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Experimental investigation of evolutive mode-I and mode-II fracture behavior of fiber-reinforced cemented paste backfill:Effect of curing temperature and curing time

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Frontiers of Structural and Civil Engineering 2023年第2期17卷 256-270页

作者： Kun FANG Liang CUI School of Mines China University of Mining&TechnologyXuzhou 221116China Department of Civil Engineering Lakehead UniversityOntario P7B 5E1Canada

The curing temperature-dependent cement hydration causes the nonlinear evolution of fracture behavior and properties of fiber-reinforced cemented paste backfill(CPB)and thus influences the stability of mine backfill materials in deep mines.Therefore,the coupled effect of curing temperature(20,35,and 45℃)and cement hydration at different curing times(3,7,and 28 d)on the mode-I and mode-II fracture behavior and properties of fiber-reinforced CPB is investigated.A comprehensive experimental testing program consisting of semicircular bend tests,direct shear tests,measurement of volumetric water content and matric suction,TG/DTG tests,and SEM observation is carried out.The results show that the coupled thermochemical effect results in strongly nonlinear development of pre-and post-peak behavior of fiber-reinforced CPB.Moreover,the results discover a positive linear correlation between fracture toughness and shear strength parameters and also reveal the vital role played by matric suction in the formation of fracture toughness.Furthermore,predictive functions are developed to estimate the coupled thermochemical effect on the development of KIc and KIIc.Therefore,the findings and the developed mathematical tools have the potential to promote the successful application of fiber-reinforced CPB technology in deep underground mines.

关键词： fiber reinforcement cemented paste backfill fracture behavior underground mine cement hydration

The NMR core analyzing tomograph:a multi-functional tool for non-destructive testing of building materials

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Magnetic Resonance Letters 2023年第3期3卷 207-219,I0003页

作者： Sabine Kruschwitz Sarah Munsch Melissa Telong Wolfram Schmidt Thilo Bintz Matthias Fladt Ludwig Stelzner Bundesanstalt für Materialforschung und-prüfung Unter den Eichen 87Berlin12205Germany Technische Universitat Berlin Gustav-Meyer-Allee 25Berlin13355Germany

NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material.Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure.Moreover it enables the determination of moisture transport properties and the(re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing.However,as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale(<10 mL)samples.This paper describes the capabilities of an NMR tomograph,which has been specifically optimized for the investigation of larger,heterogeneous building material samples(diameters of up to 72 mm,length of up to 700 mm)with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times(50-80 ms).

关键词： Natural stone Concrete Sensitivity Moisture transport cement hydration Supplementary cementitious materials Frost and salt attack Fire spalling

Early Age Compressive Strength of Pastes by Electrical Resistivity Method and Maturity Method

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Journal of Wuhan University of Technology(Materials Science) 2011年第5期26卷 983-989页

作者：肖莲珍 School of Materials Science and Engineering Wuhan Institute of Technology

The compressive strength development of Portland cement pastes was investigated by the electrical resistivity method and the maturity method.The experiments were carried out on the cement pastes with different water-cement ratios at different curing temperatures.The results show that the application of the maturity method has limitation to obtain the strength.It is found that both of the compressive strength and the electrical resistivity follow hyperbolic trend for all the mixes.The hyperbolic equation of each mix is obtained to estimate the ultimate resistivity value which can probably be reached.The relationship between electrical resistivity and compressive strength of the cement pastes is established based on the test results and interpreted by the empirical Archie equation and a strength-porosity equation.The relationship between the electrical resistivity after temperature correction and the compressive strength was linear and independent of curing temperature and water-cement ratio.

关键词： electrical resistivity cement hydration compressive strength maturity method

Characteristics and Mechanism of Modified Triethanolamine as cement Grinding Aids

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Journal of Wuhan University of Technology(Materials Science) 2015年第1期30卷 134-141页

作者：赵计辉王栋民 WANG Xueguang LIAO Shucong School of Chemical and Environment Engineering China University of Mining & Technology

