scholarly journals Effect of Manufactured Sand with Different Quality on Chloride Penetration Resistance of High–Strength Recycled Concrete

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7101
Author(s):  
Jincai Feng ◽  
Chaoqun Dong ◽  
Chunhong Chen ◽  
Xinjie Wang ◽  
Zhongqiu Qian
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
High Strength ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Manufactured Sand ◽  
Chloride Penetration Resistance ◽  
Powder Content

High–strength manufactured sand recycled aggregate concrete (MSRAC) prepared with manufactured sand (MS) and recycled coarse aggregate (RCA) is an effective way to reduce the consumption of natural aggregate resources and environmental impact of concrete industry. In this study, high–, medium– and low–quality MS, which were commercial MS local to Changzhou and 100% by volume of recycled coarse aggregate, were used to prepare MSRAC. The quality of MS was determined based on stone powder content, methylene blue value (MBV), crushing value and soundness as quality characteristic parameters. The variation laws of compressive strength and chloride penetration resistance of high–strength MSRAC with different rates of replacement and different qualities of MS were explored. The results showed that for medium– and low–quality MS, the compressive strength of the MSRAC increased first and then decreased with increasing rate of replacement. Conversely, for high–quality MS, the compressive strength gradually increased with increasing rate of replacement. The chloride diffusion coefficient of MSRAC increased with decreasing MS quality and increasing rate of replacement. The chloride diffusion coefficient of MSRAC basically met the specifications for 50–year and 100–year design working life when the chloride environmental action was D and E. To prepare high–strength MSRAC, high–quality MS can 100% replace RS (river sand), while rates of replacement of 50–75% for medium–quality MS or 25–50% for low–quality MS are proposed. Scanning Electron Microscope (SEM) images indicated that an appropriate amount of stone powder is able to improve the compressive strength of RAC, but excessive stone powder content and MBV are unfavorable to the compressive strength and chloride penetration resistance of RAC.

The Time-Dependence of Chloride Penetration Resistance of Concrete by the Rapid Chloride Permeability Test

2013 ◽  
Vol 357-360 ◽  
pp. 651-654 ◽  
Author(s):  
Yan Jun Hu ◽  
Yan Liang Du
Keyword(s):  
Penetration Resistance ◽  
Chloride Penetration ◽  
Mineral Admixtures ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Curing Time ◽  
Permeability Test ◽  
Chloride Permeability ◽  
Chloride Penetration Resistance ◽  
Rapid Chloride Permeability

In this paper, the Rapid Chloride Permeability Test (RCPT)-ASTM C1202-91 and Conductance test were employed to measure the effect of curing time on the chloride penetration resistance of concrete. The results indicate that the concrete specimens with longer curing time have higher chloride penetration resistance no matter the concrete with or without mineral admixtures, the concrete conductance has the similar variation trend and similar mathematical descriptions as the chloride diffusion coefficient D with the passage of curing time, and it is a very useful method to measure concrete conductance to estimate the chloride permeability variation at different curing or exposure time.

Influence of Stone Dust in Manufactured Sand on Resisting Chloride Penetration in Marine Concretes

2012 ◽  
Vol 174-177 ◽  
pp. 1419-1423
Author(s):  
Jian Bo Xiong ◽  
Peng Ping Li ◽  
Sheng Nian Wang
Keyword(s):  
Diffusion Coefficient ◽  
Pore Structure ◽  
Binding Capacity ◽  
Chloride Penetration ◽  
Dust Content ◽  
Chloride Diffusion ◽  
Fine Aggregate ◽  
Chloride Diffusion Coefficient ◽  
Manufactured Sand ◽  
Stone Dust

