Effect of Carbonation on the Microstructure of Concrete Containing Fly Ash and Expansive Admixture

2011 ◽  
Vol 347-353 ◽  
pp. 4074-4080
Author(s):  
Liu Qing Tu ◽  
Zhong He Shui ◽  
Wei Chen ◽  
Wen Bing Xu ◽  
Jun Tao Ma
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Hydration Product ◽  
Dsc Analysis ◽  
Accelerated Carbonation ◽  
Carbonation Reaction ◽  
Carbonation Process ◽  
Internal Pore Structure ◽  
Internal Pore

The effects of carbonation on the microstructure of concrete containing fly ash and expansive admixture are investigated in this paper. Eight mix proportions of the concrete are designed in the experiment with the different replacement levels of the Portland cement with the fly ash and the expansive admixture. The specimens cured in accelerated carbonation condition for 3 days, 7 days and 28 days are used for macro and micro tests. MIP test is used to analyze the influence on internal pore structure of concrete by carbonation reacts. The changes of Ca(OH)2 and CaCO3 contents are measured with TG/DSC analysis. The results indicate that carbonation reaction can make concrete denser. Replacing Portland cement with fly ash and expansive admixture increases the carbonation rate of concrete and fly ash blended in concrete can improve the pore structure of concrete. Apart from the reaction of Ca(OH)2 and CO2, the carbonation reaction of other hydration product also exit in the accelerated carbonation process.

scholarly journals Effect of CaSO4 Incorporation on Pore Structure and Drying Shrinkage of Alkali-Activated Binders

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1673 ◽  
Author(s):  
Hyeongmin Son ◽  
Sol Moi Park ◽  
Joon Ho Seo ◽  
Haeng Ki Lee
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Drying Shrinkage ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
Activated Slag ◽  
Capillary Tension ◽  
Alkali Activated Binders ◽  
Internal Pore Structure ◽  
Alkali Activated

This present study investigates the effects of CaSO4 incorporation on the pore structure and drying shrinkage of alkali-activated slag and fly ash. The slag and fly ash were activated at a 5:5 ratio by weighing with a sodium silicate. Thereafter, 0%, 5%, 10%, and 15% of CaSO4 were incorporated to investigate the changes in phase formation and internal pore structure. X-Ray Diffraction (XRD), thermogravimetry (TG)/derivative thermogravimetry (DTG), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and drying shrinkage tests were carried out to find the correlation between the pore structure and drying shrinkage of the specimens. The results showed that CaSO4 incorporation increased the formation of thenardite, and these phase changes affected the pore structure of the activated fly ash and slag. The increase in the CaSO4 content increased the pore distribution in the mesopore. As a result, the capillary tension and drying shrinkage decreased.

Change of internal/pore structure in alumina green body during initial sintering

1992 ◽  
Vol 27 (24) ◽  
pp. 6609-6614 ◽  
Author(s):  
Jin-Young Kim ◽  
Masayori Miyashita ◽  
Nozomu Uchida ◽  
Keizo Uematsu
Keyword(s):  
Pore Structure ◽  
Green Body ◽  
Internal Pore Structure ◽  
Internal Pore

scholarly journals Effects of Mixing and Curing Temperature on the Strength Development and Pore Structure of Fly Ash Blended Mass Concrete

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Ki-Bong Park ◽  
Takafumi Noguchi
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Weather Conditions ◽  
Strength Loss ◽  
Curing Temperature ◽  
Strength Development ◽  
Mass Concrete ◽  
Term Strength

The aim of this work is to know clearly the effects of temperature in response to curing condition, hydration heat, and outside weather conditions on the strength development of high-performance concrete. The concrete walls were designed using three different sizes and three different types of concrete. The experiments were conducted under typical summer and winter weather conditions. Temperature histories at different locations in the walls were recorded and the strength developments of concrete at those locations were measured. The main factors investigated that influence the strength developments of the obtained samples were the bound water contents, the hydration products, and the pore structure. Testing results indicated that the elevated summer temperatures did not affect the early-age strength gain of concrete made using ordinary Portland cement. Strength development was significantly increased at early ages in concrete made using belite-rich Portland cement or with the addition of fly ash. The elevated temperatures resulted in a long-term strength loss in both belite-rich and fly ash containing concrete. The long-term strength loss was caused by a reduction in the degree of hydration and an increase in the total porosity and amount of smaller pores in the material.

scholarly journals The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

2021 ◽  
Author(s):  
Bassili Guirguis ◽  
Medhat Shehata ◽  
Josée Duchesne ◽  
Benoît Fournier ◽  
Benoît Durand ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Heat Of Hydration ◽  
Iron Sulphide ◽  
Oxidizing Agent ◽  
Field Exposure ◽  
Bar Test ◽  
Reactive Alumina ◽  
Mortar Bar