Effects of modified triethanolamine as cement grinding aids on particles characteristics and mechanical property of cement were studied, and its reaction mechanism was analyzed by IR, Zeta potential, SEM, XRD and TG-DTA. The results show that the content of 3-32 μm particles for cement with 0.015% modified triethanolamine（M-TEA） is increased by 12.4%, and the compressive strengths of cement with 0.03% M-TEA are increased by 5.5 and 8.2 MPa at 3 and 28 days, respectively. And both the grinding and enhancement effects of M-TEA on cement are better than triethanolamine. The mechanism analysis shows that M-TEA not only has the amino and hydroxyl groups of TEA, but also has the ester, carbonyl, carboxyl groups which easily combine with metal ions of cement minerals, resulting in that M-TEA can promote surface adsorption and shield the unsaturated charges in the surface and crack section of particles, thus particles reunion is prevented and grinding efficiency is improved. Enhancement of M-TEA on cement mainly lies in that it can promote or induce hydration reaction of cement mineral with gypsum and water, which accelerates formation of hydration products, and then improves the structure and morphology of cement hydration products, thus the uniformity and compactness of product structure is increased.

关键词： modified triethanolamine grinding aids cement particles characteristics mechanical property mechanism cement hydration

Coupled Effects of Heat and Moisture of Early-Age Concrete

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Fluid Dynamics & Materials Processing 2021年第4期17卷 845-857页

作者： Yang Wang Hanxi Wang Linwei Yang Li Qian School of Urban Construction and Transportation Hefei UniversityHefei230601China School of Electronic Science and Applied Physics Hefei University of TechnologyHefei230601China

In order to analyze the coupled influence of temperature and humidity on early-age concrete(including cement and copper tailings),a mathematical model is introduced on the basis of the Krstulovic-Dabic hydration reaction kinetic equations.In such a framework,the influence of hydration-released heat and water consumption are also taken into account.The results provided by such a model are verified by means of experiments and related sensor measurements.The research results show that this model can adequately predict the internal temperature and the humidity temporal evolution laws.

关键词： Composite cementitious materials cement hydration micro-structure diffusion coefficient coupled of heat and moisture

EFFECT OF STONE POWDER ON STONE CHIPPINGS CONCRETE

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Journal of Wuhan University of Technology(Materials Science) 1996年第4期11卷 29-34页

作者：周明凯彭少明徐健朱承华 Research centre of Materials Engineering.Wuhan Univ.of Tech..Wuhan 430070.China Enshi Communication Bureau.*Enshi Highway Bureau.Enshi 445000.Hubei

In this paper, the effect and mechanism of calcareous stone powder with size less than 0.074 mm are investigated in stone chippings concrete. The results show that the stone powder can participate in hydration reaction and acts as crystal nucleus in hydration process, namely, it has hydration activity to an extent. The strength of stone chippings concrete is enhanced and the easy-mixing capacity of the concrete mortar is modified when stone chippings contain a proper amount of stone powder. The stone powder has little effect on the wearability of the concrete.

关键词： calcareous stone powder stone chippings concrete cement hydration application

Monitoring lime and cement improvement using spectral induced polarization and bender element techniques

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第1期13卷 202-211页

作者： Bate Bate Junnan Cao Chi Zhang Na Hao Song Wang Institute of Geotechnical Engineering College of Civil Engineering and ArchitectureZhejiang UniversityHangzhou310058China Department of Civil and Environmental Engineering Colorado School of MinesGoldenColombia80401USA Department of Geology University of KansasLawrenceKS66045USA Department of Civil Engineering and Construction Management Georgia Southern UniversityStatesboroGA30458USA

Spectral induced polarization(SIP)and bender element(BE)techniques show a high sensitivity to particle size,particle distribution and content of generated hydration products,which essentially govern the efficiency of ground improvement.In this context,both SIP and BE were integrated on a column setup to monitor the processes of lime and cement stabilization.A 5 mmol/L Na2CO3 solution was injected into the sand-lime mixture to produce CaCO3 precipitation,while deionized water was injected into the sandcement mixture to induce the hydration of cement.The average diameters of the precipitated particles or clusters were calculated from the relaxation time,which was a significant parameter of SIP signals,via the Schwarz equation.Two pairs of BE were used to demonstrate the heterogeneity of the product precipitation,which was probably caused by the location of the inflow and outflow on the SIP-BE column.SIP and BE showed the capability of nondestructively monitoring the spatiotemporal chemical evolution processes,which could be helpful for engineering applications.

关键词： Particle size and distribution Spectral induced polarization(SIP) Bender element(BE) cement hydration Complex conductivity Shear wave velocity Heterogeneity