Monitoring autogenous shrinkage in cellulose microfiber-reinforced GGBFS composites using ultrasonic interferometry

This study investigates the applicability of ultrasonic wave interferometry for monitoring the shrinkage of GGBFS composites and the mitigating role of cellulose microfibers (CMFs) through internal curing. Prismatic specimens were prepared with 5-mm-long kenaf-derived CMFs at dosages of 0-1.2 wt% of the binder. Ultrasonic and autogenous shrinkage tests were conducted in a humidity-controlled room for 48 days. After 48 days of curing, specimens containing 1.2 wt% CMFs exhibited significantly lower autogenous shrinkage (average: -99.9 με) than specimens without CMFs (average: -537.6 με). Ultrasonic tests revealed relative velocity changes of 10.9 % for CMF-incorporated specimens and 7.2 % for specimens without CMFs. Strong mixture-specific linear relationships were observed between autogenous shrinkage and relative velocity change, with correlation coefficients ranging from 96.5 to 98.3 % across the investigated CMF contents. These results demonstrate the effectiveness of ultrasonic measurements for tracking shrinkage and highlight the potential of CMFs to enhance dimensional stability and long-term durability in GGBFS-based cementless composites.