Corrosion of Steel in Portland Cement Concrete: Fundamental Studies

2008 ◽  
pp. 5-5-9 ◽  
Author(s):  
CE Locke
Keyword(s):  
Portland Cement ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Corrosion Of Steel

Chloride Ion Diffusion of Phosphoaluminate Cement Concrete

2009 ◽  
Vol 79-82 ◽  
pp. 99-102 ◽  
Author(s):  
Zhu Ding ◽  
Feng Xing ◽  
Ming Zhang ◽  
Peng Liu
Keyword(s):  
Portland Cement ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Hydration Products ◽  
Portland Cement Concrete ◽  
Ion Diffusion ◽  
Cement Concrete ◽  
Dense Microstructure ◽  
Corrosion Of Steel ◽  
Chloride Ion Diffusion

Penetration and diffusion of chloride ions in concrete can lead to the corrosion of steel bar and shorten the service life of concrete structures. Phosphoaluminate cement (PAC) is a new cementitious material which has many special properties compared to Portland cement (PC). In the study, chloride ion diffusion in PAC concrete was tested with RCM method. The phase composition and morphology of hydration products, pore volume of hardened paste cured for 28d were analyzed with X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that chloride ion diffusion coefficient of PAC concrete is much lower than that of Portland cement concrete under the same test conditions. The hydration products of PAC are main micro-crystalline phase and gel of phosphate and/or phophoaluminate, which formed a dense microstructure. There is no calcium hydroxide produced in the PAC hydration system. In hardened PAC paste, chloride ions might replace the atom group [OH] - and [PO4]3- of hydrates and become stable compounds. The resistance to chloride ion diffusion of PAC concrete will increase with the hydration age, because its microstructure becomes denser with the hydration age increasing.

Electrochemical Behavior of Steel in Concrete as a Result of Chloride Diffusion into Concrete: Part 2

CORROSION ◽  
1982 ◽  
Vol 38 (9) ◽  
pp. 494-499 ◽  
Author(s):  
Changiz Dehghanian ◽  
Carl E. Locke
Keyword(s):  
Portland Cement ◽  
Electrochemical Techniques ◽  
Chloride Diffusion ◽  
Hardened Concrete ◽  
Type I ◽  
Portland Cement Concrete ◽  
Salt Solutions ◽  
Cement Concrete ◽  
Type V ◽  
Corrosion Of Steel

Abstract Penetration of chloride salts into concrete from sources such as deicing-salts or sea water causes a severe corrosion problem to reinforcing steel. In this paper, the effect of salt penetration into concrete on the corrosion process was investigated by electrochemical techniques such as anodic and cathodic polarization. The potential measurements of steel in concrete were also made to compare the data with the results obtained from the polarization curves. Concretes made of Type I and Type V Portland cement were used. It was found that corrosion of steel in Type I Portland cement concrete is more rapid than in the Type V Portland cement concrete when the steel is exposed to salt solutions. This may be due to the differences in alkalinites which exist between the Types I and V Portland cement, whereas steel in the concrete with high pH can tolerate more Cl− than in concrete with lower pH. Corrosion of steel is more severe in the presence of chlorides added externally to hardened concrete than in the presence of chloride mixed with fresh concrete. Anodic and cathodic current densities for steel in concrete made of Types I and V Portland cement increase with the time that the concrete remains in the salt solutions.

Development of a Capacitor Probe to Detect Subsurface Deterioration in Concrete

1997 ◽  
Vol 503 ◽  
Author(s):  
B. K. Diefenderfer ◽  
I. L. Al-Qadi ◽  
J. J. Yoho ◽  
S. M. Riad ◽  
A. Loulizi
Keyword(s):  
Dielectric Constant ◽  
Portland Cement ◽  
Electromagnetic Waves ◽  
Low Cost ◽  
Complex Dielectric Constant ◽  
Life Cycle Costs ◽  
Parallel Plates ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Set Up

ABSTRACTPortland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. By developing techniques that would enable civil engineers to evaluate PCC structures and detect deterioration at early stages (without causing further damage), optimization of life-cycle costs of the constructed facility and minimization of disturbance to the facility users can be achieved.Nondestructive evaluation (NDE) methods are potentially one of the most useful techniques ever developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part, termed the “loss factor,” describes the conductivity of PCC and the attenuation of electromagnetic waves.Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1 to 40.1MIHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation. A new capacitor probe has been developed which consists of two plates, located within the same horizontal plane, for placement upon the specimen to be tested. Preliminary results show that this technique is feasible and results are promising; further testing and evaluation is currently underway.

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