Chloride diffusion coefficient of recycled aggregate concrete under compressive loading

2016 ◽  
Vol 49 (11) ◽  
pp. 4729-4736 ◽  
Author(s):  
Wang Wenjian ◽  
Wu Jin ◽  
Wang Zhe ◽  
Wu Guanzheng ◽  
Yue Anyi
Keyword(s):  
Diffusion Coefficient ◽  
Compressive Loading ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Aggregate Concrete

Diffusion of Multi-Ionic Species in Recycled Aggregate Concrete

2011 ◽  
Vol 477 ◽  
pp. 56-64 ◽  
Author(s):  
Nattapong Damrongwiriyanupap ◽  
Yu Chang Liang ◽  
Yun Ping Xi
Keyword(s):  
Diffusion Coefficient ◽  
Cement Paste ◽  
Recycled Aggregate Concrete ◽  
Phase Model ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Aggregate Concrete ◽  
Multi Scale ◽  
Multi Phase

In recent years, recycled aggregate concrete has been used in reinforced concrete structures. Concrete structures exposed to chloride environment often encountera premature deterioration due to corrosion of steel reinforcement. In order to avoid unplanned maintenances or repairs, it is necessary to develop a reliable prediction model for the chloride diffusion in concrete. The basic formulation of the transport theory will be presented first and then its application to Recycled Aggregate Concrete (RAC) will follow. Chloride diffusion in RAC is different from the diffusion in regular concrete, because the material parameters of RAC such as chloride diffusion coefficient are different from those of regular concrete. In this paper, a multi-scale and multi-phase model will be developed to characterize theinternal structure of the recycled aggregate with a layer of residual cement paste on the surface of natural aggregate and another layer of surface treatment material on the surface of the residual cement paste. The multi-scale and multi-phase model will also be used to characterize the chloride diffusion coefficient of RAC. The numerical analysis of the diffusion equations is performed by using finite element method.

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.

Chloride Diffusion Characteristics of the New Interface Transition Zone in Recycled Aggregate Concrete

2011 ◽  
Vol 261-263 ◽  
pp. 104-110
Author(s):  
Hai Long Wang ◽  
Jun Jie Wang ◽  
Xiao Yan Sun ◽  
Juan Cheng
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Transition Zone ◽  
Chloride Transport ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Aggregate Concrete ◽  
Phosphorous Slag

A three-part model (mortar, original concrete and ITZ) was established in this study to analyze the chloride coefficient of the new interfacial transition zone (ITZ) in recycled aggregate concrete (RAC). Based on this model, a formula for calculation was derived from the chloride transport characteristics in the steady state. Two types of RAC were used to study the properties of ITZ by steady-state migration test and Scanning Electron Microscope (SEM) method. The results indicate that the chloride diffusion coefficient of new ITZ in RAC is about 1 to 4 cm2/year, and that the addition of superfine phosphorous slag (PHS) not only reduces the chloride diffusion coefficient of mortar but also decreases the thickness and the chloride diffusion coefficient of new ITZ in RAC due to its pozzolanic reaction effect. The chloride permeability of mortar containing 20% PHS is only 1/5 of that in normal RAC. The chloride diffusion coefficient of ITZ in normal RAC is about 10 times greater than that of ordinary mortar. When modified with PHS and superplasticizer, the permeability of chloride in new ITZ is 3 to 7 times greater than that in the ordinary bulk cement paste. Furthermore, the mechanism and the effects of superfine phosphorous slag (PHS) on the resistivity of chloride permeation were discussed on basis of the experimental results and the images of SEM.

scholarly journals On the Structural Performance of Recycled Aggregate Concrete Columns with Glass Fiber-Reinforced Composite Bars and Hoops

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1508
Author(s):  
Ali Raza ◽  
Ahmad Rashedi ◽  
Umer Rafique ◽  
Nazia Hossain ◽  
Banjo Akinyemi ◽  
...  
Keyword(s):  
Glass Fiber ◽  
Compressive Loading ◽  
Reinforcement Ratio ◽  
Recycled Aggregate Concrete ◽  
Experimental Results ◽  
Recycled Aggregate ◽  
Fiber Reinforced ◽  
Aggregate Concrete ◽  
Gfrp Bars ◽  
Glass Fiber Reinforced

Structural members comprising geopolymer recycled aggregate concrete (RAC) reinforced with glass fiber-reinforced polymer (GFRP) bars have not been investigated appropriately for axial compressive loading cases. The present study addresses this knowledge gap by evaluating the structural efficiency of GFRP-reinforced geopolymer recycled aggregate concrete (GGRAC)-based members subjected to axial compressive loading. A total of nine compressive members (250 mm in cross-section and 1150 mm in height) were constructed to examine the effect of the number of longitudinal GFRP bars and the vertical spacing of transverse GFRP hoops/ties. The experimental results portrayed that the ductility of GGRAC compressive members improved with the reduction in the pitch of GFRP hoops. The axial load-carrying capacity (LCC) of GGRAC compressive members increased by increasing the number of GFRP bars up to eight (corresponding to a reinforcement ratio of 2.11%) while it decreased by using ten longitudinal GFRP bars (corresponding to a reinforcement ratio of 2.65%). Additionally, an empirical model was suggested to predict the axial LCC of GGRAC compressive members based on a large amount of experimental data of similar members. The experimental results and related theoretical predictions substantially prove the applicability and accuracy of the proposed model. The proposed column represents a feasible structural member in terms of material availability and environmental sustainability.

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.

Chloride Diffusion Property of Recycled Aggregate Concrete Treated with Water Repellent Agents-Silane

2010 ◽  
Vol 168-170 ◽  
pp. 755-761
Author(s):  
Ya Guang Zhu ◽  
Jian Guo Dai ◽  
Qiu Yi Li
Keyword(s):  
Treatment Method ◽  
Recycled Aggregate Concrete ◽  
Test Method ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Water Repellent ◽  
Diffusion Property ◽  
Aggregate Concrete ◽  
Astm C1202 ◽  
Better Than

Silane-base water repellent agents can significantly suppress the capillary water absorption of concrete and consequently improve the durability of the concrete and protects the internal steel reinforcement. This paper presents test result on chloride diffusion property of natural and recycled aggregate concrete externally and internally treated with silane-based water repellent agents based on the ASTM C1202 test method. The effects of concrete cracks on the chloride diffusion property were also investigated. After the tests, the impregnation depth of silane into the natural and recycled aggregate concrete, the total charges passing the testing samples and penetration depth of chloride during the testing period were determined. It was found that, for both cracked and uncracked concrete, externally treated natural and recycled aggregate concrete performed better than internally treated ones. The water repellent treatment method is more effective for recycled aggregate concrete than natural aggregate concrete because a deeper impregnation depth can be achieved in the former case.

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