Risk Assessment and Diagnostic Method of Sulfate Attack of Cement-Based Material

2012 ◽  
Vol 174-177 ◽  
pp. 121-126
Author(s):  
Feng Chen Zhang ◽  
Yong Hao Fang ◽  
De Jian Shen ◽  
Ji Kai Zhou
Keyword(s):  
Risk Assessment ◽  
Diagnostic Method ◽  
Cement Mortar ◽  
Sulfate Attack ◽  
Building Structures ◽  
Sulfate Ions ◽  
Local Climate ◽  
Service Environment ◽  
Micro Analysis ◽  
Concrete Component

It is very difficult to evaluate risk of sulfate attack and diagnose the form of sulfate attack of cement mortar and concrete because of the diversity of attack form and complexity of erosion phases during sulfate attack, which affect repair of concrete component damaged by sulfate attack mostly. From the sulfate ions, ambient temperature and humidity of service environment as well as local climate characteristics, key components of building structures suffered great risk of sulfate attack should be inspected well and master the property of cement-based material, and then evaluate the risk of sulfate attack. In this foundation, three main erosion phases which are ettringite, gypsum and thaumasite are distinguished by micro-analysis and so the form of sulfate attack can be identified.

scholarly journals Deterioration Process of Concrete Exposed to Internal Sulfate Attack

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1336 ◽  
Author(s):  
Weifeng Chen ◽  
Bei Huang ◽  
Yuexue Yuan ◽  
Min Deng
Keyword(s):  
Compressive Strength ◽  
Sulfate Attack ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Great Loss ◽  
Sulfate Ions ◽  
Coarse Aggregates ◽  
Deterioration Process ◽  
One Year ◽  
Internal Sulfate Attack

Damage to concrete structures with gypsum-contaminated aggregate occurs frequently. Aggregates in much of the southern part of China are contaminated with gypsum. Therefore, in this study, the effects of using different quantities of gypsum-contaminated aggregate on the expansion and compressive strength of concrete were investigated over a period of one year. Two groups of concrete were designed with the gypsum-contaminated aggregate containing different parts of fine and coarse aggregate, respectively. The SO3 contents were 0%, 0.5%, 1%, 1.5%, 3%, 5%, and 7% by weight of aggregate. X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC) were used to analyze the change in mineral composition over time. The microstructure was also studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that significant expansion and great loss in compressive strength did not occur in concrete if the content of SO3 lay below 1.5% and 3% in fine and coarse aggregates, respectively. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Ettringite was the main reason for the expansion damage of concrete. Additionally, the fracture mode of internal sulfate attack on concrete was the crack extension from gypsum to paste; finally, the aggregate separated from the paste.

Effect of Erosion Damage on Diffusion of Sulfate Ions in Concrete

2011 ◽  
Vol 243-249 ◽  
pp. 4683-4686 ◽  
Author(s):  
Chao Sun ◽  
Jian Kang Chen
Keyword(s):  
Differential Equation ◽  
Diffusion Equation ◽  
Numerical Method ◽  
Nonlinear Diffusion ◽  
Damage Evolution ◽  
Sulfate Attack ◽  
Nonlinear Diffusion Equation ◽  
Second Law ◽  
Sulfate Ions ◽  
Erosion Damage

Based on Fick’s second law and the damage evolution due to sulfate attack, a new model is proposed to analyze the diffusion of sulfate ions in concrete. The relation between erosion damage and erosion time, as well as the concentration of sulfate ions is firstly investigated by virtue of the ultrasonic experimental results. Furthermore, the damage evolution is treated as the increase of porosity, and a new nonlinear differential equation on the diffusion of sulfate ions is established by substituting such an increasing porosity into Fick’s law. The nonlinear diffusion equation is then solved by numerical method. It is found that the erosion damage can significantly affect the diffusion of sulfate ions in concrete.

Strength Loss Method to Evaluate the Sulfate Attack Resistance of the Cement-Porous Silica Fume Mortar

2014 ◽  
Vol 576 ◽  
pp. 133-141
Author(s):  
Shou Qi Zhang ◽  
Shu Xiong Zhang ◽  
Yu Fang Fu ◽  
Dong Min Wang
Keyword(s):  
Silica Fume ◽  
Cement Mortar ◽  
Porous Silica ◽  
Acid Leaching ◽  
Strength Loss ◽  
Sulfate Attack ◽  
Holding Time ◽  
Mineral Admixture ◽  
Material Development ◽  
Asbestos Tailings

The key factors for activity of asbestos tailings acid leaching residue (ATALR) and activated process were researched by the way of orthoplan, so as to make a new type of high-active mineral admixture in cement-based material, named as porous silica fume (PSF). Then with the strength loss indexes designed, the sulfate attack resistance of cement-PSF mortars was evaluated, which was dunked in solution of sodium sulfate during from 6 to 12 months. The results indicated that thermal activated temperature and holding time was the key factor for compressive strength, while holding time and grinding time for flexural strength. The optimal activated process was the thermal activated temperature at800°C needing to hold for 1 hour before grinding for 20minuteswhilethe appropriate amount of PSF was 5%~12% in cement mortar. When 5%~8% PSF contained, the sulfate attack resistance of cement mortar can be improved obviously, and the role was similar to silica fume (SF). PSF activated from ATALR is helpful for resource utilization of asbestos tailings, in order to improve ecological environment in the asbestos mine town and promote cement-based material development.

