Methods for improving the microstructure of recycled concrete aggregate: A review

Wang, Ruijun; Yu, Ning; Li, Yang

doi:10.1016/j.conbuildmat.2020.118164

Cited by 228 publications

(68 citation statements)

References 111 publications

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“…The RCA samples present lower specific gravity (Figure 6a) values than the NA, and consequently a higher water absorption (Figure 6b). This finding is according to many researchers, and it is due to the existence of attached mortar [48,49], because of the lower density and higher porosity of cement paste attached to the RCA [9].…”

Section: Resultsmentioning

confidence: 53%

Combining Reclaimed Asphalt Pavement (RAP) and Recycled Concrete Aggregate (RCA) from Cuba to Obtain a Coarse Aggregate Fraction

et al. 2020

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In Cuba, tons of construction and demolition waste (CDW) are generated during urban construction and reconstruction activities every year. The use of CDW, such as recycled concrete aggregates (RCA) and reclaimed asphalt pavement (RAP), in pavement construction is a viable solution to preserve the consumption of natural aggregates (NA), and to minimize the impact of landfill. The main objective of this work is to obtain a 5–10 mm aggregate fraction of RCA and RAP, to obtain an appropriate recycled coarse aggregate for manufacturing hot mix asphalt (HMA). Each source of RCA, RAP and NA, and the combinations RCA/RAP (0/100, 25/75, 50/50, 75/25 and 100/0) were characterized (moisture, asphalt content of RAP, specific gravity, water absorption, and flakiness index) for determining a better combination. The results showed that the combination (RCA/RAP) that best meets the NA aggregates specifications used for hot mix asphalt were RCA/RAP: 25/75 and 50/50. The results show the possibility of combining both wastes to obtain a coarse aggregate fraction with a high environmental benefit, by reducing the use of natural resources.

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Section: Resultsmentioning

confidence: 53%

Combining Reclaimed Asphalt Pavement (RAP) and Recycled Concrete Aggregate (RCA) from Cuba to Obtain a Coarse Aggregate Fraction

et al. 2020

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“…Take Equation (12) into Equations (7) and (8), then add Equation (10) (i.e., ε 0p ), the creep equation of the improved Burgers model can be obtained, and its model is shown in Equation (13) and Figure 16. 13) particles. From the experimental analysis, it can be known that the rate of fragmentation and slippage of CDW particles changes with the load and the deformation gradually stabilizes with time, which is inconsistent with the trend of 1 /η σ t 0 .…”

Section: Creep Model and Parametersmentioning

confidence: 99%

“…The improved Burgers model, which can better describe the creep characteristics of CDW filler, and the effects of load and ratio on the creep parameters are analyzed using the equivalent creep compliance. This study is of great significance for the promotion of CDW and meets the requirements of sustainable development.Sustainability 2020, 12, 1924 2 of 22 for the adverse effects of recycled aggregates [12][13][14]. When recycled aggregate is used to produce recycled asphalt, Subhy et al [15] and Menegusso et al [16] have studied the effects of its content and treatment method on fatigue performance.…”

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confidence: 99%

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Investigation into Creep Characteristics and Model of Recycled Construction and Demolition Waste Used in Embankment Filler

