scholarly journals Carbonization Law of Fly Ash Concrete under Freeze-Thaw Cycles Based on Image-Pro Plus

2020 ◽  
Vol 44 (6) ◽  
pp. 393-398
Author(s):  
Jing Yuan ◽  
Boxin Zhao ◽  
Zhenqiang Wang ◽  
Yan Liu
Keyword(s):  
Fly Ash ◽  
Linear Relationship ◽  
Concrete Structures ◽  
Ash Content ◽  
Experimental Results ◽  
Freeze Thaw ◽  
Fly Ash Concrete ◽  
Convergence Point ◽  
Research Findings

To understand the influence of freeze-thaw on the carbonization performance of concrete in severe cold areas, this paper conducted experiments to explore the carbonization law of fly ash concrete under freeze-thaw cycles. First, carbonization tests were conducted under different freeze-thaw cycles and fly ash contents; then PS (Photoshop) and IPP (Image-Pro Plus) were adopted to measure the carbonized area and calculate the ratio of carbonized area (RCA). The experimental results showed that, when the fly ash content was between 10% and 30%, RCA increased slowly; when the fly ash content was 20%, the convergence point showed up; when the fly ash content was 0, the air-entrained fly ash concrete had the best resistance to carbonation. With the help of PS and IPP, this paper calculated the RCA more accurately and found that, the freeze-thaw cycles can aggravate carbonization, and there is a linear relationship between carbonization depth and RCA. The research findings in this paper can provide a reference for the durability evaluation and design of concrete structures in severe cold areas.

Carbonation of Fly Ash Concrete and Micro-Hardness Analysis

2011 ◽  
Vol 378-379 ◽  
pp. 56-59 ◽  
Author(s):  
Liu Qing Tu ◽  
Wen Bing Xu ◽  
Wei Chen
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Transition Zone ◽  
Ash Content ◽  
Experimental Results ◽  
Micro Hardness ◽  
Carbonation Depth ◽  
Carbonation Reaction ◽  
Micromechanical Analysis ◽  
Fly Ash Concrete

The effects of carbonation age, fly ash content in the binder and the water to binder ratios on the carbonation depth of fly ash concrete is investigated and the micromechanical properties of the hardened paste and the inter facial transition zone is analyzed with the micro-hardness method. The experimental results show that replacing Portland cement in concrete with fly ash increases the carbonation rate at early ages, while the late age carbonation rate is lowered. Micromechanical analysis shows that the carbonation reaction increases the micro-hardness of the paste and the compactness of the ITZ. For the relative low replacement levels, the width of the ITZ is reduced if the concrete is carbonated.

Experimental Research on Chloride Ingress into Concrete Exposed to Freeze-Thaw Cycles

2013 ◽  
Vol 357-360 ◽  
pp. 621-625
Author(s):  
Si Jia Chen ◽  
Xiao Bing Song ◽  
Xi La Liu
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Experimental Research ◽  
Salt Solution ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Ash Content ◽  
Experimental Results ◽  
Chloride Ingress ◽  
Freeze Thaw

The most important mechanism of deterioration occurring in concrete in the cold regions are chloride ingress and freeze-thaw cycles. In this paper, the process of chloride ingress into concrete exposed to freeze-thaw cycles is experimentally researched. From the experimental results, it appears that freeze-thaw cycles make the effective diffusion coefficient become bigger. As w/c ratio increasing and fly ash content decreasing, the effective diffusion coefficient increases. The concentration of salt solution has little influence on the effective diffusion coefficient of concrete.

Study on the Influence of Freeze-Thaw on the Carbonation Property of Fly Ash Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 939-943 ◽  
Author(s):  
Jian Gang Niu ◽  
Liang Yan ◽  
Hai Tao Zhai
Keyword(s):  
Fly Ash ◽  
Laboratory Simulation ◽  
Influence Coefficient ◽  
Carbonation Depth ◽  
Freeze Thaw ◽  
Fly Ash Concrete ◽  
Concrete Carbonation ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

Based on the coupling testing program of freeze-thaw and carbonation, the laboratory simulation test is carried out. The laws of carbonation depth of the fly ash concrete suffered the freeze-thaw cycle in different test modes and the influence of fly ash dosage on concrete carbonation depth after the freeze-thaw cycle are studied. Defining the influence coefficient of the freeze-thaw cycles on carbonation depth of concrete, the mechanism of coupling of freeze-thaw and carbonation is analyzed,and the role of freeze-thaw and carbonation in the coupling process are obtained.

