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Influence Mechanism of Curing Regimes on interfacial transition zone of Lightweight Ultra-High Performance Concrete

Journal of Wuhan University of Technology(Materials Science) 2023年第3期38卷 591-603页

作者：李洋张高展 YANG Jun ZHANG Jian DING Qingjun ZHAO Mingyu Advanced Building Materials Key Laboratory of Anhui Province Anhui Jianzhu UniversityHefei 230022China Anhui Construction Engineering Building Materials Co. LtdHefei 230001China State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan 430070China Anhui Survey&Design Institute of Water Resources&Hydropower Co.Ltd Hefei 230001China School of Materials Science and Engineering Shenyang Jianzhu UniversityShenyang 110168China

This study aims to clarify the effects of curing regimes and lightweight aggregate(LWA)on the morphology, width and mechanical properties of the interfacial transition zone(ITZ) of ultra-high performance concrete(UHPC), and provide reference for the selection of lightweight ultra-high performance concrete(L-UHPC) curing regimes and the pre-wetting degree LWA. The results show that, under the three curing regimes(standard curing, steam curing and autoclaved curing), LWA is tightly bound to the matrix without obvious boundaries. ITZ width increases with the water absorption of LWA and decreases with increasing curing temperature. The ITZ microhardness is the highest when water absorption is 3%, and the microhardness value is more stable with the distance from LWA. Steam and autoclaved curing increase ITZ microhardness compared to standard curing. As LWA pre-wetting and curing temperatures increase, the degree of hydration at the ITZ increases, generating high-density CSH(HD CSH) and ultra-high-density CSH(UHD CSH), and reducing unhydrated particles in ITZ. ITZ micro-mechanical properties are optimized due to hydration products being denser.

关键词： curing regime ultra-high performance concrete lightweight aggregate interfacial transition zone meso-mechanical properties micro-mechanical properties

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Multiphysics processes in the interfacial transition zone of fiber-reinforced cementitious composites under induced curing pressure and implications for mine backfill materials: A critical review

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International Journal of Minerals,Metallurgy and Materials 2023年第8期30卷 1474-1489页

作者： Brett Holmberg Liang Cui Department of Civil Engineering Lakehead UniversityThunder BayON P7B 5E1Canada

The mesoscale fiber-matrix interfacial transition zone(FM-ITZ) under induced curing pressure plays a key role in the effectiveness of fiber reinforcement and the engineering application of fiber-reinforced cementitious composites(FRCCs). This critical review establishes the link among induced curing pressure(i.e., external loading condition), multiphysics processes(i.e., internal governing mechanism), and interface behavior(i.e., material behavior) for FRCC materials through analysis of the state-of-the-art research findings on the FM-ITZ of FRCC materials. The following results are obtained. For the mechanical process, the induced curing pressure changes the stress state and enhances multicracking behavior, which can strengthen the FM-ITZ. For the hydraulic process, the strengthened seepage of the FM-ITZ under induced curing pressure weakens the effective stress and exaggerates the deficiency in water retention capacity between the bulk matrix and the FMITZ. For the thermal process, the induced curing pressure causes a steep temperature gradient in the FM-ITZ and thus influences the temperature evolution and thermally-induced microcracks in the FM-ITZ. For the chemical process, the induced curing pressure enhances hydration kinetics and results in the formation of additional hydration products in the FM-ITZ. Moreover, recommendations are proposed on the basis of findings from this review to facilitate the implementation of fiber reinforcement in cemented paste backfill technology.

关键词： cemented paste backfill cementitious composites interfacial transition zone fiber reinforcement multiphysics induced curing pressure

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Nanomechanical Characteristics of interfacial transition zone in Nano-Engineered Concrete

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Engineering 2022年第10期17卷 99-109页

作者： Xinyue Wang Sufen Dong Zhenming Li Baoguo Han Jinping Ou School of Civil Engineering Dalian University of TechnologyDalian 116024China School of Transportation and Logistics Dalian University of TechnologyDalian 116024China Department of Materials and Environment(Microlab) Faculty of Civil Engineering and GeoscienceDelft University of TechnologyDelft 2628 CNNetherlands

This study investigates the effects of nanofillers on the interfacial transition zone(ITZ)between aggregate and cement paste by using nanoindentation and statistical nanoindentation ***,the underlying mechanisms are revealed through micromechanical *** nanoindentation results indicate that incorporating nanofillers increases the degree of hydration in the ITZ,reduces the content of micropores and low-density calcium silicate hydrate(LD C-S-H),and increases the content of highdensity C-S-H(HD C-S-H)and ultra high-density C-S-H(UHD C-S-H).In particular,a new phase,namely nano-core-induced low-density C-S-H(NCILD C-S-H),with a superior hardness of 2.50 GPa and an indentation modulus similar to those of HD C-S-H or UHD C-S-H was identified in this *** modeling results revealed that the presence of nanofillers increased the packing density of LD CS-H and significantly enhanced the interaction(adhesion and friction)among the basic building blocks of C-S-H gels owing to the formation of nano-core-shell elements,thereby facilitating the formation of NCILD C-S-H and further improving the performance of the *** study provides insight into the effects of nano fillers on the ITZ in concrete at the nanoscale.

