Effect of type of mixer on rheological and mechanical behavior of ultra high-performance concrete

摘要

Ultrahigh-performance concrete (UHPC) is becoming increasingly frequent in several civil construction projects such as industries, buildings, and even infrastructure. The rheological and mechanical behaviors, coupled with durability, are the driving motives for this increase in use over the last few decades. However, the type of mixer used in UHPC production considerably affects the final composites performance due to variations in mixing velocity and the need to disperse particles with low granulometry. This study evaluated the effect of type of mixer in the properties of UHPC in the fresh and hardened states. This study evaluates three types of mixers: planetary vertical axis, horizontal axis, and drum. Results showed that the drum mixer was the least efficient in homogenizing the composite. It showed an average mixing time about 126% longer than planetary vertical or horizontal-axis mixers to reach the same level of flowability. The composite from the drum mixer also had the most entrained air and void index. The planetary vertical-axis mixer was the most efficient, with the resulting composite having a potential compression strength of 169.1 MPa, 19.3% higher than the composite from the horizontal-axis mixer.