Width Of Interfacial Transition Zone Research Articles

Effect of silica fume on frost resistance and recyclability potential of recycled aggregate concrete under freeze–thaw environment

In this study, the effects of silica fume (SF) dosages (0 %, 3 %, 5 %, 8 %, 11 %, 13 %, and 16 %) on the mechanical properties (compressive strength and splitting tensile strength) and frost resistance (relative dynamic elasticity modulus and mass loss rate) of recycled aggregate concrete (RAC) prepared with 100 % recycled concrete aggregate (RCA) under freeze–thaw (F-T) environment were investigated. To assess the recyclability potential of RAC, the apparent density, water absorption, crushing index, and attached mortar content of second-generation RCA after F-T cycles were also studied. The phase composition and microstructure near the interfacial transition zone (ITZ) of RAC were characterized by X-ray diffraction, thermogravimetric, scanning electron microscopy, and microhardness. The results indicate that the incorporation of SF effectively improves the mechanical properties and frost resistance of RAC, with an optimal SF dosage around 13 %. After 400 F-T cycles, the compressive strength of RAC with 13 % SF dosage can still reach 40.1 MPa, which is classified as medium-strength concrete. All second-generation RCAs achieves Class III, but RCA obtained from RAC containing 13 % SF has higher potential to upgrade to Class II and reuse in 40 MPa structural concrete. During the F-T process, the ITZ width of RAC with 13 % SF dosage only increased by 3 μm, and the average hardness of ITZ decreased by 6.7 %. The microscopic analysis showed that an appropriate dosage of SF is conducive to denser ITZ with higher hardness and narrower crack width, thereby hindering crack propagation within RAC during F-T cycles.

Enhancing cementitious grouting performance through carbon nanotube-coated fly ash incorporation

Cementitious composites reinforced with carbon nanotubes (CNTs) offer notable benefits compared to conventional cement-based materials in terms of durability and strength. Despite these advantages, the widespread implementation of CNTs in cement-based grouting engineering has not been carried out due to the limitations of dispersion issues. In order to facilitate the progression of carbon nanotubes (CNTs) from laboratory experiments to engineering applications, we proposed a method of using amino-functionalised functional groups to coat CNTs on the fly ash (FA) particles’ surfaces to assist the dispersion and prepare cost-effective, low-carbon emission, energy consumption-saving and high-performance cementitious slurry. The experimental results exhibit that compared with plain cement-based grouting materials, incorporating 0.023 wt% CNTs and 14.3 wt% FA can reinforce the compressive and tensile strength by 14.2–25.8% and improve the workability by about 21.0%. The application of coated CNTs induces nucleation and pore-infilling effects within the interfacial transition zone (ITZ) of the cementitious composites. This action leads to a reduction in ITZ width and a decrease in crack occurrence within the ITZ. Consequently, these effects contribute to an augmentation in the consolidation strength of the slurry. Acoustic emission and fracture surface fractal analysis further reveal that incorporating CNTs enhances the resist-loading ability of the cement matrix by increasing its energy absorption capability. The innovative coating method reported in this work is expected to facilitate the future application of CNTs in practical grouting engineering.

Effect of different aggregates on the properties of carbonated self-pulverized low-calcium clinker mortar

This study investigated the effects of four aggregates - standard sand, manufactured sand, slag, and coal gangue - on the properties of carbonated self-pulverized low-calcium clinker (SPLCC) mortars. The SPLCC, aggregates, and water were mixed in a mass ratio of 1.00:2.50:0.15 and compaction molded, then carbonation cured by 99.99 % CO2 exposure at 0.2 MPa. Tests determined the weight gain, compressive strength, water absorption, and interfacial transition zone (ITZ) microstructure after 1, 4, and 24 h of curing. Results showed the manufactured sand mortar had the highest compressive strength (39.7 MPa) and lowest water absorption (3.50 %) at 24 h, indicating the best macroscopic performance. This was due to the manufactured sand's stone powder content improving SPLCC binding and accelerating calcium carbonate accumulation in the ITZ. Nanoindentation revealed the manufactured sand mortar had the narrowest ITZ width (15 μm). SEM-BSE also showed higher Ca content in its ITZ. The Ca: Si ratio in the ITZ strongly correlated with strength and absorption. Overall, manufactured sand as aggregate can enhance carbonated SPLCC mortar properties, providing potential for precast products.