关键词： Concrete Nanofiller interfacial transition zone Nanoindentation Micromechanical modeling Nano-core effect

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Quantitative Analysis and Affecting Factors of the Overlapping Degree of interfacial transition zone between Neighboring Aggregates in Concrete

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Journal of Wuhan University of Technology(Materials Science) 2011年第1期26卷 147-153页

作者：孙国文孙伟 School of Materials Science and Engineering Southeast University Jiangsu Key Laboratory of Construction Materials

Based on the nearest surface function formula, a quantitative formula to measure the overlapping degree between the interfacial transition zone （ITZ） of neighboring aggregate particles was put forward. The formula was further deduced to quantitatively analyze the influence of the volume fraction of aggregate, ITZ thickness and the maximum aggregate diameter on the overlapping degree between neighboring ITZ. The volume of ITZ was quantitatively calculated in actual concrete by comparing the nearest surface function formula with an approximate method, that is the surface area of the aggregates multiplied by the uniform thickness of the ITZ layers. The results showed that the influencing order of these three factors on the overlapping degree between neighboring ITZ in turn was the interface thickness, aggregate volume fraction and the maximum aggregate diameter; As long as the interface thickness 50 μm and the aggregate volume fraction 50%, the calculated error between two methods mentioned above is about 10 %.

关键词： concrete interfacial transition zone degree of overlapping volume fraction 发 Fuller distribution

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Effect of the Entrained Air Void on Strength and interfacial transition zone of Air-Entrained Mortar

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Journal of Wuhan University of Technology(Materials Science) 2015年第5期30卷 1020-1028页

作者：高辉 ZHANG Xiong ZHANG Yongjuan Key Laboratory of Advanced Civil Engineering Materials of the Ministry of Education Tongji University Tianjin Institute of Building Research

In order to facilitate the development and application of air entraining agents (AEA) in the high performance concrete, entrained air void structure parameters (air void size range from 10 to 1 600 mu m) of 28 d sifted mortar were measured by image analysis method. The relationship between the air void size distribution and strength of mortar was studied by methods of grey connection analysis and multiple linear regression analysis. The multiple linear regression equation was established with a correlation coefficient of 0.966. The weight of the affection of hierarchical porosity on the compressive strength ratio was also obtained. In addition, the effect of air voids on the paste-aggregate interfacial transition zone (ITZ) was analyzed by microhardness. The results show that the correlation between different pore size range and the compressive strength is negative. The effect of air void size distribution on 28 days compressive strength is different: under the condition of similar total porosity, with the increase of the porosity of the air void size, ranging from 10 to 200 mu m, and the decrease of the porosity, ranging from 200 to 1 600 mu m, the average air void diameter and mean free spacing are decreased; as well as the width of ITZ. On the contrary, the microhardness of the ITZ is increased while the compressive strength loss is decreased.

关键词： air void structure compressive strength interfacial transition zone grey connection linear regression

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Study of interfacial transition zones between magnesium phosphate cement and Portland cement concrete pavement

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第3期11卷 523-537页

作者： Fei Liu Baofeng Pan Changjun Zhou Ge Li Xiaocun Wang Jiaquan Li Faculty of Infrastructure Engineering Dalian University of TechnologyDalian 116024China Tongren City Transportation Bureau Tongren 554300China Beijing Civil Aviation Design and Research Institute of China Design Group Beijing 101318China

The Portland cement concrete pavement(PCCP)often suffers from different environmental distresses and vehicle load failure,resulting in slab corner fractures,potholes,and other *** repair has become one of the effective ways to open traffic *** this study,a novel type of rapid repair material,basalt fiber reinforced polymer modified magnesium phosphate cement(BFPMPC),is used to rapidly repair ***,the mechanical properties and characteristics of the repair interfaces which are named interfacial transition zones(ITZs)formed by BFPMPC and cement concrete are focused on as a decisive factor for the performance of the rapid *** changing trend of the elastic moduli was studied by nanoindentation experiments in the ITZs with the deconvolution analysis that the elastic moduli of certain kinds of substances can be *** experimental results show that the elastic modulus of ITZ-1 with a width of about20μm can be regarded as 0.098 times of the aggregate,and 0.51 times of the ordinary Portland cement(OPC)*** BFPMPC-OPC mortar ITZ has roughly the same mechanical properties as the ITZ between aggregate and BFPMPC.A multi-scale representative two-dimensional model was established by random aggregate and a two-dimensional extended finite element method(XFEM)to study the mechanical properties of the repair *** simulation results show that the ITZ formed by the interface of BFPMPC and OPC mortar and basalt aggregate is the most vulnerable to failure,which is consistent with the nano-indentation experimental results.

