Non-thermal process for producing a powder containing calcium carbonate (CaCO₃) and magnesium hydroxide (Mg (OH) ₂) from dolomite by means of mechanochemical treatment was developed. This process consists of two steps : The first step is a grinding operation of a powder mixture of dolomite and solid sodium hydroxide (NaOH) for forming Ca (OH) ₂, Mg (OH) ₂ and Na₂CO₃ mechanochemically. The second step is a washing operation with water of the ground mixture for enabling us to remove Na₂CO₃ from the ground product. During the washing operation, Ca (OH) ₂ is changed into CaCO₃, so that the washed powder is composed of CaCO₃ and Mg (OH) ₂. The reactivity of the washed powder with sulfuric acid solution is also investigated and its high reactivity is confirmed when the mechanochemical reaction takes place completely during the milling operation.

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Calcium oxide and silica-gel mixtures milled by a planetary mill was subjected to heating and watering operations. The milled and heated mixtures and their hydration behavior were investigated by X-ray diffraction and differential thermal analyses. Dicalcium silicate (C₂S) is formed by heating the mixture milled for 30 minutes or more at about 750 K, while it appears at 1170 K in the case of the unmilled mixture. Amount of the C₂S formed at the relatively low temperature is increased with an increase in milling time of the mixture. The crystallizing temperature appeared at 1170 K is shifted towards the lower side with an increase in milling time, and comes close to 750 K. The crystallinity of C₂S hydrates formed by adding water to the heated mixtures after milling operation is inferior to that to the milled one without heating.

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Comparing with crystalline materials, there are not so many method for quantitative analysis of slag, due to its glassy state. In this study, a method for quantitative analysis using fluorescent light from slag excited by ultra violet was discussed. The wave length of ultra violet and fluorescent light were 257 nm and 541 nm, respectively. The effects of particle size of hydrated samples and the ratio of silica fume and/or silica sand on the intensity of fluorescent light were discussed.

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The hardening accelerators were prepared from calcium-aluminate glass, anhydrite and/or sodium carbonate, and the effects of the sodium carbonate on the hydration and the properties of the hardening accelerator based on calcium-aluminate glass were discussed. In this study, the CaO/Al₂O₃ molar ratio of calcium-aluminate glass was about 1.7, corresponding to 12CaO·7Al₂O₃. Ordinary Portland cement and the hardening accelerator were mixed, and the behavior of setting and hardening, the amount of hydration products and the ion concentrations in the solution extracted from paste samples were measured. The results obtained are as follows; 1) Sodium carbonate extended the workable time of the mortar containing the accelerator.This was caused by the deterrent effect of sodium carbonate on the formation of ettringite at very early stage of hydration.
2) Sodium carbonate canceled the inhibitory action of Al-rich gelous hydrates produced by the hydration of calcium-aluminate glass, and recovered the development of strength at 1 day. It is considered that these effects were caused by the accelerating action on the early hydration of cement.
3) The formation of ettringite, which significantly influences the hardening behavior, was mainly controlled by the dissolution of calcium-aluminate glass in the case that the accelerator containing sodium carbonate was used. And in the case that the accelerator without sodium carbonate was mixed with cement, it was mainly controlled by the dissolution of anhydrite.

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Calcium carbonate was prepared electrochemically in the electrolytic cell which had three compartments separated by semipermeable membranes each other, by applying constant voltages, 5-10 V, to the electrolyte between two platinum electrodes as an anode and a cathode in the central compartment of the cell. Calcium nitrate (as a calcium ion source) and sodium bicarbonate (as a carbonate ion source) were supplied into the other compartments of the cell, each the cathode side and the anode side, respectively. The addition of sodium nitrate into the electrolyte was found to be effective for the formation of calcium carbonate both calcite and vaterite. The ratio of vaterite to calcite increased with the increase of the sodium nitrate concentration. This fact suggests that vaterite can be synthesized selectively by using this method.

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In order to produce Ag-coated CaCO₃ particles, reaction conditions for preparation of precursor Ag₂CO₃-coated CaCO₃ particles by an ion-exchange method were investigated. Ag₂CO₃-coated CaCO₃ particles could be prepared at 40°C under suspension of CaCO₃ in AgNO₃ aqueous solution.
The separate formation of Ag₂CO₃ particles occured and the conversions of AgNO₃ into Ag₂ CO₃ were decreased at 60°C or above. Ag₂CO₃-coated CaCO₃ particles were converted into Agcoated CaCO₃ by heating at 400°C in air.

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