Minoru Morioka

INFLUENCE OF WATER ON CARBONATION OF γ-C₂S AND CARBONATION BEHAVIOR OF HARDENED PASTE CONTAINING γ-C₂S

This paper investigates the influence of water on carbonation of γ-C₂S (γ-2CaO・SiO₂) and carbonation behavior of γ-C₂S contained in hardened cement paste. From the result of accelerated carbonation (40℃, 50%RH, 20%CO₂), carbonation ratio of γ-C₂S without adding anything increased to 4% at age of 28 days. By the addition of water to γ-C₂S before accelerated carbonation, carbonation ratio of γ-C₂S reached 33%. Further, carbonation ratio of C₂S increased to 71% by continuous supply of water. It was found that carbonation ratio of γ-C₂S depended on the supply condition of water. On the other hand, carbonation ratio of γ-C₂S in hardened cement paste continued to increase without water supply under same accelerated carbonation conditions. In the surface portion, the carbonation ration of γ-C₂S contained in hardened cement paste reached 64% at age of 28 days and 75% at age of 91 days. This result suggested that, in case of hardened cement paste, the carbonation of γ-C₂S progressed effectively by water supply from micro-pore structure and carbonated cement hydrates. Based on the above result, the use of γ-C₂S as the cement admixture could be considered effective combination for carbonation progress of γ-C₂S.γ-2CaO・SiO₂（γ-C₂S）と、γ-C₂Sを混和したセメント硬化体の炭酸化挙動を比較検討した。γ-C₂Sを炭酸化する際に水を添加することで、28日における反応率は4％から33％に増加し、更に継続的に水を供給することで、71％まで増加した。一方、セメント硬化体中のγ-C₂Sは、水の供給を行っていないにも関わらず、継続的に炭酸化が進行し、反応率は促進91日で75％まで増加した。セメント硬化体の細孔中に存在する水や、セメント水和物が炭酸化して分解する際に放出される水によってγ-C₂Sの炭酸化が効果的に進行すると考察した。γ-C₂SをOPCと併用することが、γ-C₂Sの炭酸化を促進する効果的な組み合わせであることが明らかになった。

INSTIGATION ON MECHANISM OF LONG-TERM STRENGTH DEVELOPMENT OF CARBONATED CEMENT-TREATED SAND

The mechanism of the long-term strength development of carbonated cement-treated soils was experimentally investigated. The unconfined uniaxial compressive strength of the carbonated specimen of the cement-treated soil was larger than that of the non-carbonated specimen cured in the sealed condition. In the carbonated specimens, the strength of the specimen carbonated in the air was larger than that of the specimen carbonated in the accelerated camber. The effect of the carbonation method on the strength was analyzed. Then, it was found that forms of carbonated C-S-H gel has significant effect on the strength development rather than the amount of reacted CO₂ and chemically bound water. In the case of the specimen containing bentonite, the strength of the carbonated specimen cured in the air was almost same as the strength of the specimen cured in the sealed condition. It was caused that the carbonation prevented the additional increase of the strength by pozzolanic reaction.炭酸化したセメント系砂質改良土の長期強度発現メカニズムを解明するために各種試験を実施した。セメント系砂質改良土を炭酸化すると、封緘養生に比べ、一軸圧縮強さが大きくなった。炭酸化方法により強度発現に違いが有り、促進炭酸化養生よりも気中養生を施した場合に強度が増進した。各種分析結果から、炭酸化したときの強度の増進にはCO2含有量や結合水量よりも炭酸化したC-S-Hの形態が影響している。ベントナイトを混合した場合、封緘養生と気中養生の長期強度は同等であった。これは気中養生では炭酸化に伴い、ポゾラン反応が阻害されたためであると考えられる。

PHYSICAL PROPERTIES OF HARDENED BLAST FURNACE SLAG CEMENT COATED WITH ORGANIC - INORGANIC COMPOUND TYPE CURING AGENT

Organic-inorganic compound type curing agent （CP）was spread on the hardened blast furnace slag cement that was demold at the age of 1 day, and basic physical properties were examined. As a result, the following experimental results were obtained. ① The mass change was equal to the one that sealed curing was done until the age of 7 days. ② compressive strength was equal to the one that sealed curing was done until the age of 7 days. ③ The neutralization resistance was more excellent than the one that sealed curing was done until the age of 14 days. ④ Ignition loss and the amount of calcium hydroxide were more than the one that sealed curing was done until the age of 7 days or 14 days. It was confirmed that the hydration of the blast furnace slag cement was appropriately progressed. ⑤ Pore size distribution was equal to the one that sealed curing was done until the age of 7days.有機－無機複合型塗膜剤（CP）を材齢1日で脱型した高炉セメント硬化体に塗布して基礎物性を調べた。その結果、以下の実験結果を得た。①質量変化率は材齢7日まで封緘養生を行ったものと同等であった。②圧縮強度は材齢7日まで封緘を行ったものと同等以上であった。③中性化抵抗性は材齢14日まで封緘養生を行ったものよりも良好であった。④結合水量や水酸化カルシウムの生成量は材齢7日もしくは材齢14日まで封緘養生を行ったものと同等以上であった。CPは高炉セメントの水和を適切に進行させることを確認した。⑤細孔径分布は材齢7日まで封緘養生を行ったものと同程度であった。