scholarly journals The Influence of C3A Content in Cement on the Chloride Transport

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Min Jae Kim ◽  
Ki Beom Kim ◽  
Ki Yong Ann
Keyword(s):  
Pore Structure ◽  
Chloride Transport ◽  
Binding Capacity ◽  
Setting Time ◽  
Chloride Concentration ◽  
Hardened Concrete ◽  
Chloride Ingress ◽  
Chloride Binding ◽  
Free Service ◽  
Chloride Profiles

The present study concerns the influence of C3A in cement on chloride transport in reinforced concrete. Three modified cement was manufactured in the variation of the C3A content, ranging from 6.0 and 10.5 up to 16.9%. The setting time of fresh concrete was measured immediately after mixing, together with the temperature at the time of initial set. For properties of hardened concrete in the variation in the C3A, a development of the compressive strength and chloride permeation were measured using mortar specimens. Simultaneously, chloride binding capacity was measured by the water extraction method. To ensure the influence of pore structure on chloride transport, the pore structure was examined by the mercury intrusion porosimetry. As a result, it was found that an increase in the C3A content resulted in an increase in chloride binding capacity. However, it seemed that increased binding of chlorides is related to the higher ingress of chlorides, despite denser pore structure. It may be attributed to the higher surface chloride, which could increase the gradient of chloride concentration from the surface, thereby leading to the higher level of chloride profiles. Substantially, the benefit of high C3A in resisting corrosion, arising from removal of free chlorides in the pore solution, would be offset by increased chloride ingress at a given duration, when it comes to the corrosion-free service life.

Cement-Free Mortar Using Ground Granulated Blast-Furnace Slag with Different Alkali-Activators

2014 ◽  
Vol 578-579 ◽  
pp. 1430-1440 ◽  
Author(s):  
Joon Woo Park ◽  
Sung In Hong ◽  
Hee Jun Yang ◽  
Thamara Tofeti Lima ◽  
Ki Yong Ann
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Pore Structure ◽  
Blast Furnace Slag ◽  
Chloride Transport ◽  
Setting Time ◽  
Total Pore Volume ◽  
Granulated Blast Furnace Slag ◽  
Hydroxyl Ion ◽  
Furnace Slag

The present study concerns a development of cement-free concrete using ground granulated blast-furnace slag (GGBS) with alkali-activators such as KOH, NaOH, and Ca (OH)2. To find out the development among three different activators, the concentration of hydroxyl ion was kept 0.5%, 1.0%, 1.5%, 2.0% and 3.0% by weight of binder irrespective of cations. The setting time was measured by penetration resistance immediately after casting of mortar. The development of compressive strength was measured at 7, 14, 28, and 91 days. The pore structure of cement-free mortar was examined by the mercury intrusion porosimetry (MIP) and rapid chloride penetration test (RCPT). Simultaneously, grew sample was used to microscopically observe at the XRD. For strength of cement-free mortar, mixed with KOH or NaOH was as high as OPC at 3.0 % by weight of binder. However, the compressive strength of cement-free concrete mixed with 3.0 % Ca (OH)2 by weight of binder had just half strength of OPC mortar. Cement-free concrete activated with NaOH and Ca (OH)2 had higher total pore volume, however, it had lower ionic penetrability due to the pore type which mostly consist of gel pores. For pore structure of cement-free mortar mixed with KOH, the total volume had similarity to that of OPC mortar, however, it had lower penetrability. Therefore, it may have higher resistance to chloride transport than that of OPC mortar.

scholarly journals Estimation of Corrosion-Free Life for Concrete Containing Ground Granulated Blast-Furnace Slag under a Chloride-Bearing Environment

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Sung In Hong ◽  
Ki Yong Ann
Keyword(s):  
Blast Furnace ◽  
Service Life ◽  
Blast Furnace Slag ◽  
Chloride Transport ◽  
Binding Capacity ◽  
Chloride Diffusion ◽  
Chloride Binding ◽  
Replacement Ratio ◽  
Granulated Blast Furnace Slag ◽  
Furnace Slag

The rate of chloride transport by diffusion in concrete containing ground granulated blast-furnace slag (GGBS) was mathematically estimated to predict the corrosion-free service life of concrete structures exposed to seawater environment. As a factor to corrosiveness of steel embedment, replacement ratio of GGBS was selected, accounting for 25 and 50% to total binder. As a result, it was found that an increase in the GGBS content resulted in an increase in the chloride binding capacity, which would give rise to a lower chloride diffusion rate, thereby reducing the risk of chloride-induced corrosion. When it comes to the sensitivity of parameters to service life, the effective diffusivity showed a marginal influence on serviceability, irrespective of GGBS contents while surface chloride content and critical threshold concentration revealed more crucial factors to long term chloride diffusion. As the GGBS replacement increased, the variation in service life has become less influential with changing parameters. Substantially, GGBS concrete at high replacement ratio enhanced the service life due to a combination of dense pore structure and enhanced chloride binding capacity.

