scispace - formally typeset
Search or ask a question
Topic

Air entrainment

About: Air entrainment is a research topic. Over the lifetime, 3064 publications have been published within this topic receiving 39470 citations.


Papers
More filters
Book
01 Jan 1978
TL;DR: In this article, the authors provide an overview of concrete mixtures with information on the types, mode of action, effect and application of the major types of chemical admixtures in the following sections: water-reducing agents, air-entraining agents, concrete waterproofers; accelerators; application of admixtures; and, analysis of hardened concrete for admixture type and quantity.
Abstract: Following the substantial increase in the use of chemical admixtures in concrete, the book provides information on materials of this type. Details are given of the specification, use and design of concrete mixtures with information on the types, mode of action, effect and application of the major types of chemical admixtures in the following sections: water-reducing agents; air-entraining agents; concrete waterproofers; accelerators; application of admixtures; and, analysis of hardened concrete for admixture type and quantity. (TRRL)

431 citations

01 Jan 1950
TL;DR: In this article, the authors investigated the effect of infrained air on VOID SPACING and found that VOIDS need to be sufficiently well-spaced to prevent failure of simulated pasting.
Abstract: ACCORDING TO THE HYDRAULIC-PRESSURE HYPOTHESIS OF FROST ACTION ON CONCRETE, THE EFFECTIVENESS OF ENTRAINED AIR DEPENDS ON VOID SPACING. THE THEORETICAL MAXIMUM PERMISSIBLE SPACING IS FOUND ANALYTICALLY TO BE A FUNCTION OF PASTE PROPERTIES, DEGREE OF SATURATION OF THE PASTE, AND RATE OF COOLING. APPLIED TO EXPERIMENTAL DATA FROM SIX DIFFERENT PASTES, COOLED AT 20 F. PER HOUR, THE THEORETICAL CALCULATIONS GAVE SPACING FACTORS RANGING FROM 0.01 TO 0.026 IN. OR MORE, DEPENDING ON PASTE CHARACTERISTICS AND VOID SIZE. A SPACING FACTOR FOR THE VOIDS IN HARDENED CONCRETE, AS WELL AS THE TOTAL VOLUME OF AIR, CAN BE CALCULATED FROM DATA OBTAINABLE BY THE LINEAR TRANSVERSE METHOD. THE NECESSARY MATHEMATICAL RELATIONSHIPS ARE GIVEN IN THIS PAPER. THE ACTUAL MAXIMUM SPACING FACTOR FOR CERTAIN FROST RESISTANT CONCRETES WAS ESTIMATED TO BE ABOUT 0.01 IN., A RESULT CONSIDERED TO BE IN EXCELLENT AGREEMENT WITH THAT OBTAINED FROM THE THEORETICAL CALCULATIONS. THE AIR REQUIREMENT IS THAT AMOUNT THAT MEETS THE SPACING REQUIREMENTS. IN GENERAL, THE AIR REQUIREMENT FOR A GIVEN RATE OF COOLING DEPENDS UPON THE PASTE CONTENT, THE SPECIFIC SURFACE OF THE VOIDS, AND THE MAXIMUM PERMISSIBLE SPACING FACTOR. WHEN VOIDS ARE TOO WIDELY SPACED TO PREVENT FAILURE OF SATURATED PASTE, FAILURE WILL ALSO OCCUR AT MOISTURE CONTENTS BELOW SATURATION. WITHIN LIMITS, THE DENSER THE PASTE THE LOWER THE DEGREE OF SATURATION AT FAILURE. /AUTHOR/

412 citations

Journal ArticleDOI
TL;DR: In this paper, the authors synthesize available literature and field experience and provide a framework for understanding the fundamental aspects of air entrainment in concrete, such as concrete temperature, the physical and chemical characteristics of constituent materials, and mixing and placing techniques.

390 citations

Journal ArticleDOI
TL;DR: In this article, an overview of the influence of various types of viscosity-enhancing admixture on high-range water reducer demand, resistance to water dilution, static and forced bleeding, segregation, settlement, setting time and air entrainment is presented.
Abstract: Viscosity-enhancing admixtures, also known as anti-washout admixtures, are water-soluble polymers that increase the viscosity and cohesion of cement-based materials. Such enhancement of the liquid-phase viscosity is essential in flowable systems in order to reduce the rate of separation of material constituents and improve the homogeneity and performance of the hardened product. Viscosity-enhancing admixtures are mostly used along with a high-range water reducer to obtain a highly fluid, yet cohesive cement-based material that can flow readily into place with minimal separation of the various constituents of different densities and minimal intermixing with the surrounding water whenever cast under water. This paper reviews the types and modes of action of commonly used viscosity-enhancing admixtures and highlights their influence on the rheological properties of water and cement paste. An overview of the influence of various types of viscosity-enhancing admixture on high-range water reducer demand, resistance to water dilution, static and forced bleeding, segregation, settlement, setting time, and air entrainment is presented. The influence of such admixtures on bond to anchored reinforcing bars, frost durability, mechanical properties, and rapid-chloride permeability is also highlighted. Special applications where such relatively new admixtures can significantly enhance performance are highlighted, including their incorporation in concrete intended for underwater placement and repair, self-consolidating and segregation-free concrete for abovewater construction, and structural grout for filling post-tensioning ducts.