Fly-Ash Concretes of 50% of the Replacement Ratio to Reduce the Cracking in Concrete Structures

2013 ◽  
Vol 405-408 ◽  
pp. 2665-2670 ◽  
Author(s):  
Ming Jie Mao ◽  
Qiu Ning Yang ◽  
Wen Bo Zhang ◽  
Isamu Yoshitake
Keyword(s):  
Fly Ash ◽  
Concrete Structures ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Early Age ◽  
Replacement Ratio ◽  
Fly Ash Concrete ◽  
Massive Concrete ◽  
Normal Strength

Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

Influence of Mixture Proportion and Curing Condition on Contribution of Fly Ash to Strength of Concrete

2006 ◽  
Vol 302-303 ◽  
pp. 235-241 ◽  
Author(s):  
F.-R. Wu ◽  
Yoshihiro Masuda ◽  
S. Nakamura ◽  
S. Sato
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Cement Content ◽  
Ash Content ◽  
K Value ◽  
Fly Ash Concrete ◽  
Curing Condition ◽  
Strength Difference

To investigate the strength efficiency of fly ash in concrete, the contribution of fly ash to strength, k value was calculated with the equation: the strength difference between fly ash concrete and control concrete with no fly ash due to the different fly ash content divides by the strength difference between both control concrete with no fly ash due to the different cement content which equals to the former different fly ash content. The k values were organized with fly ash specific surface area, concrete curing condition and age of specimens. Based on a large number of data collected from several proceedings and journals published in Japan during 1981 to 2003, the influences of fly ash property, mixture proportion and curing condition on k value were investigated. Within the range of study the following observations were made: (1) When fly ash concrete kept in moist curing, the k value of fly ash with specific surface area from 250 to 500 m2/kg is averagely 0.5 to 0.6 or higher at an age of 91 days and later, whereas that of fly ash with specific surface area from 150 to 250 m2/kg is around 0.4 to 0.5, and with some cases contributing little to the strength. (2) In the range of a portland cement content of 250 to 450 kg/m3, the strength contribution tends to increase as the cement content increases. (3) The contributions of fly ash to strength at 91 and 364 days are 1.44 to 1.97 times as large as those at 28 days, respectively, by standard curing, but conversely decrease to 0.75 to 0.79 times those at 28 days by air curing.

scholarly journals Carbonation Depth Model and Prediction of Hybrid Fiber Fly Ash Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jing-shuang Zhang ◽  
Meng Cheng ◽  
Jian-hua Zhu
Keyword(s):  
Fly Ash ◽  
Polypropylene Fiber ◽  
Basalt Fiber ◽  
Ash Content ◽  
Prediction Formula ◽  
Hybrid Fiber ◽  
Carbonation Depth ◽  
Weakly Alkaline ◽  
Fly Ash Concrete ◽  
Steel Bar

The concrete is weakly alkaline, the alkalinity of the concrete will be reduced after being carbonized, and the protective effect of the concrete on the steel bar will be weakened, even leading to corrosion of the steel bar. In this paper, fly ash is used to replace cement in the same amount, and basalt fiber and polypropylene fiber are added in a certain amount to make hybrid fiber fly ash concrete. Through rapid carbonation test, the influence of carbonation time and fly ash content on carbonation performance of hybrid fiber fly ash concrete is studied. The curve is fitted according to a single factor carbonation model with fly ash content as the main parameter, and the fitting curve and prediction formula are obtained. The results show that, in the same carbonization time, compared with the concrete without fly ash, the concrete with fly ash content of 5%, 10%, 20%, and 30% has average carbonization depth promotion rates of 6.4%, 14.9%, 59.8%, and 73.5%. When the fly ash content varies in the range of 10%∼20%, the carbonation resistance of hybrid fiber concrete changes most sensitively. At the same fly ash content, with the increase of carbonization time, the carbonization depth of concrete increases by 41.7%∼62.3%; Through the verification of the fitting curve and fitting formula obtained after fitting, it is concluded that the error of the prediction formula of carbonation depth of hybrid fiber fly ash concrete is within 9.1%, and the error of carbonation depth of 14 d and 28 d is within 4.3%. Replacing cement with fly ash has certain engineering significance and can achieve the purpose of recycling waste materials.