Yan

Liu

et al. 2020

Sustainability

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The creep deformation of recycled construction and demolition waste (CDW) filler is an important factor affecting road performance. In this paper, a series of laboratory tests, including a compaction test, sieving test, California bearing ratio (CBR) test, creep test and unloading test are conducted on CDW filler. The engineering properties of different ratios of CDW mixture are systematically analyzed, the CBR value of CDW filler meets the requirements of an embankment. The creep type of CDW filler under a test load is stable creep, the results of the creep characteristics are analyzed from a microscopic point of view. The filler with a 7:2:1 ratio (brick slag: concrete: mortar) has the densest structure, which is dense and less porous, and the deformation is the smallest. Reasonable proportion control is the key to reducing embankment deformation. The improved Burgers model, which can better describe the creep characteristics of CDW filler, and the effects of load and ratio on the creep parameters are analyzed using the equivalent creep compliance. This study is of great significance for the promotion of CDW and meets the requirements of sustainable development.Sustainability 2020, 12, 1924 2 of 22 for the adverse effects of recycled aggregates [12][13][14]. When recycled aggregate is used to produce recycled asphalt, Subhy et al. [15] and Menegusso et al. [16] have studied the effects of its content and treatment method on fatigue performance. In addition, recycled aggregates are used for roadbed fillers, Javier et al. [17] found that the bearing capacity of the recycled aggregates increased with time in the structural layer, which is inconsistent with the trend of natural aggregates. Vegas et al. [18] and Yin et al. [19] studied the properties of recycled concrete applied to an embankment and introduced its permanent deformation characteristics.The application of CDW materials to embankments has great economic and environmental benefits, but the composition of recycled CDW material is complex, and its settlement after construction is difficult to predict and control, therefore, a study into its creep characteristics and mechanisms is urgently needed. The CDW mixture belongs to coarse-grained materials and the creep deformation of coarse-grained materials can be divided into stable creep and unstable creep types, according to the magnitude of stress [20,21]. The rheological curve of coarse-grained materials can be divided into three stages: linear, decaying rheology, and stability [22]. With the increase in dam height, the particle breakage of the rockfill in the rock dam increased significantly, and the particle breakage directly changed the rockfill structure [23,24]. From their triaxial creep shear test, Jiang et al. concluded that particle motion, rotation, and damage are the main causes of coarse-grained material deformation [25]. In addition to the time-dependent strain under a constant load, changes in the external environment tend to have a large effect on creep deformation, especially as immersion i...

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“…As is known to all, there are at least two interface transition zones (ITZs) in RAC (Tam et al, 2005;Xiao et al, 2013): 1) the old ITZ between NA and its adhered old cement mortar, which already exist in RA; and 2) the new ITZ between the RA and new cement mortar. Compared to traditional concrete, this caused more defects in mechanical properties and more significant hidden dangers of durability problems (Bao et al, 2020a;Wang et al, 2020). Thus far, investigations mainly focused on the mechanical properties of RAC (Folino and Xargay, 2014;Kim and Yun, 2014;Velay-Lizancos et al, 2018;Wang and Xiao, 2018;Munir et al, 2020), yet still limited in durability problems.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Water Transport in Unsaturated Recycled Aggregate Concrete

et al. 2020

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The old mortar attached to recycled aggregate (RA) is the main reason for the difference in water movement between RA concrete (RAC) and natural aggregate concrete. In this study, considering the old and new interfacial transition zones, a five-phase composite model for describing the water transport and distribution in RAC is established at the mesoscale. The key parameters describing water unsaturated transport in two types of mortar, saturated hydraulic conductivity (K s) and van Genuchten model parameters (α, n), are obtained through the constant-head permeability test and isothermal adsorption test. By using the finite element method, the numerical simulations of unsaturated moisture movement in the homogeneous mortar, natural aggregate concrete, and five-phase RAC are systematically carried out. The proposed water transport model in the matrix is validated by comparison with the available experimental findings from the literature. The results show that the model can well predict unsaturated water transport in cement-based materials, including RAC. A parameter sensitivity analysis is undertaken to ascertain the main influencing factors of water transport in RAC. It is concluded that the RA replacement rate (R ra), the thickness of the old mortar (d m), and the aggregate volume fraction (F a) are the primary parameters affecting moisture movement in RAC.

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Methods for improving the microstructure of recycled concrete aggregate: A review

Cited by 228 publications

References 111 publications

Combining Reclaimed Asphalt Pavement (RAP) and Recycled Concrete Aggregate (RCA) from Cuba to Obtain a Coarse Aggregate Fraction

Combining Reclaimed Asphalt Pavement (RAP) and Recycled Concrete Aggregate (RCA) from Cuba to Obtain a Coarse Aggregate Fraction

Investigation into Creep Characteristics and Model of Recycled Construction and Demolition Waste Used in Embankment Filler

Numerical Simulation of Water Transport in Unsaturated Recycled Aggregate Concrete

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