REVIEW ON THE IMPACT OF AIR ENTRAINTMENT ON THE PROPERTIES OF CONCRETE STRUCTURES (original) (raw)
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Effect of Air Entrainment on Compressive Strength, Density, and Ingredients of Concrete
The micro air bubbles in concrete mix act as fine aggregates which lead to reduction of the aggregates. The reduction of fine aggregates will cause reduction of water required for concrete mix without impairing the strength of concrete mix. This reduction has to be considered in designing an air entrained concrete mix. Theoretical (equations) and experimental study have been carried out to study the effect of air entrainment on compressive strength, density and ingredients of fresh concrete mix. During all the study, water cement ratio (w/c) was maintained constant at 0.5 to study the affection of air entrainment (a %) on concrete mix. The results have shown substantial decreasing in cement, water, aggregates and concrete density followed with decreasing in compressive strength of concrete. The results of this study has given more promising to use it as a guide for concrete mix design to choose the most appropriate concrete mix design economically.
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The paper presents the evaluation of the influence of calcium sulfate on the air void microstructure in concrete and its action mechanism depending on the character of the air-entraining agent. Gypsum dehydration has been previously proven to negatively influence the air void structure of air-entrained concrete. Ettringite, nucleating from tricalcium aluminate and calcium sulfate, influences the adsorption and mode of action of anionic-based polycarboxylate ether admixtures. The authors suspected the admixture’s air-entraining mechanism was also affected by these characteristics. Gypsum dehydration was confirmed to influence the air void structure. In the case of the anionic surfactant, the content of air bubbles smaller than 300 µm was lower compared to cement with gypsum and hemihydrate. On the other hand, the content of air voids with a diameter up to 60 µm, which are the most favorable, was higher. The results obtained led to the conclusion that the mechanism of air entrainment ...
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This document reports the results of a comprehensive study pertaining to the determination of causes and mechanisms resulting in a reduction of strength in concrete mixtures containing Synthetic air entraining admixtures. The study involved experimentation with concrete mixtures containing both the Synthetic and Vinsol resin admixtures. Tests involved determination of air content for fresh concrete and air bubble characteristics including size and distribution for hardened concrete. Compressive strength of concrete samples were determined at ages 7, 14, 28 & 56 days. Petrographic analysis of the hardened samples revealed that the Vinsol resin admixture produces more of the smaller bubbles desirable for protection against frost. However, Synthetic admixtures induce more of the larger air bubbles with the cement paste. This explains the much lower compressive strength associated with Synthetic air concretes. It is believed that the larger air bubbles are produced due to the inability of the Synthetic air entraining agents to lower the surface tension in the mixture. This will allow the smaller air bubbles to coalesce into larger ones. Based on the results of the study, recommendations were made that follow up research should involve determination of surface tension in such mixtures. synthetic air, resin admixtures, strength reduction, concrete
AIR-ENTRAINED CONCRETE KATHAN PATEL
Air entrained concrete is an ordinary concrete having added air bubbles entrapped intentionally in it. Air entrained concrete has less strength but also has less weight than ordinary concrete. Air entrained concrete helps reduce the roof's weight and can help to save material used in building the load-bearing structure below the roof; it can resist the freeze and thaw cycles more compared to the ordinary concrete and can impart more workability in less water-cement ratio. One solution of sloped roofing Mangalore tiles can be replaced with air-entrained concrete tiles that can make the roofing system more efficient. The ingredients used to make air-entrained concrete were Ordinary Portland Cement (OPC), water, airentraining admixture, internal waterproofing agent, silica sand, and Alkali Resistant glass fiber. An agitating machine was used to produce foam for the dry mix of cement and sand. A semi-automatic machine was used to make a wet mixture. The mixture was tried with different proportions of the ingredients to find the most suitable mixture. The targeted properties of Aire Entrained tiles are durability, heaviness, and temperature resistance.
Characteristics of concrete mix air-entrainment applying the sequential pressure method
Roads and bridges - Drogi i mosty, 2020
The purpose of introducing air into the concrete mix is to increase the freeze-thaw and scaling resistance of hardened concrete. The utility of the sequential pressure method ( Super Air Meter - SAM) for assessment of the air entrainment quality was verified by comparing the results obtained with this method with the results of the air-void analysis of hardened concrete. The results of the tests carried out on mixes designed and produced at a laboratory and the mixes produced on an industrial scale during expressway construction are considered. Furthermore, the relationships between the SAM number and the micro air-void content A 300 in hardened concrete and the freeze-thaw and de-icing salt resistance are analysed as part of this research. A clear co-relation between the SAM number, a parameter that characterises the air-entrainment of the concrete mix, and the microvoid content has been demonstrated.
Characterization of air entraining admixtures in concrete using surface tension measurements
Cement and Concrete Composites, 2017
Air entraining admixtures (AEA) are generally used to increase the workability and resistance to freezing and thawing in concrete. These admixtures generate air bubbles with diameters ranging from 10 µm to < 1 mm, providing spaces for the expansion of ice, and therefore facilitate frost protection. In this study, performances of AEAs were investigated based on surface tension measurements, accounting for the effect of AEAs on surface tension. For this purpose, a new test method was developed which depends on surface tension measurements according to the Du Nouy ring method. All types of AEAs used in the scope of this research presented a substantial influence on the surface tension. It was observed that a significant relationship between the air void system and surface tension exists. The surface tension method was found as a useful tool to determine the AEA type and content to obtain the desired air void system in concrete.
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
Air entrained concrete can be produced by introducing suitable air-entraining agent, one such commonly available material in India is hydrogen peroxide which is being used in my experimental work. The primary objective of this study to find the appropriate amount of hydrogen peroxide (3%) for strength and density, water absorption, other properties of concrete. For which the amount of H2O2 is varied from 0 %, 2.5%, 5%, and 7.5% H2O2 by weight of 100 kg of cement. The test which was carried out in the experimental work were density, workability, strength, water absorption, the slump of air-entrained concrete and aggression resistance of air-entrained concrete against an acid attack such as H2SO4, etc. Total 48 No. of the concrete cube was cast for the experimental work. The result of the experiment work shows if H2O2 is used in the range of 5-6% it will provide better workability, less water absorption and improved resistance against acid attack with acceptable 5-7% decrease in compressive strength I. INTRODUCTION A. General Cement concrete is perhaps the most widely construction material across the world. Advances in construction methods and a better understanding of concrete engineering has led to concrete being used in more challenging and harsher conditions. There is also a growing realization that concrete is not a maintenance free material. At the same time, several cases of premature deterioration have also been reported. These factors have led to a lot of research in diverse areas related to durability of concrete structures. The present work is also an effort to improve the understanding of the role of special absorbing formwork in improving the quality of concrete close to the surface (referred to as 'near surface concrete'), and thereby contributing to the durability of the structure.
Quality assurance and quality control of air entrained concrete
Cement and concrete …, 1994
It is generally recognized that the air void structure of concrete is a critical parameter for the durability of concrete subjected to frost/thaw action and deicing salts. In the first part of this article an overview is given of the different methods characterizing the air void structure in fresh and hardened concrete. The calculation of the parameters from a traditional air void analysis following ASTM C 457 is compared with more advanced calculation methods on results obtained from point, chord, diameter and area measurements. A new parameter is formulated which characterizes the spacing between the air bubbles more precisely.