TY - JOUR
T1 - Highly thixotropic ultra-high-performance concrete (UHPC) as an overlay
AU - Du, Jiang
AU - Guo, Pengwei
AU - Liu, Zhuo
AU - Meng, Weina
N1 - Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2023/2/22
Y1 - 2023/2/22
N2 - Ultra-high-performance concrete (UHPC) is an emerging overlay material for the bridge deck rehabilitation. As a durable material, UHPC overlay can effectively extend the service life of the bridge. In this study, the highly thixotropic UHPC overlay was designed and developed to facilitate sloped overlay construction with minimum formworks. A new type of water-based and well-dispersed nanoclay suspension was utilized to enhance the thixotropy. Two indices, including initial fluctuation of yield stress (τfloc) and thixotropy index (IA), were proposed to evaluate the thixotropy of fresh UHPC. It was found that, as nanoclay contents increased from 0 to 0.20 % (by mass of binders), the initial fluctuation of yield stress (τfloc) increased from 392.7 Pa to 3290.1 Pa and the thixotropy index (IA) increased from 9.7 Pa/min to 16.4 Pa/min, representing the significant enhancement on thixotropy. The highly thixotropic UHPC overlay showed good shape stability after the placement, but showing plenty of defects on the interface. It was shown that the bond strengths between thixotropic UHPC overlay and substrate are reduced by over 30 %. To address this issue, the application of proper vibration index on highly thixotropic UHPC overlay was investigated. Results showed that the bond strength between thixotropic UHPC overlay and substrate was increased by 45 % after the optimal vibration index. The SEM observation of the interface confirmed the increased air voids for highly thixotropic UHPC overlay and the reduced air voids after optimal vibration index. This study will promote the acceptance of highly thixotropic UHPC as an overlay.
AB - Ultra-high-performance concrete (UHPC) is an emerging overlay material for the bridge deck rehabilitation. As a durable material, UHPC overlay can effectively extend the service life of the bridge. In this study, the highly thixotropic UHPC overlay was designed and developed to facilitate sloped overlay construction with minimum formworks. A new type of water-based and well-dispersed nanoclay suspension was utilized to enhance the thixotropy. Two indices, including initial fluctuation of yield stress (τfloc) and thixotropy index (IA), were proposed to evaluate the thixotropy of fresh UHPC. It was found that, as nanoclay contents increased from 0 to 0.20 % (by mass of binders), the initial fluctuation of yield stress (τfloc) increased from 392.7 Pa to 3290.1 Pa and the thixotropy index (IA) increased from 9.7 Pa/min to 16.4 Pa/min, representing the significant enhancement on thixotropy. The highly thixotropic UHPC overlay showed good shape stability after the placement, but showing plenty of defects on the interface. It was shown that the bond strengths between thixotropic UHPC overlay and substrate are reduced by over 30 %. To address this issue, the application of proper vibration index on highly thixotropic UHPC overlay was investigated. Results showed that the bond strength between thixotropic UHPC overlay and substrate was increased by 45 % after the optimal vibration index. The SEM observation of the interface confirmed the increased air voids for highly thixotropic UHPC overlay and the reduced air voids after optimal vibration index. This study will promote the acceptance of highly thixotropic UHPC as an overlay.
KW - Bond strength
KW - Thixotropy
KW - Vibration index
KW - Water-based nanoclay
KW - ultra-high-performance concrete (UHPC) overlay
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U2 - 10.1016/j.conbuildmat.2022.130130
DO - 10.1016/j.conbuildmat.2022.130130
M3 - Article
AN - SCOPUS:85145250646
SN - 0950-0618
VL - 366
JO - Construction and Building Materials
JF - Construction and Building Materials
M1 - 130130
ER -