Internal Curing - Real World Ready Mix Production and Applications: A Practical Approach to Lightweight Modified Concrete

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Title: Internal Curing - Real World Ready Mix Production and Applications: A Practical Approach to Lightweight Modified Concrete

Author(s): V.H. Villarreal

Publication: Special Publication

Volume: 256

Issue:

Appears on pages(s): 45-56

Keywords: internal curing; lightweight aggregate; moisture conditioning

Date: 10/1/2008

Abstract:
The benefits of using lightweight aggregate (LWA) to replace a portion of the normalweight aggregates in concrete mixtures have been investigated by many researchers. The main purpose of this substitution has been to provide a source of moisture for internal curing that will promote more complete hydration of the cementitious materials. The adequate initial moisture conditioning of the LWA is the most crucial step in the ready mixed concrete production cycle. Once the LWA has been satisfactorily saturated, the potential for field problems is insignificant. Any shortcuts in this fundamental procedure can result in the failure of the concept and reluctance on the part of the concrete contractor to adapt this technology. The problems can range from yield issues to slump loss, segregation, finishability, and pumpability. The slow release of moisture from the lightweight aggregate to the concrete matrix has resulted in the mitigation or elimination of plastic and drying shrinkage cracking, as well as limiting the effects of self-desiccation. Enhanced workability and better consolidation due to an improved total grading provided by the use of an intermediate aggregate is also evident; contractors have reported that it reduces the total placing time.