Numerical Investigation of Sulfate Diffusion Characteristics in Recycled Aggregate Concrete Based on Mesoscale Multiphase Analysis

Sulfate-induced deterioration can reduce the service life of recycled aggregate concrete (RAC). To demonstrate the transport behavior of sulfate ions in RAC, a two-dimensional, six-phase numerical model of RAC is proposed in this study. Sulfate ion diffusion coefficients were defined for different phases [attached mortar, new mortar, interfacial transition zone (ITZ) between attached mortar and original aggregate, ITZ between the new mortar and original aggregate, and ITZ between the new mortar and attached mortar] of RAC. The effects of ITZ width and porosity on ion transport behavior in RAC were analyzed. The results show that the numerical model agrees with the experimental data. Numerical results indicate that the six-phase model of RAC provides more-accurate simulation results because tortuosity is reflected in the model. The width and porosity of ITZs both affect the diffusion of sulfate ions in concrete. However, due to the low volume fraction of ITZ in concrete, just improving ITZ performance has no significant effect on ion attack resistance of concrete. The ITZ is a crucial zone where damage may originate and develop.

Graphene oxide-coated fly ash for high performance and low-carbon cementitious composites

Graphene oxide (GO) opens a new pathway for reducing carbon footprint in the construction industry and fabricating high-strength cementitious composites. However, due to the dispersion limitation, the application of GO in practical engineering has not been widely accepted. Hence, we evaluated the potential of the GO-fly ash hybrid as additives in cement under a coating method to assist the dispersion of the GO nanosheets. The results demonstrated that the GO could be successfully coated on the surface of the fly ash particles with good dispersion and strong connection via the proposed coating method. Besides, the coating method allowed more GO nanosheets to concentrate in the interfacial transition zone (ITZ) between fly ash and cement particles, making GO application more economical. The coated GO could then generate nucleation effects to promote the hydration process and provide pore-infilling effects to decrease the ITZ width (about 12.5%) and the crack ratio in ITZ (over 10%). Compared with the plain cement pastes, the workability, mechanical strength, and impermeability of the GO-coated fly ash modified cementitious slurry can be significantly reinforced up to 21.6%, 38.4% and 106.4%, respectively. The enhancement rate is further improved by about 7.1–58.5% compared with the traditional ultrasonic dispersion method. We expect the proposed innovative coating method would provide a good perspective of the future application of high-performance, cost-effective and environmentally friendly cementitious composites.

Understanding the role of carbon nanotubes in low-carbon concrete: From experiment to molecular dynamics

This research aligns with green and sustainable development principles, aiming to augment concrete's mechanical properties and durability. The low-carbon reactive powder concrete was developed by substituting ordinary Portland cement with sulfoaluminate cement. Additionally, an effective method was proposed to enhance the interfacial transition zone (ITZ), involving the pre-saturation of sand particles in a dispersion of carbon nanotubes (CNTs). The role of CNTs on the concrete's mechanical property, hydration process, and microstructure was extensively explored using experiments and MD (molecular dynamics) simulations. The results indicated a 27.8% and 10.1% increase in 28-day compressive strength, along with a 16.7% and 6.3% rise in 28-day flexural strength for the sample with pre-saturated sand dispersed in CNTs (CS2), in comparison to samples without CNTs (C0) and those with dispersed CNTs (C2). The primary enhancement mechanism is ascribed to the CNTs' ability to improve the ITZ through adsorption and nucleation. The CNTs facilitated the generation of AFt (ettringite) and AH3 (gibbsite), enhancing the hydration degree. This mechanism was corroborated by MD simulations that analyzed the effect of CNTs' on the mobility of calcium ions (Ca2+). When dispersed at the ITZ, CNTs had a seeding effect, leading to the generation of AFt and AH3 around the CNTs. This, in turn, reduced the ITZ's width and dramatically improved the bonding between the CNTs and the ITZ, thus effectively enhancing the ITZ's microscopic structure.

