Analysis of the Effect of Crystallization Additives on the Resistance of Self-Compacting Concrete Exposed to Aggressive Gases

2021 ◽  
Vol 325 ◽  
pp. 194-199
Author(s):  
Ámos Dufka ◽  
Tomáš Žlebek ◽  
Tomáš Melichar
Keyword(s):  
Pore Structure ◽  
Self Compacting Concrete ◽  
Aggressive Environment ◽  
Physico Chemical ◽  
Influence Of Crystallization ◽  
Long Life ◽  
Capillary Pore

The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.

The Evaluation of the Effect of Crystallization Additives on Long Term Durability of Cement Composites

2018 ◽  
Vol 276 ◽  
pp. 265-270
Author(s):  
Ámos Dufka ◽  
Tomáš Melichar
Keyword(s):  
Pore Structure ◽  
Cement Composites ◽  
Self Compacting Concrete ◽  
Aggressive Environment ◽  
Physico Chemical ◽  
Influence Of Crystallization ◽  
Long Life ◽  
Capillary Pore

The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.

scholarly journals Relating Rapid Chloride Migration Coefficient of Blast Furnace Slag Concrete to Capillary Pore Structure Parameters

2019 ◽  
Vol 278 ◽  
pp. 01007
Author(s):  
Chao Yang ◽  
Shuguang Wang ◽  
Feng Xu ◽  
Weiwei Li ◽  
Dongsheng Du
Keyword(s):  
Blast Furnace ◽  
Pore Structure ◽  
Blast Furnace Slag ◽  
Pore Radius ◽  
Structure Parameters ◽  
Capillary Porosity ◽  
Chloride Resistance ◽  
Chloride Migration ◽  
Furnace Slag ◽  
Capillary Pore

Blast furnace slag blended concrete is widely used in infrastructure, and its chloride resistance is of great concern. This paper experimentally investigated the capillary pore structure and chloride resistance of blast furnace slag blended concrete. Blast furnace slag was proved to be able to optimize the critical pore radius and decrease the proportion of detrimental capillary pores (with radius between 50 nm and 10,000 nm). Meanwhile, the benefit of BFS in improving the chloride resistance was proved. Finally, regression analysis showed that the rapid migration coefficient is proportional to the critical pore radius and the detrimental capillary pore proportion. Nevertheless, the rapid migration coefficient is not closely related to the capillary porosity.

Experiment Study on the Durability of Dry-Mixing Self-Compacting Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 493-496 ◽  
Author(s):  
Lan Zong ◽  
Shi Ping Zhang ◽  
Pei Xin Liang
Keyword(s):  
Pore Structure ◽  
Frost Resistance ◽  
Chloride Ions ◽  
Experiment Study ◽  
Self Compacting Concrete ◽  
Freeze Thaw ◽  
Coarse Aggregates ◽  
Carbonation Resistance ◽  
Dry Mixing ◽  
Chloride Ions Diffusion

Durability of dry-mixing self-compacting concrete was evaluated through carbonation testing, freeze-thaw testing and chloride ions diffusion testing. The results indicate that carbonation resistance, frost resistance and chloride ions diffusion of durability of dry-mixing self-compacting concrete are excellent, compared with normally vibrated concrete (NVC). Durability of dry-mixing self-compacting concrete shows a better pore structure. Furthermore, the more the content of coarse aggregates is, the poorer the pore structure becomes.

scholarly journals A Comprehensive Study on the Hardening Features and Performance of Self-Compacting Concrete with High-Volume Fly Ash and Slag

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4286
Author(s):  
Zhenghong Yang ◽  
Sijia Liu ◽  
Long Yu ◽  
Linglin Xu
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Free Water ◽  
High Volume ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Main Concern ◽  
Self Compacting Concrete ◽  
Chloride Permeability ◽  
Early Hydration

