Replacement of the Foam Index Test with Surface Tension Measurements

The foam index test is the method usually employed to determine the degree of fly ash interference with air entrainment agents in concrete. The test involves the use of commercial air-entraining agents (AEAs) and visual observation of foam stability. These facts reduce the reproducibility of the test, because commercially available AEAs vary in strength, and the criteria for foam stability are operator dependent. Therefore, it is of interest to develop a reproducible method, which is able to determine the fly ash quality with respect to air entrainment in concrete. This paper presents efforts toward the development of a new method based on dynamic surface tension measurements, using the bubble pressure method, on filtrate from a fly ash and cement suspension. A pure surfactant is added to the suspension as a substitute for a commercial AEA. The new method and the foam index test have been compared on fly ashes acquired from power plants in Denmark and the U.S. The results reveal a good relationship between the two methods, but the new method requires further work before a finished procedure is accomplished. Finally, it has been shown that changes in temperature affect both test methods.

[1]  Robert H. Hurt,et al.  The effect of solid fuel type and combustion conditions on residual carbon properties and fly ash quality , 2002 .

[2]  Robert H. Hurt,et al.  Adsorption of surfactants on unburned carbon in fly ash and development of a standardized foam index test , 2003 .

[3]  T. Schmitt.  Analysis of Surfactants , 1991 .

[4]  M. Mercedes Maroto-Valer,et al.  Characterization of differing forms of unburned carbon present in fly ash separated by density gradient centrifugation , 2001 .

[5]  Robert H. Hurt,et al.  Size distribution of unburned carbon in coal fly ash and its implications , 2004 .

[6]  R. Pugh,et al.  Diffuse layer electrostatic potential and stability of thin aqueous films containing a nonionic surfactant , 1991 .

[7]  Bruno Carré,et al.  Role of surfactant structure on surface and foaming properties , 2001 .

[8]  James C. Hower,et al.  Investigation of fly ash carbon by thermal analysis and optical microscopy , 1998 .

[9]  P. Joos,et al.  The measurement of dynamic surface tension by the maximum bubble pressure method , 1994 .

[10]  R. J Pugh,et al.  From stability in aqueous solutions of nonionic surfactant and inorganic electrolyte , 1992 .

[11]  O. Manz,et al.  Coal fly ash: a retrospective and future look , 1999 .

[12]  Robert H. Hurt,et al.  Adsorptive and Optical Properties of Fly Ash from Coal and Petroleum Coke Co-firing , 2000 .

[13]  R. Helmuth,et al.  Fly Ash in Cement and Concrete , 1987 .

[14]  S. I. Andersen,et al.  Effect on molecular interactions of chemical alteration of petroleum asphaltenes. I , 2005 .

[15]  R. N. Swamy.  First international conference on the use of fly ash, silica fume, slag and other mineral by-products in concrete: La Chateau Montebello, Montebello, Quebec, Canada, 31 July–5 August 1983 , 1983 .

[16]  Chunlong Zhang,et al.  Aerobic biodegradation kinetics of four anionic and nonionic surfactants at sub- and supra-critical micelle concentrations (CMCs) , 1999 .

[17]  Sydney Ross,et al.  The Measurement of Foam Stability1a , 1944 .

[18]  Leonard W. Bell,et al.  CHEMICAL ADMIXTURES FOR CONCRETE , 1999 .

[19]  E. Manev,et al.  Correlation in the properties of aqueous single films and foam containing a nonionic surfactant and organic/inorganic electrolytes. , 2003, Journal of colloid and interface science.

[20]  G. M. Bruere.  Air‐entraining actions of anionic surfactants in portland cement pastes , 2007 .

[21]  Kartic C. Khilar,et al.  Stability of aqueous foams with polymer additives: II. Effects of temperature , 1990 .

[22]  N Bouzoubaâ,et al.  Laboratory-produced high-volume fly ash blended cements: compressive strength and resistance to the chloride-ion penetration of concrete , 2000 .

[23]  John P. Baltrus,et al.  Measurement of adsorption of air-entraining admixture on fly ash in concrete and cement , 2001 .

[24]  Per Stenius,et al.  Precipitation of surfactant salts: II. The effect of nonionic surfactants on precipitation of calcium dodecyl sulfate , 1988 .

[25]  P. Hewlett,et al.  Lea's chemistry of cement and concrete , 2001 .

[26]  Elizabeth Freeman,et al.  Interactions of carbon-containing fly ash with commercial air-entraining admixtures for concrete , 1997 .

[27]  David J. Corr,et al.  Air void morphology in fresh cement pastes , 2002 .

[28]  James C. Hower,et al.  An examination of fly ash carbon and its interactions with air entraining agent , 1997 .

[29]  Yuming Gao,et al.  Surfactant adsorptivity of solid products from pulverized-coal combustion under controlled conditions , 1998 .

[30]  A. Samarin,et al.  The Use of Fly Ash in Concrete-Australian Experience , 1983 .

[31]  B. Allred,et al.  ENHANCED ANIMAL WASTE MANAGEMENT THROUGH APPLICATION OF SURFACTANTS TO SOIL MATERIAL: LABORATORY FEASIBILITY TESTING , 2001 .

[32]  D. Shaw,et al.  Introduction to colloid and surface chemistry , 1970 .

[33]  L. Schulze,et al.  Diagnosing the condition of washing and rinsing liquids with a new surface measurement technique , 1999 .

[34]  Robert H. Hurt,et al.  Effects of carbon on air entrainment in fly ash concrete : The role of soot and carbon black , 1997 .