Study of Fine-Grained Composites Exposed to Sulfuric Acid and Sodium Sulfate

2016 ◽  
Vol 827 ◽  
pp. 275-278
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková
Keyword(s):  
Waste Water ◽  
Sulfuric Acid ◽  
Sodium Sulfate ◽  
Sulfate Attack ◽  
Sewer Pipes ◽  
Sulfate Ions ◽  
Fine Grained ◽  
One Year ◽  
Corrosion Of Steel ◽  
Loss Of Strength

The degradation of concrete due to ingress of sulfate ions from the environment plays an important role in the durability of concrete constructions, especially in sewage collection systems where concrete sewer pipes are exposed to sulfates from waste water and from biogenic activity of bacteria. During this process the pH of the surface of concrete sewer pipes is reduced and it may lead to the steel depassivation and results in the corrosion of steel reinforcement. Damage due to sulfate interaction can result in the cracking and softening, with loss of strength of concrete. This paper is focused on the sulfate attack on fine-grained concrete where the effect of one-year contact of 0.5% H2SO4, and 5% Na2SO4 on changes of pH and content of sulfates in 7 types of concrete has been analyzed. It was found that after one year of sulfate attack on concrete, significant growth of content of sulfates is observed in the lowermost layer of the samples. Samples treated by 5% Na2SO4 contain slightly more sulfates in the upper layers than samples treated by sulfuric acid. The reduction in pH of aqueous leaches occurred in all layers of the samples. However, even in the lower layers of the samples, the reduction of pH below 9.5 did not turn up (except for SRS sample), and thus the conditions for the depassivation of reinforcement were not met.

scholarly journals Calculating earthquake damage building by building: the case of the city of Cologne, Germany

2022 ◽  
Author(s):  
Cecilia I. Nievas ◽  
Marco Pilz ◽  
Karsten Prehn ◽  
Danijel Schorlemmer ◽  
Graeme Weatherill ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Census Data ◽  
Open Data ◽  
Region Of Interest ◽  
Exposure Model ◽  
Building Structures ◽  
Natural Risk ◽  
Earthquake Scenario ◽  
Damage Data ◽  
Damage Estimates

AbstractThe creation of building exposure models for seismic risk assessment is frequently challenging due to the lack of availability of detailed information on building structures. Different strategies have been developed in recent years to overcome this, including the use of census data, remote sensing imagery and volunteered graphic information (VGI). This paper presents the development of a building-by-building exposure model based exclusively on openly available datasets, including both VGI and census statistics, which are defined at different levels of spatial resolution and for different moments in time. The initial model stemming purely from building-level data is enriched with statistics aggregated at the neighbourhood and city level by means of a Monte Carlo simulation that enables the generation of full realisations of damage estimates when using the exposure model in the context of an earthquake scenario calculation. Though applicable to any other region of interest where analogous datasets are available, the workflow and approach followed are explained by focusing on the case of the German city of Cologne, for which a scenario earthquake is defined and the potential damage is calculated. The resulting exposure model and damage estimates are presented, and it is shown that the latter are broadly consistent with damage data from the 1978 Albstadt earthquake, notwithstanding the differences in the scenario. Through this real-world application we demonstrate the potential of VGI and open data to be used for exposure modelling for natural risk assessment, when combined with suitable knowledge on building fragility and accounting for the inherent uncertainties.

scholarly journals Evaluation of external sulfate attack (Na2SO4 and MgSO4): Portland cement mortars containing fillers

2020 ◽  
Vol 13 (3) ◽  
pp. 644-655 ◽  
Author(s):  
D. J. DE SOUZA ◽  
M. H. F. MEDEIROS ◽  
J. HOPPE FILHO
Keyword(s):  
Portland Cement ◽  
Linear Expansion ◽  
Sulfate Attack ◽  
Hardened Cement ◽  
X Ray Diffraction ◽  
Limestone Filler ◽  
Sulfate Ions ◽  
X Ray ◽  
Cement Mortars ◽  
Physical And Chemical

Abstract Sulfate attack is a term used to describe a series of chemical reactions between sulfate ions and hydrated compounds of the hardened cement paste. The present study aims to evaluate the physical (linear expansion, flexural and compressive strength) and mineralogical properties (X-ray diffraction) of three different mortar compositions (Portland Cement CPV-ARI with limestone filler and, with a quartz filler, in both cases with 10% replacement of the cement by weight) against sodium and magnesium sulfate attack (concentration of SO4 2- equal to 0.7 molar). The data collected indicate that the replacing the cement by the two fillers generate different results, the quartz filler presented a mitigating behaviour towards the sulfate, and the limestone filler was harmful to Portland cement mortars, in both physical and chemical characteristics.

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