-
Pittsburgh, Pa. 15213 and Les D. Robertson American Cement Corporation Riverside, California 92502
I
I
in the Cement Industry Solved by Modern Research Techniques
In the past half century, increasingly sophisticated techniques have been developed for the elucidation of practical chemical problems in the cement industry. Several substantial advances have equipped the chemist to delve more deeply into the intricacies of chemical bonding and stability. With each successive technique, the ability to solve the variety of problems previously precluded from experimental investigation has been enhanced. I n the basic sciences, the effects of these technological advances are far reaching. The subsequent amenability of these techniques to applied research and practical industrial problems is equally important. This paper is concerned with the general applications of analytical techniques to solving practical problems in the cement industry. This is neither an attempt to provide an indepth explanation of the physical and chemical principles governing these techniques, nor to present details of sample preparation and experimental parameters. The purpose is to briefly describe several problems encountered in the authors' investigations and the techniques used to solve them. Infrared Spectroscopy
Infrared spectroscopy is the method of choice for the qualitative and quantitative analysis of trace organic constituents in cementitious materials, and has been the single most useful method for detecting and identifying organic admixtures in cement. A large number of commercial admixtures are available such as set regulators for cementitious systems. Those admixtures used to retard set consist chiefly of various lignosulfonates, organic acids, metal oxides, and sugars. The problems most often encountered relate to improper proportioning of these admixtures into the cement system, resulting in an undesirable hydration rate. When confronted with a problem in which setting time and/or rate of strength gain is affected, and when the inorganic constituents of the cement are found to be normal, the infrared spectrophotometer is employed. To obtain an infrared spectrum of an organic compound from a cement or concrete sample, a stepwise procedure must he followed. The initial and probably the most difficult step is the isolation of the organic compound(s). Often the organic material may he removed by a simple extraction technique using solvents Paper war presented at the March 1971 WESTEC Conference in Los Angeles.
' To whom correspondence should be addressed 522 / Journal of Chemical Education
such as chloroform, acetone, or sodium carbonate, depending upon the nature of the organic phase. In difficult cases, in which the organic material may have formed a physical or chemical bond with the cement gel, it is necessary to destroy the cement,/concrete paste structure by acid digestion. Very often this procedure complicates the analysis by altering the structure of the organic compound. This, and the high probability of organic phase conversion by other interactions, makes it necessary to use "chemical intuition" vhen extrapolating back from the spectral assignment to the original organic compound. If time permits, a test of the results should be made by t n b i t ~ i n n o t ccmmtitio~~in.:lc.tsl.rs and rht. "idrntifid" ureanic .;ub.
