scholarly journals Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6508
Author(s):  
Pejman Azarsa ◽  
Rishi Gupta ◽  
Peiman Azarsa ◽  
Alireza Biparva
Keyword(s):  
Concrete Structures ◽  
Superior Performance ◽  
Cell Potential ◽  
Freeze Thaw ◽  
Linear Polarization Resistance ◽  
Chemical Admixtures ◽  
Ideal Solutions ◽  
Promising Solution ◽  
Concrete Matrix ◽  
The Ideal

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate.

Passive corrosion control and active corrosion prevention of the reinforced concrete structures by electrochemical chloride removal and inhibitors

2013 ◽  
Vol 61 (1) ◽  
pp. 32-37 ◽  
Author(s):  
Guofu Qiao ◽  
Yi Hong ◽  
Tiejun Liu ◽  
Jinping Ou
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Concrete Cover ◽  
Reinforced Concrete Structures ◽  
Reinforcing Steel ◽  
Corrosion Control ◽  
Cell Potential ◽  
Content Type ◽  
Chloride Removal ◽  
Active Corrosion

Purpose – The aim of this paper was to investigate the passive corrosion control and active corrosion protective effect of the reinforced concrete structures by electrochemical chloride removal (ECR) method and inhibitors approach, respectively. Design/methodology/approach – The concentration of aggressive chloride ion distributed from the reinforcing steel to the surface of the concrete cover was analyzed during the ECR processes. Besides, the half-cell potential, the concrete resistance R c , the polarization resistance R p and the capacitance of double layer C dl of the steel/concrete system were used to characterize the electrochemical performance of the concrete prisms. Findings – The effectiveness of ECR could be enhanced by increasing the amplitude of potential or prolonging the time. Inhibitor SBT-ZX(I) could successfully prevent the corrosion development of the reinforcing steel in concrete. Originality/value – The research provides the scientific basis for the practical application of ECR and inhibitors in the field.

scholarly journals Atomic Modulation of 3D Conductive Frameworks Boost Performance of MnO2 for Coaxial Fiber-Shaped Supercapacitors

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Xiaona Wang ◽  
Zhenyu Zhou ◽  
Zhijian Sun ◽  
Jinho Hah ◽  
Yagang Yao ◽  
...  
Keyword(s):  
Energy Density ◽  
Specific Capacitance ◽  
High Performance ◽  
High Specific Capacitance ◽  
Superior Performance ◽  
High Mass ◽  
Mass Loading ◽  
Energy Storage Devices ◽  
Free Standing ◽  
Cell Potential

Abstract Coaxial fiber-shaped supercapacitors are a promising class of energy storage devices requiring high performance for flexible and miniature electronic devices. Yet, they are still struggling from inferior energy density, which comes from the limited choices in materials and structure used. Here, Zn-doped CuO nanowires were designed as 3D framework for aligned distributing high mass loading of MnO2 nanosheets. Zn could be introduced into the CuO crystal lattice to tune the covalency character and thus improve charge transport. The Zn–CuO@MnO2 as positive electrode obtained superior performance without sacrificing its areal and gravimetric capacitances with the increasing of mass loading of MnO2 due to 3D Zn–CuO framework enabling efficient electron transport. A novel category of free-standing asymmetric coaxial fiber-shaped supercapacitor based on Zn0.11CuO@MnO2 core electrode possesses superior specific capacitance and enhanced cell potential window. This asymmetric coaxial structure provides superior performance including higher capacity and better stability under deformation because of sufficient contact between the electrodes and electrolyte. Based on these advantages, the as-prepared asymmetric coaxial fiber-shaped supercapacitor exhibits a high specific capacitance of 296.6 mF cm−2 and energy density of 133.47 μWh cm−2. In addition, its capacitance retention reaches 76.57% after bending 10,000 times, which demonstrates as-prepared device’s excellent flexibility and long-term cycling stability.

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 Diagnosis of concrete structures distress due to alkali-aggregate reaction

2015 ◽  
Vol 63 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Z. Owsiak ◽  
J. Zapała-Sławeta ◽  
P. Czapik
Keyword(s):  
Concrete Structures ◽  
Chemical Exposure ◽  
Alkali Silica Reaction ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Alkali Aggregate Reaction ◽  
Freeze Thaw Cycle ◽  
Concrete Elements ◽  
Reaction Attack

Abstract Damage and defects observed in concrete elements, such as a network of microcracks, popouts and eflorrescence can be caused by a variety of deleterious processes. The causes can include mechanical (overloading), physical (freeze-thaw cycle) or chemical exposure (sulphate corrosion, alkali-aggregate reaction). This paper analyses distress due to alkali-silica reaction, detected in selected concrete structures. The analysed concrete elements exhibited cracking, exudations and surface popouts. Identification of the presence of hydrated sodium-potassiumcalcium silicate gel can be considered the primary symptom suggestive of an alkali-silica reaction attack. Other damage-causing mechanisms can occur simultaneously.

