Influence of Measurement Technique on the Air-Void Structure of Hardened Concrete

10.14359/9779 ◽  
1995 ◽  
Vol 92 (6) ◽  
Keyword(s):  
Measurement Technique ◽  
Hardened Concrete ◽  
Void Structure ◽  
Air Void ◽  
Air Void Structure

Influence of Air Content and Vibration Time on Frost Resistance of Air Entrained Concrete

2013 ◽  
Vol 857 ◽  
pp. 110-115 ◽  
Author(s):  
Xiu Hua Zheng ◽  
Yong Ge ◽  
Jie Yuan
Keyword(s):  
Frost Resistance ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
High Durability ◽  
Void Structure ◽  
Vibration Time ◽  
Air Void ◽  
Air Void Structure ◽  
Air Entrained Concrete

Air-entraining agent turely is one of the necessary compositions of the high durability concrete. The influence of air content and vibration time on the frost resistance of concrete was researched, and air void characteristics of hardened concrete was analysed. The results showed that the air contents could reduce the compressive strengthof hardened concrete excessively, but it made the spacing factor reduce obviously and significantly improve the frost resistance of concrete.The air voids with different structure in concrete were realized by vibration time. It was found that the air void structure and the frost resistance properties were influenced by the vibration time largely. The optimized vibration time is 30s, the appropriate vibration time is 20s~30s, no more than 35s.

scholarly journals Effects of Parameters of Air-Avid Structure on the Salt-Frost Durability of Hardened Concrete

2020 ◽  
Vol 10 (2) ◽  
pp. 632 ◽  
Author(s):  
Hui Zhang ◽  
Peiwei Gao ◽  
Zhixiang Zhang ◽  
Youqiang Pan ◽  
Weiguang Zhang
Keyword(s):  
Frost Resistance ◽  
Fresh Concrete ◽  
Close Correlation ◽  
Hardened Concrete ◽  
Air Content ◽  
Spacing Factor ◽  
Void Structure ◽  
Air Void ◽  
Frost Durability ◽  
Air Void Structure

Through laboratory testing, this research studied the connection between air-void structures of hardened concrete and fresh concrete and discussed the effects of the air-void structure on the salt-frost durability of the concrete. The results demonstrate that, in comparison with fresh concrete, the air-void spacing factor shows a close correlation with hardened concrete air-content and decreases in the form of a power function as the air-content increases. When the fresh concrete air-content is more than 6% and the hardened concrete air-void spacing factor is less than 0.18 mm, the influence of parameters of air-void structure on the salt-frost resistance of the concrete reduces. The air-void spacing factor more significantly affects the salt-frost resistance of the concrete compared with air content and the correlation reaches 0.93. Therefore, air-content and air-void spacing factor are recommended for dual control.

Effect of fine fly ash and calcium hydroxide on air void structure in very-early-strength latex-modified concrete

2015 ◽  
Vol 42 (10) ◽  
pp. 797-807
Author(s):  
Pangil Choi ◽  
Sung Il Jeon ◽  
Kyong-Ku Yun
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Bridge Decks ◽  
Time Frame ◽  
Early Age ◽  
Freeze Thaw ◽  
Void Structure ◽  
Early Strength ◽  
Air Void ◽  
Air Void Structure

