Showing papers on "Air entrainment published in 1971"

Method and apparatus for treating porous material with fluid

Abstract: In air-through dryers for wet sheet-like material, such as paper, textiles, etc., the moist sheet-like material is passed adjacent a high velocity air hood so as to be subjected to an air pressure differential across the same. Thus, heated or unheated air is caused to be engaged against one side of the sheet-like material and pass therethrough to the other side thereof to remove moisture from such sheet-like material as the air passes therethrough, such moisture being removed by a pushing out of the moisture by the air, by air entrainment and/or by adiabatic evaporation. A belt means of this invention comprising a perforated flexible wall carrying a felt, fabric or other similar material on one side thereof is utilized in a manner to engage against the moist sheet-like material to compress the same during the passage of air through the perforated flexible wall and through the moist sheet-like material to assist in the water removal thereof by either tending to cause the porosity of the drying sheet-like material to remain substantially constant so that an optimum substantially constant air flow passes therethrough or to cause a greater air flow rate through the wetter portions of said sheet-like material than through the drier portions thereof.

Method and apparatus for treating sheet-like material with fluid

Abstract: In air-through dryers for wet sheet-like material, such as paper, textiles, etc., the moist sheet-like material is passed adjacent a high velocity air hood so as to be subjected to an air pressure differential across the same. Thus, heated or unheated air is caused to be engaged against one side of the sheet-like material and pass therethrough to the other side thereof to remove moisture from such sheet-like material as the air passes therethrough, such moisture being removed by a pushing out of the moisture by the air, by air entrainment and/or by adiabatic evaporation. A belt means of this invention comprising a perforated flexible wall carrying felt, fabric or other similar material on one side thereof is utilized in a manner to engage against the moist sheet-like material to compress the same during the passage of air through the perforated flexible wall and through the moist sheet-like material to assist in the water removal thereof by either tending to cause the porosity of the drying sheet-like material to remain substantially constant so that an optimum substantially constant air flow passes therethrough or to cause a greater air flow rate through the wetter portions of said sheet-like material than through the drier portions thereof.

Lightweight concrete containing expanded polystyrene

Abstract: A low density concrete having an oven dry density of 15 to 35lbs./cu ft. has, as its aggregate, closed-cell, foamed plastics, particularly polystyrene particles of density 1 to 10, preferably 1 to 3lbs./cu. ft. A typical mixture consists of polystyrene foamed particles 7.8 parts by wt., Portland cement 100, water 51, surface active additive 0.36, and air entraining synergist 0.56. The resultant concrete is fire-resistant, can be fashioned with carpenter's tools, and can be used as the core material in laminates.

Effects of combining two or more admixtures in concrete

Abstract: TWO LABORATORY INVESTIGATIONS WERE CONDUCTED TO DETERMINE PREDICTABILITY OF PERFORMANCE OF CONCRETE MIXES (MADE WITHOUT ADMIXTURE AND WITH ONE OR MORE ADMIXTURES) WITH RESPECT TO COMPRESSIVE STRENGTH. TWO PROGRAMS, CONDUCTED 5 YEARS APART, USED DIFFERENT SOURCES OF MATERIALS-AIR- ENTRAINED CONCRETE AND NON-AIR-ENTRAINED CONCRETE RESPECTIVELY-AND TWO BASIC APPROACHES TO ASCERTAIN EQUIVALENCY OF PERFORMANCE LEVELS. IN THE FIRST PROGRAM, THE ADMIXTURE, OR ADMIXTURES, WERE ADDED TO THE CEMENT. IN THE SECOND PROGRAM, CEMENT CONTENTS WERE REDUCED TO COMPENSATE FOR EQUIVALENCY OF PERFORMANCE BY USE OF ONE OR MORE ADMIXTURES. LIBRARY RESEARCH WAS RELIED ON TO GIVE ADDITIONAL BACKGROUND INFORMATION. DATA SHOW THAT EXISTING CONCRETE TECHNOLOGY CAN SERVE AS A GUIDE IN PROPORTIONING CONCRETE MIXTURES CONTAINING ONE OR MORE ADMIXTURES AND THAT RESULTS CAN BE PREDICTED WITH REASONABLE ACCURACY. /AUTHOR/

