This study is related to techniques to analyze type and polymorphism of gypsum in Portland cement.
DSC peaks caused by dehydration of dihydrate and hemihydrate were separated sufficiently by sealing sample cells with a lid with a micro-hole of 30, umφ. Quantities of dihydrate determined by DSC agreed with quantities determined by TG. Quantities of hemihydrate determined by DSC were smaller than quantities determined by TG by about 7%.
Ratio of transformation from hemihydrate to II-anhydrate by heating samples at 200°C for 24 hr is proportional to the ratio of α-and /β-hemihydrete. By measurement of ratios of transformation to II-anhydrate of commercial cements, the existence of α-hemihydrate in portland cement is suggested.

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Various calcium aluminates with CaSO₄ were widely used for main composition of super high early strength cements and rapid hardening cements. Recently the demands of highly flowable rapid hardning concrete are increased for the repair methods of construction.
Application of limestone powder have been investigated for cement of functional cement for flowable concrete. For the development of new construction methods, the combination of limestone powders and the super high early strength cement will be important as advanced construction technology.
This paper discussed the influence of the amounts of CaSO₄ addition on the hydration of various calcium aluminates such as C₃A, C₁₁A₇·CaF₂ or C₁₂A₇ glass-CaSO₄-CaCO₃ systems and the reaction ratio of CaCO₃ in these hydration systems.
In the case of C₃A-CaSO₄-CaCO₃ system having the molar ratio of C₃A/CaSO₄ =1, monosulphate, ettringite, monocarbonate and hemicarbonate were produced at 7 days. After 7 days, monosulphate was reacted with CaCO₃ and their products were ettringite and monocarbonate. Compare with 7 days, the amount of ettringite was increased at 28 days. Delayed Ettringite Formation (D.E.F) was occurred.
On the other hand, all reaction ratio of CaCO₃ decreases with the increasing of amounts of CaSO₄ addition. When the molar ratios of CaSO₄ to C₃A, C₁₂A₇ glass and C₁₁A₇·CaF₂ were 3, 12 and 12 respectively, only ettringite or the ettringite with Al (OH) ₃ or Al (OH) ₂F were produced respectively and monosulphate was not produced. In those case. CaCO₃ was not reacted and D. E. F. was not observed.

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To determine chemical composition and formation of a new calcium ferrite oxychloride which called A pattern found in the previous work, the characterization of calcium ferrite monochloride hydrates obtained at various compounding ratios (6.0/2.0-4.0/2.0) of CaO/FeCl₃ and their heat-treated products were carried out by means of various instruments of XRD, FT-IR, TEM and SEM-EDX. Hydrates as starting materials before heat-treating are identified with a mixture of calcium ferrite monochloride hydrate and amorphous iron oxyhydroxide hydrate with partial carbonation by XRD and FT-IR studies. By electron microdiffraction study on the products heated at 600°C and 700°C, respectively, authors find new two orthogonal reciprocal patterns : B and C except A pattern. By supposing these B and C pattern to be orhorhombic symmetry lattice, principal diffraction lines of XRD pattern of heat-treating products are indexed reasonablly as orthorhombic lattice [B pattern : a=1.015 nm, b=1.781 nm and c=0.440nm] and orthorhombic lattice [C pattern : a= 0.740 nm, b=1.704 nm and c=0.510 nm], respectively. Probable chemical compositions of B and C pattern are estimated to be Ca_1.6Fe_2.0Cl_0.8O_4.2 and Ca_1.9Fe_2.0Cl_0.4O_4.7, respectively by EDX microanalysis.

