Takeshi Iyoda

Study on estimation technique of hydration on concrete in the mold by electrical resistance value

Strength and durability of concrete is important for using long-term structure. In order to obtain enough strength and durability, it is necessary to progress hydration on concrete during the early age. Therefore, it is important to monitor the hydration in the mold. However it is difficult to check the state of concrete in the mold. Then, we focused on the electrical resistance as a method to check hardening concrete for in the non-destructive test. It has been reported that the electric resistance of the hardening concrete has a correlation with compressive strength at remolding time and carbonation ratio. However, it is not measured in the fresh concrete. So, we measured the electrical resistance of fresh concrete in the mold. As a result, the behavior of the electric resistance is very similar to the results of heat of cement hydration measured by the conduction calorimeter. Moreover, the behavior of the electric resistance was correlated with the setting time. Thus, it can be monitored the hydration on concrete from fresh to harden in the mold by using the electrical resistance. Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure – Bakker, Frangopol & van Breugel (Eds)

Effect of prevention for chloride ion using both of CA2 and expansive admixture to low heat portland cement

Salt damage is one of the serious causes of deterioration in reinforced concrete. However, when building mass concrete under salt damage environment, we have to use cement with a heat suppression effect which has low resistance for chloride ion. In this research, we focused on the CA2 which is admixture for salt damage prevention.CA2 reacts with calcium hydroxide from cement hydration and makes hydrocalumite. Thus, the soluble chloride ion is reduced. Finally, concrete using CA2 has high resistance for salt damage. LPC concrete using CA2 has low resistance for chloride ion than OPC concrete using CA2. After that, we had XRD measurement, and we have confirmed that hydration product is different in LPC and OPC when adding CA2 and expansive admixture. We think that the difference of hydration product is reason for difference of salt damage prevention by difference of ability to immobilize chloride ion. Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure – Bakker, Frangopol & van Breugel (Eds)

Comparison for permeability resistance between concrete and mortar

Mortar using for repairing on reinforced concrete structures. The substances such as carbon dioxide and chloride ion will be penetrated into the concrete or mortar. However, it is existing the interfacial transition zone between the aggregate interface and paste in the concrete. In this study, using a mortar obtained by removing the coarse aggregate from concrete, it was carried out a comparison of resistance of permeability between concrete and mortar. As a result, it decreases the permeability resistance by the water cement ratio is increased in ordinary Portland cement and blast furnace slag cement by carbonation resistant. The permeability resistance of concrete tends to decrease significantly compare to mortar by the interfacial transition zone. On the other hand, in case of the salt resistant, it is not clear the effect of it. Thus, it becomes formed pores like water reservoir to the lower surface aggregates by bleeding. Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure – Bakker, Frangopol & van Breugel (Eds)

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。