Investigation of the Wet and Thermal Conditions Effect on the Micro-Scale Characteristics of Interfacial Transition Zone of Porous Asphalt Mixture

Complex environmental factors can significantly influence the micro-properties of porous asphalt (PA) mixture. Therefore, the effects of short-term and long-term thermal aging and moisture immersion on the micromechanics properties, micro-morphology, and chemical element distributions of the interfacial transition zone (ITZ) of PA mixture were studied to reveal the mechanisms by which environmental degradation impact performance by means of nanoindentation (NI), backscattering scanning electron microscope (BSEM), and energy-dispersive X-ray spectroscopy (EDS) analysis techniques. The results show that the ITZ is not the softest part of the PA mixture, and the order of modulus is aggregate > ITZ > asphalt mastic. ITZ thickness is about 10–20 μm. Thermal aging has negligible effect on the width of ITZ. With increasing aging degree, the asphalt mastic and ITZ modulus increase, while water damage reduces the modulus of ITZ and slightly increases the width of ITZ. Thermal aging has little effect on the morphology of ITZ, while water damage will lead to microcracks and micropores in ITZ. Compared with thermal aging, water damage has a greater effect on the morphology of ITZ and leads to softening of the interfacial transition zone and asphalt mastic phase. The width of ITZ obtained by EDS line scanning is basically consistent with that of nanoindentation. Overall, external environmental factors have a more significant effect on the mechanical properties than the micro-morphology of ITZ. The outcomes of this research provide a better understanding of the impact of the service environment on the microscopic characteristics of PA mixture.

Deterioration mechanism on Micro-structure of unsaturated polyester resin modified concrete for bridge deck pavement under salty Freeze-thaw cycles

To investigate the dynamic evolution characteristics on the microstructural deterioration of unsaturated polyester resin modified concrete (UPMC) for bridge deck paving layer in the salt freeze–thaw environment, the four-stage experimental layout under two freeze–thaw (FT) cycles regimes (i.e., FT-fresh water and FT-salty water) were schemed. The dynamic deterioration rule and mechanism of the interior pore structure, microcrack and interfacial transition zone (ITZ) under different FT stages were analyzed through quantitatively characterizing the corresponding characteristics parameters utilizing mercury intrusion approach (MIP), SEM, digital image processing and energy dispersive spectrum (EDS) test. The test results demonstrated that FT cycles would exacerbate the damnification degree of the interior pores and microcracks and the ITZ expansion inside concrete, especially under FT-salt water, due to crystallization pressure and expansion stress and a pumping effect from FT cycles, as well as chloride-induced corrosion. Nevertheless, the introduction of unsaturated polyester resin (UPR) could restrain the germination, propagation and nucleation of interior microdefects, diminish the morphologic irregularities of crack structure, exert a replenishing and refinement effect on the internal micropores and retard the expansion in ITZ width range irrespective of FT types.

Chloride Ion Transport Properties in Lightweight Ultra-High-Performance Concrete with Different Lightweight Aggregate Particle Sizes.

In this paper, the microstructure and resistance to chloride ion penetration of ultra-high-performance concrete (UHPC) prepared from lightweight aggregate (LWA) were studied through simulation and experiment. The effects of LWA with different particle sizes on the chloride ion transport properties of lightweight ultra-high-performance concrete (L-UHPC) were discussed through simulation test results. The random delivery model of LWA in L-UHPC was established by MATLAB, and the model was introduced into COMSOL. Through the comparative analysis of experimental data and simulation results, the repeatability of the proposed model and the simulation accuracy were verified. The results show that when the LWA particle size changes from 0.15–4.75 mm to 0.15–1.18 mm, the width of interfacial transition zone (ITZ) and the overall porosity of L-UHPC decrease. This is because the large particle size LWA has more open pores with larger pore diameters and related interconnections, which are potential channels for chloride ion transport. Therefore, the chloride ion transport properties in L-UHPC are inhibited, which is manifested by the “tortuosity effect” of the LWA.

Effect of the Moisture Content of Recycled Aggregate on the Mechanical Performance and Durability of Concrete.

Wasted concrete was often used as a recycled aggregate instead natural stone in fresh concrete to reduce the environmental impact in a decade. However, because of the residual mortar interface, the performance of recycled aggregate was weaker. In this paper, the recycled aggregate was prewetted, and the effects of prewetted degree on the workability, strength, and durability of concrete were studied. The properties of the interfacial transition zone (ITZ), including microhardness, pore structure, and width, were also investigated. The results show that the workability intensity increased with the increase in prewetted degree from 0% to 100%, while the strength was first increased and then decreased with the optimal value of 43.3 MPa when the prewetted degree was 50–65%. The water absorption and chloride ion diffusion coefficient were also decreased by approximately 10% at minimum with the prewetted degree around 55% because of the declined fraction of pores larger than 50 μm and smaller porosity. The width of ITZ was first sharply decreased with a prewetted degree of 50–65%, then increased again with higher moisture, while microhardness of the ITZ showed the opposite trend and reached 82.7 MPa at maximum, at 50%. The appropriate moisture (50–65%) improved the pore structure and hydration products with an internal curing effect. When the moisture content was too high, the excess water was released from aggregate to the matrix, causing a higher water–cement ratio at ITZ; the porosity and the number of macrospores were increased to weaken the performance of concrete.