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

Diffusion and Pore Structure in Portland Cement Pastes Blended with Low Calcium Fly Ash

1985 ◽  
Vol 65 ◽  
Author(s):  
Amitabha Kumar ◽  
Della M. Roy
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Pore Size ◽  
Size Distributions ◽  
Cation Diffusion ◽  
Cement Pastes ◽  
Effective Coefficients ◽  
Pore Size Distributions ◽  
Diffusion Rates

ABSTRACTEffective coefficients for the diffusion of Cs+ and Cl− ions accross hardened plates of Portland cement and Portland cement-fly ash blend pastes were measured at 27°, 38° and 60° for samples cured up to 28 d. The porosity and pore size distributions of the same hardened plates were also determined. The fly ash blends show lower anion and cation diffusion rates at higher temperatures, although the porosity is not significantly different from the neat paste. The finer pore size is considered responsible for the slower diffusion in the blends. The electronegative nature of the pore surfaces also contributes to the slower cation diffusion.

Carbonation Behavior of Concrete in Cyclic Wetting-Drying Environment

2012 ◽  
Vol 450-451 ◽  
pp. 126-130
Author(s):  
Jun Tao Ma ◽  
Zhong He Shui ◽  
Wei Chen ◽  
Xiao Xing Chen
Keyword(s):  
Pore Structure ◽  
Structure Analysis ◽  
Standard Condition ◽  
Experimental Results ◽  
Hardened Concrete ◽  
Carbonation Depth ◽  
Carbonation Reaction ◽  
Carbonation Process ◽  
Drying Condition ◽  
Curing Condition

The cyclic wetting-drying environment affects the internal microstructure and durability of hardened concrete. The carbonation behavior of concrete in cyclic wetting-drying condition and standard condition is investigated in this study. The concrete specimens are designed with different contents of mixed mineral and carbonated in different curing condition. The carbonation depth is tested to study the carbonation process in combination of pore structure analysis and microstructural observations. The experimental results show that the carbonation reaction of concrete in cyclic wetting-drying condition proceeds more rapidly. When mixed mineral is added, difference in the curing condition shows less effect on the carbonation behavior of concrete.

The Influence on the Concrete Durability in Bleed Air Performance Caused by Concrete Admixture

2013 ◽  
Vol 690-693 ◽  
pp. 767-770
Author(s):  
Yu Xian Zheng ◽  
Xun Guo Zhu
Keyword(s):  
Pore Structure ◽  
Frost Resistance ◽  
Performance Test ◽  
Concrete Durability ◽  
Air Content ◽  
Environmental Actions ◽  
Internal Pore Structure ◽  
Internal Pore

The article issued the influence on concrete durability caused by concrete admixture, based on the further study on concrete admixture bleed air performance test, and researched the influence on concrete durability caused by it. The experiments show that the admixtures of air-entraining performance improve internal pore structure of concrete and increase the compacting condition concrete. Concrete admixture also can improve the impermeability of concrete frost resistance and improve the resistance to environmental actions, and proposed concrete air content of the Dalian region suitable value.

scholarly journals Study on the Process and Characteristics of Clogging for Ceramic Permeable Brick

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zizeng Lin ◽  
Hai Yang ◽  
Huiming Chen
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Pore Structure ◽  
Size Distribution ◽  
Permeability Coefficient ◽  
Simulated Rainfall ◽  
Experimental Conditions ◽  
Internal Pore Structure ◽  
Internal Pore ◽  
Insight Into

A ceramic permeable brick was selected for study in a device that was designed to fully investigate the process and characteristics of clogging in permeable bricks. In order to evaluate the permeability influenced by clogging, a simulated rainfall was filtered through the permeable brick placed in an innovative device. The macroscopic and microscopic changes in the brick and the filtrate were all measured to fully investigate the causes and process of clogging. Then, the mechanism of clogging in the permeable brick pores was further discussed. The results showed that the clogging risk of permeable brick was extremely high, and it can result in a complete clogging in only 5–10 years under the experimental conditions. The permeability coefficient and porosity both decreased exponentially with the increase in filtrate, which was attributed to the clogging of the internal pore structure due to particle interception. The chord size distribution results stressed that the blockage mainly occurred in the upper layer pores in the range of 0.5–1.5 mm, which is relatively sensitive to clogging due to the particle size distribution in rain water. The particle size distribution of the influent and effluent indicated that the clogging process could completely remove particles larger than 88 µm but showed variable removal efficiency for particles with sizes of 20–88 µm. This research offers new insight into the clogging of permeable bricks and provides theoretical guidance for restoring the brick permeability.

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