Monitoring of Capillary Pressure Evolution in Young Age Concrete Using High Capacity Tensiometers

Owing to their high surface-to-volume ratio, concrete pavements and slabs are more prone to shrinkage, leading to premature cracking and, as a result, loss of serviceability. Capillary pressure in concrete, identified as the main contributor to shrinkage, needs to be frequently monitored to evaluate the shrinkage behaviour of concrete. However, capillary pressure measurement is currently limited to 100 kPa, covering only the initial few hours of age due to the low capacity of existing capillary pressure sensors. This results in very limited record of capillary pressure during the processes occurring within concrete after casting and has prevented a better understanding of the influence of capillary pressure on concrete durability. In this study, high capacity tensiometers (HCTs) were used for the first time to investigate the evolution of capillary pressure in early age concrete over longer periods and at higher capillary pressure values. The results showed that HCTs can quantify the evolution of capillary pressure up to 2000 kPa, a twenty fold increase in comparison to existing methods. This new transformative technology is a major step forward in concrete research and can provide new insights into the shrinkage behaviour of early age concrete. Furthermore, this novel technique can be used in situ in construction projects to monitor the real-time development of capillary pressure of concrete at an early age, aiding practitioners in the decision-making for the employment of effective mitigation strategies to reduce shrinkage and, in turn, increase the durability of infrastructures.