Effect of High Volumes of Fly Ash on Flowability and Drying Shrinkage of Engineered Cementitious Composites

2011 ◽  
Vol 675-677 ◽  
pp. 61-64
Author(s):  
Yu Zhu ◽  
Ying Zi Yang ◽  
Yan Yao
Keyword(s):  
Fly Ash ◽  
Drying Shrinkage ◽  
Ash Content ◽  
Experimental Results ◽  
Replacement Ratio ◽  
Slump Flow ◽  
Binder Ratio ◽  
Deformation Test ◽  
Flow Deformation ◽  
Water Binder Ratio

In order to investigate flowability and drying shrinkage of ECC, mini-slump flow deformation test and drying shrinkage are employed to analyse the influence of fly ash on the flowability and shrinkage of ECC. The water-binder ratio is kept at 0.25. The replacement ratio of cement by fly ash is 50%, 60%, 70% and 80%, respectively. The experimental results show that fluidity of fresh cment paste increases obviously as the fly ash becomes larger. The drying shrinkage of ECC specimens is greatly reduced as the content of fly ash increases from 50% to 80%. The measured drying shrinkage strian of ECC specimens with 80% fly ash at 28 days is less than 1000×10-6. 25% reduction of drying shrinkage of ECC is found when the fly ash content increases from 50% to 80%.

Estimating the Importance Degree of Influence Factors on Concrete Durability Based on Rough Set Theory

2014 ◽  
Vol 988 ◽  
pp. 191-194
Author(s):  
Xiao Ping Su ◽  
Hao Yue Sun
Keyword(s):  
Fly Ash ◽  
Set Theory ◽  
Rough Set ◽  
Loss Rate ◽  
Elasticity Modulus ◽  
Rough Set Theory ◽  
Ash Content ◽  
Concrete Durability ◽  
Freeze Thaw ◽  
Air Content

Under the saline soil environment in the western area of Jilin Province, the concrete durability is affected by a lot of factors, which include wet-dry cycles, freeze-thaw cycles, wet-dry and freeze-thaw cycles, salt soaking time, salts concentration, fly-ash content, air content. These factors impact on the durability of concrete is uncertain, and there may be a problem of duplicate action, with some roughness characteristics. In this article, the rough set theory is used to analyze the degree that these seven factors affect the concrete durability, and to calculate weights. In this article, the loss rate of dynamic elasticity modulus is looked as the evaluation index of concrete durability. The results show that: the importance degrees of 7 factors influencing the loss rate of concrete dynamic elasticity modulus in order are: wet-dry and freeze-thaw cycles > wet-dry cycle > freeze-thaw cycles > multiple salts concentration > air content > long-term soak > fly-ash content.

Evaluation of Relations among Basic Mechanical Properties of Fly-Ash Concrete with Machine-Made Sand

2013 ◽  
Vol 438-439 ◽  
pp. 15-19
Author(s):  
Chun Jie Liu ◽  
Chun Yan Jia ◽  
Chang Yong Li
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
Concrete Structures ◽  
Ordinary Concrete ◽  
Strength Grade ◽  
Fly Ash Concrete ◽  
Axial Compressive Strength

Although the machine-made sand was widely used for concrete in recent years in China, it was short of studies on the relations among the basic mechanical properties of fly-ash concrete with machine-made sand (MSFAC). However, these relations such as the compressive strength, the tensile strength and the elastic modulus with the cubic compressive strength (i.e. strength grade) are the basis of design for concrete structures. This paper summarizes the test data from the published references, and discusses the relations among these properties by statistical analyses compared with those of ordinary concrete. The results show that only the tensile strength of MSFAC can be safely forecasted by the same formula of ordinary concrete specified in current Chinese design code. When the strength grade is higher than C45, the axial compressive strength of MSFAC is largely forecasted by the formula of ordinary concrete. The elastic modulus of MSFAC is larger than that of ordinary concrete, which should be prospect by the formula in this paper. This work gives out some cautions for the proper use of the MSFAC in concrete structures.

scholarly journals Life cycle sustainability assessment of fly ash concrete structures

2017 ◽  
Vol 80 ◽  
pp. 1162-1174 ◽  
Author(s):  
JingJing Wang ◽  
YuanFeng Wang ◽  
YiWen Sun ◽  
Danielle Densley Tingley ◽  
YuRong Zhang
Keyword(s):  
Life Cycle ◽  
Fly Ash ◽  
Sustainability Assessment ◽  
Concrete Structures ◽  
Life Cycle Sustainability Assessment ◽  
Fly Ash Concrete
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