Most tunnel lining concretes have sidewall of negative angle, so bugholes on the concrete surface frequently appear. The bugholes are caused from entrapped air in concrete placing; the part of bugholes remains on concrete surface even after adequate vibrating for consolidation. In the previous investigation, the authors have studied on the generation mechanism of bugholes in a visible test and examined the reducing effects by covering sheet for concrete forms. According to the investigation, it was found that the water-permeable sheet causes color irregularity of concrete surface while the sheet is effective to decrease the bugholes. Hence, the present study also focuses on the effect of sheets reducing bugholes. The foci of this study are to develop an effective sheet for aesthetic of concrete surface and to reevaluate the effectiveness for reduction of bugholes. Fundamental test using a model form and various covering sheets was performed by referring to the previous investigation. The test confirms that the developed sheet adequately contributes on decrease of bugholes without the color irregularity of concrete. The observations may be useful for most concrete construction as well as tunnel lining concrete.
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