scholarly journals Residual Properties Analysis of Steel Reinforced Recycled Aggregate Concrete Components after Exposure to Elevated Temperature

2018 ◽  
Vol 8 (12) ◽  
pp. 2377 ◽  
Author(s):  
Zongping Chen ◽  
Rusheng Yao ◽  
Chenggui Jing ◽  
Fan Ning
Keyword(s):  
Elevated Temperature ◽  
Energy Dissipation ◽  
Mass Loss ◽  
Bearing Capacity ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Residual Properties ◽  
Significant Fluctuation ◽  
Capacity Degradation

The application of recycled aggregate concrete (RAC) has developed rapidly in recent years. But how to evaluate the residual properties of RAC after the fires is more beneficial to the further popularization and application of RAC. This paper presents the residual properties of RAC and steel reinforced recycled aggregate concrete (SRRAC) components after exposure to elevated temperature. A total of 176 specimens (120 rectangular prisms specimens, 24 SRRAC short columns and 32 SRRAC beams) were designed and tested after exposure to elevated temperature. The parameters were considered in the test, including replacement percentage of recycled coarse aggregate (0%, 30%, 50%, 70% and 100%) and exposure to different temperatures (20, 200, 400, 600 and 800 degrees centigrade). According to the test results, heat damage and residual properties of specimens were analyzed in detail, such as surface change, mass loss, bearing capacity degradation, stiffness degradation, ductility and energy dissipation of specimens under the elevated temperature. The results showed that a series of significant physical phenomena occurred on the surface of RAC and SRRAC components after exposure to elevated temperature, such as the color changed from green-grey to gray-white, chapped on the concrete surface after 400 degrees centigrade and the mass loss of concrete is less than 10%. The degradation of mechanical properties degenerated significantly with the increase of temperature, such as the strength of RAC, and compressive capacity, bending capacity, shear capacity and stiffness of SRRAC components, among that, the degradation of the strength of RAC was most obvious, up to 26%. The ductility and energy dissipation of SRRAC components were insignificant affected by the elevated temperature. Mass loss ratio, peak deformation and bearing capacity showed a slight increase trend with the increase of replacement percentage. But the stiffness showed significant fluctuation when replacement percentage was 70% to 100%. And the ductility and energy dissipation showed significant fluctuation when replacement percentage was 30% to 70%.

scholarly journals Analysis on Mechanical Properties of Recycled Aggregate Concrete Members after Exposure to High Temperatures

2019 ◽  
Vol 9 (10) ◽  
pp. 2057 ◽  
Author(s):  
Zongping Chen ◽  
Ji Zhou ◽  
Peihuan Ye ◽  
Ying Liang
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Bearing Capacity ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Displacement Ductility ◽  
Energy Dissipation Capacity

In order to study the mechanical properties of recycled aggregate concrete (RAC) specimens after exposure to high temperatures, 120 RAC prism specimens, 57 reinforced recycled aggregate concrete (RRAC) specimens, and 56 steel reinforced recycled aggregate concrete (SRRAC) specimens were designed, involving two varying parameters such as recycled coarse aggregate (RCA) replacement percentage and temperature. The performance degradation of RCA materials, RRAC members, and SRRAC members after exposure to high temperatures was analyzed in depth. The research results show that after exposure to high temperatures the surface color of members may change from cinereous to gray-white. Some cracks may appear on surface of members and the mass of members may be lighter. With the increase of the experiencing temperatures, the bearing capacity (compressive, bending, and shearing) of RAC and its members are reduced, but their ductility and energy dissipation capacity have little effect on the change of high temperature. With the increase of the RCA replacement percentage, the mass loss ratio, ultimate bearing capacity, and peak deformation of each RAC and its members increase slightly, and the displacement ductility and energy dissipation capacity of the RRAC members decrease slightly. With the increase in replacement percentage of RCA, mechanical properties of RAC and their members have little effect after exposure to elevated temperatures, and the fluctuation range is within 20%.

scholarly journals Seismic Behavior of Concrete-Filled Circular Steel Tubular Column–Reinforced Concrete Beam Frames with Recycled Aggregate Concrete

2020 ◽  
Vol 10 (7) ◽  
pp. 2609 ◽  
Author(s):  
Zongping Chen ◽  
Ji Zhou ◽  
Zhibin Li ◽  
Xinyue Wang ◽  
Xingyu Zhou
Keyword(s):  
Reinforced Concrete ◽  
Energy Dissipation ◽  
Seismic Behavior ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Scale Model ◽  
Hysteresis Curve ◽  
Small Scale ◽  
Skeleton Curve ◽  
Aggregate Concrete

