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Mechanical properties of steel fiber-reinforced reactive powder concrete at high temperature and after cooling

Procedia Engineering 2017年 210卷 597-604页

作者： Muhammad Abid Xiaomeng Hou Wenzhong Zheng Ghulam Qadir Waqar Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin 150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China

Reactive powder concrete (RPC) is advanced cement-based material. It is produced through microstructure enhancement technique. Like other types of concretes, RPC has also been affected by severe environmental conditions such as accidental fire. Up to date, very limited research has been carried out to compare the performance of RPC at fire and after cooling. To address this gap in knowledge, the mechanical properties such as compressive strength, split-tensile strength, flexural strength and elastic modulus have been studied at high temperature and after cooling. 72 cubic specimens and 72 prismatic samples were tested. The hot and residual strength results were plotted as a function of temperature. The results indicated a higher residual strength than hot-strength in the temperature range of 20-300℃. Above 300℃, there was no sizable difference between the hot and residual strength of PRC. A comparison has also been made among the test data with current design codes.

关键词： Reactive powder concrete high temperature hot behavior residual behavior mechanical properties

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Study on the effect of ground motion direction on the response of engineering structure

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 649-656页

作者： Sun Menghan Fan Feng Sun Baitao Zhi Xudong Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology School of Civil Engineering Harbin Institute of Technology Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration

Due to the randomness of earthquake wave magnitude and direction, and the uncertain direction of strong axis and weak axis in the construction of engineering structures, the effect of the direction of ground motion on a structure are studied herein. Ground motion records usually contain three vertical ground motion data, which are obtained by sensors arranged in accordance with the EW （East -West） direction, NS （South- North） direction and perpendicular to the surface （z） direction, referring to the construction standard of seismic stations. The seismic records in the EW and NS directions are converted to Cartesian coordinates in accordance with the rotation of θ = 0°-180°, and consequently, a countless group of new ground motion time histories are obtained. Then, the characteristics of the ground motion time history and response spectrum of each group were studied, resulting in the following observations：（1） the peak and phase of ground motion are changed with the rotation of direction θ, so that the direction θ of the maximum peak ground motion can be determined; （2） response spectrum values of each group of ground motions change along with the direction θ, and their peak, predominant period and declining curve are also different as the changes occur; then, the angle θ in the direction of the maximum peak value or the widest predominant period can be determined; and （3） the seismic response of structures with different directions of ground motion inputs has been analyzed under the same earthquake record, and the results show the difference. For some ground motion records, such as the Taft seismic wave, these differences are significant. Next, the Lushan middle school gymnasium structure was analyzed and the calculation was checked using the proposed method, where the internal force of the upper space truss varied from 25% to 28%. The research results presented herein can be used for reference in choosing the ground motion when checking the actual damage to struct

关键词： direction of grotmd motion structure effect coordinate transformation response spectrum

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Evaluation of residual mechanical properties of steel fiber-reinforced reactive powder concrete after exposure to high temperature using nondestructive testing

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Procedia Engineering 2017年 210卷 588-596页

作者： Xiaomeng Hou Muhammad Abid Wenzhong Zheng Ghulam Qadir Waqar Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin 150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China

Reactive powder concrete (RPC) is classified as ultra-high performance concrete, owing to its superior strength, excellent durability and high fracture energy. However, RPC may also be severely affected by devastating fire exposures. This paper presents the variations in residual mechanical properties of RPC after exposure to high temperature. The strength of RPC after cooling was also assessed by nondestructive tests (NDTs). The ultrasonic pulse velocity (UPV) method and resonance frequency (RF) method were used. The samples were subjected to the target temperature of 120℃, 300℃, 500℃, 700℃ and 900℃. The heating was continued for further 3 hours so that steady state condition was achieved. The available equations have been used for determination of dynamic elastic modulus of RPC using UPV and RF measurements. The residual mechanical properties, RF and UPV were plotted as a function of temperature. The result shows that the residual strength increases from room temperature to 300℃. However, above 300℃, it’s decreasing gradually. Various comparisons have been made between residual mechanical strength versus UPV and RF measurements. Relationships have been proposed among residual mechanical properties versus NDTs values. These relationships can be employed for post-fire strength assessment of RPC structures.

