scholarly journals Chloride Transport in OPC Concrete Subjected to the Freeze and Thaw Damage

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ki Yong Ann ◽  
Min Jae Kim ◽  
Jun Pil Hwang ◽  
Chang-geun Cho ◽  
Ki Hwan Kim
Keyword(s):  
Pore Structure ◽  
Cement Content ◽  
Chloride Transport ◽  
Microstructural Analysis ◽  
Free Water ◽  
Frost Damage ◽  
Freezing And Thawing ◽  
Freeze And Thaw ◽  
Chloride Migration ◽  
Chloride Attack

To predict the durability of a concrete structure under the coupling degradation consisting of the frosting and chloride attack, microstructural analysis of the concrete pore structure should be accompanied. In this study, the correlation between the pore structure and chloride migration for OPC concrete was evaluated at the different cement content in the concrete mix accounting for 300, 350, and 400 kg/m3 at 0.45 of a free water cement ratio. The influence of frosting damage on the rate of chloride transport was assessed by testing with concrete specimens subjected to a rapid freezing and thawing cyclic environment. As a result, it was found that chloride transport was accelerated by frost damage, which was more influential at the lower cement content. The microscopic examination of the pore structure showed that the freezing environment increased the volume of the large capillary pore in the concrete matrix.

scholarly journals The Rapid Chloride Migration Test in Assessing the Chloride Penetration Resistance of Normal and Lightweight Concrete

2021 ◽  
Vol 11 (16) ◽  
pp. 7251
Author(s):  
Jorge Pontes ◽  
José Alexandre Bogas ◽  
Sofia Real ◽  
André Silva
Keyword(s):  
Lightweight Concrete ◽  
Chloride Transport ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Migration Test ◽  
Simple Method ◽  
Chloride Migration ◽  
Binder Ratio ◽  
Chloride Penetration Resistance ◽  
Water Binder Ratio

Chloride-induced corrosion has been one of the main causes of reinforced concrete deterioration. One of the most used methods in assessing the chloride penetration resistance of concrete is the rapid chloride migration test (RCMT). This is an expeditious and simple method but may not be representative of the chloride transport behaviour of concrete in real environment. Other methods, like immersion (IT) and wetting–drying tests (WDT), allow for a more accurate approach to reality, but are laborious and very time-consuming. This paper aims to analyse the capacity of RCMT in assessing the chloride penetration resistance of common concrete produced with different types of aggregate (normal and lightweight) and paste composition (variable type of binder and water/binder ratio). To this end, the RCMT results were compared with those obtained from the same concretes under long-term IT and WDT. A reasonable correlation between the RCMT and diffusion tests was found, when slow-reactive supplementary materials or porous lightweight aggregates surrounded by weak pastes were not considered. A poorer correlation was found when concrete was exposed under wetting–drying conditions. Nevertheless, the RCMT was able to sort concretes in different classes of chloride penetration resistance under distinct exposure conditions, regardless of the type of aggregate and water/binder ratio.

The Effect of Cracks on Chloride Penetration into Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 769-772 ◽  
Author(s):  
In Seok Yoon ◽  
Erik Schlangen ◽  
Mario R. de Rooij ◽  
Klaas van Breugel
Keyword(s):  
Service Life ◽  
Crack Length ◽  
Significant Influence ◽  
Crack Width ◽  
Chloride Transport ◽  
Crack Depth ◽  
Chloride Penetration ◽  
Critical Crack ◽  
Chloride Migration ◽  
Migration Testing

This study is focused on examining the effect of critical crack width in combination with crack depth on chloride penetration into concrete. Because concrete structures have to meet a minimum service-life, critical crack width has become an important parameter. Specimens with different crack width / crack length have been subjected to rapid chloride migration testing (RCM). The results of this study show a critical crack width of about 0.012 mm. Cracks smaller than this critical crack width are considered not to have a significant influence on the rate of chloride transport inwards, while chloride penetration does proceed faster above this critical crack width.

scholarly journals Investigating the Effect of Solid Components on Yield Stress for Cemented Paste Backfill via Uniform Design

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Yong Wang ◽  
Aixiang Wu ◽  
Lianfu Zhang ◽  
Fei Jin ◽  
Xiaohui Liu
Keyword(s):  
Yield Stress ◽  
Mass Fraction ◽  
Cement Content ◽  
Uniform Design ◽  
Free Water ◽  
Experimental Program ◽  
Cemented Paste Backfill ◽  
Free Water Content ◽  
Key Factor ◽  
Paste Backfill

Cemented paste backfill (CPB) technology has been applied quite popular around the world. Yield stress is a key factor determining whether CPB could be transported. In order to reveal the effect of solid components on yield stress of CPB, a uniform design experimental program (four factors and six levels) was conducted to test the rheological property of a mine’s CPB. The tested four factors including mass fraction, cement versus other solids ratio, coarse tailings, and gravel contents were considered during the experiment design. Likewise, six experimental levels were given to each factor. Results of the test show that yield stress increased with the mass fraction and cement content. However, the trend reversed for the content of coarse tailings and gravel. Contribution of the four factors to yield stress in descending order is mass fraction > content of gravel > content of coarse tailings > cement versus other tailings ration. Effect of solid components on the yield stress of CPB is mainly due to the different flocculation structure inside the CPB. These various flow structures result in the different free-water content of CPB, leading to a different yield stress value.

scholarly journals Rheological Behavior and Microstructure Characteristics of SCC Incorporating Metakaolin and Silica Fume

