An Experimental Study on the Period of Cold Joint Occurrence Effecting Shear Bond Performances of UHSCC

Title & Authors
An Experimental Study on the Period of Cold Joint Occurrence Effecting Shear Bond Performances of UHSCC
Kim, Min-Seong; Yang, Hyun-Min; Lee, Han-Seung; Cho, Keun-hee;

Abstract
The purpose of this study is to evaluate the performance on the compressive bonding shear strength of ultra-high strength steel fiber reinforced cementitous composites(UHSCC). As a result of compressive bonding shear strength through Direct shear test, It was found that the specimen($\small{150{\times}150{\times}150mm}$) of NC(Normal concrete) + NC showed similar compressive bonding shear strength at whole experimental level. On the other hand, the specimen of UHSCC + UHSCC showed decrease of compressive bonding shear strength from after 30 minutes of the retarded placement than 0 minute. As a result of analyzing failure mode of bonding interface, It was found that the specimen of NC + NC showed mixed failure at whole experimental level. In case of the specimen of UHSCC + UHSCC, it showed interface failure from the specimen that are 30 minutes, 60 minutes and 90 minutes of delay of concrete placing. As a result of analyzing XRD test in terms of the placement interface on the specimen of NC and UHSCC, relatively much amount of $\small{SiO_2}$ was detected from the specimen of UHSCC than that of NC. It is judged that the most of main components of coating film shown in the specimen of UHSCC is $\small{SiO_2}$. In conclusion, it is judged that UHSCC which is made from after 30 minutes of delay of concrete placing is unable to be used as structural member because of deterioration of bonding performance. From later study, it is judged that the improvement of bonding performance from the part of cold joint occurrence is necessary through the interface preparation method.
Keywords
Ultra-High Strength Fiber Reinforced Cementitious Composites(UHSCC);Cold joint;Retarding placement;Compressive shear strength;
Language
Korean
Cited by
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