Effect of Ultra-fine Powder and Superplasticizer on Fresh Performance of Ultra-high Performance Concrete
YU Xuejuan1, ZHENG Xiaobo2,*, LIU Jianzhong2, HAN Fangyu2, SHA Jianfang2, FANG Ruoquan1
1 Jiangsu Transportation Engineering Construction Bureau, Nanjing 210001, China 2 Jiangsu Research Institute of Building Science Co., Ltd., Nanjing 210008, China
Abstract: By establishing a method for determining and testing the pulping time, the impact of ultra-fine powder and superplasticizer on the mixing process of ultra-high performance concrete (UHPC) was investigated. The adsorption amount of superplasticizer, particle packing density and water film thickness were tested to reveal the mechanism of pulping time based on particle packing behavior. The results show that UHPC during the mixing process undergoes a wet particle formation period, a wet particle growth period, and a critical state of coacervate (pulping state), and then quickly forms agglomerates and transforms into a paste. The criteria for the pulping state and the pulping time test methods are proposed. Compared with ultra-fine powder, the superplasticizer has less impact on pulping time of UHPC. The pulping time of micron particle system is significantly shorter than that of nanoparticle system, and the pulping time of spherical particle system is significantly shorter than that of irregular particle system. The particle packing density and the water film thickness are the keys to controlling the pulping time, among these, the water film thickness determines the base and range of the pulping time, and the particle packing density and the water film thickness determine the variation pattern of the pulping time.
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2025, Vol. 39 
