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 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.

Theoretical and Experimental Research on Compressive Strength of High Fly-Ash Content Concrete

2011 ◽  
Vol 477 ◽  
pp. 257-262 ◽  
Author(s):  
Hong Mei Ai ◽  
Li Jiu Wang ◽  
Jing Wei ◽  
Jun Ying Bai ◽  
Pu Guang Lu
Keyword(s):  
Growth Rate ◽  
Compressive Strength ◽  
Fly Ash ◽  
Ash Content ◽  
Theoretical Formula ◽  
Term Strength ◽  
Single Factor ◽  
Binder Ratio ◽  
Water Binder Ratio

Introduced the concept of “Cementitious Coefficient” of fly ash, theoretical formula of strength of HFCC at a certain age was found with two variables: actual water-binder ratio and micro-aggregate-binder ratio. Development regularity of compressive strength of HFCC was studied and formula of long-term strength coefficient D28t was settled. Influence of actual water-binder ratio and micro-aggregate-binder ratio on long-term strength of HFCC was analyzed. Experimental results showed that along with the single-factor increase of actual water-binder ratio and micro-aggregate-binder ratio, growth rate of long-term strength of HFCC increased; influence of actual water-binder ratio was deeper than that of micro-aggregate-binder ratio.

scholarly journals Influence of slag content and water-binder ratio on leaching behavior of cement pastes

2016 ◽  
Vol 129 ◽  
pp. 61-69 ◽  
Author(s):  
Yu-Juan Tang ◽  
Xiao-Bao Zuo ◽  
Shao-Li He ◽  
Olawale Ayinde ◽  
Guang-Ji Yin
Keyword(s):  
Leaching Behavior ◽  
Cement Pastes ◽  
Binder Ratio ◽  
Water Binder Ratio ◽  
Slag Content

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.

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.

scholarly journals Effects of Different Content of Phosphorus Slag Composite Concrete: Heat Evolution, Sulphate-Corrosion Resistance and Volume Deformation

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1293
Author(s):  
Kuisheng Liu ◽  
Yong Cui
Keyword(s):  
Temperature Rise ◽  
Control Sample ◽  
Drying Shrinkage ◽  
Strength Loss ◽  
Adiabatic Temperature ◽  
Adiabatic Temperature Rise ◽  
Binder Ratio ◽  
L 22 ◽  
Water Binder Ratio

Phosphorus slag (PS) and limestone (LS) composite (PLC) were prepared with a mass ratio of 1:1. The effects of the content of PLC and the water/binder ratio on the mechanical properties, durability and dry shrinkage of concrete were studied via compressive strength, electric flux, sulfate dry/wet cycle method, saturated drainage method, isothermal calorimeter, adiabatic temperature rise instrument and shrinkage deformation instrument. The results show that PLC can greatly reduce the adiabatic temperature rise of concrete. The adiabatic temperature rise is 55 °C with 33 wt.% PLC, 10 °C lower than that of the control sample. The addition in the content of PLC does not affect the long-term strength of concrete. When the water/binder ratio decreases by 0.1–0.15, the long-term strength of concrete with PLC increases by about 10%, compared with the control group. At the age of 360 days, the chloride permeability of L-11 (i.e., the content of PLC was 20%, the water/binder ratio was 0.418) and L-22 (i.e., the content of PLC was 33%, the water/binder ratio was 0.39) decrease to the “very low” grade. The strength loss rate of L-11 and L-22 after 150 sulfate dry/wet cycles is about 18.5% and 19%, respectively, which is 60% of the strength loss rate of the control sample. The drying shrinkage of L-11 and L-22 reduces by 4.7% and 9.5%, respectively, indicating that PLC can also reduce the drying shrinkage.

Effects of calcium leaching on the physical and mechanical properties of aerial lime-cement mortars

2019 ◽  
Vol 17 (3) ◽  
pp. 649-666
Author(s):  
Soufyane Bellifa ◽  
Nadir Boumechra
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Calcium Hydroxide ◽  
Nitrate Solution ◽  
Physical And Mechanical Properties ◽  
Rate Of Change ◽  
Content Type ◽  
Calcium Leaching ◽  
Ammonium Nitrate Solution ◽  
Cement Mortars

Purpose This paper aims to assess the effects of chemically accelerated leaching on the physical and mechanical properties of aerial lime–cement mortars (LCMs). Design/methodology/approach Two aerial LCMs, differencing mainly in their calcium hydroxide content, were degraded by the use of an ammonium nitrate solution as a leaching agent. The leaching effects were studied by evaluating the rate of change in physical (sorptivity and mass loss) and mechanical (flexural and compressive strength) characteristics of aerial LCMs. To quantify the evolution and kinetics of degradation, the leached depth was then characterized at different levels of degradation by means of a phenolphthalein solution. Findings The experimental results showed that the dissolution of binder decreases the mass, alkalinity and strength of aerial LCMs but increases their sorptivity. A linear relationship was derived by plotting the values of leached depth against the square root of immersion time in an aggressive solution. It was found that the leached depth followed diffusion-controlled kinetics. Originality/value It was found that the global loss of compressive strength of aerial LCMs because of complete dissolution of calcium hydroxide can reach up to 80 per cent.

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