How Long Should UHPC Be Mixed? A Study on Qinglong's UHPC Mixing Process

The mixing time of UHPC has a significant impact on its performance. Based on Qinglong's extensive test data, the optimal mixing time is generally 5-8 minutes, and the specific value must be determined according to the mix proportion and equipment performance.

In the Shenzhen Yirui Biotechnology Building project, Qinglong determined the optimal mixing process through systematic testing: pre-mixing the dry materials for 1 minute, mixing for 3 minutes after adding water, and finally adding fibers and mixing for another 2 minutes, for a total time of 6 minutes. This staged mixing process ensured uniform fiber distribution, with the strength variation coefficient of the products controlled within 5%. Project inspection data showed that after adopting the optimized process, the standard deviation of product compressive strength was reduced from the traditional 8% to 3%, with significantly improved uniformity.

Impact of Mixing Equipment

Forced-action mixers are highly efficient and can reach a uniform state in 3 minutes. Planetary mixers require 5-6 minutes. The time should be adjusted according to equipment performance.

Impact of Material Properties

Increased fiber content requires longer mixing time. When the steel fiber content is 2%, the mixing time needs to be extended by 2 minutes compared with ordinary concrete.

Impact of Temperature Factors

High summer temperatures require shorter mixing times. The optimal time parameters at different temperatures should be determined through testing.

Mixing time must be scientifically determined. It is recommended to determine the optimal process parameters through trial mixing.