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Experimental and mesoscopic investigation on the dynamic properties of coral aggregate concrete in compression

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Science China(Technological Sciences) 2021年第6期64卷 1153-1166页

作者： WU Zhang yu ZHANG JinHua yu hongfa FANG Qin CHEN Li yuE ChengJun Department of Civil and Airport Engineering Civil Aviation CollegeNanjing University of Aeronautics and AstronauticsNanjing 210016China School of Civil Engineering Southeast UniversityNanjing 210096China Engineering Research Center of Safety and Protection of Explosion&Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing 211189China Department of Civil Engineering Army Engineering University of PLANanjing 210007China

To investigate the dynamic responses and comprehending the damage mechanism of coral aggregate concrete(CAC) in compression, both the experimental and numerical investigations were implemented in the present work. Firstly, the dynamic mechanical properties of CAC at different strain rates were tested through the Split-Hopkinson pressure bar(SHPB) ***, the effects of concrete strength grade and strain rate on CAC were discussed and analyzed. Subsequently, we developed the three-dimensional(3D) random mesoscale model considering the randomness of aggregate shape, size and distribution at meso-level, which was validated and employed in the numerical simulation of CAC in compression. The results indicate that the splitting failure passing through the coral aggregate is CAC’S primary failure mode. It has been found that the failure pattern, deformation process, and dynamic increasing factor of CAC are associated with both the strain rate and concrete strength grade. Furthermore, by comparing the experimental and mesoscopic results, it has been proven to be reliable to employ the developed 3D mesoscale modelling method to simulate CAC’s dynamic performances, which has enormous potential in future research of CAC under intense dynamic loadings.

关键词： coral aggregate concrete 3D mesoscopic modelling SHPB strain rate DIF

Mesoscopic Modeling Approach and Application for Steel Fiber Reinforced Concrete under Dynamic Loading:A Review

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Engineering 2022年第9期16卷 220-238页

作者： Jinhua Zhang Zhangyu Wu hongfa yu Haiyan Ma Bo Da School of Civil Engineering Southeast UniversityNanjing 210096China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Science and Technology on Near-Surface Detection Laboratory Wuxi 214035China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

Steel fiber reinforced concrete(SFRC)has drawn extensive attention in recent years for its superior mechanical response to dynamic and impact *** on the existing test results,the highstrength steel fibers embedded in a concrete matrix usually play a strong bridging effect to enhance the bonding force between fiber and the matrix,and directly contribute to the improvement of the post-cracking behavior and residual strength of *** gain a better understanding of the action behavior of steel fibers in matrix and further capture the failure mechanism of SFRC under dynamic loads,the mesoscopic modeling approach that assumes SFRC to be composed of different mesoscale phases(i.e.,steel fibers,coarse aggregates,mortar matrix,and interfacial transition zone(ITZ))has been widely employed to simulate the dynamic responses of SFRC material and structural *** paper presents a comprehensive review of the state-of-the-art mesoscopic models and simulations for SFRC under dynamic *** approaches for the SFRC mesoscale model in the simulation works,including steel fiber,coarse aggregate,and the ITZ between them,are reviewed and compared *** material models for different phases and the interaction relationship between fiber and concrete matrix are summarized ***,some example applications for SFRC under dynamic loads(i.e.,compression,tension,and contact blast)simulated using the general mesoscale models are ***,some critical analysis on the current shortcomings of the mesoscale modeling of SFRC is highlighted,which is of great significance for the future investigation and development of SFRC.

关键词： Steel fiber reinforced concrete Mesoscale modeling Dynamic loading Materials model Interfacial characteristic

Compressive Strength of Basic Magnesium Sulfate Cement Coral Aggregate Concrete(MCAC)on Non-Destructive Testing

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Journal of Wuhan University of Technology(Materials Science) 2023年第5期38卷 1086-1095页

作者： GUO Jianbo yu hongfa MA Haiyan CHANG yun MEI Qiquan ZHANG Yan Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Architectural Engineering Nanjing University of EngineeringNanjing 210009China

Basic magnesium sulfate cement coral aggregate concrete(MCAC)is a new type of concrete consisting of basic magnesium sulfate cement,coarse coral aggregate,coral reef sand and *** rebound hammer(RH),the ultrasonic pulse velocity(UPV)and the compressive strength(fcu)tests of 14 sets of cube specimens of the MCAC after 28 d of aging were *** impact of the content and length of sisal fiber on the relationship between the fcu-RH and the fcu-UPV was determined.A mathematical model was established to predict the strength of the MCAC using the UPV,RH,and comprehensive UPV/RH methods and to obtain the curves of test *** applicability of the test strength curves of ordinary portland concrete(OPC),light-weight aggregate concrete(LAC),and coral aggregate concrete(CAC)to MCAC was *** results showed that the test strength curves of OPC,LAC and CAC were inappropriate to determine the strength of MCAC using non-destructive *** relative standard error of the curves of test strength of the RH method and the comprehensive method met the specifications,whereas that of the UPV method did not.

