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.

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.

scholarly journals Mechanical Properties of High Volume Fly Ash Concrete Reinforced with Hybrid Fibers

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Rooban Chakravarthy ◽  
Srikanth Venkatesan ◽  
Indubhushan Patnaikuni
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Polypropylene Fiber ◽  
Basalt Fiber ◽  
High Volume ◽  
Single Type ◽  
Hybrid Fibers ◽  
Brittle Behavior ◽  
Fly Ash Concrete ◽  
High Volume Fly Ash

Fly ash substitution to cement is a well-recognized approach to reduce CO2emissions. Although fly ash concrete is prone to brittle behavior, researchers have shown that addition of fibers could reduce brittle behavior. Previous research efforts seem to have utlised a single type of fiber or two types of fibers. In this research, three types of fibers, steel, polypropylene, and basalt as 0%, 0.50%, 0.75%, and 1% by volume of concrete, were mixed in varying proportions with concrete specimens substituted with 50% fly ash (class F). All specimens were tested for compressive strength, indirect tensile strength, and flexural strength over a period of 3 to 56 days of curing. Test results showed that significant improvement in mechanical properties could be obtained by a particular hybrid fiber reinforcement combination (1% steel fiber, 0.75% polypropylene fiber, and 0.75% basalt fiber). The strength values were observed to exceed previous research results. Workability of concrete was affected when the fiber combination exceeded 3%. Thus a limiting value for adding fibers and the combination to achieve maximum strengths have been identified in this research.

scholarly journals Mechanical and Dynamic Properties of Hybrid Fiber Reinforced Fly-Ash Concrete

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Dan-Yang Su ◽  
Jian-Yong Pang ◽  
Xiao-Wen Huang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Dynamic Compression ◽  
Basalt Fiber ◽  
Splitting Tensile Strength ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Fly Ash Concrete

In order to explore the influence of basalt-polypropylene hybrid fiber on the static mechanical properties and dynamic compression properties of fly-ash concrete, 16 groups of basalt-polypropylene hybrid fiber fly-ash concrete (HBPC) and 1 group of benchmark concrete were designed and prepared. The slump, static compressive strength, static splitting tensile strength, and dynamic compressive performance tests were tested. At the same time, the mechanism of the mechanical properties of hybrid fiber reinforced fly-ash concrete was analyzed by means of scanning electron microscopy (SEM). The results show that the failure of the benchmark concrete is mainly brittle failure. Compared with the benchmark concrete, the static compressive strength and splitting tensile strength of HBPC are significantly enhanced. Basalt-polypropylene hybrid fiber, polypropylene fiber, and basalt fiber, are extremely significant factors affecting the slump, static compressive strength, and static splitting tensile strength of HBPC, respectively. The peak stress of the benchmark concrete and HBPC increases with the increase of the loading air pressure, showing a certain strain rate effect. SEM shows that the fibers have good dispersibility in the concrete and good adhesion with the concrete matrix interface, but excessive fibers will cause fiber agglomeration, which increases the internal defects of HBPC.

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.

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.

Variation of Carbonation Coefficient of Pumping Concrete with Moist-Curing Time at early Ages and Fly-Ash Content

2011 ◽  
Vol 287-290 ◽  
pp. 899-905
Author(s):  
Qing Ye ◽  
Zhi Wei Song ◽  
Guo Rong Yu
Keyword(s):  
Fly Ash ◽  
Concrete Cover ◽  
Ash Content ◽  
Curing Time ◽  
Accelerated Carbonation ◽  
Carbonation Depth ◽  
Carbonation Resistance

Based on accelerated carbonation test, the variation of carbonation resistance of pumping concrete (C40 grade) with moist-curing time at early ages and fly-ash content was studied. Results indicate that the carbonation coefficient and the accelerated carbonation depth of the concrete increased obviously with a reduction in the moist-curing time at early ages and with an increase in the fly-ash content. For example, in conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at 20 0C with above 95% RH at early ages and then 0, 21, 25, 26 and 27 d air curing at 20 0C with 60% RH, respectively, carbonation coefficients of the concrete incorporated with 30% fly-ash were 2.04, 2.49, 3.16, 3.86 and 5.42 mm/a0.5 respectively, and thus it can be seen that the calculated times when concrete cover (25 mm) was completely carbonated naturally in now atmosphere (0.04% CO2) were 164, 104, 66, 44 and 21 years respectively. The results suggest that for the carbonation resistance of the C40 concrete incorporated with up to 30% fly-ash, the moist-curing time of 7 days at early ages should be necessary.

Research on the Variation of pH Value of the Ordinary Concrete and Fly Ash Concrete in the Carbonation Process

2011 ◽  
Vol 374-377 ◽  
pp. 1934-1937 ◽  
Author(s):  
Guang Zheng Qi ◽  
Di Tao Niu ◽  
Cheng Fang Yuan ◽  
Fu Zhen Duan
Keyword(s):  
Fly Ash ◽  
High Performance ◽  
Ph Value ◽  
Economic Benefits ◽  
Carbonation Depth ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Ordinary Concrete ◽  
Fly Ash Concrete ◽  
Carbonation Process

The accelerated carbonation test was carried out for the ordinary concrete and fly ash concrete. Influences of water-cement ratio, carbonation age and fly ash content on pH value were researched. The results show that carbonation depth, including incomplete carbonized zone, can be effectively reduced by reducing water-cement ratio. So lower water-cement ratio means high performance of resistance of carbonate. The use of fly ash can optimize concrete pore morphology, it’s beneficial for anti-carbonation. However, It disadvantageous to anti-carbonation because of less carbonation material. By taking appropriate mixture of fly ash we can not only enhance the anti-carbonation ability of concrete, but also reduce the use of cement to get well economic benefits.

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