Numerical investigations on the influence of ITZ and its width on the carbonation depth of concrete with stress damage

The effect of the interfacial transition zone (ITZ) on carbonation of stress damaged concrete is investigated by a joint simulation using ABAQUS and COMSOL. Two FEM software use identical mesh and respectively determine the stress damage and carbonation depth. The parameters utilised in the simulation are obtained by a uniaxial test of mortar cylinders and a 450-day carbonation test of cubic concrete. The influence of ITZ and its width (20–100 μm) on carbonation are studied. For undamaged concrete, ITZ reduces the aggregate-phile effect by 10%. For stress damaged concrete, uneven carbonation fronts are observed, and ITZ increases the maximum carbonation depth by 7–11 and 6.8 times within 1000 days under compression and tension, respectively. An increasing ITZ width also spreads the concentrated damage and promotes the carbonation depth. Comparing the result of ITZ = 100 μm to that of 20 μm, the maximum carbonation depth is doubled, and the average carbonation depth is increased by 37%.

Particle size distribution of aggregate effects on the reinforcing roles of carbon nanotubes in enhancing concrete ITZ

By virtue of their superior mechanical properties and huge surface area, carbon nanotubes (CNTs) have become a potential representative in the field of the nanoengineered concrete, which provides an excellent opportunity to reinforce concrete interfacial transition zone (ITZ) characteristics. Adjusting the most reasonable aggregate gradation of concrete to maximize the enhancement effects of CNTs to ITZ is the key to popularizing the application of nano reinforcement in practical engineering. Hence, in this work, we investigated the reinforcing roles and mechanisms of CNTs on the concrete ITZ, and the corresponding influence on the mechanical performance and impermeability properties under different aggregate particle size distributions. The results reveal that CNTs can promote nucleation effects to generate hydration products growth and act as the refined templates to produce finer microstructure in concrete ITZ. Compared with plain concrete, the reinforcing ratios of CNTs on the ITZ characteristics, mechanical performance and impermeability present a quadratic function correlation with the Talbot index. The optimal effects of CNTs on the reinforcement of concrete ITZ characteristics appear at 0.8 Talbot index, reducing about 30% ITZ width and 22.8% abrasion crack width in ITZ. The corresponding mechanical properties and impermeability improve 20.7–35.6% and 38.1–43.6%, respectively. Low Talbot gradation index would result in the uneven dispersion of CNTs among the capillary pores. In contrast, high Talbot gradation index may enlarge the ITZ range, increase the amount and width of abrasion cracks in ITZ, and further weaken the reinforcing effects of CNTs.

Stress Distribution in Microregion of Core–Shell Structure Lightweight Aggregate Concrete

An in-depth understanding of the effect of cordierite/belite core–shell structure lightweight aggregate (CSLWA) on the mechanical performance of LWA concrete (LWAC) is critical for improving the failure resistance of LWAC. In this study, the stress distribution of the microregion in CSLWA was systematically investigated via a finite element analysis to explore its effect on the mechanical properties of LWAC. In detail, the material components, core–shell thickness ratio, porosity and width of interfacial transition zone (ITZ), and absence or presence of interfacial bonding zone (IBZ) were considered during the stress distribution analysis of the microregion of LWAC. The results showed that a reduction in the material components, with a high-elastic modulus in the core, a decrease in the core–shell thickness ratio, and the formation of the core–shell IBZ are beneficial for optimizing the stress distribution of the microregion and alleviating the stress concentration phenomenon of LWAC. Moreover, due to the continuous hydration of belite shell, the ITZ of CSLWA becomes increasingly dense, thus the stress distribution is more uniform than that of ordinary LWAC, indicating that CSLWA exhibits the potential to improve the failure resistance of LWAC. This study helps to develop an understanding of the role played by the core–shell structure in improving the toughness of LWAC, and provides a new solution and methodology for improving the brittleness of LWAC.