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2576 ◽  
Author(s):  
Gang Ling ◽  
Zhonghe Shui ◽  
Tao Sun ◽  
Xu Gao ◽  
Yunyao Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Free Water ◽  
Hydration Product ◽  
Replacement Ratio ◽  
Microstructure Characteristics ◽  
Beneficial Effects ◽  
Slump Flow ◽  
Strength And Durability

This study explores the effects of metakaolin (MK) and silica fume (SF) on rheological behaviors and microstructure of self-compacting concrete (SCC). The rheology, slump flow, V-funnel, segregation degree (SA), and compressive strength of SCC are investigated. Microstructure characteristics, including hydration product and pore structure, are also studied. The results show that adding MK and SF instead of 4%, 6% and 8% fly ash (FA) reduces flowability of SCC; this is due to the fact that the specific surface area of MK and SF is larger than FA, and the total water demand increases as a result. However, the flowability increases when replacement ratio is 2%, as the small MK and SF particles will fill in the interstitial space of mixture and more free water is released. The fluidity, slump flow, and SA decrease linearly with the increase of yield stress. The total amount of SF and MK should be no more than 6% to meet the requirement of self-compacting. Adding MK or SF to SCC results in more hydration products, less Ca(OH)2 and refinement of pore structure, leading to obvious strength and durability improvements. When the total dosage of MK and SF admixture is 6%, these beneficial effects on workability, mechanical performance, and microstructure are more significant when SF and MK are applied together.

scholarly journals Relating Rapid Chloride Migration Coefficient of Blast Furnace Slag Concrete to Capillary Pore Structure Parameters

2019 ◽  
Vol 278 ◽  
pp. 01007
Author(s):  
Chao Yang ◽  
Shuguang Wang ◽  
Feng Xu ◽  
Weiwei Li ◽  
Dongsheng Du
Keyword(s):  
Blast Furnace ◽  
Pore Structure ◽  
Blast Furnace Slag ◽  
Pore Radius ◽  
Structure Parameters ◽  
Capillary Porosity ◽  
Chloride Resistance ◽  
Chloride Migration ◽  
Furnace Slag ◽  
Capillary Pore

Blast furnace slag blended concrete is widely used in infrastructure, and its chloride resistance is of great concern. This paper experimentally investigated the capillary pore structure and chloride resistance of blast furnace slag blended concrete. Blast furnace slag was proved to be able to optimize the critical pore radius and decrease the proportion of detrimental capillary pores (with radius between 50 nm and 10,000 nm). Meanwhile, the benefit of BFS in improving the chloride resistance was proved. Finally, regression analysis showed that the rapid migration coefficient is proportional to the critical pore radius and the detrimental capillary pore proportion. Nevertheless, the rapid migration coefficient is not closely related to the capillary porosity.

scholarly journals Effects of Cyclic Freeze–Thaw on the Steel Bar Reinforced New-To-Old Concrete Interface

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1251
Author(s):  
Tao Luo ◽  
Chi Zhang ◽  
Xiangtian Xu ◽  
Yanjun Shen ◽  
Hailiang Jia ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Concrete Structures ◽  
Freezing Temperature ◽  
Frost Damage ◽  
Freezing And Thawing ◽  
Shear Properties ◽  
Freeze Thaw ◽  
Steel Bar ◽  
Concrete Interface

Frost damage of concrete has significant effects on the safety and durability of concrete structures in cold regions, and the concrete structures after repair and reinforcement are still threatened by cyclic freezing and thawing. In this study, the new-to-old concrete interface was reinforced by steel bar. The shear strength of the new-to-old concrete interface was tested after the new-to-old combination was subjected to cyclic freeze–thaw. The effects of the diameter of the steel bar, the compressive strength of new concrete, the number of freeze–thaw cycles and the freezing temperatures on the shear properties of new-to-old concrete interface were studied. The results showed that, in a certain range, the shear strength of the interface was proportional to the diameter of the steel bar and the strength of the new concrete. Meanwhile, the shear strength of the reinforced interface decreased with the decreasing of the freezing temperature and the increasing of the number of freeze–thaw cycles.

scholarly journals Effect of the Electric Field on the Distribution Law of Chloride Ions and Microstructure in Concrete with the Addition of Mineral Admixtures

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1380 ◽  
Author(s):  
Xiaoli Xie ◽  
Qingge Feng ◽  
Zheng Chen ◽  
Wei Lu
Keyword(s):  
Electric Field ◽  
Pore Structure ◽  
Chloride Ions ◽  
Mineral Admixtures ◽  
Chloride Diffusion ◽  
Electric Field Effect ◽  
Nacl Solution ◽  
Distribution Law ◽  
Chloride Migration ◽  
Chloride Profile

Migration testing of chloride under an electric field is a fast and effective method to determine the corrosion resistance of reinforced concrete against chloride. In this study, a series of admixture-involved (fly ash and slag) concrete specimens were produced for an accelerating chloride diffusion test in 3% NaCl solution under an electric field and natural chloride diffusion in 165 g/L NaCl solution under immersion conditions. Then, the chloride profile and pore structure of concretes aged 56 and 91 days were compared to investigate the effect of the electric field on chloride diffusion as well as the microstructure of the concrete. The results showed that, under accelerating electric field conditions, the degree to which chloride refined the internal pore structure of the concrete was weaker than that under natural immersion conditions. The applied electric field changed the pore structure inside the concrete, but it had little effect on the distribution of total, free, and bound chlorides and their mutual relationship. In addition, it is necessary to consider that the electric field effect on chloride migration varies with the concrete mix proportions.

Sign in / Sign up

Export Citation Format

Share Document