Relations between compressive and indirect-tensile strengths of concrete

Abstract: The performance of a concrete road slab is critically affected by its ability to withstand the tensile stresses imposed upon it caused by temperature movements and loading. The quality of concrete used in road slabs is therefore most logically specified in terms of its tensile strength. The cylinder-splitting test, which gives an indirect measure of tensile strength, is likely to be used in a future revision of the Department of the Environment's 'Specification for road and bridge works'. This report describes studies that have been made to investigate the effect of different materials on the indirect-tensile strength and on its relation with the cube-crushing strengths. It is shown how the relation between compressive and indirect-tensile strength is dependent on aggregate type and how the relation is affected by entrained air and different sources of cement. Data presented in the report should assist in the design of mixes on the basis of indirect-tensile strength for both plain and air-entrained concretes. /TRRL/

Self-Aerated Flow Characteristics in Wall Region

Abstract: Characteristics of self-aerated flows in the wall region are studied. The distribution of velocity and air concentration in the wall turbulent zone is studied by dividing the wall turbulent zone into an inner and outer region according to the eddy viscosity distribution. It is shown that the inner region ceases to exist under certain conditions. Air concentration on the wall is estimated. The values of the Karman constant and Manning’s roughness coefficient show an increase in their value as air concentration increases. An estimation of the average velocity and the probable diameter of an air bubble shows a definite relation with mean air concentration in the wall region.

Methods of controlling grout for prestressed, post- tensioned structures

Abstract: A STUDY WAS MADE TO DETERMINE THE EFFECTS OF VARIOUS ADMIXTURES, CEMENT BRANDS, AND AIR ENTRAPMENT/ENTRAINMENT ON THE QUALITY OF CEMENT GROUT. THE RELATIONSHIP BETWEEN THESE PARAMETERS AND COMPRESSIVE STRENGTH WAS ALSO INVESTIGATED. A NUMBER OF LABORATORY GROUT MIXING EXPERIMENTS WERE PERFORMED. RESULTS ARE TABULATED FOR COMPARISON, AND WHERE APPLICABLE, STATISTICAL ANALYSES PERFORMED. IT WAS FOUND THAT ADMIXTURES, IN THE QUANTITY USED FOR THIS STUDY, IN ALL CASES, DECREASED COMPRESSIVE STRENGTHS AND INCREASED THE BLEEDING OF GROUT. HIGHER MIXING SPEEDS TENDED TO RESULT IN SLIGHTLY MORE AIR ENTRAPMENT. /FHWA/

Theoretical analysis of the effects of air voids in concrete

Abstract: A PHYSICALLY DESCRIPTIVE MODEL IS ESTABLISHED FOR POROUS MATERIALS SUCH AS CONCRETE. THE MODEL CONSISTS OF A SOLID MATRIX CONTAINING RANDOMLY DISTRIBUTED, FLUID-FILLED VOIDS OF IRREGULAR SHAPES AND VARIOUS SIZES. THE ELASTIC MODULUS AND SPEED OF SOUND IN THIS MODEL ARE INVESTIGATED ANALYTICALLY, AND MATHEMATICAL RELATIONSHIPS BETWEEN THESE PROPERTIES AND THE POROSITY ARE OBTAINED. USING DATA DUE TO KAPLAN THE THEORETICAL RESULTS ARE FOUND TO DESCRIBE THE BEHAVIOR OF POROUS CONCRETE VERY NICELY, AND SOME INSIGHT IS GAINED INTO THE DIFFERENCES BETWEEN THE EFFECTS OF ENTRAINED AIR AND AIR DUE TO INCOMPLETE CONSOLIDATION. /AUTHOR/

Centrifuged concrete of high frost resistance, with air-entraining additives

Abstract: 1. The investigations carried out demonstrate the effectiveness of air-entraining and multiple additives for increasing the frost resistance of centrifuged concrete. 2. The air entrained into the concrete mass is not expelled by centrifugation. 3. Elements with a high frost resistance were obtained from centrifuged concrete containing multiple additives. 4. On the basis of the investigations, a wide application of centrifuged hollow piles was developed under working conditions, using highly frost-resistant concrete obtained by introducting multiple additives into its composition.