The application of recycled aggregate concrete (RAC) in concrete filled steel tubular (CFST) structures can eliminate the deterioration of concrete performance caused by the original defects of the recycled aggregate, which also provides an effective way for the recycling of waste concrete. In this paper, a test of a small scale model of a circular CFST column-reinforced concrete (RC) beam frame with RACs under low cyclic loading was presented in order to investigate its seismic behavior. The failure modes, plastic hinges sequence, hysteresis curve, skeleton curve, energy dissipation capacity, ductility and stiffness degeneration of the frame were presented and analyzed in detail. The test results show that the design method of the recycled aggregate concrete filled circular steel tube (RACFCST) frame complies with the seismic design requirements of a stronger joint followed by the stronger column and the weaker beam. The hysteresis curve of the frame is symmetrical, showing a relatively full shuttle shape; at the same time, the ductility coefficient of the frame is greater than 2.5, showing good deformation performance. In addition, when the frame is damaged, the displacement angle is greater than 1/38, and the equivalent damping ratios coefficient is 0.243, which indicates that the frame has excellent anti-collapse and energy dissipation abilities. In summary, the RACFCST frame has good seismic behavior, which can be applied to high-rise buildings in high-intensity seismic fortification areas.

scholarly journals Compressive Strength Study on the Freeze-thaw Resistance of Recycled Aggregate Concrete Members

2017 ◽  
Vol 11 (1) ◽  
pp. 270-280 ◽  
Author(s):  
Haicheng Niu ◽  
Yonggui Wang ◽  
Xianggang Zhang ◽  
Xiaojing Yin
Keyword(s):  
Compressive Strength ◽  
Mass Loss ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Surface Scaling

Introduction: Freeze-thaw resistance of recycled aggregate concrete with partial or total replacement of recycled aggregate compared with that of natural aggregate concrete was investigated in this paper. Method: Ninety specimens were fabricated to study the influence of different recycled aggregate replacement ratios on the surface scaling, mass loss, and residual compressive strength after 100 freeze-thaw cycles. Results: The experiment results indicate that the type of recycled aggregate and its replacement ratio have significant effects on the freeze-thaw performance. The cubic compressive strength of recycled aggregate concrete is overall slightly lower than that of normal concrete. After 100 freeze-thaw cycles, the compressive strength decreases and the reduction extent increases with increasing replacement rate of recycled aggregate. The surface scaling of reinforced recycled concrete prisms tends to be more severe with the increase of freeze-thaw cycles. Conclusion: Furthermore, a notable rise in mass loss and the bearing capacity loss is also found as the substitution ratio increases. Under the same replacement rate, recycled fine aggregate causes more negative effects on the freeze-thaw resistance than recycled coarse aggregate.

scholarly journals Effect of Recycled Aggregates on the Energy Dissipation Capacity of RC Beam subjected to Reverse Cyclic Flexural Loading

2021 ◽  
Vol 40 (1) ◽  
pp. 140-151
Author(s):  
Muhammad Rizwan Riaz ◽  
Rashid Hameed ◽  
Usman Akmal ◽  
Asad Ali Gillani ◽  
Muhammad Ilyas
Keyword(s):  
Energy Dissipation ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Rc Beam ◽  
Rc Beams ◽  
Aggregate Concrete ◽  
Flexural Loading ◽  
Energy Dissipation Capacity ◽  
Natural Aggregates

The energy dissipation capacity of concrete is an important aspect for a Reinforced Concrete (RC) structure to be seismically resistant. Various types of concrete incorporating sustainable materials are being developed these days such as recycled aggregate concrete. Determination of energy dissipation capacity of such new types of concrete is of great importance for their application in RC structures which are to be constructed in seismically active areas. In this regard, the experimental study presented in this contribution investigated the energy dissipation capacity of RC beams constructed using recycled aggregate concrete and subjected to three different deflection amplitude levels of reverse cyclic flexural loading. For this purpose, a total of 20 RC beams of cross section 75 x 150 mm and length of 1350 mm were cast using five different concrete compositions and tested. Among five different concrete compositions, one was control concrete containing 100% natural aggregates while the remaining four compositions were of recycled aggregate concrete containing natural and recycled aggregates. Four replacement levels (25%, 50%, 75%, and 100%) of natural aggregates with recycled aggregates were examined. Results indicated that the amplitude level of imposed deflection is an important factor which influenced the value of energy dissipated by RC beams. Further, results showed that RC beam constructed using recycled aggregate concrete containing 25% recycled aggregates exhibited energy dissipation capacity similar to or even better than that of control RC beam containing 100% natural aggregates.

