Abstract
The objective of this paper is to investigate the characterization of moisture diffusion inside early-age concrete slabs subjected to curing. Time-dependent relative humidity (RH) distributions of three mixture proportions subjected to three different curing methods (i.e., air curing, water curing, and membrane-forming compounds curing) and sealed condition were measured for 28 days. A one-dimensional nonlinear moisture diffusion partial differential equation (PDE) based on Fick’s second law, which incorporates the effect of curing in the Dirichlet boundary condition using a concept of curing factor, is developed to simulate the diffusion process. Model parameters are calibrated by a genetic algorithm (GA). Experimental results show that the RH reducing rate inside concrete under air curing is greater than the rates under membrane-forming compound curing and water curing. It is shown that the effect of water-to-cement (w/c) ratio on self-desiccation is significant. Lower w/c ratio tends to result in larger RH reduction. RH reduction considering both effect of diffusion and self-desiccation in early-age concrete is not sensitive to w/c ratio, but to curing method. Comparison between model simulation and experimental results indicates that the improved model is able to reflect the effect of curing on moisture diffusion in early-age concrete slabs.
Highlights
An understanding of temperature curling and moisture warping gradients in Portland cement concrete (PCC) pavement slabs due to environmental loads plays an important and fundamental role in the process of rigid pavement stress analysis
relative humidity (RH) reductions caused by cement self-desiccation at three w/c ratios were measured for three sealed specimens
Lower w/c ratio tends to result in larger RH reduction
Summary
An understanding of temperature curling and moisture warping gradients in Portland cement concrete (PCC) pavement slabs due to environmental loads plays an important and fundamental role in the process of rigid pavement stress analysis. Temperature gradients and their resulting curling effects on slabs have been well solved and implemented in the pavement engineering community while a sound interpretation of moisture warping which is caused by a nonuniform moisture distribution through the depth of slabs is still lacking [1]. Accurate and validated moisture transport modeling in PCC pavement slabs which can properly incorporate all these influencing factors is critical for developing moisture gradients and calculating warping stresses in slabs
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