Pore structure and chloride diffusivity of recycled aggregate concrete with nano-SiO2 and nano-TiO2

2017 ◽  
Vol 150 ◽  
pp. 49-55 ◽  
Author(s):  
Jingwei Ying ◽  
Bin Zhou ◽  
Jianzhuang Xiao
Keyword(s):  
Pore Structure ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Nano Tio2 ◽  
Aggregate Concrete ◽  
Nano Sio2 ◽  
Chloride Diffusivity

The Multiscale Spectral Stochastic Finite Element Method for Chloride Diffusion in Recycled Aggregate Concrete

2017 ◽  
Vol 15 (01) ◽  
pp. 1750078 ◽  
Author(s):  
Yuching Wu ◽  
Jianzhuang Xiao
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Digital Image ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Stochastic Finite Element Method ◽  
Stochastic Finite Element ◽  
Aggregate Concrete ◽  
Chloride Diffusivity

In this study, the multiscale stochastic finite element method (MsSFEM) was developed based on a novel digital image kernel to make analysis for chloride diffusion in recycled aggregate concrete (RAC). It is significant to study the chloride diffusivity in RAC, because when RAC was applied in coastal areas, chloride-induced rebar corrosion became a common problem for concrete infrastructures. The MsSFEM was an efficient tool to examine the effect of microscopic randomness of RAC on the chloride diffusivity. Based on the proposed digital image kernel, the Karhunen–Loeve expansion and the polynomial chaos were used in the stochastic homogenization process. To investigate advantages and disadvantages of both generation and application of the proposed digital image kernel, it was compared with many other kernels. The comparisons were made between the method to develop the digital image kernel, which is called the pixel-matrix method, and other methods, and between the application of the kernel and various other kernels. It was shown that the proposed digital image kernel is superior to other kernels in many aspects.

Experimental Study on the Chloride Diffusivity of Recycled Aggregate Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 1404-1408
Author(s):  
He Ying Qin ◽  
Yan Lin Zhao ◽  
Bo Guang Luo ◽  
Yi Hu Chen
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Silica Fume ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Partial Replacement ◽  
Chloride Diffusion Coefficient ◽  
Aggregate Concrete ◽  
Chloride Diffusivity

The study presented herein has been carried out in order to investigate the chloride diffusivity of recycled aggregate concrete (RAC). Meanwhile, the effect of the binder type, involving cement replacement materials such as, fly ash, slag and silica fume on the chloride diffusivity has also been investigated. For this purpose, RAC and concrete containing the different type of binders with w/b ratios of 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 were used. As a result, the chloride diffusion coefficient of RAC is higher than that of natural concrete and the partial replacement of cement with fly ash, slag and silica fume is effective in decrease in the chloride diffusion coefficient, measured by a rapid chloride conductivity test.

scholarly journals The Permeability of Waste Fiber Recycled Concrete

2019 ◽  
Vol 26 (2) ◽  
pp. 210-217 ◽  
Author(s):  
Jinghai ZHOU ◽  
Tianbei KANG ◽  
Fengchi WANG
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Gas Permeability ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Cement Ratio

Permeability is one of the major performances for recycled aggregate concrete, which affects the durability and service life of concrete structures. In most cases, the main factor affecting the permeability of recycled aggregate concrete is the pore structure. Considering water-cement ratio, replacement rate of recycled aggregates, waste fiber length, and volume fraction of waste fibers as the design variables, pore structure and gas permeability were studied experimentally. In addition, fractal theory was here used to assess the pore structure of waste fiber recycled concrete and study the effects of pore structure on permeability. The results showed that the pore size distribution had a small impact on the permeability with the water-cement ratio and replacement rate of recycled aggregates increasing. The fractal dimension can be used to describe the complexity of the pore structure quantitatively. There is an obvious linear relationship between fractal dimension and gas permeability. The larger the pore volume fractal dimension, the better the impermeability of waste fiber recycled concrete.

scholarly journals Influence of Nano-SiO2 on the Mechanical Properties of Recycled Aggregate Concrete with and without Polyvinyl Alcohol (PVA) Fiber

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1446
Author(s):  
Shenglin Wang ◽  
Baolong Zhu
Keyword(s):  
Mechanical Properties ◽  
Polyvinyl Alcohol ◽  
Triaxial Compression ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Compression Tests ◽  
Aggregate Concrete ◽  
Nano Sio2 ◽  
Pva Fiber ◽  
Strength Improvement

In recent years, recycled aggregate concrete (RAC) has become a research hotspot in the field of urban construction because of its resource utilization of construction waste. However, compared with original concrete, its strength is still low, which requires additional nano-SiO2 (NS) and fiber. In order to study the mechanism of strength improvement of RAC, this paper takes NS and polyvinyl alcohol (PVA) fiber as variable parameters; uniaxial and triaxial compression tests were carried out on RAC with PVA fiber and NS, and the mechanical properties of RAC were investigated The result shows that within the range of 3% NS content, an increase in the NS substitution rate causes the mechanical properties of RAC to improve significantly. The compressive strength of RAC increases again after adding PVA fiber; through a SEM (scanning electron microscopy) analysis of the specimen, it was found that the NS filled the micro-pores and micro-cracks in the RAC, and the PVA fiber changed the contact range between recycled aggregate and mortar, so the microstructure of the material was more compact. The mechanism of RAC strength improvement is explained in the microcosmic view.

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