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The theoretical Ca/Si atomic ratio in tobermorite of 0.83 was a fairly good approximation to that of 0.9 for cement hydrate powder in particle sizes of 44 to 125μm obtained by separating coarse aggregate in crushed waste concrete. A study was made to investigate hydrothermal synthesis of tobermorite from cement hydrate powder by changing hydrothermal conditions such as Ca/ (Si+Al) atomic ratio, initial pH, temperature and reaction time. The tobermorite was synthesized by hydrothermal treatment of the suspension (water/solid weight ratio 20) which added silica stone to cement hydrate powder. Characterization of the product was determined by means of X-ray diffraction, specific surface area measurement and scanning electron microscopic observation.
The formation of high crystalline tobermorite from the cement hydrate powder as raw material was promoted by adjusting synthetic condition such as Ca/ (Si+Al) atomic ratio of 0.74 and initial pH of 13.0 in suspension under constant state at 183°C for 20 hours. Also, the synthesis of tobermorite under constant state (pH 13.0, Ca/ (Si + Al) atomic ratio 0.74) was possible under low temperature at 140°C and short time for 12 hours as compared with result of usual hydrothermal synthesis of CaO-SiO₂ system. The carbonation control of tobermorite was discussed from amounts of calcium carbonate and adsorption of carbon dioxide.

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The antimony (III) and manganese (II) activated apatite phosphor for fluorescent lamp was produced by burning of mixture such as calcium hydrogen phosphate anhydride (CaHPO₄), calcium carbonate (CaCO₃), calcium fluoride (CaF₂), calcium chloride (CaCl₂), antimony trioxide (Sb₂0₃) and manganese carbonate (MnCO₃) under high temperature at 1200°C and it was hoped to energy-saving by decreasing burning temperature.
The present work was investigated about preparation of antimony and manganese activated apatite phosphor under low temperature from fine amorphous calcium phosphate (Ca₃ (PO₄) ₂ nH₂O, ACP) with high activity as raw material. The phosphor was characterized by means of X-ray diffractometry, thermal analysis (TG-DTA), fluorescent spectrophotometer, scanning electron microscopic observation and chemical analysis.
The relative emission intensity of antimony and manganese activated apatite phosphor was affected remarkably by preparative conditions such as burning temperature, time, F/ (F+Cl), Sb/Ca and Mn/Ca atomic ratios. The most suitable compounding ratios were 0.04 of Sb/Ca atomic ratio and 0.02 of Mn/Ca atomic ratio. Also, the emission spectrum of phosphor obtained by ACP was showed similar to marketing apatite phosphor with the blue luminescence of 460 nm and yellow luminescence of 575 nm. The shape of phosphor was spherical particle with a diameter of 1 μm which was superior to high spreadability.

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Non-crystalline fine particles in Na₂O-SiO₂ system were prepared by a sol-gel method. The sol-gel method consists of two processes; hydrolysis and condensation of tetraethylorthosilicate, and ion exchange between sodium ions and protons of OH groups in cluster. The effects of the conditions of each process and the addition of hydroxypropyl cellulose on the formation of fine particles were investigated to expand the composition range of the particles. The fine particles containing much amount of sodium were obtained by synthesizing under the optimal conditions. The maximum Na/Si ratio of the particles was estimated to 0.85. The composition range of the particles was influenced by the ion exchange because the condensation was inhibited by terminators or caps that the ion exchange resulted in. The results indicated that the control of the condensation was indispensable to obtain the high homogeneous fine particles.

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Reactions between asbestos dispersed in water and carbon dioxide were carried out at 30 to 80°C at atmospheric pressure. The reactions proceeded rapidly within 20 min and thereafter remained almost constant irrespective of reaction time. One of the reaction products was MgCO₃·5H₂O. The others were silica, which were divided into three types. They were films, spherical particles, and agglomerated thin plates depending on the preparation conditions. The asbestos annealed at 100 to 600°C showed increased reactivity with carbon dioxide as an increasing temperature, but on the contrary the asbestos annealed at higher temperature than 650°C decreased the reactivity with temperature. The reaction mechanism of asbestos with carbon dioxide and the formation mechanism of spherical silica from Si (OH) ₄ solution were briefly discussed.

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Formation of ZnO is examined by the homogeneous precipitation method in which ZnCl₂, (CH₂) ₆N₄ and NH₄Cl are used. The homogeneous precipitation method becomes advantageous to apply with increasing concentration of (CH₂) ₆N₄ and increasing ratio of NH₄Cl to ZnCl₂. Furthermore, formation of ZnO becomes easy. However, the precipitation becomes difficult.

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