389 citations

Book
01 Jan 1996
TL;DR: In this article, the authors investigated the air bubble entrainment in free-surface turbulent shear flows and developed an analysis of the air entraining processes in free surface flows.
Abstract: In high velocity water flows, large quantities of air bubbles are entrained at the free-surfaces. Practical applications are found in Chemical, Civil, Environmental, Mechanical, Mining and Nuclear Engineering. Air-water flows are observed in small-scale as well as large-scale flow situations. E.g., thin circular jets used as mixing devices in chemical plants (Qw ~ 0.001 L/s, diameter ~ 1 mm), and spillway flows (Qw > 10,000 m3/s, flow thickness over 10 m). In each case, however, the interactions between the entrained air bubbles and the turbulence field are significant. This monograph investigates the "air bubble entrainment in free-surface turbulent shear flows". It develops an analysis of the air entrainment processes in free-surface flows. The air-water flows are investigated as homogeneous mixtures with variable density. The variations of fluid density result from the non-uniform air bubble distributions and the turbulent diffusion process. Several types of air-water free-surface flows are studied : plunging jet flows (Part II), open channel flows (Part III), and turbulent water jets discharging into air (Part IV). Each configuration can be characterised as a high-velocity free-surface flow with turbulent shear layer and large air bubble content. Experimental observations confirm the conceptual idea that the air-water mixture behaves as a homogeneous compressible fluid. The monograph presents numerous and recent experimental investigations with mean velocities up to 57 m/s and mean air contents up to 70%. The analysis of experimental studies provides new information on the air-water flow field : air bubble distributions, air-water velocity profiles, air bubble sizes and bubble-turbulence interactions. The results show a strong similarity between all the flow patterns. In each case the distributions of air concentration (i.e. void fraction) can be approximated by a simple advective diffusion theory. New analysis is developed for each flow configuration and compared successfully with model and prototype data. The velocity distributions in air-water flows have the same shape as for monophase flows. However the presence of air bubbles modifies some turbulence characteristics while the turbulence controls the mechanism of bubble breakup. The book presents new useful information for design engineers and research-and-development scientists who need a better understanding of the fluid mechanics of air-water flows. Both qualitative and quantitative information are provided. In some cases the limits of our knowledge are pointed out. The book consists of five parts. Part I introduces the topic and its relevance, develops a dimensional analysis and discusses the air-water gas transfer process. In each subsequent part, the distributions of air content and air-water velocity are described. The results are grouped as : plunging jet flows (Part II), open channel flows (Part III) and high-velocity water jets discharging into the atmosphere (Part IV). In Part V, an analogy between the various types of air-water flows is developed. In the appendices, tables of physical and chemical properties of fluids are provided in appendix A. The report presents results expressed in SI Units. A table of unit conversions is given in appendix B. Estimates of bubble rise velocity are discussed in appendix C. Appendix D develops sound celerity calculations in two-phase flows. Appendices E, G, H and I present complete calculations of the air bubble diffusion process. Boundary layer characteristics and jet trajectory calculations are detailed in appendices F and J respectively. Appendix K defines bubble size distribution characteristic parameters. Observations by LEONARDO DA VINCI are recounted in appendix L. 'Errare Humanum Est'. Appendix M presents a correction form. Readers who find an error or mistake are welcome to record the error on the page and to send a copy to the author. At the beginning of the book, the reader will find the table of contents, a list of symbols, a glossary and an album of colourful photographs of 'white waters'.

363 citations


Network Information
Related Topics (5)
Reynolds number
68.4K papers, 1.6M citations
77% related
Turbulence
112.1K papers, 2.7M citations
77% related
Heat transfer
181.7K papers, 2.9M citations
77% related
Laminar flow
56K papers, 1.2M citations
77% related
Combustion
172.3K papers, 1.9M citations
77% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202367
2022148
202193
2020131
2019154
2018204