Influence of Silane Treatment on the Freeze-Thaw Resistance of Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 565-568 ◽  
Author(s):  
Xiao Jian Gao ◽  
Hong Wei Deng ◽  
Ying Zi Yang
Keyword(s):  
Surface Treatment ◽  
Water Adsorption ◽  
Concrete Structures ◽  
Air Entrainment ◽  
Concrete Surface ◽  
Silane Treatment ◽  
Cold Regions ◽  
Bonding Force ◽  
Freeze Thaw ◽  
Surface Impregnation

The influences of silane impregnation on water adsorption, bonding force between ice and concrete surface and resistance to freeze-thaw of concretes were studied. Two strength grades (C30 and C50) and the air entrainment were considered for concrete preparation. The results show that surface impregnation with silane reduces the final water adsorption of concrete by more than 90% when compared with the untreated specimen. The silane treatment significantly decreases the bonding force between ice and concrete surface. The resistance to freeze-thaw of both new and old concretes can be improved by the silane treatment. Therefore, the surface treatment with silane is suggested as an effective method to improve the durability of concrete structures in cold regions.

scholarly journals Experimental and Empirical Time to Corrosion of Reinforced Concrete Structures under Different Curing Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ahmed A. Abouhussien ◽  
Assem A. A. Hassan
Keyword(s):  
Reinforced Concrete ◽  
Corrosion Test ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Cell Potential ◽  
Accelerated Corrosion ◽  
Curing Conditions ◽  
Expected Time ◽  
Corrosion Initiation ◽  
Accelerated Corrosion Test

Reinforced concrete structures, especially those in marine environments, are commonly subjected to high concentrations of chlorides, which eventually leads to corrosion of the embedded reinforcing steel. The total time to corrosion of such structures may be divided into three stages: corrosion initiation, cracking, and damage periods. This paper evaluates, both empirically and experimentally, the expected time to corrosion of reinforced concrete structures. The tested reinforced concrete samples were subjected to ten alternative curing techniques, including hot, cold, and normal temperatures, prior to testing. The corrosion initiation, cracking, and damage periods in this investigation were experimentally monitored by an accelerated corrosion test performed on reinforced concrete samples. Alternatively, the corrosion initiation time for counterpart samples was empirically predicted using Fick’s second law of diffusion for comparison. The results showed that the corrosion initiation periods obtained experimentally were comparable to those obtained empirically. The corrosion initiation was found to occur at the first jump of the current measurement in the accelerated corrosion test which matched the half-cell potential reading of around −350 mV.

scholarly journals A new approach to the Tarry–Escott problem

2017 ◽  
Vol 13 (02) ◽  
pp. 393-417 ◽  
Author(s):  
Ajai Choudhry
Keyword(s):  
Positive Integer ◽  
New Method ◽  
New Approach ◽  
Parametric Solutions ◽  
Ideal Solutions ◽  
The Ideal

In this paper we describe a new method of obtaining ideal solutions of the well-known Tarry–Escott problem, that is, the problem of finding two distinct sets of integers [Formula: see text] and [Formula: see text] such that [Formula: see text], [Formula: see text], where [Formula: see text] is a given positive integer. When [Formula: see text], only a limited number of parametric/numerical ideal solutions of the Tarry–Escott problem are known. In this paper, by applying the new method mentioned above, we find several new parametric ideal solutions of the problem when [Formula: see text]. The ideal solutions obtained by this new approach are more general and, very frequently, simpler than the ideal solutions obtained by the earlier methods. We also obtain new parametric solutions of certain diophantine systems that are closely related to the Tarry–Escott problem. These solutions are also more general and simpler than the solutions of diophantine systems published earlier.

Utilization of the Capacity for Energy Absorption of Concrete Structures under Impact

2016 ◽  
Vol 711 ◽  
pp. 806-813 ◽  
Author(s):  
Carlos Zanuy ◽  
Gonzalo Ulzurrún ◽  
Iván M. Díaz
Keyword(s):  
Reinforced Concrete ◽  
Energy Absorption ◽  
Shear Failure ◽  
Concrete Structures ◽  
Fiber Reinforced Concrete ◽  
Different Types ◽  
Local Shear ◽  
Three Degree Of Freedom ◽  
Concrete Matrix ◽  
Higher Sensitivity

Concrete structures subjected to impact have shown a higher sensitivity to develop a brittle shear failure than under quasi-static loading. The differences between the dynamic and static behavior are due to the strain-rate dependence of material properties and the presence of inertial forces. Both effects should be accounted for when performing analyses of structures under impact. In the present paper, a simplified three-degree-of-freedom model is used to understand the improved impact response of reinforced concrete when steel fibers are added to the concrete matrix. The analysis shows that the higher capacity for energy absorption of fiber-reinforced concrete (FRC) may avoid local shear failure when the FRC is able to develop strain hardening prior to the peak strength. Various analyses are presented in order to understand the influence of different types and contents of fibers.

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