Effect of the optimized triple mixing method on the ITZ microstructure and performance of recycled aggregate concrete

Zhang, Wenlong; Wang, Shoude; Zhao, Piqi; Lu, Lingchao; Cheng, Xin

doi:10.1016/j.conbuildmat.2019.01.071

Cited by 74 publications

(20 citation statements)

References 34 publications

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“…Therefore, it can be inferred that that the ITZ was the main reason for the bearing capacity decrease of RAC. This is probably due to that fact that the mass of RCA was higher and the area of ITZ was greater [37,38] and the strength of concrete with RCA was lower than that with RFA, as shown in Figures 5 and 6. Moreover, the slightest strength decline of specimens mixed with only RFA can be ascribed to the RAF itself.…”

Section: Mechanical Propertiesmentioning

confidence: 95%

“…The mass of the recycle aggregates with double replacement of RCA and RFA was the highest, then RCA, and RFA was the least. Since RA has inherent defects, such as numerous micro-cracks, large porosity, and low strength [31,32,37,38], the increase of its content will introduce more flaws into concrete, leading to the rise of fragility and more severe degradation of mechanical performances. Moreover, it can be seen from Figure 5 that when the RFA dosage was lower than 70%, the compressive strength of specimens was higher than 32.5 MPa and the drop degree was within 15%, which was superior to that of RFA concrete in other studies [9,11,14].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…interface transition zones (ITZ) between the RA and the new cement paste and the RA and the old mortar differ a lot and are very complicated [37,38], which greatly influences the performance of RAC.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Feasibility of Utilizing Recycled Aggregate Concrete for Revetment Construction of the Lower Yellow River

Pan

Chang

et al. 2019

Materials

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To explore the feasibility of utilizing recycled aggregate concrete (RAC) in revetment construction of the lower Yellow River, a series of mix proportions with local recycled aggregates (RA) were designed to evaluate its mechanical properties and durability. The morphology and micro-hardness of the interface transition zone (ITZ) were also characterized to explain the performance of RAC. Based on the compressive strength data of 13 groups of mixtures, which is larger than 30 MPa, and with the RA substitution rate not less than 50%, the RAC containing 50% recycled fine aggregate (RFA) (HDX50), 70% RFA (HDX70), and 50% recycled coarse aggregate (RCA) (HDC50) were selected. The experiment results suggest that the mechanical performance, frost resistance, and carbonation resistance of the selected RAC is generally poorer than that of natural aggregate concrete (NAC), but can meet the performance requirement of concrete for the revetment construction of the lower Yellow River. The comprehensive performance of these three mixtures ranks as: HDX50 > HDX70 > HDC50. When considering the RA substitution ratio as a priority, HDX70 would be the best choice and can be applied in the revetment engineering. A number of defects are observed on the surface of RA with old pastes attached. Furthermore, the ITZs formed around RA are loose and with low micro-hardness, which is deemed to be the dominating reasons leading to the weaker performance of RAC than that of NAC.

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Section: Mechanical Propertiesmentioning

confidence: 95%

Section: Mechanical Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Feasibility of Utilizing Recycled Aggregate Concrete for Revetment Construction of the Lower Yellow River

Pan

Chang

et al. 2019

Materials

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“…In particular, the ITZ has an obvious effect on the mechanical behavior of concrete, and thus it is an important component of concrete when investigating its mechanical properties. However, the thickness of the ITZ is commonly considered to between 15 and 40 µm [28,29], which is much smaller than the size of the aggregate, i.e., more than 2 mm commonly. Therefore, when investigating the geometric characteristics of the concrete meso-structure, we assumed that the ITZ can be neglected.…”

Section: Fractal Dimension Of Aggregates and Cementmentioning

confidence: 99%

Effect of Fractal Dimension in Concrete Meso-Structure on Its Axial Mechanical Behavior: A Numerical Case Study

Dai

et al. 2021

Fractals

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The numerical meso-modeling method is a powerful tool for simulating concrete and studying the influence of the geometric form of meso-structure on its mechanical behavior. It is still uncertain regarding how to most effectively characterize the geometric form of the concrete meso-structure and its effect on the observed macro behavior. In this study, the fractal dimension of cement paste was used to describe the geometric form of concrete at the meso-level. A group of meso-models of concrete with various fractal dimensions and coarse aggregate contents were simulated using the Random Fractal Modeling method, and the numerical results under compression and tension were studied and discussed. The simulation results suggested that the compressive initial modulus, the compressive strength decreased, the strain corresponding to the maximum compressive stress decreased with increasing fractal dimension. However, the fractal dimension did not influence the tensile initial modulus, the tensile strength, and the strain corresponding to the maximum tensile stress obviously. The comprehensive consideration of the fractal characterize can provide a reasonable tool for understanding and predicting the observed macroscopic behavior of concrete.

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“…This was mainly due to the presence of cracks and micro-cracks in RA which provide paths for chloride penetration. 33 Moreover, the RAC possessed two ITZs, one between the recycled aggregate and the new cement paste, and the other between the aggregate and the old mortar which consisted of pores and cracks and forms a new weak link in concrete. The presence of new ITZ also critically affected the durability of RAC.…”

Section: Effect Of Aggregate Typementioning

confidence: 99%

Quantitative evaluation of interfacial transition zone of sustainable concrete with recycled and steel slag as aggregate

Zhang

et al. 2020

Structural Concrete

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Utilizing steel slag and recycled concrete as fine aggregate could save the consumption of natural resource and reduce the environmental pollution. In this work, the effect of steel slag aggregate and recycled aggregate on the compressive strength and chloride migration coefficient of three types of concretes were investigated and compared with natural aggregate. The interfacial transition zone (ITZ) microstructure and the connection between aggregate and bulk cement matrix was determined by using a quantitative backscattered electron (BSE) image analysis, N 2 adsorption-desorption and X-ray diffraction analysis.Results showed that the compressive strength and chloride resistance ability of natural aggregate concrete (NAC) and steel slag aggregate concrete (SAC) was highly dependent on aggregate volume content. The performance of recycled aggregate concrete (RAC) were much poorer than that of SAC and NAC. Pore structure and phase analysis confirmed that the improved properties of SAC can be partially attributed to the densified ITZ. Regarding RAC, a porous ITZ was observed in BSE image and pore structure analysis, which caused a poor compressive strength and a large chloride migration coefficient. It was found that the improvement of chloride resistance ability by using supplementary cementitious materials in NAC was more remarkable than that in SAC.

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Effect of the optimized triple mixing method on the ITZ microstructure and performance of recycled aggregate concrete

Cited by 74 publications

References 34 publications

Feasibility of Utilizing Recycled Aggregate Concrete for Revetment Construction of the Lower Yellow River

Feasibility of Utilizing Recycled Aggregate Concrete for Revetment Construction of the Lower Yellow River

Effect of Fractal Dimension in Concrete Meso-Structure on Its Axial Mechanical Behavior: A Numerical Case Study

Quantitative evaluation of interfacial transition zone of sustainable concrete with recycled and steel slag as aggregate

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