A new four stage model of capillary pressure in early age concrete: Insights from high capacity tensiometers. (November 2022)

• Record Type: Journal Article
• Authors: Jamali, Armin; Mendes, Joao; Nagaratnam, Brabha; Lim, Michael
• Is Part Of: Cement and concrete research. Volume 161(2022)
• Publication Date: 2022-11
• Subjects: Capillary pressure -- High capacity tensiometer -- Early age shrinkage -- Self-consolidating concrete -- Curing duration -- Shrinkage reducing admixture; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2022.106955
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: Capillary pressure is frequently measured to evaluate the shrinkage performance of concrete but has been limited to pressures <100 kPa preventing a better understanding of the early age factors affecting concrete durability. In this study, high capacity tensiometers (HCTs) were employed for the first time to investigate the behavior of early age concrete. The evolution of capillary pressure in Self-Consolidating Concrete (SCC) with and without shrinkage reducing admixture was evaluated. The results demonstrate that HCTs are capable of measuring capillary pressure beyond 1500 kPa. This transformative new record of capillary pressure behavior has enabled the development of a model for the capillary pressure in early age concrete correlated to water evaporation, self-desiccation, setting time, temperature, and hydration processes. This ability to quantify real-time capillary pressure change in concrete generates important implications for optimizing the commercial durability of SCC and for understanding the link between early age concrete processes and resultant mechanical performance. Highlights: A new four stage model of the capillary pressure in early age concrete is presented. Bleeding, setting time, evaporation, and hydration govern the length of stages. A novel technique consisting of the use of HCT is used to measure the capillary pressure of SCC up to 2 MPa. Evaporation and self-desiccation govern the rate and value of capillary pressure. The effect of curing time on the capillary pressure of SCC with/out SRA is different.