A practical procedure for the analysis ofmoisture transfer within concrete due to drying

Abstract

The prediction of moisture transfer within concrete is necessary in order to evaluate its durability, because moisture transfer is related to shrinkage cracks and the transfer of chloride ions. Moisture transfer within concrete during drying has been analysed by many investigators using a non-linear diffusion equation. In the present paper, a comprehensive analytical procedure using a diffusion equation is established by comparing calculated results with experimental data for a wide range of concrete mix proportions. These experiments involved observing the effect of one-face drying and six-face drying on the water content profiles and mass decreases in prismatic specimens. The values of the coefficient required for the analysis are reported for a wide range of water/cement ratios, and the effect of these coefficients on the calculated results is discussed.

A model for reactive porous transport during re-wetting of hardened concrete

“…This fitting yields an estimate of A = 0.0028 cm 2 /day which is consistent with values reported by other authors such as [1]. A plot of the computed wetting front location (without reactions) is displayed in Fig.…”

Enhanced accelerated drying of concrete floor slabs

“…Moisture diffusion through concrete (Akita et al, 1997) largely depends on several factors. These include the concrete mix constituents, namely the w/c ratio (primarily as this determines the quantity and connectedness of the capillary pores and the chemically uncombined water), the cement type (for example, some supplementary cementitious materials tend to give denser packing and lower permeability) and the RH concentration gradient between adjacent pores.…”

Impacts of Trace Additives and Early-Stage Curing Conditions on the Shrinkage Cracking Resistance of Blast-Furnace Slag Cement Concrete

“…Among many water transfer models, this study adopted the method proposed by Akita et al (1997) because their experimental conditions and specimen shape are similar to those of this study and the normalized moisture content R was used as the driving force. Distributions of R with the distance from the drying surface can be given by the numerical solution of the governing equations (7)- (8) adopting initial and boundary conditions expressed by (9)-(10).…”

“…Because use of blast furnace slag cement type B and experimental condition of the ambient temperature of 30°C were parameters out of the range of this model, data of ordinary Portland cement and ambient temperature of 20°C were adopted instead. Details of analysis are given in the literature (Akita et al 1997). It should be noted that the most important parameter in this water transfer analysis, D, is defined as a function of R. However, the formula determining D in terms of R is assumed independent of age by following Akita et al (1997).…”

“…Details of analysis are given in the literature (Akita et al 1997). It should be noted that the most important parameter in this water transfer analysis, D, is defined as a function of R. However, the formula determining D in terms of R is assumed independent of age by following Akita et al (1997).…”