scholarly journals Chloride Diffusivity in Blended Cement Made from Selected Industrial and Agrowastes

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Jackson Muthengia Wachira ◽  
Joseph Mwiti Marangu
Keyword(s):  
Profile Analysis ◽  
Bleaching Earth ◽  
Blended Cement ◽  
Calcium Carbide ◽  
Chloride Ions ◽  
Chloride Ingress ◽  
Chloride Diffusivity ◽  
Lower Chloride ◽  
Set Up ◽  
Chloride Environment

This paper reports study findings on the diffusivity of chloride ions in potential blended cement. The cement, abbreviated as PCDC, was made from blending ordinary Portland cement (OPC) with dried calcium carbide residue and an incinerated mix of rice husks, spent bleaching earth, and broken bricks. The aim of the study was to investigate the ability of PCDC to withstand aggressive chloride environment. 10 cm × 10 cm mortar cubes were prepared using PCDC and cured for 28 days in saturated calcium hydroxide solution. The cured mortar cubes were subjected to aggressive chloride media in a laboratory set up. The test cement was subjected to chloride profile analysis with depth of cover as a function of w/c ratio and curing period in alternate dry and wet environments of 3.5 percent sodium chloride solution. The experiments were carried alongside neat OPC and OPC + 25% pulverised fuel ash (OPC + 25% PFA). Results showed that PCDC exhibited lower chloride ingress as the depth of cover increased. In conclusion, the study showed that PCDC was a potential cementitious material with high ability to withstand aggressive environment of chlorides.

scholarly journals AERVA LANATA LEAF EXTRACT AS A CORROSION INHIBITOR FOR CARBON STEEL IN CHLORIDE ENVIRONMENT

2018 ◽  
Vol 6 (11) ◽  
pp. 153-162
Author(s):  
Rajesh V. ◽  
E. U. B. Reddi ◽  
T. Byragi Reddy ◽  
Ch. Durga Prasad ◽  
B. Prasanna Kumar
Keyword(s):  
Carbon Steel ◽  
Corrosion Inhibitor ◽  
Leaf Extract ◽  
Inhibition Efficiency ◽  
Aggressive Medium ◽  
Chloride Ions ◽  
Aqueous Environment ◽  
Aerva Lanata ◽  
Ph Range ◽  
Chloride Environment

The present study was initiated with an objective of investigating a plant extract as an effective corrosion inhibitor useful for protection of carbon steel in aqueous environment containing chloride ions. For this purpose, the leaf extract of the plant ‘Aerva lanata’ belonging to Amaranthaceae family of genus Aerva was chosen. The required optimum concentration of the extract for an effective inhibition was found to be 5 %, resulting in the inhibition efficiency of 95 % against corrosion of carbon steel in 200 ppm of NaCl solution. The extract introduced as a corrosion inhibitor was found to be effective in the pH range from 4.0 to 9.0. The extract could retain its inhibition efficiency for about an immersion period of 60 days and also up to a temperature of 333 K. The 5 % extract was found to control corrosion of carbon steel in highly aggressive medium containing 300 ppm of NaCl also. In order to maintain the protective nature, the required concentration of the extract was 2 %. From these studies, it was inferred that the Aerva lanata leaf extract exhibits good inhibitive properties for carbon steel in aqueous environment in wide ranges of pH, temperature and aggressiveness of medium.

scholarly journals Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Joseph Mwiti Marangu ◽  
Joseph Karanja Thiong’o ◽  
Jackson Muthengia Wachira
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Strength Development ◽  
Chloride Ingress ◽  
Calcined Clay ◽  
Apparent Diffusion Coefficients ◽  
Apparent Diffusion ◽  
Lower Porosity ◽  
Lower Chloride

Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800°C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na2SO4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients (Dapp) were estimated from solutions to Fick’s second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of Dapp, compared to OPC, PPC, and nonactivated PCC35.

Corrosion Resistance Performance of Ethylamines in Fly Ash Blended Cement Concrete

2014 ◽  
Vol 507 ◽  
pp. 286-290
Author(s):  
V. Rajkumar
Keyword(s):  
Corrosion Resistance ◽  
Fly Ash ◽  
Blended Cement ◽  
Impedance Measurement ◽  
Chloride Ions ◽  
Experimental Investigations ◽  
Optimal Dosage ◽  
Cement Concrete ◽  
Chloride Permeability ◽  
Resistance Performance

The main aim of this investigation is to study the influence of monoethylamine, diethylamine and triethylamine inhibitors on the corrosion resistance performance of 25% fly ash blended cement concrete. These inhibitors were added in dosages of 1%, 2%, 3% and 4% by weight of cement and experimental investigations have been carried out to compare the effectiveness of these three inhibitors with regard to strength and corrosion resistance. The mechanical strength properties studied were compressive, split tensile, flexural and bond strengths. The resistance to corrosion was evaluated based on the performance of the concrete for the penetration of chloride ions by means of impressed voltage technique, Rapid chloride permeability test (RCPT), AC impedance measurement, and weight loss measurement and ultimately the most effective of the three inhibitors and its optimal dosage has been determined.

