Deterioration of Concrete by Leaching in Conditions of Long-Term Bending Performance - Simplified Theoretical Approach

2016 ◽  
Vol 691 ◽  
pp. 28-39
Author(s):  
Peter Paulík
Keyword(s):  
Experimental Data ◽  
Theoretical Approach ◽  
Nitrate Solution ◽  
Theoretical Models ◽  
Main Task ◽  
Bending Performance ◽  
Ammonium Nitrate Solution ◽  
Diffusion Function ◽  
Concrete Elements

Based on the results of previous research it could be stated that the deterioration of concrete elements by leaching process could be described by the simplified diffusion function. However the results of Schneider and Chen showed that the deterioration of concrete elements by leaching could differ significantly if they are subjected to permanent bending performance. Their experimental data pointed out that after a certain time the deterioration course of loaded concrete elements significantly changes and these elements lose their strength faster than the unloaded control specimens.Article outlines the possible theoretical solution of this phenomenon. The developed theoretical models where applied to the experimental results of Schneider and Chen [3], [2]. The main task was to find a simplified engineering solution to the problem of the stress corrosion of the concrete in ammonium nitrate solution.

Prediction of the Deterioration Depth of Concrete by Accelerating Calcium Leaching Test

2011 ◽  
Vol 365 ◽  
pp. 3-7 ◽  
Author(s):  
An Cheng ◽  
Sao Jeng Chao ◽  
Wei Ting Lin ◽  
Jia Liang Chang
Keyword(s):  
Nitrate Solution ◽  
Leaching Behavior ◽  
Calcium Leaching ◽  
Ammonium Nitrate Solution ◽  
Binder Ratio ◽  
Two Stages ◽  
Strength And Durability ◽  
Calcium Ion Leaching ◽  
Water Binder Ratio

The concrete is a solid and porous composite materials, when the concrete exposure to moisture environment for a long-term, the pore water will penetrate into concrete cause hydration products leaching. Leaching of calcium ions increase in porosity and resulting in harmful ions ingress into concrete to reduce strength and durability of concrete. The purpose of this study is to evaluate the effect of water-binder ratio on calcium ion leaching behavior of cement-based material. The ammonium nitrate solution was used to accelerate leaching process. Leaching duration was 56 days, 91 days and 140 days, respectively. The leaching depth and compressive strength were measured. The results showed that leaching resistance increased with a decrease in water/binder ratio. The leaching depth showed that leaching behavior of the specimens without minerals admixtures can be divided into two stages, the first stage was leaching of calcium hydroxide and than the C-S-H gel were leaching.

The design and performance of a nitrifying vertical-flow reed bed treatment system

1997 ◽  
Vol 35 (5) ◽  
pp. 215-221 ◽  
Author(s):  
Paul Cooper ◽  
Mark Smith ◽  
Henrietta Maynard
Keyword(s):  
Nitrate Solution ◽  
Treatment System ◽  
Vertical Flow ◽  
Biological Filter ◽  
Ammonium Nitrate Solution ◽  
Reed Bed ◽  
And Performance ◽  
Long Term Performance ◽  
Term Performance

The paper describes the design, construction and the monitoring of a vertical-flow Reed Bed Treatment System (RBTS) which achieves tertiary nitrification of the effluent from a biological filter, treating the sewage flow from a population of about 200 people. It treats the flows from toilets, kitchen laboratories and a saline wastewater. The RBTS system takes effluent from an old biological filter and produces a nitrified effluent from a two-stage intermittently-dosed system. The paper shows the long-term performance of the system over a 4 year period and also describes experiments to assess the nitrification performance using a step-feed of ammonium nitrate solution. The system shows a removal of 8-13 g NH4-N/m3 of bed day. The design basis is shown and the operational features described.