关键词： non-destructive testing basic magnesium sulfate cement coral aggregate corcrete ultrasonic pulse velocity rebound hammer specific test strength curves

Three-Dimensional Mesoscopic Investigation on the Impact of Specimen Geometry and Bearing Strip Size on the Splitting-Tensile Properties of Coral Aggregate Concrete

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Engineering 2022年第10期17卷 110-122页

作者： Zhangyu Wu Jinhua Zhang hongfa yu Qin Fang Haiyan Ma Li Chen Department of Civil and Airport Engineering Civil Aviation CollegeNanjing University of Aeronautics and AstronauticsNanjing 210016China School of Civil Engineering Southeast UniversityNanjing 210096China Engineering Research Center of Safety and Protection of Explosion and Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing 211189China Army Engineering University of PLA Nanjing 210007China

The use of coral aggregate concrete(CAC)as a novel construction material has attracted significant attention for the construction of reef engineering *** investigate the static splitting-tensile behaviors of CAC under the influence of two factors,namely specimen geometry and bearing strip size,a three-dimensional(3D)mesoscale modeling approach with consideration for aggregate randomness in shape and distribution was adopted in this *** established 12 different specimen models with two specimen shapes(i.e.,a cube with an edge length of 150 mm and a cylinder with dimensions ofφ150 mm×300 mm)and six strip widths(i.e.,6,9,12,15,18,and 20 mm)for *** effects of specimen geometry and strip width on the splitting-tensile properties of CAC,such as failure processes,final failure patterns,and splitting-tensile strength(fst),are analyzed and discussed *** results indicate the high reliability of the developed mesoscale modeling approach and reveal the optimal computational parameters for simulating and predicting the splitting-tensile properties of *** fstvalues of CAC are associated with both the specimen geometry and width of the bearing *** fstvalues of the cube model are slightly higher than those of the cylinder model for the same bearing strip size,representing geometry effects that can be explained by differences in fracture ***,the fstvalue of CAC gradually increases with the relative width of the bearing strip ranging from 0.04 to *** on the elastic solution theory,the variation area of CAC fstvalues with the relative width of the bearing strip was determined preliminarily,which has great significance for studying the tensile performance of CAC.

关键词： Coral aggregate concrete 3D mesoscopic modelling Splitting-tensile test Tensile strength Specimen geometry Bearing strip

Service Life Design for Concrete Engineering in Marine Environments of Northern China Based on a Modified Theoretical Model of Chloride Diffusion and Large Datasets of Ocean Parameters

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Engineering 2022年第10期17卷 123-139页

作者： Taotao Feng hongfa yu Yongshan Tan Haiyan Ma Mei Xu Chengjun yue Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of Materials Science and Engineering Southeast UniversityNanjing 211189China College of Civil Science and Engineering Yangzhou UniversityYangzhou 225127China

In this study,through experimental research and an investigation on large datasets of the durability parameters in ocean engineering,the values,ranges,and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were *** on a modified theoretical model of chloride diffusion and the reliability theory,the service lives of concrete structures exposed to the splash,tidal,and underwater zones were *** concrete proportions meeting the requirement of a service life of 100 or 120 years were designed,and a cover thickness requirement was *** addition,the effects of the different time-varying relationships of the boundary condition(Cs)and diffusion coefficient(Df)on the service life were compared;the results showed that the time-varying relationships used in this study(i.e.,Cscontinuously increased and then remained stable,and Dfcontinuously decreased and then remained stable)were beneficial for the durability design of concrete structures in marine environment.

关键词： Large datasets Modified theoretical model Reliability theory Service life Boundary condition Diffusion coefficient

Influence of steel corrosion on axial and eccentric compression behavior of coral aggregate concrete column

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Frontiers of Structural and Civil Engineering 2021年第6期15卷 1415-1425页

作者： Bo DA Yan CHEN hongfa yu Haiyan MA Bo yu Da CHEN Xiao CHEN Zhangyu WU Jianbo GUO State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan 430070China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China Key Laboratory of Coastal Disaster and Defence of Ministry of Education Hohai UniversityNanjing 210098China Guangxi Key Laboratory of Disaster Prevention and Engineering Safety Guangxi UniversityNanning 530004China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

To study the behavior of coral aggregate concrete(CAC)column under axial and eccentric compression,the compression behavior of CAC column with different types of steel and initial eccentricity(ei)were tested,and the deformation behavior and ultimate bearing capacity(Nu)were *** results showed that as the ei increases,the Nu of CAC column decreases ***,the steel corrosion in CAC column is severe,which reduces the steel section and steel strength,and decreases the Nu of CAC *** durability of CAC structures can be improved by using new organic coated *** the influence of steel corrosion and interfacial bond deterioration,the calculation models of Nu under axial and eccentric compression were presented.

