The effect of crystal grain size of the starting limestones on the properties of the resulting hydrated limes in the dry hydration method has been investigated using seven natural limestones from different districts and a synthetic calcium carbonate as a reference. Two types of the limestone sample, i.e., the massive sample of the limestone quarried out and the molding briquette sample of the powder limestone (under 250 μm and 710 μm in size) under high pressure, were prepared for the experiments. The degree of shrinkage of the quicklime obtained by the calcination of the samples in the temperature range of 900 to 1300°C under air atmosphere has been measured first. Then, the fractional part of the fine hydrated lime passed through under 45 μm in size was measured in the following process as well as other physical properties. As the results, it was found that the degree of shrinkage of the massive sample and the fractional part of the fine hydrated lime were increased with decreasing the particle size of the starting limestone samples. The difference in the degree of shrinkage for the kind of the sample was also found to be larger for the massive samples than for the molding briquette samples. For both samples the proportional relationship between the degree of shrinkage and the fractional part of the fine hydrated lime was confirmed (the massive sample; r=0.942, the molding briquette 710 sample; r=0.921, the molding briquette 250 sample; r=0.896). This result can be a technical guideline for preparing.

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塩基性リン酸カルシウム二水和物 (DCPD) やα-リン酸三カルシウム (α-TCP), β-リソ酸三カルシウム (β-TCP) のようなリン酸カルシウムとカルシウムアルミノシリケートガラスを水熱処理した・反応生成物はXRDで測定し, 圧縮強度も測定した.ガラスはSiO₂がおおよそ40重量%, CaOが30から50重量%, Al₂O₃が10から30重量%の組成であった.これら混合物を250℃までの条件で水熱処理した.DCPD単独のものは硬化せず, ヒドロキシアパタイト (HAp) を生成しなかったが, 高温では塩基性リン酸無水物 (DCPA) が生成した.しかし, CaO含有量の多いガラスが共存すると, HApを生成するとともに, 強度も発現した・α-TCP単独のものは, 105℃でHApが生成したり, 高強度のものがえられた.しかし, 温度が高くなると強度は低下した.α-TCPは水和の途中でβ-TCPに転化した.β-TCP単味のものはα-TCPより反応性は低いが, 硬化した.β-TCPは0度DCPAに転化し, その後水和してHApになることがわかった.

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The effect of the addition of acrylamide on hardening of calcium phosphate cements with different Ca/P mixing ratios was investigated. The cements with a Ca/P ratio ranging from 1.44 to 1.67 were prepared by mixing thermal decomposition product of hydroxyapatite with dicalcium phosphate anhydrous. The cement pastes with or without acrylamide were cured at 37°C for 45 h. The added acrylamide was polymerized when the setting reaction of calcium phosphates proceeded. In cements with polyacrylamide, the bending strength of hardened cements showed the maximum value of 16-17 MPa at Ca/P ratios in the range of 1.50 to 1.53, and it decreased as a Ca/P ratio increased from 1.55 to 1.67. X-ray diffraction analysis showed that the extent of conversion of α-tricalcium phosphate to hydroxyapatite decreased as a Ca/P ratio increased in cements with polyacrylamide. In cements without additives, the bending strength of hardened cements showed the value of 10-12 MPa at Ca/P ratios in the range of 1.44 to 1.62. The results suggested that using a Ca/P mixing ratio from 1.50 to 1.53 was favorable for improving mechanical properties of the calcium phosphate cements by the addition of acrylamide.

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Characteristics of the coal ash from a 75-t/h coal-fired fluidized-bed combustion boiler were studied experimentally. After producing solidified coal ash using a 75-t/d plant, its characteristics in both block and crushed forms were also studied experimentally. Results can be summarized as follows.
1) A solid phase reaction takes place between coal ash and CaO at around 850°C, the FBC boiler bed temperature, generating a large amount of hydraulic substances.
2) Coal ash consisting of 10-20% of CaO and 15% or less of unburnt carbon can be turned into a solid of high strength after steam curing at 60°C.
3) Granular solidified coal ash can satisfy the Standards of Upper Subbase Materials and the Enviromental Standards for Soil.

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The suspension grout is difficult to be injected into the ground composed of comparatively fine sand. In this paper, the main cause of the difficulty of the grout penetration into the fine sand was investigated and the countermeasure for ensuring the satisfactory injection was proposed. As a result, it was suggested that ultrafine cement particles agglomerated easily in suspension grout and formed many particles larger than the maximum cement size of 12 μm and this would be the main reason why the grout tends to be injected unsatisfactorily into the fine sand. Therein, the simultaneous application, namely addition of chemical admixture and short time use of a ultrasonic vibrator was helpful to prevent the particles from agglomerating in the grout for a long time, and facilitated the grout penetration even into the fine sand.

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