关键词： Reactive powder concrete high temperature residual mechanical properties ultrasonic pulse velocity resonance frequency

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Water transport properties for unsaturated cement-based materials

Water transport properties for unsaturated cement-based mate...

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第三届中国国际复合材料科技大会

作者： Chunsheng Zhou Wei Wang Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry and Information Technology Harbin Institute of Technology

The durability performance of cement-based material is actually and mostly determined by the penetration process of deleterious agents and possible chemical and physical reactions between them, where water always plays an important role. In addition, the transport properties of other agents also depend seriously on the water content. It is rather essential to understand the distribution of water and its transport in partially saturated cement-based materials, which are facilitated herein through low-field nuclear magnetic resonance(NMR) technique and gas permeability testing on partially saturated white cement mortar specimens. It is found that most water is stored in inter-layer pores when it is equilibrated with relative humidity below 75%. Due to the marked contraction or swelling of interlayer pores during drying or wetting, the gel pores and inter-hydrate pores are greatly changed while the overall porosity is little altered. At totally drying state, the pore structure of cement-based material becomes obviously coarser, making the gas permeability remarkably larger than water permeability by as large as 2-3 orders of magnitudes. The intrinsic gas permeability obtained on partially saturated specimens reveals that, both the permeability to water and gas depend nonlinearly on the water content, which are well characterized by the models we suggested. Not only the water saturation degree but also the induced pore structure evolution should be incorporated when modelling the transport of water.

关键词： Durability permeability pore structure saturation degree low-field NMR

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An on-site evaluation method for corrosion degradation of in-service cable wires by image histogram matching 11

An on-site evaluation method for corrosion degradation of in...

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11th International Workshop on Structural Health Monitoring 2017: Real-Time Material State Awareness and Data-Driven Safety Assurance, IWSHM 2017

作者： Xu, Yang Li, Shunlong Li, Hui Gu, Chenyu Li, Xinbin Chen, Xiaowei Qiao, Weidong Key Lab of Intelligent Disaster Mitigation Ministry of Industrial and Information Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China School of Transportation Science and Engineering Harbin Institute of Technology Harbin150090 China

ISBN: (纸本)9781605953304

This paper proposes a novel non-destructive method by image histogram matching to evaluate the corrosion degradation of cable wires in service quantitatively. Artificial accelerated salt spray test is adopted to simulate the corrosion environment, and adequate RGB images are taken by a consumer-grade camera to cover the whole information of corroded surface for each specimen under different corrosion periods. Histogram distribution analysis is applied to study the concentrated modes of RGB images, and joint Gaussian distribution is fitted to capture location parameters. Timevariant models of the location parameters are regressed and then the mechanical properties are learnt by tensile and fatigue tests. Once the features of RGB corrosion images of steel wires are matched to the proposed time-variant models, the corresponding corrosion degree and mechanical properties can be estimated. The proposed method is meaningful for the on-site evaluation of cable wires in service with no need to carry on corrosion and mechanical degradation tests after replacing cables.

关键词： Graphic methods

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Experimental study on pore structure and chloride ion diffusion of negative temperature cement-based materials

Experimental study on pore structure and chloride ion diffus...

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第三届中国国际复合材料科技大会

作者： Guan Xinchun Bai Shuai Li Hui Ou Jinping Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology

The early frost may cause serious injury to the internal pore structure of concrete, and hence has a strong influence on the impermeability and mechanical properties of concrete. In this paper, the chloride ion diffusion coefficient of different frozen level and different kind negative temperature cement-based materials was studied. The pore structures of those negative temperature cement-based materials was studied by fractal theory. The correlation between chloride ion diffusion coefficient and fractal dimension was discussed. Experimental results show that the pore structure of negative temperature cement-based materials possesses fractal characteristics and fractal dimension has good correlation with chloride ion diffusion coefficient. The results can provide a reference to application of negative temperature concrete.

