Early-Age Autogenous Effects in Internally Cured Concrete and Mortar


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Title: Early-Age Autogenous Effects in Internally Cured Concrete and Mortar

Author(s): Benjamin E. Byard, Anton K. Schindler, and Robert W. Barnes

Publication: Special Publication

Volume: 290


Appears on pages(s): 1-18

Keywords: Autogenous shrinkage, cracking, early-age stresses, internal curing, lightweight aggregate, internal relative humidity.

Date: 9/14/2012

One strategy for achieving excellent long-term performance of concrete bridge decks is to combine low permeability with minimal early-age cracking. Low permeability can be achieved through the use of concretes with low water-cement ratios; however, topical curing techniques are usually insufficient to maximize hydration and minimize autogenous shrinkage effects. This autogenous shrinkage causes stresses in restrained concrete, which can lead to deleterious early-age cracking. Curing effectiveness can be enhanced through the implementation of prewetted lightweight fine aggregates. Internal curing is provided as the aggregate water gradually desorbs into the surrounding paste. A study of the early-age behavior of internally cured concrete is described in this paper. Internal curing was provided by means of expanded shale, clay, and slate lightweight fine aggregates. Ten mixtures with water-cement ratios of 0.42, 0.36, and 0.30 were investigated. Compressive and tensile strengths of the internally cured concretes were similar to or slightly greater than the strengths of their non-internally cured counterparts, and concrete stiffness decreased as expected in the internally cured mixtures. Autogenous shrinkage strains and stresses were found to increase as the water-cement ratio decreases. However, the autogenous effects were reduced or eliminated in the internally cured concretes.