Understanding geopolymer binder-aggregate interfacial characteristics at molecular level

The interfacial characteristics of geopolymer binder to aggregate composites are poorly understood, especially at molecular level. Herein, molecular models are developed to study, for the first time, the geopolymer-aggregate interface. Chemically, various forms of interfacial bonding are characterized, including Al-O-Si bonding through condensation reactions, NaO and H-bonding. An atomic-level interfacial transition zone (ITZ) is identified, attributed to the concentration of –OH groups. Increasing the Si/Al ratio of geopolymer is found to decrease the ITZ density, but have limited effect on the ITZ width. A heterogeneous diffusion characteristic occurs in geopolymer, due to the weak interfacial interaction. Mechanically, lowering the Si/Al ratio promotes the interfacial strength due to the stronger interfacial interaction and higher cross-linking degree in geopolymer. Under loading the interfacial fracture undergoes three stages: crack propagation, chain bridging (including aluminosilicate and ionic bridging) and breakage. The above atomic-level findings may facilitate a better design of geopolymer concrete in engineering.

Influence of ultrasonication energy on reinforcing-roles of CNTs to strengthen ITZ and corresponding anti-permeability properties of concrete

Concrete is the most common material used extensively in fundamental construction and engineering. The interfacial transition zone (ITZ), as the region of the cementitious pastes around the aggregate particles, is the weakest area and always limits the performance and application of the concrete. In this study, we used carbon nanotubes (CNTs) as nano-additives to strengthen the ITZ characteristics in concrete and the corresponding anti-permeability reinforcement under different ultrasonication energy (UE). The results prove that balancing the separating and shearing forces during the ultrasonication processes is crucial to ensure the dispersion and suitable particle size of CNTs in their further application. It is found that ultrasonication energy of between 225 J/mL and 338 J/mL can simultaneously ensure the degree of dispersion and the tube-length of CNTs in the suspension, and optimize the ITZ width and abrasion crack width in the ITZ in concrete to 30%–40.2%. The relationship between the ITZ characteristics and UE can be described using a quadratic function. Both the ITZ width and abrasion crack width in the ITZ have a linear correlation with permeability-related parameters in the concrete. After mixing CNTs into concrete specimens, the corresponding anti-permeability properties increased by more than 43% under 270–338 J/mL UE. Scanning electron microscopy observation further reveals that CNTs not only have a nucleating role in generating a higher hydration reaction but also form net-like distributions in the hardened concrete to reinforce the microstructure of the ITZ. However, both insufficient and excess UE will inhibit the superior reinforcing ability of CNTs.

Salt frost resistance and micro characteristics of polynary blended concrete using in frost areas

To explore the deterioration process and improvement mechanism concrete blended with supplementary cementitious materials (fly ash, slag, and silica fume) in frozen areas, the SCM content, w/b ratio, curing age, freeze-thaw (F-T) cycle, and salt-frost (S-F) cycle were varied to systematically evaluate the chloride permeability resistance and S-F resistance. Pore structures, hydration degree, phase composition and interfacial transition zone (ITZ) between aggregate and matrix of investigated mixtures were characterized by mercury intrusion porosimetry (MIP), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and SEM-EDS, respectively. The S-F resistance of blended concrete is greater than that of control mixture without SCMs. The crystallization pressure is dominated by larger saturation with higher salt concentration at the early stage of S-F cycles, and greatly affected by the actual volume expansion of salt solutions at its later stage. SCMs can compensates the structure deterioration under S-F and F-T conditions, where quaternary blends shows an optimal refinement for the pore structures. It is found that the total pore volume, average pore size, and porosity are highly correlated with the chloride permeability resistance of concrete by grey degree analysis. The SCMs blends can improve cement hydration degree by pozzolanic and hydraulic reactions at the later curing age. With the S-F cycles, the internal stresses could cause pore nucleation and crack propagation, while SCMs can effectively control the ITZ width and mitigate the structural deterioration of concrete.

