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.

A Review on Fly Ash Based Geopolymer Rubberized Concrete

2016 ◽  
Vol 700 ◽  
pp. 183-196 ◽  
Author(s):  
Ahmad Azrem Azmi ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Che Mohd Ruzaidi Ghazali ◽  
Andrei Victor Sandu ◽  
Kamarudin Hussin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Unit Weight ◽  
Hardened Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Freezing And Thawing ◽  
Tire Rubber ◽  
Air Content ◽  
Waste Tire ◽  
Waste Tire Rubber

Utilization of waste materials such as waste tire rubber in the building industry can help prevent environmental pollution whilst contributing to the design of more economical buildings. Preliminary studies show that workable rubberized portland cement concrete mixtures can be made provided that appropriate percentages of tire rubber are used in such mixtures. This article provides the overview of some of published paper using tire waste rubber in portland cement concrete. The researchers mostly investigated the properties of fresh and hardened concrete. The workability, density, air content, unit weight, compressive strength, modulus of elasticity, freezing and thawing resistance, abrasion resistance and thermal properties of the waste tire rubber in concrete were discussed.

scholarly journals Quantification of Segregation in Portland Cement Concrete Based on Spatial Distribution of Aggregate Size Fractions

2020 ◽  
Vol 39 (3) ◽  
pp. 147-159
Author(s):  
Murat Ozen ◽  
Murat Guler
Keyword(s):  
Spatial Distribution ◽  
Portland Cement ◽  
Cross Section ◽  
Coarse Aggregate ◽  
Hardened Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Segregation Index ◽  
Size Fractions ◽  
Quality Control Tool

Segregation is one of the quality standards that must be monitored during the fabrication and placement of Portland cement concrete. Segregation refers to separation of coarse aggregate from the cement paste, resulting in inhomogeneous mixture. This study introduces a digital imaging based technique to quantify the segregation of Portland cement concrete from 2D digital images of cut sections. In the previous studies, segregation was evaluated based on the existence of coarse aggregate fraction at different geometrical regions of a sample cross section without considering its distribution characteristics. However, it is shown that almost all particle fractions can form clusters and increase the degree of segregation, thus deteriorating the structural performance of concrete. In the proposed methodology, a segregation index is developed by based on the spatial distribution of different size fractions of coarse aggregate within a sample cross section. It is shown that degradation in mixture’s homogeneity is controlled by the combined effect of particle distribution and their relative proportions in the mixture. Hence, a segregation index characterizing the mixture inhomogeneity is developed by considering not only spatial distribution of aggregate particles, but also their size fractions in the mixture. The proposed methodology can be successfully used as a quality control tool for monitoring the segregation level in hardened concrete samples.

The Effect of Simulated Large Pour Curing Conditions on the Temperature Rise and Strength Growth of PFA Containing Concrete

1986 ◽  
Vol 86 ◽  
Author(s):  
M. J. Coole ◽  
A. M. Harrisson
Keyword(s):  
Portland Cement ◽  
Temperature Rise ◽  
Elevated Temperatures ◽  
Pozzolanic Reaction ◽  
Hardened Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Acid Dissolution ◽  
Curing Conditions ◽  
The Difference

ABSTRACTWhen concrete is poured in large volumes, it is necessary to be able to predict the temperature rise which may occur inside the mass because of the effect this may have on the ultimate properties of the hardened concrete. It is known that the elevated temperatures generated may have a detrimental effect on final strengths and that if the difference in temperature between the centre and the surroundings exceeds 20–25°C, cracking may occur. In order to study these effects, a calorimetric controlled apparatus has been designed that is able to simulate the temperature rise profile occurring within any size of concrete pour. The apparatus is also used to control a curing bath thus enabling the compressive strength of match cured concrete to be determined. Results have been obtained for both temperature rise and strength growth at the centre of simulated 0.8, 1.5 and 3 m deep pours, using plain Portland and Portland PFA cement concrete. These show that in the larger sized pours the strength of concrete from a Portland PFA cement blend grows, after 2–3 days, at a greater rate than that of pure Portland cement, while giving lower temperature rises. Comparative strengths at 28 days are 48 Nmm−2 for the PFA cement concrete and 38 Nmm−2 for the pure Portland cement concrete. The influence of temperature on the reactivity of the PFA under these conditions has been studied using a dilute acid dissolution method. The hydrates formed and the progress of the pozzolanic reaction within the actual concretes has been monitored using scanning electron microscopy.

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.

A Study on the Chloride Diffusion into Portland Limestone Cement Concrete

2010 ◽  
Vol 636-637 ◽  
pp. 1355-1361 ◽  
Author(s):  
Sotiris Tsivilis ◽  
A. Asprogerakas
Keyword(s):  
Chloride Transport ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Hardened Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Portland Limestone Cement ◽  
Limestone Cement

In this paper the diffusion of chloride ions through limestone cement concrete is studied. The Portland limestone cements have many benefits and the new European Standard EN 197-1 identifies 4 types of Portland limestone cement containing 6-20% limestone (types II/A-L and II/A-LL) and 21-35% limestone (types II/B-L and II/B-LL), respectively. Portland limestone cements of different fineness and limestone content (0-35% w/w) have been produced by inter-grinding clinker, gypsum and limestone. Six concrete mixtures were prepared and the Nordtest Method (accelerated chloride penetration) was applied for the determination of penetration parameters for estimating the resistance against chloride penetration into hardened concrete. The diffusion equation of Fick’s second law was used for the determination of the effective chloride transport coefficient. It is concluded that Portland limestone cement concrete indicates competitive behavior with the Portland cement concrete. Limestone content up to 15% has a positive effect on the concrete resistance against chloride penetration.

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.

Sign in / Sign up

Export Citation Format

Share Document