Chloride Binding of Cementitious Pastes

2010 ◽  
Vol 152-153 ◽  
pp. 363-367
Author(s):  
Ke Feng Tan ◽  
Qing Cao
Keyword(s):  
Cement Paste ◽  
Binding Capacity ◽  
Steel Slag ◽  
Chloride Concentration ◽  
Solution Concentration ◽  
Test Method ◽  
Mineral Admixtures ◽  
Chloride Binding ◽  
Test Results ◽  
Blastfurnace Slag

An experiment was undertaken to investigate the effect of mineral admixtures, w/b, external chloride solution concentration, and carbonation on chloride binding capacity of cementitious paste. The test method was based on equilibrium method. Test results show that incorporating metakaolin, blastfurnace slag, steel slag, and flyash increases chloride binding capacities by 65.9%, 55.3%, 43.9%, and 26.8% respectively. Increasing external chloride concentration and w/c ratio can improve the chloride capacity of pure cement paste. Carbonation of cement paste will reduce the chloride capacity. Chloride binding do affect the durability of reinforced concrete in saline environment.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

scholarly journals Chloride Binding Capacity and Its Effect on the Microstructure of Mortar Made with Marine Sand

2021 ◽  
Vol 13 (8) ◽  
pp. 4169
Author(s):  
Congtao Sun ◽  
Ming Sun ◽  
Tao Tao ◽  
Feng Qu ◽  
Gongxun Wang ◽  
...  
Keyword(s):  
Binding Capacity ◽  
Chloride Content ◽  
Chloride Ions ◽  
Fine Aggregate ◽  
Chloride Binding ◽  
River Sand ◽  
Total Chloride ◽  
Curing Period ◽  
Marine Sand ◽  
Bound Chloride

Chloride binding capacity and its effect on the microstructure of mortar made with marine sand (MS), washed MS (WMS) and river sand (RS) were investigated in this study. The chloride contents, hydration products, micromorphology and pore structures of mortars were analyzed. The results showed that there was a diffusion trend for chloride ions from the surface of fine aggregate to cement hydrated products. During the whole curing period, the free chloride content in the mortars made by MS and WMS increased firstly, then decreased and stabilized finally with time. However, the total chloride content of three types of mortar hardly changed. The bound chloride content in the mortars made by MS and WMS slightly increased with time, and the bound chloride content included the MS, the WMS and the RS arranged from high to low. C3A·CaCl2·10H2O (Friedel’s salt) was formed at the early age and existed throughout the curing period. Moreover, the volume of fine capillary pore with a size of 10–100 nm increased in the MS and WMS mortar.

scholarly journals Numerical Simulation of Non-Uniformly Distributed Corrosion in Reinforced Concrete Cross-Section

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3975
Author(s):  
Magdalena German ◽  
Jerzy Pamin
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Chloride Transport ◽  
Chloride Concentration ◽  
Corrosion Current ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Initiation Phase ◽  
Chloride Corrosion ◽  
Cover Thickness

Reinforced concrete structures can be strongly damaged by chloride corrosion of reinforcement. Rust accumulated around rebars involves a volumetric expansion, causing cracking of the surrounding concrete. To simulate the corrosion progress, the initiation phase of the corrosion process is first examined, taking into account the phenomena of oxygen and chloride transport as well as the corrosion current flow. This makes it possible to estimate the mass of produced rust, whereby a corrosion level is defined. A combination of three numerical methods is used to solve the coupled problem. The example object of the research is a beam cross-section with four reinforcement bars. The proposed methodology allows one to predict evolving chloride concentration and time to reinforcement depassivation, depending on the reinforcement position and on the location of a point on the bar surface. Moreover, the dependence of the corrosion initiation time on the chloride diffusion coefficient, chloride threshold, and reinforcement cover thickness is examined.

Effect of triethanolamine on the chloride binding capacity of cement paste with a high volume of fly ash

2021 ◽  
pp. 125612
Author(s):  
Yibiao Teng ◽  
Songhui Liu ◽  
Zhaocai Zhang ◽  
Jiangwei Xue ◽  
Xuemao Guan
Keyword(s):  
Fly Ash ◽  
Cement Paste ◽  
Binding Capacity ◽  
High Volume ◽  
Chloride Binding

Improving the chloride binding capacity of cement paste by adding nano-Al2O3

2019 ◽  
Vol 195 ◽  
pp. 415-422 ◽  
Author(s):  
Zhiqiang Yang ◽  
Yun Gao ◽  
Song Mu ◽  
Honglei Chang ◽  
Wei Sun ◽  
...  
Keyword(s):  
Cement Paste ◽  
Binding Capacity ◽  
Chloride Binding
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