モンモリロナイト族鉱物含有骨材を使用したコンクリートの凝結特性

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The authors recognized in the previous study that major problem of the quality of aggregate containing montmorillonite group was rather in workability loss than in properties of hardened concrete such as reduced strength or resistance to freezing and thawing and increased of drying shrinkage. In this study, the influence of montmorillonite group on the fresh concrete properties, especially setting property was examined. The main results obtained in this study are as follows: 1) Flow value was reduced and setting time was accelerated in mortar containing montmorillonite group compared to those in mortar without montmorillonite group. These phenomena related to montmorillonite group content and cation exchange capacity of aggregate. 2) Aggregate containing montmorillonite group, indicating high water absorption, affected both flow value and setting time. But aggregate without montmorillonite group, having high water absorption, simply affected flow value, did not setting time. 3) Potassium ion and sulfate ion concentration of pore solution obtained by mortar containing montmorillonite group was low compared to that of mortar without montmorillonite group at the early age. The ratio of exchangeable potassium ion at surface layer to that of in core of aggregate containing montmorillonite group was increased through the early age of mortar. 4) Accelerated setting was observed in case of mortar containing montmorillonite group which exchange-able cation was exchanged by sodium or calcium ion, but not observed in case of that exchanged by potassium ion. 5) In the case of mortar containing montmorillonite group, the third exothermic peak was observed between first peak and second peak in hydration process. The third peak was not recognized in the case of mortar without montmorillonite group. The accelerated initial setting was observed during the third peak period. The calorific value of the third peak closely related to the montmorillonite group content of aggregate and reaction ratio of gypsum of cement. 6) From the results described above, accelerated setting by montmorillonite group might be caused by following process. Ion exchange between calcium ion in montmorillonite group of aggregate and potassium ion in mortar pore solution from cement happens. Calcium ion concentration of pore solution is increased. Dissolution of gypsum from cement is controlled by high calcium ion concentration of pore solution. Hydration process of cement mineral, such as C_3A and C_3S is changed. Accelerated hydration is recognized as third exothermic peak. Finally, accelerated setting by aggregate containing montmorillonite group occurs.
一般社団法人日本応用地質学会の論文
1993-12-10

モンモリロナイト族鉱物含有骨材を使用したコンクリートの凝結特性

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