Abstract

Shrinkage-induced cracking is a critical durability concern in concrete structures, particularly those with low volume-to-surface ratios, leading to increased maintenance costs and reduced service life. Early-age concrete is especially vulnerable to shrinkage cracking due to its limited strength development. Capillary pressure is a primary driver of early-age shrinkage; however, conventional measurement techniques are limited to pressures below 100 kPa and durations of approximately seven hours post-casting, restricting a comprehensive understanding of capillary pressure evolution and its correlation with shrinkage and cracking potential. This study utilises a novel high-capacity tensiometer (HCT) capable of measuring capillary pressures up to 2000 kPa, significantly extending the measurement range. The relationship between capillary pressure evolution and early-age shrinkage was investigated across different concrete mixtures, including a control mix, a mix incorporating ground granulated blast-furnace slag (GGBS), and shrinkage-reducing admixture (SRA). Additionally, experimentally measured early-age shrinkage values were compared with theoretical predictions based on the Gauss-Laplace equation and elasticity theory. A comprehensive experimental program was conducted, encompassing setting time determination, capillary pressure monitoring, early-age shrinkage measurement, and elastic modulus evaluation. The findings indicate that substantial shrinkage occurs during the initial and final setting phases while the concrete remains in a semi-plastic state, with minimal capillary pressure evolution. A notable discrepancy was observed between experimentally measured shrinkage values and theoretical predictions immediately after the final setting time across all mixtures. This divergence is attributed to the nonlinear stress-strain behaviour of concrete in the semi-plastic phase. However, as the concrete transitions to a hardened state, the experimental and theoretical shrinkage values converge, demonstrating the improved predictive accuracy of the model in later stages. These insights contribute to a deeper understanding of early-age shrinkage behaviour and provide a basis for optimizing mix designs to mitigate shrinkage-induced cracking in concrete structures.

Keywords

capillary pressure, early-age shrinkage, shrinkage cracking, high-capacity tensiometer.

DOI

10.5703/1288284318140

Download

Share

COinS
 

Investigation of Capillary Pressure Evolution and Early-Age Shrinkage in Concrete Using a High-Capacity Tensiometer

Shrinkage-induced cracking is a critical durability concern in concrete structures, particularly those with low volume-to-surface ratios, leading to increased maintenance costs and reduced service life. Early-age concrete is especially vulnerable to shrinkage cracking due to its limited strength development. Capillary pressure is a primary driver of early-age shrinkage; however, conventional measurement techniques are limited to pressures below 100 kPa and durations of approximately seven hours post-casting, restricting a comprehensive understanding of capillary pressure evolution and its correlation with shrinkage and cracking potential. This study utilises a novel high-capacity tensiometer (HCT) capable of measuring capillary pressures up to 2000 kPa, significantly extending the measurement range. The relationship between capillary pressure evolution and early-age shrinkage was investigated across different concrete mixtures, including a control mix, a mix incorporating ground granulated blast-furnace slag (GGBS), and shrinkage-reducing admixture (SRA). Additionally, experimentally measured early-age shrinkage values were compared with theoretical predictions based on the Gauss-Laplace equation and elasticity theory. A comprehensive experimental program was conducted, encompassing setting time determination, capillary pressure monitoring, early-age shrinkage measurement, and elastic modulus evaluation. The findings indicate that substantial shrinkage occurs during the initial and final setting phases while the concrete remains in a semi-plastic state, with minimal capillary pressure evolution. A notable discrepancy was observed between experimentally measured shrinkage values and theoretical predictions immediately after the final setting time across all mixtures. This divergence is attributed to the nonlinear stress-strain behaviour of concrete in the semi-plastic phase. However, as the concrete transitions to a hardened state, the experimental and theoretical shrinkage values converge, demonstrating the improved predictive accuracy of the model in later stages. These insights contribute to a deeper understanding of early-age shrinkage behaviour and provide a basis for optimizing mix designs to mitigate shrinkage-induced cracking in concrete structures.