EXPERIMENTAL INVESTIGATION OF AIR VOID FORMED AROUND STEEL BAR USING X-RAY CT SCANNING

Author(s): T. Ikeda, H. Hamada, Y. Sagawa and M. FunahashiI
Paper category: Proceedings
Book title: Proceedings of CONSEC13 Seventh International Conference on Concrete under Severe Conditions - Environment and Loading Volume I
Editor(s): Z.J. Li, W. Sun, C.W. Miao, K.Sakai, O.E. Gjørv, N.Banthia
ISBN: 978-2-35158-124-7
e-ISBN: 978-2-35158-134-6
Publisher: RILEM Publications SARL
Publication year: 2013
Pages: 748-754
Total Pages: 961
Language : English

Abstract: Corrosion of Steel bar is affected by several factors such as chloride ion concentration, oxygen and water supply. Interfacial zone between concrete and steel bar is also important factor on steel corrosion. It is well known that air void formed around steel bar accelerates corrosion, however air void structure such as size and distribution were not fully understood. This study presents the observation results of three dimensional structure of air void around steel bar obtained by X-ray CT (Computed Tomography) scanning. Mortar specimens with height of 500mm and cross section of 150×150mm are prepared. Water to cement ratio of mortars are varied 3 types to change bleeding ratio. Aluminum bar are used as alternative material for steel bar because X-ray can not transmit in steel. Two bars with different height, 30mm from top and bottom, are embedded in each specimen. One month after casting, observation using X-ray CT scanning is carried out. As a result, 2~5mm of thickness of air void is formed around top bar. On the other hands, the average thickness of air void around bottom bar is 0.1~0.3mm. However, several air voids with mm-ordered size are detected on bottom bar which can cause macro-cell corrosion. Air void size around top bar depended on water to cement ratio, larger void is formed in specimen with higher water to cement ratio. Using X-ray CT scanning is effective to evaluate air void structure quantitatively.

Online publication : 2013
Publication type : full_text
Public price (Euros) : 0.00