Roles of carbon nanotubes in reinforcing the interfacial transition zone and impermeability of concrete under different water-to-cement ratios

Concrete plays a central role in fundamental construction and engineering. However, the interfacial transition zone (ITZ), as the area between the aggregates and cementitious pastes, is the weakest component in concrete and always limits the properties and application of the concrete. Here, we reveal the potential of carbon nanotubes (CNTs) as superior additives for reinforcing the ITZ in concrete and the corresponding impermeability enhancement against various of water-to-cement (W/C) ratios. The results suggest that CNTs not only promote higher hydration reaction and generate more hydrated products to dense ITZ area, but also form net-like distributions to inhibit flaws propagation at the microscale. Compared with the plain concrete specimens, the addition CNTs micrified the ITZ width by 14.3–30% and reduced the abrasion crack width by 19.5–35%. The reinforcing effects of CNTs on ITZ characteristics are consistent with Gauss fitting and achieve the highest enhancement at 0.4 W/C ratio. The corresponding impermeability properties of concrete present a linear correlation with both ITZ width and abrasion crack width, which can be strengthened by approximately 10.9%-35.8% assisted by CNTs. Furthermore, selecting the appropriate W/C ratios is the key to make full use of CNTs roles in strengthening the ITZ of concrete. High W/C ratios may lead to the re-agglomeration of CNTs and low W/C ratios would promote CNTs to act as pulled-out roles and weaken their ability to inhibit flaws propagation.

Strength enhancement of artificial aggregate prepared with waste concrete powder and its impact on concrete properties

Waste concrete powder (WCP), a byproduct generated in the production of recycled concrete aggregates, is proposed as the main material for manufacturing artificial aggregate (WCPA) through cold-bonding pelletization. The addition of cement, ground granulated blast furnace slag and calcium hydroxide as well as the application of CO2 curing are integrated with the purpose of strength enhancement. Experimental results indicate that aggregate strength increases in proportion with cement and slag dosages while calcium hydroxide content reaches the optimum at 3%. By optimizing mix proportion, the aggregate obtains the highest strength of 3.0 MPa and the lowest water absorption of 6.3%. In addition, when it is incorporated in concrete, WCPA shows stronger interactions with cement matrix as compared with natural aggregate and ceramsite since the width of interfacial transition zone is only 30 μm as compared to 60 μm in the reference groups. The compressive strength of WCPA concrete reaches over 30 MPa, suggesting the viability of WCPA in many civil engineering applications; however, it is found that the drying shrinkage tends to increase by up to 47%. Overall, this study contributes to the establishment of waste to resources chain with regards to the concrete industry through the green production of artificial aggregate with WCP.

Influence of Annealing Treatment on Microstructure Evolution and Mechanical Property of Friction Stir Weld AZ31 Mg Alloys

In order to improve microstructure distribution and mechanical properties of Mg alloy joint by annealing treatment, die-casting AZ31 Mg alloy was successfully welded at rotation speed of 1 400 rpm and travel speed of 200 mm/min. The welded joints were annealed at 150–300 °C for 15–120 min and then were subjected to transverse tensile. The microstructure of annealed joints was analyzed by optical microscopy and electron backscatter diffraction. The experimental results indicate that (0001) texture intensity in stir zone significantly reduces and sharp transition of grain size is relieved in the interface between stir zone and thermo-mechanically affected zone after annealed at 200 °C for 30 min. Meanwhile, the elongation is increased from 7.5% to 13.0% and strength is increased slightly. It is because that annealing treatment can inhibit twin transformation and retain its ability to coordinate deformation during tensile deformation, which contributes to the improvement of plasticity. In addition, annealing treatment can increase the width of interfacial transition zone and lead to gradual transition of grain size between the SZ and TMAZ, which balances dislocation diffusion rate in different zone.

Numerical Study on Diffusion of Chloride and Induced Rebar Corrosion by Two-Dimensional Multiscale Approach

Modeling approach for mesoscopic model of concrete depicting mass transportation and physicochemical reaction is important since there is growing demand for accuracy and computational efficiency of numerical simulation. Mesoscopic numerical simulation considering binder, aggregate, and interfacial transition zone (ITZ) generally produces huge number of DOFs, which is inapplicable for full structure. In this paper, a two-dimensional multiscale approach describing three-phase structure of concrete was discussed numerically. An effective approach generating random aggregate in polygon based on checking centroid distance and intersection of line segment was introduced. Moreover, ITZ elements were built by parallel expanding the edge of aggregates on inner side. By combining mesoscopic model including full-graded aggregate and macroscopic model, cases related to diffusivity and width of ITZ, volume fraction, and grade of aggregate were studied regarding the consideration of multiscale compensation. Result clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Finally, this paper addressed some noteworthy conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar diameter, concrete cover, and exposure period.