关键词： Portland cement concrete pavement interfacial transition zone Magnesium phosphate cement Repair interface Nanoindentation Mechanical properties and characteristics

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Mesoscale Mechanical Properties and Influencing Factors of Concrete under Uniaxial Tension

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1156-1168页

作者： CHEN Tao LI Kungang XIAO Shiyun State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

Monte Carlo simulations were carried out to generate a mesoscale model of concrete with randomly packed aggregates with different shapes and *** mechanical properties of concrete specimens under uniaxial tensile loads were studied using statistical *** results indicated that the entire process of damage and failure of specimens exhibited mainly two failure types:fracture patternsⅠandⅡ.Furthermore,the influences of the aggregate content ratio,aggregate shape,aggregate size,interfacial transition zone(ITZ)strength,and porosity ratio on the concrete specimens were *** numerical simulation results showed that the elastic modulus of the concrete specimens increased approximately linearly with the aggregate volume ratio but decreased linearly with the porosity and was not affected by the ITZ *** tensile strength decreased with the increases in the aggregate content and porosity of the sample,but increased linearly with the ITZ *** addition,the aggregate shape led to a difference in the tensile strength of the concrete.

关键词： concrete mechanical behavior aggregate interfacial transition zone pore

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Discrete Element Modelling of Damage Evolution of Concrete Considering Meso-Structure of ITZ

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 3495-3511页

作者： Weiliang Gao Shixu Jia Tingting Zhao Zhiyong Wang Institute of Defense Engineering Academy of Military SciencesChinese People’s Liberation ArmyBeijing100850China College of Mechanical and Vehicle Engineering Taiyuan University of TechnologyTaiyuan030024China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

The mechanical properties of interfacial transition zones(ITZs)have traditionally been simplified by reducing the stiffness of cement in previous simulation methods.A novel approach based on the discrete element method(DEM)has been developed for modeling *** new approach efficiently simulates the meso-structure of ITZs,accurately capturing their heterogeneous *** against established uniaxial compression experiments confirms the precision of *** proposedmodel canmodel the process of damage evolution containing cracks initiation,propagation and *** increasing loads,cracks within ITZs progressively accumulate,culminating in macroscopic fractures that traverse themortarmatrix,forming the complex,serpentine path of *** study reveals four distinct displacement patterns:tensile compliant,tensile opposite,mixed tensile-shear,and shear opposite patterns,each indicative of different stages in concrete’s damage *** widening angle of these patterns delineates the progression of cracks,with the tensile compliant pattern signaling the initial crack appearance and the shear opposite pattern indicating the concrete model’s ultimate failure.

关键词： Discrete element method damage evolution interfacial transition zone meso-structure model

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The ITZ microstructure,thickness,porosity and its relation with compressive and flexural strength of cement mortar;influence of cement fineness and water/cement ratio

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Frontiers of Structural and Civil Engineering 2022年第2期16卷 191-201页

作者： Tahereh KOROUZHDEH Hamid ESKANDARI-NADDAF Ramin KAZEMI Department of Civil Engineering Hakim Sabzevari UniversitySabzevar***Iran

A new insight into the interfacial transition zone(ITZ)in cement mortar specimens(CMSs)that is influenced by cement fineness is *** importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive(Fc)and flexural strength(Ff),and porosity at various water/cement *** findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous *** increasing cement fineness by about 25%of,the ITZ thickness of CMSs was reduced by about 30%and Fc was increased by 7%–52%and Ff by 19%–40%.These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词： cement fineness interfacial transition zone compressive and flexural strength

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Quality Improvement of Recycled Concrete Aggregate by Accelerated Carbonation under Different Pressure

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Journal of Wuhan University of Technology(Materials Science) 2023年第3期38卷 623-631页

作者：丁亚红武军 ZHANG Xianggang XU Ping NING Wei LI Yajing School of Civil Engineering Henan Polytechnic UniversityJiaozuo 454003China School of Civil Engineering and Architecture XinxiangUniversityXinxiang453003China

Due to the presence of old mortar (OM) and interfacial transition zone (ITZ),recycled concrete aggregate (RCA) is inferior to natural aggregate (NA).The purpose of this paper was to study the effect of accelerated carbonation on the macro-properties and micro-properties of RCA under different pressure(0.05,0.15,0.30 MPa).The macro-property tests included colour change,apparent density,water absorption,and crushing value of *** micro-property tests included scanning electron microscopy (SEM),X-ray diffraction (XRD),thermogravimetry-differential scanning calorimetry (TG-DSC),and Vickers micro-hardness(VMH).The results showed that the change trends of apparent density,water absorption,and crushing value of RCA displayed exponential relationships as pressure increasing,with the optimum pressure of 0.30 *** images indicated that the calcite caused by the hydration products in RCA and the Ca(OH)_(2) derived from saturated lime water improved the properties of RCA;as the apparent density increased,the water absorption and crushing value *** results of XRD and TG-DSC indicated that,as the pressure increased,the masses of Ca(OH)_(2) in carbonated RCA gradually decreased,while those of CaCO_(3) gradually increased,which demonstrated that the carbonation degree gradually ***,ITZ-2 was the weakest phase in RCA,but its improvement degree of VMH by accelerated carbonation was higher than that of ***,RCA was not completely carbonated,but only carbonated in a certain depth after 24 h accelerated carbonation.

关键词： recycled concrete aggregate treatment method accelerated carbonation interfacial transition zone saturated lime water calcite

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