Internal Curing Study with Intermediate Lightweight Aggregate

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Title: Internal Curing Study with Intermediate Lightweight Aggregate

Author(s): W.A. Pyc, M.A. Caldarone, D. Broton, and D. Reeves

Publication: Special Publication

Volume: 256

Issue:

Appears on pages(s): 13-34

Keywords: concrete; internal curing; lightweight aggregate

Date: 10/1/2008

Abstract:
The purpose of this study was to quantify the degree to which moisture-bearing lightweight aggregate can contribute to cement hydration in low, intermediate and high water/cement ratio "normal" density concrete. This was accomplished using chemical testing methods (x-ray fluorescence and thermal gravimetric analysis) supplemented by physical strength testing. To study the influence of lightweight aggregate as a function of paste density water/cement ratio), three cement contents were chosen to represent low, intermediate, and high water/cement ratio concrete. The three water/cement ratios examined were 0.37, 0.47, and 0.57. Each series consisted of a control mixture containing no lightweight aggregate, and a test mixture containing 6 ft3 of presoaked 3/8 in. to No. 8 intermediate lightweight aggregate used in substitution of a portion of the coarse and fine aggregate. The results of this study provide quantitative validation to the theory that the addition of an effectively preconditioned lightweight aggregate will provide moisture for cement hydration in the concrete. The significance of the findings present an improvement of the performance characteristics of concrete by providing additional internal moisture minimizing the effect of self-desiccation by maintaining a fairly high degree of saturation during the critical strength gain period.