out in order to assess its potential as a sustainable cementitious binder. Several grindingparameters influence a MCA product. The filling ratio of the jar, the rotation speed, the time of grinding,as well as wet and dry environment, are variated to optimize the MCA process. The MCA process doesnot require high temperatures or added chemicals and shorter processing times can avoid high-energyrequirements during fine grinding. The structural changes of the clay were analysed by X-Ray Diffraction(XRD). Analysis of the particle size distribution of the raw and processed clay suggested a correlation withthe grinding duration. An increased ratio of grinding media versus the amount of ground material, whilelonger grinding duration increased the overall efficiency of the MCA process. The strength activity index(SAI) indicated an enhanced pozzolanic activity for the mechanochemically processed clay. Compressivestrength tests have shown a strong correlation between an enhanced amorphization rate and increasedcompressive strength values.

  • 4.
    Tole, Ilda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Optimization of the Process Parameters Controlling the Degree of Amorphization during Mechanical Activation of Clay Using the Taguchi Method2019In: 1st International Conference on  Smart Materials for Sustainable Construction—SMASCO 2019, Luleå, Sweden, 10–12 December 2019, Proceedings, 2019, Vol. 34Conference paper (Refereed)
    Abstract [en]

    Mechanical activation in a planetary ball mill (BM) is an environmentally friendly process able to enhance the chemical and pozzolanic activity of natural clays. Those materials can be used as supplementary cementitious materials (SCMs) to partially replace Portland cement in concrete. The process parameters of the BM are directly related to the degree of amorphization and thus to the enhancement of the chemical activity. Design of experiments (DOE) is a well-known statistical tool, which can assist in selecting optimized conditions and in obtaining systematic data. However, full factorial design requires a large number of experiment. Taguchi method is based on the use of an Orthogonal Array (OA) to evaluate optimization of the selected factors but with less required experiments. In this study, three factors, each on 2 levels, were selected: ball to powder ratio (B/P) with level 3 and 25, time of grinding with level 5 and 20, and water to powder ratio (W/P) with level 0 and 1. The degree of amorphization (DOA) was selected as the main response for the Taguchi method. DOA was calculated as the ratio between the integral intensities of the main peak of the kaolinite [001] before and after grinding. For dry grinding, the predicted optimized value of DOA complied with the experimental results. Maximized DOA value was achieved for B/P equal to 25 and the grinding duration of 20. This method can be a valuable tool to predict the amorphization degree of minerals present in the natural clay, leading to the optimization of the mechanical activation process.

  • 5.
    Tole, Ilda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Rajczakowska, Magdalena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Activation of a Raw Clay by Mechanochemical Process: Effects of Various Parameters on the Process Efficiency and Cementitious Properties2018In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, no 10, article id 1860Article in journal (Refereed)
    Abstract [en]

    The efficiency of the mechanochemical activation (MCA) is influenced by various process parameters as well as by the properties of the treated material. The main objective of this research was to optimize the MCA process, gaining enhancement of the chemical reactivity of a Swedish raw clay, which is going to be used as an alkali-activated cementitious binder. The effects of the amount of water, the filling ratio, the rotation speed, and the grinding duration on the amorphization degree were evaluated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Generally, wet and dry processes showed an extensive amorphization of both kaolinite and muscovite minerals present in the studied clay. On the contrary, quartz was amorphized mainly by the wet grinding process. The efficiency of both dry and wet grinding processes was enhanced by the increased number of grinding media versus the amount of the activated material. However, longer processing times caused significant agglomeration while a higher rotational speed enhanced the amorphization. Preliminary tests have shown that alkali activation of the processed clays produced hardened samples. Furthermore, the increased amorphization corresponded to the increased compressive strength values.

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