Assessment of Concrete Curing Duration using Bulk Electrical Conductivity and Porosity

Abstract

Controlling permeability of concrete is essential for enhancing durability and, thus, the service life. Concrete permeability is affected by the total volume of permeable voids and the continuity of the capillary pore structure. Even though concrete strength is the typical performance parameter used to define a wet curing duration, it is important to maintain wet curing until concrete develops a discontinuous capillary pore structure with a minimum volume of total permeable voids to assure durability. Therefore, the required wet curing period can be defined as the longest duration out from the (i) time to achieve the specified strength, (ii) time to develop a discontinuous capillary pore structure, and (iii) time to develop a minimum volume of total permeable voids. Since concrete strength evaluation methods are well developed, there is a need for developing procedures to evaluate concrete pore structure characteristics to decide on the wet curing duration. This study investigated the use of bulk electrical conductivity and porosity test methods described in ASTM C1760 and C642 to evaluate the (i) time to develop a discontinuous capillary pore structure and (ii) time to develop a minimum volume of total permeable voids, respectively. The suggested procedure of wet curing duration assessment is demonstrated for two concrete mixes: one with only Type I cement and the other with Type I cement and slag.