Application of electrical fields to reduce chloride ingress into concrete structures

2021 ◽  
pp. 1-27
Author(s):  
Carla Driessen-Ohlenforst ◽  
Michael Raupach
Keyword(s):  
Chloride Ions ◽  
Chloride Ingress ◽  
Textile Reinforced Concrete ◽  
Electrical Field ◽  
Joint Research ◽  
Electrical Fields ◽  
Joint Research Project ◽  
Anodic Polarisation ◽  
Current Densities ◽  
Field Strengths

In the context of a joint research project, a system for monitoring, protection and strengthening of bridges by using a textile reinforced concrete interlayer has been developed which consists of two carbon layers with a spacing of 15 mm and a special mortar. This setup led to the idea to build up an electrical field between the carbon meshes, which suppresses the ingress of chlorides into the concrete. This paper focuses on the question which voltages and electrical field strengths are necessary to prevent critical chloride contents at the reinforcing steel. For this purpose, extensive laboratory tests have been performed, followed by a numerical simulation study. By applying an electrical field, the negatively charged chloride ions are forced to move to the upper carbon mesh that is polarized as an anode. It has been investigated whether the voltages to implement an electrochemical chloride barrier are smaller than they have to be for the common preventive cathodic protection. One advantage of this chloride barrier is that because of the lower current densities the anodic polarisation of the carbon meshes can be reduced. Therefore, different voltages, electrical field strengths, anode materials and anode arrangements were investigated.

Flexural performance of TRC-strengthened RC beam under chloride environment

2018 ◽  
Vol 65 (5) ◽  
pp. 444-450 ◽  
Author(s):  
Yin Shi-ping ◽  
Yu Yulin ◽  
Yunping Xi
Keyword(s):  
Bearing Capacity ◽  
Stress Level ◽  
Salt Solution ◽  
Chloride Ions ◽  
Bending Stress ◽  
Textile Reinforced Concrete ◽  
Content Type ◽  
Flexural Performance ◽  
Steel Bars ◽  
Chloride Environment

Purpose Textile reinforced concrete (TRC) has excellent bearing capacity and anti-crack and corrosion resistance capacity, which are suitable for strengthening concrete structure under harsh environments. Design/methodology/approach In this thesis, flexural properties of RC beams strengthened with TRC under chloride wet–dry cycles were studied and the effects of the concentration of the salt solution, number of wet–dry cycles, bending stress level and TRC form were considered. Four-point bend loading mode was adopted for the step-loading procedure. Findings As the number of wet–dry cycles was relatively few, the trend of the yield and ultimate load with the increasing concentration of salt solution and wet–dry cycles were not obvious. However, the beams under high sustained bending stress level (0.5) had a decrease in the bearing capacity and an increase in mid-span deflection because of the larger degree of the corrosion of steel bars and the weaker bond capacity between the steel bar and concrete. Besides, there was little difference between the precast TRC plate and the casting TRC on beams in terms of the capacity of anti-crack, bearing and deflection. Research limitations/implications In this paper, preliminary work has been carried out, but some of the factors were not comprehensive considered, which are inevitable. As the time of dry–wet cycles was short and TRC layer had good anti-crack and anti-permeability performance, smaller chloride ions’ penetration resulted in the corrosion ratio of steel bars to be lower. Practical implications It should be noted that under high corrosion rates of the reinforcement, the whole TRC strengthening layer might be spalled off if only the strengthening form at the beam bottom is used, and thus the U-type strengthening form could be considered, which means that the beam is strengthened at both the bottom and side surfaces. Originality/value This research only considers the flexural performance of the beams strengthened with TRC in conventional environment, and there is little research on the TRC-strengthened beam under corrosion environment. On the basis of previous research, this paper carried out the experimental study on beams strengthened with TRC under chloride wet–dry cycle environment, and the effects of the concentration of the salt solution, number of wet–dry cycles, bending stress level and TRC form were considered.

Diffusion of chloride ions in limestone filler blended cement pastes and mortars

1995 ◽  
Vol 25 (8) ◽  
pp. 1667-1678 ◽  
Author(s):  
H. Hornain ◽  
J. Marchand ◽  
V. Duhot ◽  
M. Moranville-Regourd
Keyword(s):  
Blended Cement ◽  
Chloride Ions ◽  
Limestone Filler ◽  
Cement Pastes

Experimental Study on Mix Design of Chloride Resistant Cementitious Spacers

2014 ◽  
Vol 629-630 ◽  
pp. 351-357
Author(s):  
Chen Huang ◽  
Wen Ying Guo ◽  
Yi Bo Yang ◽  
Hui Zhao ◽  
Zhen Jie Li ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Design Method ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Mix Design ◽  
Easy Access ◽  
Ion Diffusion ◽  
Electric Flux ◽  
Chloride Environment ◽  
Chloride Ion Diffusion

