Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures
Ultra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure to high temperatures due to its characteristics. This work evaluates the damage and improvement of UHPC with coarse aggregates through mechanical properties (compressive strength and ultra...
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| Format: | Article |
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MDPI AG
2021-09-01
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| Series: | Buildings |
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| Online Access: | https://www.mdpi.com/2075-5309/11/9/416 |
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| author | Yunfeng Qian Dingyi Yang Yanghao Xia Han Gao Zhiming Ma |
| author_facet | Yunfeng Qian Dingyi Yang Yanghao Xia Han Gao Zhiming Ma |
| author_sort | Yunfeng Qian |
| collection | DOAJ |
| description | Ultra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure to high temperatures due to its characteristics. This work evaluates the damage and improvement of UHPC with coarse aggregates through mechanical properties (compressive strength and ultrasonic pulse velocity), transport properties (water absorption and a chloride diffusion test), and micro-properties such as X-ray diffraction (XRD), Mercury intrusion porosimetry (MIP), and Scanning electronic microscopy (SEM). The result demonstrates that polypropylene (PP) fibers are more suitable for high temperature tests than polyacrylonitrile (PAN) fibers. The result shows that 400 °C is the critical temperature point. With the increase in temperature, the hydration becomes significant, and the internal material phase changes accordingly. Although the total pore volume increased, the percentage of various types of pores was optimized within 400 °C. The mass loss gradually increased and the ultrasonic pulse velocity gradually decreased. While the compressive strength first increased and then decreased, and the increase occurred within 25–400 °C. As for the transport properties, the chloride migration coefficient and capillary absorption coefficient both increased dramatically due to the higher sensitivity to temperature changes. The results of the property improvement test showed that at temperatures above 800 °C, the compressive strength recovered by more than 65% and the ultrasonic pulse velocity recovered by more than 75%. In terms of transport properties, compared to the results before self-healing, the chloride migration coefficient decreased by up to 59%, compared with 89% for the capillary absorption coefficient, after self-healing at 800 °C. With respect to the enhancement effect after exposure to high temperatures, the environment of a 5% Na<sub>2</sub>SO<sub>4</sub> solution was not as good as the clean water environment. The corresponding changes in microstructure during the high temperatures and the self-healing process can explain the change in the pattern of macroscopic properties more precisely. |
| first_indexed | 2024-03-10T07:51:13Z |
| format | Article |
| id | doaj.art-613e6b5697fc47b2a316630606438ed8 |
| institution | Directory Open Access Journal |
| issn | 2075-5309 |
| language | English |
| last_indexed | 2024-03-10T07:51:13Z |
| publishDate | 2021-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Buildings |
| spelling | doaj.art-613e6b5697fc47b2a316630606438ed82023-11-22T12:16:00ZengMDPI AGBuildings2075-53092021-09-0111941610.3390/buildings11090416Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated TemperaturesYunfeng Qian0Dingyi Yang1Yanghao Xia2Han Gao3Zhiming Ma4College of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, ChinaCollege of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, ChinaCollege of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, ChinaCollege of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, ChinaCollege of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, ChinaUltra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure to high temperatures due to its characteristics. This work evaluates the damage and improvement of UHPC with coarse aggregates through mechanical properties (compressive strength and ultrasonic pulse velocity), transport properties (water absorption and a chloride diffusion test), and micro-properties such as X-ray diffraction (XRD), Mercury intrusion porosimetry (MIP), and Scanning electronic microscopy (SEM). The result demonstrates that polypropylene (PP) fibers are more suitable for high temperature tests than polyacrylonitrile (PAN) fibers. The result shows that 400 °C is the critical temperature point. With the increase in temperature, the hydration becomes significant, and the internal material phase changes accordingly. Although the total pore volume increased, the percentage of various types of pores was optimized within 400 °C. The mass loss gradually increased and the ultrasonic pulse velocity gradually decreased. While the compressive strength first increased and then decreased, and the increase occurred within 25–400 °C. As for the transport properties, the chloride migration coefficient and capillary absorption coefficient both increased dramatically due to the higher sensitivity to temperature changes. The results of the property improvement test showed that at temperatures above 800 °C, the compressive strength recovered by more than 65% and the ultrasonic pulse velocity recovered by more than 75%. In terms of transport properties, compared to the results before self-healing, the chloride migration coefficient decreased by up to 59%, compared with 89% for the capillary absorption coefficient, after self-healing at 800 °C. With respect to the enhancement effect after exposure to high temperatures, the environment of a 5% Na<sub>2</sub>SO<sub>4</sub> solution was not as good as the clean water environment. The corresponding changes in microstructure during the high temperatures and the self-healing process can explain the change in the pattern of macroscopic properties more precisely.https://www.mdpi.com/2075-5309/11/9/416ultra-high performance concreteelevated temperaturesself-healingtransport properties |
| spellingShingle | Yunfeng Qian Dingyi Yang Yanghao Xia Han Gao Zhiming Ma Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures Buildings ultra-high performance concrete elevated temperatures self-healing transport properties |
| title | Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures |
| title_full | Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures |
| title_fullStr | Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures |
| title_full_unstemmed | Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures |
| title_short | Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures |
| title_sort | transport properties and resistance improvement of ultra high performance concrete uhpc after exposure to elevated temperatures |
| topic | ultra-high performance concrete elevated temperatures self-healing transport properties |
| url | https://www.mdpi.com/2075-5309/11/9/416 |
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