Experimental study on seismic performance of low-rise recycled aggregate concrete shear wall with single-layer reinforcement

2016 ◽  
Vol 20 (10) ◽  
pp. 1493-1511 ◽  
Author(s):  
Zhong-yi Zhou ◽  
Wanlin Cao
Keyword(s):  
Bearing Capacity ◽  
Seismic Performance ◽  
Thermal Insulation ◽  
Single Layer ◽  
Shear Wall ◽  
Expanded Polystyrene ◽  
Recycled Aggregate Concrete ◽  
Experimental Results ◽  
Recycled Aggregate ◽  
Aggregate Concrete

A total of four full-scale low-rise recycled aggregate concrete shear wall specimens were tested adopting a quasi-static loading method to analyze the seismic performance. The low-rise shear walls consisted of recycled aggregate concrete, single-layer reinforcements, concealed special-shaped columns, and expanded polystyrene thermal insulation modules. Based on the experimental results, the seismic performance and failure characteristic of the specimens were comparatively analyzed. The factors affecting the seismic performance of the low-rise shear wall were also analyzed. The shear bearing capacity calculation model and formula of the walls were proposed based on the softened strut-and-tie model. A comparison of the calculated results and the experimental results shows that they are in good agreement. The results show that the load bearing capacity and deformation capacity can be significantly improved by expanded polystyrene thermal insulation modules, and that the shear wall specimens with higher recycled aggregate concrete strength and larger reinforcement ratio of the shear wall exhibit better seismic performance.

scholarly journals Numerical Study on Confinement Effect and Efficiency of Concentrically Loaded RACFRST Stub Columns

2021 ◽  
Vol 8 ◽  
Author(s):  
Yicen Liu ◽  
Fei Lyu ◽  
Faxing Ding ◽  
En Wang ◽  
Yunlong Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Steel Tube ◽  
Recycled Aggregate Concrete ◽  
Confinement Effect ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Superposition Method ◽  
Aggregate Concrete ◽  
Stub Columns

The mechanical behaviors of recycled aggregate concrete (RAC) are upgraded by outer steel tube confinement, and the performance of recycled aggregate concrete-filled steel tubular (RACFST) columns is similar to that of the traditional concrete-filled steel tube (CFST) columns. The purpose of this study is to investigate the behaviors of recycled aggregate concrete-filled rectangular steel tubular (RACFRST) stub columns under axial loading. Three-dimensional finite element (FE) models were established, which utilized a triaxial plastic-damage constitutive RAC model considering the replacement ratio of recycled aggregates. The finite element analysis results indicated that the lessened ultimate bearing capacity of RACFRST stub columns compared with their traditional concrete infilled counterparts was mainly due to the weakened confinement effect and confinement efficiency. A simplified formula of the bearing capacity of concentrically loaded RACFRST stub columns was proposed. The cross-sectional stress nephogram was reasonably simplified by the limited state of infilled concrete. The basics of proposed formula were the equilibrium condition and the superposition method. Finally, the formula for the bearing capacity of RACFRST stub columns was evaluated by comparing its accuracy and feasibility to some design formulae proposed by specialists and some design codes of different regions.

scholarly journals Confinement Effect and Efficiency of Concentrically Loaded RACFCST Stub Columns

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 154
Author(s):  
En Wang ◽  
Yicen Liu ◽  
Fei Lyu ◽  
Faxing Ding ◽  
Yunlong Xu
Keyword(s):  
Bearing Capacity ◽  
Ultimate Bearing Capacity ◽  
Recycled Aggregate Concrete ◽  
Confinement Effect ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Replacement Ratio ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Stub Columns

Recycled aggregate concrete-filled steel tubular (RACFST) columns are widely recognized as efficient structural members that can reduce the environmental impact of the building industry and improve the mechanical behavior of recycled aggregate concrete (RAC). The objective of this study is to investigate the behavior of recycled aggregate concrete-filled circular steel tubular (RACFCST) stub columns subjected to the axial loading. Three-dimensional finite element (FE) models were established using a triaxial plastic-damage constitutive model of RAC considering the replacement ratio of recycled aggregates. The FE analytical results revealed that the decreased ultimate bearing capacity of RACFCST stub columns compared with conventional concrete infilled steel tubular (CFST) columns was mainly due to the weakened confinement effect and efficiency. This trend will become more apparent with the larger replacement ratio of recycled aggregates. A practical design formula of the ultimate bearing capacity of RACFCST stub columns subjected to axial load was proposed on the basis of the reasonably simplified cross-sectional stress nephogram at the ultimate state. The derivation process incorporated the equilibrium condition and the superposition theory. The proposed equation was evaluated by comparing its accuracy and accessibility to some well-known design formulae proposed by other researchers and some widely used design codes.

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