Sorptivity: Parameter for the Evaluation of Cover Concrete Quality

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Title: Sorptivity: Parameter for the Evaluation of Cover Concrete Quality

Author(s): V.L. Taus, A.A. Di Maio, and L.P. Traversa

Publication: Special Publication

Volume: 229

Issue:

Appears on pages(s): 121-134

Keywords: capillary absorption; carbonation; compressive strength; conventional concrete; curing; recycled concrete; sorptivity

Date: 9/1/2005

Abstract:
The cover concrete characteristics play a significant role regarding durability of reinforcement embedded in concrete, since this layer is in direct contact with contaminated environments or with substances capable of attacking the steel. The quality of cover concrete depends directly on the structure of pores and on their distribution and connectivity. For this reason, and taking into account the lack of an unique method capable of predicting the durability or the behavior over time of a specific concrete, characterization of the cover concrete is performed through methods which measure fluid absorption and permeability. Through several experiments, it has been shown that the best method to reflect the ability of concrete to absorb and transmit a liquid by capillary action is the capillary suction rate or sorptivity, since this property represents the transport mechanism that usually occurs in concrete structures exposed to repeated cycles of wetting and drying. This paper presents the results of laboratory studies about the influence of different variables on the capillary absorption, in order to define the behavior with time of concretes with different characteristics. These variables include type (natural and recycled) and maximum size of coarse aggregate, curing conditions, strength level, carbonation, etc.