关键词： Cement-based materials Negative temperature concrete Pore structure Fractal Chloride diffusion

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Long term mechanical properties of alkali activated slag

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IOP Conference Series: Materials Science and Engineering 2018年第1期292卷

作者： J Zhu W Z Zheng Z Z Xu Y F Leng C Z Qin College of Civil Engineering and Architecture Harbin University of Science and Technology Harbin 150080 Key Lab of Structures Dynamic Behavior and Control of the Ministry Education Harbin Institute of Technology Harbin 150090

This article reports a study on the microstructural and long-term mechanical properties of the alkali activated slag up to 180 days, and cement paste is studied as the comparison. The mechanical properties including compressive strength, flexural strength, axis tensile strength and splitting tensile strength are analyzed. The results showed that the alkali activated slag had higher compressive and tensile strength, Slag is activated by potassium silicate (K2SiO3) and sodium hydroxide (NaOH) solutions for attaining silicate modulus of 1 using 12 potassium silicate and 5.35% sodium hydroxide. The volume dosage of water is 35% and 42%. The results indicate that alkali activated slag is a kind of rapid hardening and early strength cementitious material with excellent long-term mechanical properties. Single row of holes block compressive strength, single-hole block compressive strength and standard solid brick compressive strength basically meet engineering requirements. The microstructures of alkali activated slag are studied by X-ray diffraction (XRD). The hydration products of alkali-activated slag are assured as hydrated calcium silicate and hydrated calcium aluminate.

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Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

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IOP Conference Series: Materials Science and Engineering 2018年第1期292卷

作者： J Zhu W Z Zheng C Z Qin Z Z Xu Y Q Wu College of Civil Engineering and Architecture Harbin University of Science and Technology Harbin 150080 Key Lab of Structures Dynamic Behavior and Control of the Ministry Education Harbin Institute of Technology Harbin 150090

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

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Evaluation of bond-slip for CFRP-concrete interface using the stereovision method

Evaluation of bond-slip for CFRP-concrete interface using th...

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第三届中国国际复合材料科技大会

作者： SHAN Baohua XIAN Guijun HUO Xiaoyang PAN Yunfeg LIU Yang School of Civil Engineering Harbin Institute of Technology Key Lab of Structures Dynamic Behavior and Control of Ministry of Education Harbin Institute of Technology Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Minning of Industry and Information Technology Harbin Institute of Technology

The bond-slip relationship for CFRP-concrete interface has become a hot research topic. Aimed at the disadvantage of traditional measurement approaches, the binocular stereovision method using epipolar constraint is proposed to measure bond-slip curves of CFRPconcrete specimens in this paper. Based on the binocular stereovision principle, DIC method is employed to match the stereovision and sequential images of left and right cameras. Matching result of right images are corrected by using epipolar constraint. In tensile test, two CFRPconcrete specimens are measured by the stereovision measurement system, experimental results show that the bond-slip curves measured by proposed stereovision method has good agreements with that of LVDTs, the error mean is 0.01 mm. This testifies the reliability and effectiveness of the proposed method, indicating that the proposed stereovision method can accurately obtain the entire bond-slip curves of CFRP-concrete interface.

关键词： stereovision digital image correlation (DIC) epipolar constraint correction CFRP-concrete interface bond-slip

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Surface deformation evaluation of sandwich plate with aluminum foam cores under high speed impact loading based on stereovision

Surface deformation evaluation of sandwich plate with alumin...

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2016 International Conference on Smart Infrastructure and Construction, ICSIC 2016

作者： Shan, Baohua Zhang, Boyi Yan, Yu Country Key Lab of Structures Dynamic Behavior and Control Harbin Institute of Technology Harbin China Harbin Institute of Technology Harbin China

ISBN: (纸本)9780727761279

In order to evaluate surface deformation of sandwich plates with aluminum foam cores under high speed impact loading, a surface deformation detection method based on the parallel stereovision model is proposed in this paper. Total five constraints are combined together to optimize the disparity map, and the maximum and minimum disparity constraint is achieved by adjusting the disparity range to remove false parallax. 3D point clouds of deformed surface are calculated according to the parallel stereovision model, and the deformed surface are gained by Delaunay triangulation accordingly. A stereovision surface deformation measurement system is integrated on the base of the above algorithm, the surface deformation measurement test of aluminum foam cores sandwich plates under high speed impact loading is performed with the integrated system. Experimental results show that the reconstructed deformed surface can accurately display the surface deformation of sandwich plates with aluminum foam cores under high speed impact loading, this verifies the effec-Tivness and reliability of the proposed method. © The authors and ICE Publishing: All rights reserved, 2016.

关键词： Geometrical optics

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