Handbook of Analytical Techniques in Concrete Science and Technology 14379_09文档.pdfVIP

9 Rheology Leslie J. Struble and Xihuang Ji 1.0 INTRODUCTION The rheological behavior of fresh cement paste and concrete is a topic of considerable interest. Fresh concrete is a fluid material and its rheologi- cal behavior affects or even limits the ways it can be processed, therefore, measurement and control of rheological parameters are very important in the production of quality concrete. Slump, of course, is a rheological measurement, but slump only describes a part of the behavior. More importantly, slump is an empirical measure; it cannot be compared with other rheological measures. Other measures of concrete workability exist, but they are less common and share the same drawbacks. If concrete technology is going to advance, it is important to apply more basic principles of rheology. Much that is known about the flow behavior of concentrated suspensions can help us measure and understand the behavior of fresh concrete. The objective of this chapter is to present recent developments in the application of rheological principles to fresh cement paste and concrete. It covers both rheology (the study and understanding of flow behavior) and rheometry (the measurement of flow behavior). 333 334 Analytical Techniques in Concrete Science and Technology 2.0 BACKGROUND Rheology is a well established area of study for a wide range of materials. It is often included in textbooks dealing with chemistry or with fluid mechanics. An excellent introductory treatment of rheology is given by Barnes, et al.[1] A more fundamental treatment of colloid chemistry, including rheology, is given by Hunter.[2] Finally, Tattersall, and Banfill provide a thorough review and discussion of concrete rheology, though now somewhat dated.[3] Much of the information in this chapter is based on these books.