In China, manufactured sand has been widely used as fine aggregate in concrete. Therefore, it is necessary to investigate the effect of manufactured sand on durability of concrete. This research studies the influence of stone dust content in manufactured sand on resisting chloride penetration in marine concrete by strength and other physical mechanical tests, XRD, TGA and pore structure analysis. Test results have shown that the chloride diffusion coefficient increased with increasing the stone dust content in manufactured sand when the stone dust content increasing from 3% to 13%. The stone dust in fine aggregate was participated in hydration procedure of cementitious, which will promote the hydration degree of cementitious and increase the chloride binding capacity of hydration product. The influence of stone dust in fine aggregate on chloride diffusion coefficient were the combined effects of concrete pore structure and cementitious hydration products, and the porosity and pore size distribution were the main factors that influence the changes of diffusion coefficient.

scholarly journals Effect of Nano Silica Particles on Impact Resistance and Durability of Concrete Containing Coal Fly Ash

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1296
Author(s):  
Peng Zhang ◽  
Dehao Sha ◽  
Qingfu Li ◽  
Shikun Zhao ◽  
Yifeng Ling
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Coal Fly Ash ◽  
Impact Resistance ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Chloride Diffusion Coefficient ◽  
Nano Silica ◽  
Chloride Penetration Resistance ◽  
The Impact

In this study, the effect of adding nano-silica (NS) particles on the properties of concrete containing coal fly ash were explored, including the mechanical properties, impact resistance, chloride penetration resistance, and freezing–thawing resistance. The NS particles were added into the concrete at 1%, 2%, 3%, 4%, and 5% of the binder weight. The behavior under an impact load was measured using a drop weight impact method, and the number of blows and impact energy difference was used to assess the impact resistance of the specimens. The durability of the concrete includes its chloride penetration and freezing–thawing resistance; these were calculated based on the chloride diffusion coefficient and relative dynamic elastic modulus (RDEM) of the samples after the freezing–thawing cycles, respectively. The experimental results showed that the addition of NS can considerably improve the mechanical properties of concrete, along with its freezing–thawing resistance and chloride penetration resistance. When NS particles were added at different replacement levels, the compressive, flexural, and splitting tensile strengths of the specimens were increased by 15.5%, 27.3%, and 19%, respectively, as compared with a control concrete. The addition of NS enhanced the impact resistance of the concrete, although the brittleness characteristics of the concrete did not change. When the content of the NS particles was 2%, the number of first crack impacts reached a maximum of 37, 23.3% higher compared with the control concrete. Simultaneously, the chloride penetration resistance and freezing–thawing resistance of the samples increased dramatically. The optimal level of cement replacement by NS in concrete for achieving the best impact resistance and durability was 2–3 wt%. It was found that when the percentage of the NS in the cement paste was excessively high, the improvement from adding NS to the properties of the concrete were reduced, and could even lead to negative impacts on the impact resistance and durability of the concrete.

scholarly journals Effect of graphene oxide on chloride penetration resistance of recycled concrete

2019 ◽  
Vol 8 (1) ◽  
pp. 681-689 ◽  
Author(s):  
Kai Guo ◽  
Hang Miao ◽  
Lin Liu ◽  
Jinghai Zhou ◽  
Ming Liu
Keyword(s):  
Graphene Oxide ◽  
High Strength ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Recycled Concrete ◽  
Volume Stability ◽  
Micro Cracks ◽  
Structure Morphology ◽  
Chloride Penetration Resistance ◽  
Electric Flux

Abstract Graphene oxide (GO) is a nanomaterial with ultra-high strength, good hydrophilicity, and dispersibility. To study the effect of GO on chloride penetration resistance of recycled concrete, the mechanism of action is investigated. The electric flux method is used to test the chloride penetration in recycled concrete specimens with 0, 0.03%, 0.06%, and 0.09% of GO. The volume change, microscopic pore distribution, and micro-structure morphology are characterized using laser rangefinder, and techniques such as X-ray tomography and scanning electron microscopy. The results show that the "coagulation nodule" effect of GO provides a growth basis for cement hydration,which results in a more uniform distribution of the hydrate microcrystals. It fills the micro-cracks of the recycled concrete, reduces the most probable aperture, increases the number of harmless small apertures, and enhances the volume stability of recycled concrete, thereby improving the chloride penetration resistance, which is important for improving the durability of concrete.

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