Cracking characteristics and pore development in concrete due to physical attack
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ORIGINAL ARTICLE
Cracking characteristics and pore development in concrete due to physical attack Zhongya Zhang
. Jianting Zhou . Jun Yang . Yang Zou . Zongshan Wang
Received: 22 April 2020 / Accepted: 23 July 2020 Ó RILEM 2020
Abstract This study provides a fundamental understanding on the deterioration of concrete due to physical sulfate/salt attack (PSA), including local cracking and pore structure development. The results show that sulfate salt crystals in a partially immersed concrete specimen preferred to precipitate in relatively large pores (DP-III, from 1 to 100 lm in diameter) in the concrete at the early stage of exposure. The persistent formation of small pores (DP-I and DP-II) and pore throats (PT-I and PT-II) occurred at the late stage of exposure. The gel pores, transition pores and even small capillary pores played an important role in providing space for crystal growth. The pore filling during the early stage resulted in a transient gain of specimen mass due to the capacity of pre-existing voids to accumulate the precipitated crystals (buffer effect). The later cracking degeneration induced by the pressure from the crystals was found to be limited to the subflorescence zone. This cracking degeneration
Z. Zhang (&) J. Zhou (&) J. Yang State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing 400074, People’s Republic of China e-mail: [email protected] J. Zhou e-mail: [email protected] Z. Zhang J. Zhou Y. Zou Z. Wang School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, People’s Republic of China
was a time-dependent process that primarily developed along with relatively unsubstantial zones in the concrete, such as the interfacial transition zone (ITZ), until the extensive coalescence of these pressureinduced cracks. Keywords Concrete durability Sulfate attack X-ray computed tomography Porous materials Bridge engineering
1 Introduction Crystal growth in restricted spaces inside porous cement-based materials is the dominant driving mechanism for PSA. This physical process mainly impacts the macroscopic properties of the attacked materials, such as concrete, in two ways [1–3]. The first one is characterized by a typical pore filling effect where the pre-existing voids in concrete are filled with these crystals. This effect can result in an increase in the mass and even a slight enhancement in the mechanical resistance during early exposure times [4–6]. The other is the degeneration caused by a significant crystallization pressure in narrow voids inside concrete exposed to PSA. This effect may cause mass loss, structural recession and expansion during late exposure times [7–10]. Therefore, current studies mainly focus on these macroscopic consequences and
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the microdetection of associated crystal growth [11–15]. These microdetection techniques were mostly destructive and highlighted a local characteristic accompanied by certain secon
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