Papers by Keyword: Recycled Concrete (RC)

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Authors: Su Ping Cui, Qi Dong Liu, Jian Hua Yan, Xin Du
Abstract: In this paper, the construction and demolition waste (C&D waste) recycling techniques in China is summarized, and proposed the C&D waste recycling suggestions in this foundation. The C&D waste can be divided into construction waste, decorating waste, demolition waste and natural disaster ruin waste. In addition to be buried, domestic C&D waste can be made into landscape material, roadbed material, recycled aggregate, recycled brick, recycled concrete, recycled admixture and so on. The state should establish positive promoting policies, improve the recycling industrial chain, and promote the healthy development of the C&D waste recycling.
Authors: Xiao Hua Zhang, Yun Fang Meng, Rui Li
Abstract: Under the premise of sustainable development, construction waste is taken as recycled aggregates used in U-shaped lining channel project. In this paper, illustrated by an actual case, we applied the method of orthogonal experiments to research the influence on the compressive strength of the Recycled Aggregate Concrete caused by different aggregate and various amount of additional materials used. Variance analysis and range analysis adopted to conclude the main influence factor and optimal combination, to provide theoretical support for further study.
Authors: Chong Shen, Xiao Qian Qian, Kuang Liang Qian
Abstract: The first 3d early shrinkage of recycled concrete from initial setting time with different replacement rates of recycled aggregate was investigated by self-made equipment. The differences between the unimproved recycled concrete and the improved one are observed, in the latter, new mixing method was utilized,that is, R-aggregates is coated with slag and nanoCaCO3, and relevant mechanism is analyzed. The results illustrate that early shrinkage of recycled concrete outweighs natural concrete, but there is not a definite link between the replacement rate of recycled aggregate and the early shrinkage. The treatment can effectively reduce the shrinkage of recycled concrete in 10h, but can not have a sustaining effort. Prewet treatment will generate water loss channels accelerating evaporation speed of water in concrete to accelerate shrinkage of concrete. The treatment can block water loss channel by coating, and slag and nanoCaCO3 can change pore structure and humidity in concrete to reduce the first10h early shrinkage.
Authors: Wan Lin Cao, Hong Ying Dong, Jian Wei Zhang
Abstract: A comparative study is conducted on the seismic behaviors of five 1/2 scale recycled concrete short columns with 1.75 shear span ratios. The stirrup ratio in the specimens was changed from 0.4%, 0.9%, to 1.29% while the ratio of their longitudinal reinforcement was the same. Crossed reinforcing bars were set in two of the specimens. Cyclic loading test was carried out for the specimens under axial compression ratio 0.4. The stiffness and its degradation, load-carrying capacity, ductility, hysteretic behavior, energy dissipation and failure phenomena of each short column were analyzed. Results show that, with the increase of the stirrup ratio in the specimens, the shear failure of the specimens is getting lighter and lighter. And the load-carrying capacity, ductility, energy dissipation capacity are improved greatly, but the rate of the increase is tending to slow. Moreover, crossed reinforcing bars in the short columns are able to improve the seismic behavior. Recycled concrete can be used for structural columns with low axial compression ratio in earthquake area.
Authors: Xing Wen Luo, Hai Lin Yao
Abstract: Concrete demolition waste has been proved to be an excellent source of aggregates for new concrete production. Four types of recycled concrete specimens were made for cyclic loading tests in laboratory, in order to research the acoustics parameters and deformation feature of recycled concrete under cyclic loading. Acoustics parameters such as ultrasonic wave time, ultrasonic velocity and ultrasonic amplitude of recycled concrete were tested synchronously while recycled concrete were loaded. Test results show the evolution of fatigue total strain of recycled concrete undergoes three stages. The cycle times in the three stages accounted for 10%, 80% and 10% of the fatigue life respectively. These stages can be simulated by power function equations, first-order linear equations and exponential functions accordingly. Tests results show that wave time increased with the rise of cyclic times, while wave amplitude decreased in the same time.
Authors: Ya Jun Zhao, Ying Gao, Li Li He
Abstract: The mixture proportion of recycled concrete was discussed by orthogonal design method. The influence of water-cement ratio, recycled aggregate quantity on workability, cube compressive strength of recycled concrete was analyzed. The experimental results indicated that,Recycled concrete mix proportion design should consider the impact of the water absorption of recycled aggregate. Unit water amount of recycled concrete should be plain concrete unit water consumption and recycled aggregate additional amount of water. Sand ratio should increase in the corresponding ordinary aggregate concrete sand ratio on the basis of 1 to 3 percent. When the water-cement ratio is 0.36 and construction waste content of 40% slag content of 20%, 28d compressive strength of concrete is 48.1MPa, slightly higher than the reference concrete (48.0MPa).
Authors: Xue Bing Zhang, Zhi Fang
Abstract: Because there exists a used cement mortar layer outside the recycled aggregate, there are more interfaces inside recycled concrete, which would result in recycled concrete has different properties from ordinary concrete. In this paper, the effect of such key factors for recycled concrete mix ratio as water-cement ratio, cement strength, sand rate, maximum granule diameter and gradation on the properties of concrete with recycled coarse aggregate was studied by experiment, and the some useful suggestion for mix ratio of recycled concrete was provided.
Authors: Ya Li Sun, Jin Song Zhu
Abstract: This paper studies the effects of different water-cement ratio on recycled concrete strength, anti-carbonation capability, and protecting reinforce steel bar capability. Select the water-cement ratio 0.6,0.55,0.5,0.45,0.4 five cases of the pilot study.It shows that: recycled concrete cube compressive strength, anti-carbonation capacity and protecting reinforce steel bar capability are less than ordinary concrete.
Authors: Li Sun, Ying Wei Yun
Abstract: Recently recycled coarse aggregate concrete tends to be developed by using waste concrete considering environmental issues and conserving natural resources. However, performances of recycled coarse aggregate concrete are relative low compared with ordinary concrete due to the differences between recycled coarse aggregates and natural ones. In this research, developed mill is used to shuck the cement paste adhering on the surface of coarse aggregates to obtain shucking recycled coarse aggregates. Experimental results demonstrate that the performances of shucking recycled aggregates and concerned concrete are both improved.
Authors: Yue Dong Sun, Xiang Xiao
Abstract: The test confects C20, C25, C30, C35 and C40 recycled aggregate concrete, and the percentage of recycled aggregate are 0%, 20%, 30%, 50%, 70% and 100%,the test age of sample are 7d,28d and 56d.Through test, the cube crushing strength,prismatical compressive strength and elasticity modulus of recycled aggregate concrete with different recycled aggregate percentage and different ages are studied, and compare with general concrete. Test show that, with the development of age, the strength development law of recycled aggregate concrete is similar to general concrete; with the increase of amount of recycled aggregate, the strength and elasticity modulus of recycled aggregate concrete shows the trend of decline, and the basic mechanic property of recycled concrete meet the demand of existing criterion.
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