关键词： coral aggregate concrete column axial compression eccentric compression steel corrosion calculation model

Brine-freeze-thaw Durability and Crack Density Model of Concrete in Salt Lake Region

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Journal of Wuhan University of Technology(Materials Science) 2020年第3期35卷 561-570页

作者： GONG Wei yu hongfa MA Haiyan HAN Wenliang Department of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The brine-freeze-thaw durability (defined as the durability under freeze-thaw cycles in Qinghai salt lake brine) of concrete (ordinary Portland cement concrete (OPC), high performance concrete (HPC-a), high performance concrete with steel fiber (HPC-b), and high performance concrete with high Young's modulus polyethylene fiber (HPC-c)) was systematically investigated by the relative dynamic elastic modulus, the relative mass, the appearance, the scanning electron microscopy, and the X-ray diffraction. In addition, the low-temperature physical and chemical corrosion mechanism and a crack density model after the modified relative dynamic elastic modulus being taken into consideration were proposed. The results show that the deterioration of OPC is the severest, followed by HPC-a, HPC-c and HPC-b. The admixture or the fiber is mixed into concrete, which can improve the brine-freeze-thaw durability of concrete. The critical mass growth of the failure of concrete is 3.7%. The cause of the deterioration of concrete under the brine-freeze-thaw cycles is physical and chemical corrosion, not freezing and thawing. The crack density model can effectively describe the deterioration evolution of concrete.

关键词： brine-freeze-thaw durability relative dynamic elastic modulus relative mass micro-analysis modeling

Effect of Carbonation and Drying-Wetting Cycles on Chloride Diffusion Behavior of Coral Aggregate Seawater Concrete

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Journal of Ocean University of China 2022年第1期21卷 113-123页

作者： DA Bo LI Yipeng yu hongfa MA Haiyan CHEN Haoyu DOU Xuemei WU Zhangyu College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Coastal Disaster and Defence of Ministry of Education Hohai UniversityNanjing 210098China Nantong Institute of Marine and Offshore Engineering Hohai UniversityNantong 226300China CCCC Infrastructure Maintenance Group Company Limited Beijing 100010China

Based on seawater immersion,drying-wetting cycles,carbonation and drying-wetting cycles for coral aggregate sea-water concrete(CASC)with different strength grades,the effect of carbonation and drying-wetting cycles on chloride diffusion be-havior of CASC is *** results show that the free surface chloride concentration(Cs),free chloride diffusion coefficient(Df)and time-dependent index(m)of CASC in the drying-wetting cycles is obviously higher than that in seawater *** Df and m of CASC of carbonation and drying-wetting cycles is higher than that in the drying-wetting *** increases the Df and m of CASC,which is against CASC to resist chloride *** corrosion possibility of CASC structures in different ex-posed areas is as follows:splash zone(carbonation and drying-wetting cycles)>tidal zone(drying-wetting cycles)>underwater zone(seawater immersion).Besides,the chloride diffusion rate of C65-CASC is 17.8%-63.4%higher than that of C65-ordinary aggre-gate concrete(OAC)in seawater immersion(underwater zone).Therefore,anti-corrosion measures should be adopted to improve the service life of CASC structure in the oceanic environment.

关键词： coral aggregate seawater concrete chloride diffusion seawater immersion drying-wetting cycles carbonation and drying-wetting cycles

The Improvement Effects of NaH_(2)PO_(4) and KH_(2)PO_(4) on the Properties of Magnesium Oxysulfate Cement

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Journal of Wuhan University of Technology(Materials Science) 2021年第1期36卷 50-57页

作者： WANG Nan yu hongfa BI Wanli GUAN Yan GONG Wei ZHANG Na WU Chengyou Department of Civil Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Materials and Metallurgy Liaoning University of Science and TechnologyAnshan 114051China School of Civil Engineering Qinghai UniversityXinitig 810016China

Sodium dihydrogen phosphate (NaH_(2)PO_(4)) and potassium dihydrogen phosphate (KH_(2)PO_(4)) were selected as additives for magnesium oxysulfate (MOS) *** phase composition and the microstructure of MOS cement were characterized using X-ray diffraction (XRD),thermogravimetric analysis (TG-DSC),Flourier transform infrared spectroscopy (FT-IR),mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM).It is found that both NaH_(2)PO_(4) and KH_(2)PO_(4) lead to an increase in the compressive strength and an improvement in the volume stability of MOS *** XRD,MIP and SEM results show that the addition of NaH_(2)PO_(4) or KH_(2)PO_(4) does not change the phase composition of MOS cement but promotes the formation of strength phase of 5Mg(OH)_(2)·MgSO_(4)·7H_(2)O (5·1·7 phase).This phase brings a considerable improvement in the microstructure of MOS cement,which has a positive effect on the properties of MOS cement.

关键词： magnesium oxysulfate cement phosphates compressive strength volume stability microstructure