TY  - EJOU
AU  - Yang, Jin 
AU  - Zhao, Hailong 
AU  - Zeng, Jingyi 
AU  - Su, Ying 
AU  - Zhu, Mengdi 
AU  - He, Xingyang 

TI  - The Influence of Chemical Admixtures on the Fluidity, Viscosity and Rheological Properties of Ultra-High Performance Concrete
T2  - Fluid Dynamics \& Materials Processing

PY  - 2024
VL  - 20
IS  - 10
SN  - 1555-2578

AB  - To achieve higher strength and better durability, ultra-high performance concrete (UHPC) typically employs a relatively small water-binder ratio. However, this generally leads to an undesired increase in the paste viscosity. In this study, the effects of liquid and powder polycarboxylate superplasticizers (PCE) on UHPC are compared and critically discussed. Moreover, the following influential factors are considered: air-entraining agents (AE), slump retaining agents (SA), and defoaming agents (DF) and the resulting flow characteristics, mechanical properties, and hydration properties are evaluated assuming UHPC containing 8‰ powder PCE (PCE-based UHPC). It is found that the spread diameter of powder PCE is 5% higher than that of liquid PCE. Among the chemical admixtures studied, AEs have the best effect on improving UHPC workability, while DFs have the worst effect. When the addition of AE and SA is 1.25‰ and 14.7% of PCE, paste viscosity reduces by 35% and 19%, respectively compared to the paste with only 8‰ PCE. A low AE dosage (1.25‰) decreases compressive strength by 4.1%, while SA (8.1%) increases UHPC compressive strength by 9.1%. Both AE and SA significantly delay the UHPC hydration process, reducing the hydration heat release peaks by 76% and 27%, respectively.
KW  - Ultra-high performance concrete; polycarboxylate superplasticizer; air-entraining agent; slump retaining agent; rheological properties

DO  - 10.32604/fdmp.2024.055448