Storage of mine tailings and waste concrete imposes economical and environmental impacts. Researchers have attempted to reuse wastes as construction material by utilizing ordinary Portland cement (OPC) to stabilize them. This method, however, has a number of limitations related to OPC. In this research, a recent technology called geopolymerization is used to stabilize mine tailings and concrete waste so that they can be completely recycled and reused. The research includes three main parts. The first part studies the effect of different factors on the mechanical properties, micro/nano structure, and elemental and phase composition of mine tailings-based geopolymer binder. The second part investigates the feasibility of producing geopolymer bricks using mine tailings. The physical and mechanical properties, micro/nano structure, durability, and environmental performance of the produced bricks are studied in a systematic way. Moreover, the enhancement of the mine tailings-based geopolymer bricks by adding cement kiln dust (CKD) is studied. The third part of the research investigates the recycling of the fines fraction of crushed waste concrete to produce binder through geopolymerization in order to completely recycle concrete waste. The results indicate the viability of geopolymerization of mine tailings by optimizing the synthesis conditions. By properly selecting these factors, mine tailings-based geopolymer bricks can be produced to meet the ASTM standard requirements and to be environmentally safe by effectively immobilizing the heavy metals in the mine tailings. The physical and mechanical properties and durability of the mine tailings-based geopolymer bricks can be further enhanced by adding a small amount of CKD. The results also show that the fines fraction of crushed waste concrete can be used together with fly ash to produce high performance geopolymer binder. Incorporation of calcium in the geopolymer structure and coexistence of the calcium products such as CSH gel and the geopolymer gel explains the enhancement of the mine tailings-based geopolymer bricks with CKD and the high performance of geopolymer binder from the waste concrete fines and fly ash. The research contributes to sustainable development by promoting complete recycling and utilization of mine tailings and concrete waste as construction material.

The marked increase in demand for miniaturized consumer products in a broad range of potential applications including medical, telecommunication, avionics, biotechnology and electronics is a result of advancements in miniaturization technologies. Consequently, engineering components are being drastically reduced in size. This coupled with the quest for higher quality components, has imposed more stringent requirements on manufacturing processes and materials used to produce micro components. Hence, the development of ultra precision manufacturing processes to fabricate micro-scale features in engineering products has become a focal point of recent academic and industrial research. However, much attention in the area of micro-manufacturing, especially micro-mechanical machining, has been devoted to building miniature machine tools with nanometer positioning resolution and sub-micron accuracy. There is lack of fundamental understanding of mechanical machining at the micro and nano scale. Specifically, basic understanding of chip formation mechanism, cutting forces, size-effect in specific cutting energy, and machined surface integrity in micro and nano scale machining and knowledge of how these process responses differ from those in macro-scale cutting are lacking. In addition, there is a lack of investigations of micro and nano scale cutting of common engineering materials such as aluminum alloys and ferrous materials. This thesis proposes to advance the understanding of machining at the micro and nano scale for common engineering alloys. This will be achieved through a series of systematic micro and nano cutting experiments. The effects of cutting conditions on the machining forces, chip formation and machined surface morphology in simple orthogonal micro-cutting of a ferrous, P20 mold steel (30 HRC), and a non-ferrous structural alloy, aluminum AL7075 (87 HRB), used in the mold making and rapid prototyping industry will be studied. The data will also be compared with data obtained from conventional macro-scale cutting. In addition, the applicability of conventional metal cutting theory to micro and nano cutting test data will be examined. The analysis will provide a better understanding of machining forces, chip formation, and surface generation in micro and nano scale cutting process and how it differs from macro-scale cutting.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13008号 / 論工博第4133号 / 新制||工||1649(附属図書館) / 32936 / (主査)教授 北村 隆行, 教授 北條 正樹, 教授 琵琶 志朗 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM