Sulfate-Ion Diffusion Regularity and Reaction Mechanism of Sodium Sulfate Attack on Carbonized Concrete

2008 ◽  
Vol 400-402 ◽  
pp. 211-214
Author(s):  
Xiao Ke Li ◽  
Shun Bo Zhao ◽  
Chang Cheng Shi
Keyword(s):  
Reaction Mechanism ◽  
Sodium Sulfate ◽  
Concrete Specimen ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Test Results ◽  
Ion Diffusion ◽  
Sulfate Ion ◽  
Titration Method ◽  
Sulfate Solutions

The experiment has been carried out to study the sodium sulfate attack on carbonized concrete. The concrete specimens with strength grade of C50 were first carbonized for 28d in the carbonation box after standard curing, and then immersed into the sodium sulfate solutions of three different concentrations. When the immersed time were up to 30d, 90d, 180d, 270d and 360d, the sulfate-ion concentrations of every layer from the surface to the inside of concrete specimen were measured by the chemical titration method. Based on the test results, the sulfate-ion diffusion regularity and the reaction mechanism of carbonized concrete are analyzed. It can be concluded that the sulfate-ion diffusion regularity and the reaction mechanism of carbonized concrete is completely different from that of un-carbonized concrete, the diffusion of sulfate-ion occupies advantage in the pore water of carbonized concrete, which increases the depth of concrete specimen attacked by sulfate solution.

Simulations on Expansive Strain of Concrete Caused by Ettringite Growth under Sulfate Attack

2011 ◽  
Vol 250-253 ◽  
pp. 1906-1911 ◽  
Author(s):  
Xiao Bao Zuo ◽  
Wei Sun
Keyword(s):  
Sulfate Solution ◽  
Sulfate Attack ◽  
Diffusion Time ◽  
Diffusion Reaction ◽  
Sulfate Ion ◽  
Reaction Equation ◽  
Ettringite Formation ◽  
Sulfate Solutions ◽  
Calcium Aluminates ◽  
Strain Responses

In order to assess theoretically the expansive strain of concrete caused by the ettringite formation and growth under the sulfate attack, some models are proposed to investigate the strain responses of concrete exposed to the sulfate solutions. Firstly, an 1-D nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete is proposed; Secondly, based on chemical reactions between sulfate and aluminates in concrete, the expansive strain is obtained due to the ettringite growth resulting in concrete expansion. Thirdly, numerical simulations are carried out to analyze the formation process of the concrete expansive strain under the sulfate solution, and results show that the models can be used to predict the concrete responses with the diffusion time, such as the distribution concentration of sulfate ion, dissipated concentration of the calcium aluminates, expansion strain of concrete due to the formation and growth of ettringite.

X-Ray Microtomography of an Astm C109 Mortar Exposed to Sulfate Attack

1994 ◽  
Vol 370 ◽  
Author(s):  
D.P. Bentz ◽  
Nicos. S. Martys ◽  
P. Stutzman ◽  
M. S. Levenson ◽  
E.J. Garboczi ◽  
...  
Keyword(s):  
Cement Paste ◽  
Sodium Sulfate ◽  
Three Dimensional ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Sodium Sulfate Solution ◽  
Mortar Sample ◽  
Air Voids ◽  
X Ray ◽  
Dimensional Image

AbstractX-ray microtomography can be used to generate three-dimensional 5123 images of random materials at a resolution of a few micrometers per voxel. This technique has been used to obtain an image of an ASTM C109 mortar sample that had been exposed to a sodium sulfate solution. The three-dimensional image clearly shows sand grains, cement paste, air voids, cracks, and needle-like crystals growing in the air voids. Volume fractions of sand and cement paste determined from the image agree well with the known quantities. Implications for the study of microstructure and proposed uses of X-ray microtomography on cement-based composites are discussed.

scholarly journals Deterioration Regularity of Sodium Sulfate Solution Attack on Cemented Coal Gangue-Fly Ash Backfill under Drying-Wetting Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Shaojie Chen ◽  
Zhen Zhang ◽  
Dawei Yin ◽  
Junbiao Ma
Keyword(s):  
Fly Ash ◽  
Sodium Sulfate ◽  
Sulfate Solution ◽  
Coal Gangue ◽  
Salt Crystallization ◽  
Sodium Sulfate Solution ◽  
Sulfate Ion ◽  
Sulfate Ions ◽  
Ion Contents ◽  
The Masses

To research the properties of cemented coal gangue-fly ash backfill (CGFB) exposed to different concentrations of sodium sulfate solutions under drying-wetting cycles, the mass changes, uniaxial compressive strengths, sulfate ion contents at different depths, and microstructures of CGFB samples were measured in this study. The results show that the CGFB samples were damaged by salt crystallization in the dry state and attacked by the expansive products in the wet state. The sulfate ion contents in CGFB samples increased with the sulfate concentrations and drying-wetting cycles and decreased from the surface to the inside of the samples. The damage process of CGFB samples evolved from the surface to the inside. In the early stage of corrosion, sulfate ions adsorbed to the surface of CGFB samples and consumed nonhydrated particles to form acicular ettringite and other products that filled the material pores. For this stage, the driving force of sulfate ions to enter into the CGFB samples was the highest for the samples immersed in 15% sodium sulfate solution, and the masses and strengths increased the fastest. As the drying-wetting cycles continued, the nonhydrated particles inside the samples were nearly completely hydrated, and the samples were constantly damaged by salt crystallization and dissolution. The corrosion ions entered into the samples and consumed portlandite to produce a large amount of prismatic ettringite and aggravated the internal corrosion of CGFB samples. At the fifteenth drying-wetting cycle, the higher the salt concentration of the immersion solution was, the faster the masses and the strengths of CGFB samples decreased. Moreover, the surface spalling and failure of CGFB samples were more severe.

Experimental Study on Improving Concrete Sulfate Attack Resistance Ability with Silane Impregnation

2013 ◽  
Vol 405-408 ◽  
pp. 2621-2624
Author(s):  
Zhi De Huang
Keyword(s):  
Sulfate Solution ◽  
Hydration Product ◽  
Sulfate Attack ◽  
Cementitious Material ◽  
Material System ◽  
Absorption Test ◽  
Test Results ◽  
Binder Ratio ◽  
Water Absorption Test ◽  
Drying Test

Silane impregnation effects on concrete sulfate attack resistance ability are systemic researched, through forming different cementitious material system and different water cement ratio mortar specimens, treating with silane impregnation and then curing to 14d age naturally, and doing sulfate solution wetting-drying test. Results shows that silane impregnation effect is poor when fly ash amount is large or water gel is relatively low. Through XRD microscopic, the improving sulfate attack resistance ability mechanisms are analyzed from aspect of cementations material hydration product; water-binder ratio effect on silane impregnation is explained by water absorption test.

Long-term sulfate attack on recycled aggregate concrete immersed in sodium sulfate solution for 10 years

2020 ◽  
Vol 70 (337) ◽  
pp. 212
Author(s):  
L. R. Santillán ◽  
F. Locati ◽  
Y. A. Villagrán-Zaccardi ◽  
C. J. Zega
Keyword(s):  
Sodium Sulfate ◽  
Fluorescent Microscopy ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Sodium Sulfate Solution ◽  
Microscopy Image

The effect of recycled concrete aggregate (RCA) on concrete performance against external sulfate attack (ESA) is not yet fully known. In this paper, recycled aggregate concretes (RAC) with 0, 50, 75 and 100% of RCA contents were evaluated after 10 years of exposure immersed in 50g/l sodium sulfate solution. Sulfate ingress profiles were obtained by wet chemical analyses and FRX. Also, the mineralogy of the ingress profile was evaluated by thermogravimetric analyses. Finally, microcracking development in samples was evaluated by optical fluorescent microscopy image analysis. Although RAC showed a slight increase in sulfate ingress, due to its higher porosity (about 30% higher SO3 content near the surface for 50% or higher replacement ratio than control concrete), a dense new matrix still allows a good performance of RAC to external sulfate attack with even 100% RCA content.

Application of Nano Silica in Concrete for Enhanced Resistance against Sulfate Attack

2013 ◽  
Vol 829 ◽  
pp. 874-878 ◽  
Author(s):  
Amir Mahdi Moslemi ◽  
Arash Khosravi ◽  
Mohsen Izadinia ◽  
Mohaddeseh Heydari
Keyword(s):  
Compressive Strength ◽  
Concrete Structure ◽  
Concrete Specimen ◽  
Sulfate Solution ◽  
Critical Issue ◽  
Sulfate Attack ◽  
Pozzolanic Material ◽  
Enhanced Resistance ◽  
Morphology Characteristics ◽  
Durability Of Concrete

Durability of concrete structure is a critical issue especially in severe environment when the concrete structure is exposed to sulfate attack, such as shorelines. nanoSilica is high pozzolanic material which is used recently in concrete to improve its mechanical properties. However, the durability of concrete against sulfate attack containing nanoSilica (NS) has not been investigated completely. In this study, the effects of NS has been studied on compressive strength, sulfate attack and morphology characteristics. The results show that increasing of compressive strength in specimens with NS is significant in early ages. Resistance of concrete specimen against sulfate attack was measured in 5% sodium sulfate solution for expansion of prime specimens. After a period of 180 days the samples containing zero, 2, 4, 6 and 8% NS lost 3.51%, 2.4%, 2.23%, 1.13% and 1% of their weights compared to the initial weights, respectively. The results indicate that the concrete samples containing 8% NS show best performance in terms of resistance against sulfate attack.

Behaviors of Long-Term Exposure Concrete to Sulfate Solution

2011 ◽  
Vol 368-373 ◽  
pp. 790-794
Author(s):  
Shun Bo Zhao ◽  
Thomas C.K. Molyneaux ◽  
David W. Law ◽  
Yong Li ◽  
Li Yun Pan
Keyword(s):  
Compressive Strength ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Sulfate Ions ◽  
Sulfate Solutions ◽  
Collaborative Studies ◽  
Diffusion Depth ◽  
One Year ◽  
The Uk

As a part of the collaborative studies between China, Australia and the UK, examing sulfate attack on concrete, this paper reports the experimental results obtained from the Chinese laboratory. Specimens were immersed in sodium and magnesium sulfate solutions with concentrations of 500mg/L, 5000mg/L and 50000mg/L. Investigations were conducted over approximately a one year period. Susceptibility to sulfate attack was assessed in terms of changes in the mass and length of specimens, the compressive strength of the concrete, as well as the diffusion depth of sulfate-ions into the concrete at fixed intervals. Several differences were observed between these results and those reported in studies from the UK laboratory.

scholarly journals Damage and Degradation of Concrete under Coupling Action of Freeze-Thaw Cycle and Sulfate Attack

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Wei Tian ◽  
Fangfang Gao
Keyword(s):  
Fly Ash ◽  
Sodium Sulfate ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Sodium Sulfate Solution ◽  
Failure Characteristics ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Two Stages

In this study, the mechanical behaviors, failure characteristics, and microstructure of concrete containing fly ash (FA) against combined freeze-thaw cycles and sulfate attack were studied compared with normal concrete, and the formation rates of corrosion products during coupling cycles were investigated. Results showed that, during the coupling action of freeze-thaw cycles and sodium sulfate solution, concrete containing 10% fly ash exposed in 5% sodium sulfate solution exhibited better freeze-thaw resistance. Meanwhile, the variation of compressive strength of concrete during the coupling cycles could be divided into two stages, including the strength enhancement stage and the strength reduction stage. Moreover, the proportion of micropores and capillary pores decreased obviously during combined freeze-thaw cycles and sulfate attack, and excessive concentration of sodium sulfate solution led to more macropores after high-frequency freeze-thaw cycles.

scholarly journals A Chemical-Transport-Mechanics Numerical Model for Concrete under Sulfate Attack

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7710
Author(s):  
Xuandong Chen ◽  
Xin Gu ◽  
Xiaozhou Xia ◽  
Xing Li ◽  
Qing Zhang
Keyword(s):  
Numerical Model ◽  
Solid Phase ◽  
Sulfate Attack ◽  
Third Party ◽  
Time Dependent ◽  
Expansion Rate ◽  
Sulfate Concentration ◽  
Multiple Perspectives ◽  
Ion Diffusion ◽  
Sulfate Ion

Sulfate attack is one of the crucial causes for the structural performance degradation of reinforced concrete infrastructures. Herein, a comprehensive multiphase mesoscopic numerical model is proposed to systematically study the chemical reaction-diffusion-mechanical mechanism of concrete under sulfate attack. Unlike existing models, the leaching of solid-phase calcium and the dissolution of solid-phase aluminate are modeled simultaneously in the developed model by introducing dissolution equilibrium equations. Additionally, a calibrated time-dependent model of sulfate concentration is suggested as the boundary condition. The reliability of the proposed model is verified by the third-party experiments from multiple perspectives. Further investigations reveal that the sulfate attack ability is underestimated if the solid-phase calcium leaching is ignored, and the concrete expansion rate is overestimated if the dissolution of solid-phase aluminate is not modeled in the simulation. More importantly, the sulfate attack ability and the concrete expansion rate is overestimated if the time-dependent boundary of sulfate concentration is not taken into consideration. Besides, the sulfate ion diffusion trajectories validate the promoting effect of interface transition zone on the sulfate ion diffusion. The research of this paper provides a theoretical support for the durability design of concrete under sulfate attack.

Effect of Fly Ash on Resistance to Sulfate Attack of Cement-Based Materials

2013 ◽  
Vol 539 ◽  
pp. 124-129 ◽  
Author(s):  
Kai Wei Liu ◽  
Min Deng ◽  
Li Wu Mo
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Sodium Sulfate ◽  
Sulfate Solution ◽  
Length Change ◽  
Sulfate Attack ◽  
Sodium Sulfate Solution ◽  
Reaction Products ◽  
Visual Appearance ◽  
Cement Based Materials

The resistance to sulfate attack of mortars containing 0%, 20%, and 40% of fly ash cured in 5 wt. % sodium sulfate solution at 20°C was investigated in this paper. Visual appearance, cracking analysis, velocity of ultrasonic wave and length change were applied to evaluate the sulfate resistance of mortars. The phases and microstructure of the reaction products due to sulfate attack were examined by XRD and SEM, and the pore structure of the mortars was analyzed by MIP. The effects of fly ash on the sulfate attack of mortars were analyzed. Results indicated that the addition of fly ash improved the resistance of sulfate attack significantly, this probably contributed to the pozzonlanic reaction of fly ash.

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