Chloride resistant HPC and protective cover are two basic measurements to improve the durability of concrete in chloride environment. Though it provides crucial cover for concrete to resist chloride ions, spacer has limited chloride resistant ability, which is overlooked by past researchers. Cementitious spacers are easy access for chloride ions to penetrate into concrete resulting in reduction of structural durability. To improve cementitious spacers’ performance, a systematic study was conducted. Test results showed that there was major difference between mortar and concrete in terms of chloride coulomb electric flux but minor difference in terms of chloride ion diffusion coefficient, which implied using chloride ion diffusion coefficient as spacer’s durability indicator was preferable; parameters of mix design had a similar influence on mortar and concrete and, with the same mixing parameters, the strength and chloride resistant ability of mortar were weaker than concrete’s; it was feasible to develop the mix design of chloride resistant cementitious spacers based on concrete’s design method with certain adjustments, such as using stricter mix proportion, adding small-size coarse aggregate, lowering water-binder ratio and optimizing the binder proportion, to achieve higher strength and durability.

scholarly journals Diffusion Decay Coefficient for Chloride Ions of Concrete Containing Mineral Admixtures

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Jae-Im Park ◽  
Kwang-Myong Lee ◽  
Soon-Oh Kwon ◽  
Su-Ho Bae ◽  
Sang-Hwa Jung ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Concrete Structures ◽  
Blended Cement ◽  
Chloride Ions ◽  
Mineral Admixture ◽  
Curing Temperature ◽  
Mineral Admixtures ◽  
Exposure Condition ◽  
Diffusion Decay ◽  
Decay Coefficient

The diffusion coefficient for chloride ions and the diffusion decay coefficient for chloride ions are essential variables for a service life evaluation of concrete structures. They are influenced by water-binder ratio, exposure condition, curing temperature, cement type, and the type and use of mineral admixture. Mineral admixtures such as ground granulated blast furnace slag, fly ash, and silica fume have been increasingly used to improve resistance against chloride ions penetration in concrete structures built in an offshore environment. However, there is not enough measured data to identify the statistical properties of diffusion decay coefficient for chloride ions in concrete using mineral admixtures. This paper is aimed at evaluating the diffusion decay coefficient for chloride ions of concrete using ordinary Portland cement or blended cement. NT BUILD 492 method, an electrophoresis experiment, was used to measure the diffusion coefficient for chloride ions with ages. It was revealed from the test results that the diffusion decay coefficient for chloride ions was significantly influenced by W/B and the replacement ratio of mineral admixtures.

scholarly journals Prediction of Chloride Penetration into Hardening Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Wei-Jie Fan ◽  
Xiao-Yong Wang
Keyword(s):  
Cement Hydration ◽  
Binding Capacity ◽  
Numerical Procedure ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Experimental Investigations ◽  
Hydration Reaction ◽  
Degree Of Hydration ◽  
Chloride Diffusivity ◽  
Chloride Ion Penetration

In marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. Currently, most of experimental investigations about submerged penetration of chloride ions are started after the four-week standard curing of concrete. The further hydration of cement and reduction of chloride diffusivity during submerged penetration period are ignored. To overcome this weak point, this paper presents a numerical procedure to analyze simultaneously cement hydration reaction and chloride ion penetration process. First, using a cement hydration model, degree of hydration and phase volume fractions of hardening concrete are determined. Second, the dependences of chloride diffusivity and chloride binding capacity on age of concrete are clarified. Third, chloride profiles in hardening concrete are calculated. The proposed numerical procedure is verified by using chloride submerged penetration test results of concrete with different mixing proportions.

scholarly journals The cover thickness design of concrete structures subjected to chloride ingress from RBDO solution technique

2020 ◽  
Vol 13 (5) ◽  
Author(s):  
Giovanni Pais Pellizzer ◽  
Edson Denner Leonel
Keyword(s):  
Concrete Structures ◽  
Weighted Average ◽  
Threshold Level ◽  
Chloride Ions ◽  
Structural Safety ◽  
Solution Technique ◽  
Chloride Ingress ◽  
Initiation Stage ◽  
Cover Thickness ◽  
Propagation Stage

Abstract: Diffusion is the principal transport mechanism of chloride ions into concrete pores. The chlorides trigger the reinforcements’ depassivation when its concentration at the concrete/reinforcement interface reaches the threshold level. Thus, the depassivation defines the initiation stage end and the propagation stage start. The structural safety reduces widely during the propagation stage because of the various deleterious mechanisms triggered by reinforcement’s corrosion. Therefore, the engineers should accurately predict and prevent the propagation stage start. The literature describes several models for evaluating the end of the initiation stage. However, few of them applies the Boundary Element Method (BEM) for this purpose, despite its known accuracy. Besides, enormous randomness affect the phenomenon. Thus, it is adequately handled solely in the probabilistic context. Optimisation techniques may be coupled in the problem modelling to propose adequate cover thickness values accounting for probabilities of failure. This study presents a Reliability-Based Design Optimisation (RBDO) approach for designing accurately the cover thickness of concrete structures subjected to chloride ingress. The BEM handles the diffusion modelling whereas the Monte Carlo simulation assesses the probabilities of failure. The RBDO is formulated in the context of Weighted Average Simulation Method (WASM), which requires only one assessment of the reliability analysis. It leads to a reliable and computationally efficient solution technique. The problem formulation and the implemented solution scheme are described herein. Moreover, one application is presented, in which the design results are interpreted properly.

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