The main concern of this work is to evaluate the influences of supplementary cementitious materials (fly ash, slag) and a new type of polycarboxylate superplasticizer containing viscosity modifying agents (PCE-VMA) on the performance of self-compacting concrete (SCC). The workability, hydration process, mechanical property, chloride permeability, degree of hydration and pore structure of SCC were investigated. Results indicate that the addition of fly ash and slag slows down early hydration and decreases the hydration degree of SCC, and thus leads to a decline in compressive strengths, especially within the first 7 days. The addition of slag refines pore structure and contributes to lower porosity, and thus the chloride permeability of SCC is decreased during the late hydration stage. Additionally, a new factor of calculated water–binder ratio is put forward, which can directly reflect the free water content of concrete mixture after mixing, and guide the mix proportion design of SCC.

scholarly journals Sensitivity Analysis of Stochastic Calculation of SCC Regarding Aggressive Environment

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6838
Author(s):  
Petr Lehner ◽  
Marie Horňáková ◽  
Kristýna Hrabová
Keyword(s):  
Sensitivity Analysis ◽  
Bridge Deck ◽  
Concrete Bridge ◽  
Bridge Structure ◽  
Self Compacting Concrete ◽  
Reinforced Concrete Bridge ◽  
Aggressive Environment ◽  
Different Types ◽  
Ideal Tool ◽  
Concrete Bridge Deck

Probabilistic procedures considering the durability with respect to corrosion of reinforcement caused by aggressive substances are widely applied; however, they are based on narrow assumptions. The aspects need to be evaluated both in terms of the search for suitable application of the various experimental results and in terms of their impact on the result of the stochastic assessment itself. In this article, sensitivity analysis was used as an ideal tool to prove how input parameters affect the results of the evaluation, with consideration of different types of concrete (ordinary or self-compacting with and without fibres). These concretes may be used in aggressive environments, as an industrial floor or as a part of the load-bearing bridge structure. An example of a reinforced concrete bridge deck was selected as the solved structure. The results show that in the case of a classic evaluation, a larger amount of fibre reports a lower resistance of concrete, which contradicts the assumptions. The sensitivity analysis then shows that self-compacting concrete is more sensitive to the values of the diffusion coefficient, and with the consideration of fibres, the effect is even greater.

scholarly journals Catalytic Dehydration of Ethanol over W/TiO2 Catalysts Having Different Phases of Titania Support

2019 ◽  
Vol 15 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Pongsatorn Kerdnoi ◽  
Chaowat Autthanit ◽  
Nithinart Chitpong ◽  
Bunjerd Jongsomjit
Keyword(s):  
Pore Structure ◽  
Diethyl Ether ◽  
Reaction Temperature ◽  
Catalytic Properties ◽  
Chemical Properties ◽  
Major Product ◽  
Ethanol Dehydration ◽  
Physico Chemical ◽  
Tio2 Support ◽  
Ether Yield

This study aims to investigate the catalytic behaviors on W/TiO2 catalysts having different phases of TiO2 towards catalytic dehydration of ethanol to higher value products including ethylene, diethyl ether, and acetaldehyde. In fact, TiO2 support with different crystalline phases can result in differences of physico-chemical properties of the catalyst. Therefore, the present work reports on the catalytic behaviors that were altered with different phases of TiO2 in catalytic ethanol dehydration to diethyl ether or ethylene as a major product. To prepare the catalysts, three different phases [anatase (A), rutile (R), and mixed phases (P25)] of TiO2 supports were impregnated with 10 wt% of tungsten (W). It was found that the W/TiO2-P25 catalyst revealed higher activity among other catalysts. At 300 °C, all catalysts can produce the diethyl ether yield of 24.1%, 22.8%, and 10.6% for W/TiO2-P25, W/TiO2-A, and W/TiO2-R catalysts, respectively. However, when the reaction temperature was increased to 400°C, ethylene is the major product. The W/TiO2-P25 and W/TiO2-A catalysts render the ethylene yield of 60.3% and 46.2%, respectively, whereas only 15.9% is obtained from W/TiO2-R catalyst. The most important parameter influencing their catalytic properties appears to be the proper pore structure, acidity, and distribution of W species. Copyright © 2019 BCREC Group. All rights reserved 

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