Report on Measurements of Workability and Rheology of Fresh Concrete_ کتاب اندازه گیری کارایی و رئولوژی بتن تازه

Report on Measurements of Workability and Rheology of Fresh Concrete

کتاب اندازه گیری کارایی و رئولوژی بتن تازه

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI. The technical committees responsible for ACI committee reports and standards strive to avoid ambiguities, omissions, and errors in these documents. In spite of these efforts, the users of ACI documents occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. Users who have suggestions for the improvement of ACI documents are requested to contact ACI.

Since the early twentieth century, the concrete industry has recognized the need to monitor concrete workability to ensure that concrete can be properly placed and can achieve adequate properties in the hardened state. Numerous test
procedures for determining workability have been developed for research, mixture proportioning, and field use. The vast majority of these test methods hav never found any use beyond one or two initial studies. With the exception of the widely used slump test, the few methods that have been studied extensively have generally failed to gain widespread acceptance. Even with the increase in knowledge of concrete rheology, no test has been developed that is sufficiently
compelling to convince the concrete industry to replace the slump test. The term “workability” is broadly defined; no single test method measures all aspects of workability.

ACI Cement and Concrete Terminology (http://www.concrete.org/Technical/ CCT/FlashHelp/ACI_Terminology.htm) describes workability as “that property of freshly mixed concrete or mortar which determines the ease and homogeneity with which it can be mixed, placed, consolidated, and finished.” The Japanese Association of Concrete Engineers defines workability as “that property of freshly mixed concrete or mortar which determines the ease with which it can be mixed, placed, and compacted due to its consistency, the homogeneity with which it can be made into concrete, and the degree with which it can resist separation of materials” (Ferraris 1999). Neville (1996) succinctly defines workability as “the amount of useful internal work necessary to produce full compaction.” Workability depends not just on the properties of the concrete, but also on the nature of the application. A very dry concrete mixture, for example, may seem to have very low workability when it is, in fact, appropriate for the given application.

The focus of workability measurement has changed many times over the years. When the slump test was developed in the early twentieth century, concrete researchers were just beginning to recognize the importance of water content in predicting concrete strength (Wig 1912; Abrams 1922). More advanced concrete production systems have not eliminated the need to monitor concrete workability in the field. To the contrary, the advent of new high-performance concrete mixtures that are susceptible to small changes in mixture proportions has made monitoring workability even more critical. A National Ready-Mixed Concrete Association survey identified the need for a better method to characterize the workability of high-performance concrete (Ferraris and Lobo 1998). After more than 80 years of efforts, the concrete
industry is still faced with the challenge of developing a field test to measure the relevant rheological properties of concrete quickly and accurately. This section of the report describes 69 test methods that could be used for measuring concrete workability. While this list is not exhaustive, it includes most of the test methods that have been described in United States and western European literature. Many more tests have been developed for a single project or for a specific application, and have been sparsely reported in the literature, if at all. Despite the fact that many of the devices in this document will never be used and have been scarcely used in the past, an examination of tests that have failed and tests that have been supplanted by better tests is instructive in recognizing trends in concrete workability research and in selecting key concepts for the evaluation of new test methods.

This section describes key principles and trends in the measurement of workability and then describes the 69 test methods. Based on the successes and failures of past test methods and the current needs of the concrete industry, requirements are presented for evaluating the suitability of new test methods for measuring workability.

کتاب اندازه گیری کارایی و رئولوژی بتن تازه

کتاب اندازه گیری کارایی و رئولوژی بتن تازه

کتاب اندازه گیری کارایی و رئولوژی بتن تازه

برای دانلود این کتاب بر روی دانلود کلیک کنید

دانلود

دیدگاهتان را بنویسید لغو پاسخ

بازگشت به بالا

صنایع شیمیایی بتنو

دسترسی سریع

راه‌های ارتباطی

چرا ما

درباره بتنو:

بتنو به عنوان تولید کننده صنایع شیمیایی تاثیرگذار و پر مخاطب در عرصه صنعت بتن آماده و قطعات بتنی پیش ساخته و کلیه صنایع وابسته به بتن (تولید کنندگان سیمان پوزولان، سنگدانه، افزودنی های بتن، ادوات و تجهیزات تولید، حمل نقل و غیره) فرصت های بی نظیری را برای تان فراهم کرده است.

© کپی رایت 2025 | کلیه حقوق مادی و معنوی متعلق به بتنو می باشد