Bureau of Reclamation's Approach to Producing Economical, High Quality Mass Concrete


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Title: Bureau of Reclamation's Approach to Producing Economical, High Quality Mass Concrete

Author(s): William F. Kepler

Publication: Special Publication

Volume: 141


Appears on pages(s): 117-132

Keywords: aggregates; batching; consolidation; construction; cooling; cores; curing; fly ash; mass concrete; mix proportioning; placing; quality control; standard deviation; strength; General

Date: 12/1/1993

The Bureau of Reclamation has produced mass concrete since 1904. Since then, quality assurance of mass concrete has evolved from the rudimentary measurement of batch volumes to using computers to batch and evaluate concrete. The construction of Hoover Dam in 1931 was a major turning point in quality assurance of mass concrete, with the initiation of scientific evaluations of the physical properties of concrete and concrete-making materials. Reclamation's goal is to provide the most economical concrete mixture that will meet the design and construction requirements. Over the years, several effective procedures have been developed to meet that goal. The primary focus is to keep the amount of cementitious materials low. This is done in several ways. Large, nominal, maximum-sized aggregates are used, multiple coarse aggregates are blended to reduce the required mortar volume, and the fines content is kept very low. The next step is to use high quality materials. Reclamation's specifications for fly ash and aggregates are more stringent than the ASTM standards. To minimize overdesign, close control is maintained over the batching process, helping to keep a low standard deviation. Paper discusses the different methods the Bureau of Reclamation uses to produce economical, high-quality mass concrete mixtures.