Very-early-strength latex-modified concrete (VES-LMC) was developed for rapid repairs of distresses in concrete bridge decks and pavements, with the emphasis on early-age strength gain so that the repaired bridges and pavements can be opened to traffic within the time frame required in the specifications. However, there are two main concerns in the use of VES-LMC — early-age cracking and poor air void structure. The main objective of this study was to further improve VES-LMC to minimize early-age cracking and improve freeze–thaw durability, which included the use of fine fly ash (FFA) and calcium hydroxide (CH). Laboratory experiments were conducted on VES-LMC materials with cement replaced with FFA as well as CH, and various tests performed. Early-age drying shrinkages of VES-LMC containing both FFA and CH in the amounts evaluated in this study were smaller than that of VES-LMC with no replacements. It is expected that the use of FFA and CH in the range evaluated in this study will reduce the cracking potential of VES-LMC. Overall, the replacement of cement with FFA and CH improved the characteristics of entrained air void system, which will enhance the durability of VES-LMC against freeze–thaw damage. Scanning electron microscope and energy dispersive spectroscopy analysis indicate the primary mechanism of the generation of small sized air voids in concretes containing adequate amount of FFA and CH is the gas formation reaction between citric acid solutions and CH during concrete mixing. It is expected that the inclusion of adequate amounts of FFA and CH in VES-LMC will improve the performance of repaired bridge decks and pavements in terms of reduced cracking and improved freeze-thaw durability.

Pore structure of mortars with cellulose ether additions – Study of the air-void structure

2015 ◽  
Vol 62 ◽  
pp. 117-124 ◽  
Author(s):  
Mateusz Wyrzykowski ◽  
René Kiesewetter ◽  
Beat Münch ◽  
Robert Baumann ◽  
Pietro Lura
Keyword(s):  
Pore Structure ◽  
Cellulose Ether ◽  
Void Structure ◽  
Air Void ◽  
Air Void Structure

Investigation on the Property and Air Void Structure of Foamed Cement-Fly Ash-Steel Slag Concrete

2010 ◽  
Vol 150-151 ◽  
pp. 1457-1461 ◽  
Author(s):  
Yong Hao Fang ◽  
Quan Wen ◽  
Pin Dai
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Bulk Density ◽  
Volume Fraction ◽  
Steel Slag ◽  
Close Correlation ◽  
Average Shape ◽  
Void Structure ◽  
Air Void ◽  
Air Void Structure

The properties and void structures of foamed concretes prepared from portland cement, fly ash, steel slag and foam agent were investigated. The results show that substituting cement by steel slag resulted in little change in dry bulk density, but reduced the compressive strength; on the other hand, when cement was substituted with fly ash, though the dry bulk density decreased, the compressive strength increased as the proportion of substitution increased from 30%to 45%. Increasing the volume fraction of the foam decreased greatly the dry bulk density and the compressive strength, and reduced the thermal conductivity as well. Image analysis on the air void structure shows that the larger air void fraction, the larger average void size and lower void roundness. There is a close correlation between the average mean Feret diameter and the average shape factor.

scholarly journals The Flexural Strength and Frost Resistance of Air Entrained Concrete

2012 ◽  
Vol 5 ◽  
pp. 364-369 ◽  
Author(s):  
Xiu Hua Zheng ◽  
Qin Fei Li ◽  
Jie Yuan ◽  
Yong Ge
Keyword(s):  
Flexural Strength ◽  
Frost Resistance ◽  
Test Results ◽  
Key Factors ◽  
Air Content ◽  
Void Structure ◽  
Vibration Time ◽  
Air Void ◽  
Air Void Structure ◽  
Air Entrained Concrete

The flexural strength and frost resistance properties of air entrained concrete were tested in this study. Although the flexural strength of concrete does not change largely with increasing of air content, it still has a maximum value with air content of 4%. The test results show that the frost resistance increase with increasing of air content. In air entrained concrete, the total air content is not the only factor that affect the final properties of the concrete, the air void structure parameters, including void size, shape, and distribution, are key factors as well. It was found that the air void structure and the frost resistance properties were influenced by the vibration time largely. The optimized vibration time is 30s.

Effect of compaction procedure on air void structure of asphalt concrete

Measurement ◽  
2016 ◽  
Vol 90 ◽  
pp. 151-157 ◽  
Author(s):  
Rafiqul A. Tarefder ◽  
Mohiuddin Ahmad
Keyword(s):  
Asphalt Concrete ◽  
Void Structure ◽  
Air Void ◽  
Air Void Structure
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