Microstructural investigation of calcium aluminate cement-based ultra-high performance concrete (UHPC) exposed to high temperatures

Lee, N.K.; Koh, Kyung-Taek; Park, S.H.; Ryu, Gum-Sung

doi:10.1016/j.cemconres.2017.09.004

Cited by 111 publications

(55 citation statements)

References 35 publications

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“…Materials 2020, 03, x FOR PEER REVIEW 9 of 12 of the UFFA further reduce the thickness of C-S-H gel and improve the heat resistance of concrete. Furthermore, calcite could be found in the specimens and even increased in intensity at 400 °C [31,32], as illustrated in Section 3.2. Leading to a slightly increased in residual strength of the specimen subjected to 400 °C .…”

Section: Microstructure Observationsmentioning

confidence: 69%

Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

Tang

Zhang

et al. 2020

Materials

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Concrete has low porosity and compact microstructure, and thus can be vulnerable to high temperature, and the increasing application of various types of supplementary cementitious materials (SCMs) in concrete makes its high-temperature resistant behavior more complex. In this study, we investigate the effects of four formulations with typical SCMs combinations of fly ash (FA), ultra-fine fly ash (UFFA) and metakaolin (MK), and study the effects of SCMs combinations on the thermal performance, microstructure, and the crystalline and amorphous phases evolution of concrete subjected to high temperatures. The experimental results showed that at 400 °C, with the addition of 20% FA (wt %), the thermal conductivity of the sample slightly increased to 1.5 W/(m·K). Replacing FA with UFFA can further increase the thermal conductivity to 1.7 W/(m·K). Thermal conductivity of concrete slightly increased at 400 °C and significantly reduced at 800 °C. Further, combined usage of SCMs delayed and reduced micro-cracks of concrete subjected to high temperatures. This study demonstrates the potential of combining the usage of SCMs to promote the high-temperature performance of concrete and explains the micro-mechanism of concrete containing SCMs at high temperatures.

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Section: Microstructure Observationsmentioning

confidence: 69%

Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

Tang

Zhang

et al. 2020

Materials

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“…In high-temperature conditions, concrete is not stable due to the decomposition of aggregate and deformation of internal physical/chemical changes, leading to degrade and damage of concrete [2,6,7]. Previous studies revealed that the microstructure of cement-based materials changes with temperature [8][9][10][11], the disappearance of ettringite (AFt) at 100 • C, a decomposition of CH and C-S-H at 400-600 • C, and a transformation of C-S-H into the nesosilicate form could be found beyond 750 • C [7]. Hydration products originally from cementitious materials are mainly responsible for the strength of concrete, it can fill pores and delay concrete cracking.…”

Section: Introductionmentioning

confidence: 99%

Physical and Mechanical Properties of High-Strength Concrete Modified with Supplementary Cementitious Materials after Exposure to Elevated Temperature up to 1000 °C

Zhou

Yang

et al. 2020

Materials

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This paper presents the experimental findings of a study on the influence of combining usage of supplementary cementitious materials (SCMs) on the performance of high-strength concrete (HSC) subjected to elevated temperatures. In this study, four types of HSC formulations were prepared: HSC made from cement and fly ash (FA), HSC made from cement and ultra-fine fly ash (UFFA), HSC made from cement and UFFA-metakaolin (MK), and HSC made from cement and FA-UFFA-MK. Mechanical and physical properties of HSC subjected to high temperatures (400, 600, 800, and 1000 °C) were studied. Furthermore, the relation between residual compressive strength and physical properties (loss mass, water absorption, and porosity) of HSC was developed. Results showed that the combined usage of SCMs had limited influence on the early-age strength of HSC, while the 28-d strength had been significantly affected. At 1000 °C, the residual compressive strength retained 18.7 MPa and 23.9 MPa for concretes containing 30% UFFA-5% MK and 10% FA-20% UFFA-5% MK, respectively. The specimen containing FA-UFFA-MK showed the best physical properties when the temperature raised above 600 °C. Combined usage of SCMs (10% FA-20% UFFA-5% MK) showed the lowest mass loss (9.2%), water absorption (10.9%) and porosity (28.6%) at 1000 °C. There was a strongly correlated relation between residual strength and physical properties of HSC exposed to elevated temperatures.

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“…The pores are classified into two categories (a) gel pore, capillary pores, entrapped and entrained pores are characteristics of pores, while(b) macro pores, micro pores, meso pores, and larger pores are categorized according to the sizes of pores (Vodák et al 2004;Rivera et al 2016). Many techniques are available to determine the porosity in concrete such as pressure method, air-void analyzer, stereoscopic and microscopic methods (Moravcová et al 2016), torrent permeability tester (Kucharczyková et al 2010), mercury intrusion porosimetry (MIP) method widely used by researchers (Piasta et al 1984;Abell et al 1999;Chan et al 1999;Diamond 2000;Lee et al 2017), ultrasound method (Benouis and Grini 2011), water vapor adsorption, nitrogen adsorption (Moravcová et al 2016); but the limitation of these tests is that they assume that the pore geometry is regular and all the pores are interconnected. MIP measures capillary pores of size 0.005 µm to 10 µm while the adsorption techniques can predict the CSH gel pores of diameter less than 0.003 µm (Abell et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Estimation of Porosity and Pore Distribution in Hydrated Portland Cement at Elevated Temperatures using Synchrotron Micro Tomography

Pavani

Tadepalli

Agarwal

2019

ACT

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The porosity of concrete affects the mechanical properties and durability, during its exposure to extreme temperatures where the chemical and physical changes in PC affect the integrity of concrete as a whole because of its binding properties. An attempt is made to analyze the porosity in hydrated PC using synchrotron micro-tomography at temperatures of 27°C, 100°C, 400°C, 500°C, and 800°C. These temperatures are significant in the context of the mass loss and phase changes taking place during the thermal analysis. Image analysis is carried out to estimate porosity, radius, and circularity of pores for all the individual 2D slices. 3D analysis is carried out to estimate the diameter, area, and volume of pores present in the sample. The number of pores in the 2D slices has increased from 5974 to 11564 at 27°C and 800°C; while the total number of pores present in the sample at 27°C is 317 and at 800°C it is 3361. With the increase in temperatures, the area of pores 947 µm 2 contributed to 44.16 volume percent at 27°C, whereas at the temperatures of 800°C the area of 136 µm 2 pores volume percent is 41.

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Microstructural investigation of calcium aluminate cement-based ultra-high performance concrete (UHPC) exposed to high temperatures

Cited by 111 publications

References 35 publications

Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

Physical and Mechanical Properties of High-Strength Concrete Modified with Supplementary Cementitious Materials after Exposure to Elevated Temperature up to 1000 °C

Estimation of Porosity and Pore Distribution in Hydrated Portland Cement at Elevated Temperatures using Synchrotron Micro Tomography

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