1、CECW-EG Technical Letter NO. 1 1 10-2-3 64 COE ETL 3330-2-364 I 3535789 0823965 bTb W DEPARTMENT OF THE ARMY U.S. Army Corps of Engineers Washington, DC 203 14-1 O00 ETL 1 1 10-2-364 Engineering and Design POTENTIAL PROBLEM OF RAPID STIFFING OF CONCRETE MIXTURES CONTAINING CLASS C FLY ASH Distributi
2、on Restriction Statement 1 May 1994 Approved for public release; distribution is unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-COE ETL LLlO-2-364 = 3515789 0823766 532 CECW-EG Technical Letter NO. 11 10-2-364 DEPARTMENT OF THE ARMY US. A
3、rmy Corps of Engineers Washfngton, D.C. 20314-1000 ETL 1110-2464 1 May1994 I Engineering and Design POTENTIAL PROBLEM OF RAPID STtFFENING OF CONCRETE MIXTURES CONTAINING CLASS C FLY ASH 1. Purpose This engineer technical letter (ETL) provides guidance to avoid the potential problem of rapid stiffeni
4、ng when using large amounts of Qass C fly ash in coocrcte mixtures. the mataial has been used in otha projects successfully with less of a replacement rate (about 25 -0. d The fly ash from a different source was selected by the conbactot and no problem was experienced. 2. Applcabiliy 4. Dlscusoion T
5、his ETL. applies to all HQUSACE elumnb, major subordinate commands, disics, laboratories, and field operating activities having rtsponsibilities for the design of civil works projects. 3. Background a The mixture proportion for hek and Dam No. 5, Red River Waterway, required 50 percent Class C fly a
6、sh rtpiacement by vdume of cement The fly ash stlccted by thecontractor was from a prcqudified source. The sample of this fly asb was tcsted by CEW-SC in April 1992 and found satisfactory in accordance with ASRI3 C 618. It should be nocd tbat a test for setting time is not mquirc in ASTM c 618. b. I
7、n June 1992, a rapid Stiffening of the concrete mixtuR was observed during a mixer uniformity evaluation at the project site. Subsequent tests on the materiais used in the project indicate that the rapid stiffening was caused by the extrumely quick setting of the fly ash selected, as was evidenced b
8、y the generation of consierabk heat within a few minutes of mixing with water. a Bad on the limitd expience. it seems the problem of quick setting of concrete mixture may occur when (1) Class C fly ash is used at high replacement rate (50 percent or more), and (2) the Class C fly ash used displays e
9、xtremely fast setting time when mixed with water. b. Since ASTM C 618 does not requin the test of setting time for fly ash, the probkm mot be detected by the normal acceptance testing. c. A research project, as a part of thc Civil Works R & D program, will lx initiated at CEWES to determine the exte
10、nt of the problem and to develop criteria for the use of iargc amounts of Qass C fly ash in concrete mixtures. S. Action a Until more information and experiences kome available on this subject, samples of fly ash and cement shall be sent to C!EWE!j-SC-MP for evaluation when Specifying Class C fly as
11、h at a re- placement rate of 50 percent or more by volume of cernent in concrete mixwes. c. The manufacturer of the fly ash claims that Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- _ - -* - - COE ETL 3130-2-3b4 M 3535789 0823967 479 b. Any field
12、problem with an unusually fast setting of concrete mixhe wh using fly ash shell be rwd to HQUSACE, CECW-EG. FOR THE DRECIY)R OF CML WORKS: PAUL D. BARBER. P.E Chief, Engineering Division Dircctorate of Civil Works 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
