凍結融解時の収縮低減剤混和セメントペーストの膨張収縮挙動の予測

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Currently, it has been reported that the concrete added shrinkage reducing agent（SRA）is degraded by the freezing and thawing action. SRA was used a chemical admixture consisted of alkaline oxide and ethylene oxide. However, the cause of this degradation has not been understood yet. Essentially the expansion is derived from the internal stress generated during freezing and thawing process. This paper aims to confirm the effect of SRA on the resistance of frost damage, and then predict the expansion/contract behavior for hardened mortar based on the comprehensive driving forces such as hydraulic pressure, crystallization pressure and negative water pressure during freezing and thawing process. Simulation data was compared with the experimental length change data. As the results, it was confirmed that there was better correlation between them, and the main cause was due to the hydraulic pressure. Freezing and thawing test indicated the expansion of mortar with SRA during freezing process became larger than that without SRA, and the expansion increased with freezing and thawing cycles. However, the amount of frozen water in mortar with SRA was smaller than that without SRA up to -20 degree Celsius. Furthermore, it was estimated that the enhanced frost damage due to SRA was derived from an increase of viscosity of pore solution with increase of the SRA concentration in pore.本論文は、収縮低減剤（Shrinkage Reducing Agent；以下SRA）を混和したセメント硬化体の凍結融解による強度の劣化機構の解明を目的とした。その劣化の要因としてSRA混和による内部応力の差異が生じていると仮定を立て、凍結融解時に不凍水と氷晶によって発生する内部応力を予測した既往のモデルを用いる事によって内部の挙動について推定し、実際のひずみ測定のデータと比較を行った。その結果、SRA混和セメント硬化体において、内部応力が無混和のセメント硬化体より大きいことを確認し、前述のモデルの妥当性を裏付けた。また、その内部応力の差に細孔内水の粘度の増加が寄与していることが確認された。