The Leaching Effect of Cement Hydration Products

2012 ◽  
Vol 610-613 ◽  
pp. 428-435 ◽  
Author(s):  
Yu Kuan Cheng ◽  
Wei Hsing Huang
Keyword(s):  
Pure Water ◽  
Nitrate Solution ◽  
Concrete Durability ◽  
Calcium Leaching ◽  
Concrete Deterioration ◽  
Ammonium Nitrate Solution ◽  
Cement Mortars ◽  
Concrete Materials ◽  
Calcium Loss

The barrier for low-level radioactive wastes repositories calls for the use of concrete. In a underground situation, the repository may be subject to intrusion of various elements from the external environment and may cause concrete deterioration and reduces its durability. This study focuses on the effect of leaching of concrete as simulated in the laboratory to assess the durability in long term use of concrete materials. The basic mixture of cement, mortar and concrete were used to produce test specimens that were exposed to different conditions such as pure water and substitute ocean water to simulate calcium loss under different circumstances. The possible mechanism of calcium loss and potential influence on concrete durability were then carefully examined. The results of the extensive laboratory experiments show that : (1) concrete materials has better resistance against calcium leaching as compared to mortar and cement paste based on the SEM-EDS measurements on the Ca/Si ratio; (2) the increase in duration of exposure of cement mortars resulted in increases in the porosity of the specimen as exhibited by the decreases of bulk density; (3) microstructural observation showed that mortar samples in ammonium nitrate solution experience accelerated leaching, resulting in the severe deterioration of the region near the exposed surface.

Modelling of Moisture Movement in Wood during Outdoor Storage

2001 ◽  
Vol 6 (2) ◽  
pp. 3-14 ◽  
Author(s):  
R. Baronas ◽  
F. Ivanauskas ◽  
I. Juodeikienė ◽  
A. Kajalavičius
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Climatic Conditions ◽  
Two Dimensional ◽  
Moisture Movement ◽  
Finite Difference Technique ◽  
Long Term Storage ◽  
Space Formulation ◽  
Term Storage

A model of moisture movement in wood is presented in this paper in a two-dimensional-in-space formulation. The finite-difference technique has been used in order to obtain the solution of the problem. The model was applied to predict the moisture content in sawn boards from pine during long term storage under outdoor climatic conditions. The satisfactory agreement between the numerical solution and experimental data was obtained.

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

SETTING A DIAGRAM APPROACH TO CALCULATING VIBRATED, CENTRIFUGED AND VIBROCENTRIFUGED REINFORCED CONCRETE COLUMNS WITH A VARIATROPIC STRUCTURE

2020 ◽  
pp. 22-34
Author(s):  
Л. Р. Маилян ◽  
С. А. Стельмах ◽  
Е. М. Щербань ◽  
М. П. Нажуев
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Section ◽  
Concrete Columns ◽  
Reinforced Concrete Columns ◽  
The Cross ◽  
Concrete Elements ◽  
Diagram Approach

Состояние проблемы. Железобетонные элементы изготавливаются, как правило, по трем основным технологиям - вибрированием, центрифугированием и виброцентрифугированием. Однако все основные расчетные зависимости для определения их несущей способности выведены, исходя из основного постулата - постоянства и равенства характеристик бетона по сечению, что реализуется лишь в вибрированных колоннах. Результаты. В рамках диаграммного подхода предложены итерационный, приближенный и упрощенный способы расчета несущей способности железобетонных вибрированных, центрифугированных и виброцентрифугированных колонн. Выводы. Расчет по диаграммному подходу показал существенно более подходящую сходимость с опытными данными, чем расчет по методике норм, а также дал лучшие результаты при использовании дифференциальных характеристик бетона, чем при использовании интегральных и, тем более, нормативных характеристик бетона. Statement of the problem. Reinforced concrete elements are typically manufactured according to three basic technologies - vibration, centrifugation and vibrocentrifugation. However, all the basic calculated dependencies for determining their bearing capacity were derived using the main postulate, i.e., the constancy and equality of the characteristics of concrete over the cross section, which is implemented only in vibrated columns. Results. Within the framework of the diagrammatic approach, iterative, approximate and simplified methods of calculating the bearing capacity of reinforced concrete vibrated, centrifuged and vibrocentrifuged columns are proposed. Conclusions. The calculation according to the diagrammatic approach showed a significantly better convergence with the experimental data than that using the method of norms, and also performs better when using differential characteristics of concrete than when employing integral and particularly standard characteristics of concrete.

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

Sign in / Sign up

Export Citation Format

Share Document