TSINGHUA UNIVERSITY BEIJING

Microstructure model of fresh cement paste in the presence of superplasticizer

1 Images of microstructure of blank fresh cement paste at 5 min after mixing. a) 100×; b) 400× 1-9 Kong
1 Images of microstructure of blank fresh cement paste at 5 min after mixing. a) 100×; b) 400×
1-9 Kong
2 Schematic drawing of microstructure of blank fresh cement paste
2 Schematic drawing of microstructure of blank fresh cement paste
3 The variation of initial flowability of blank fresh cement pastes with W/C
3 The variation of initial flowability of blank fresh cement pastes with W/C
4 Images of microstructure of fresh cement pastes with superplasticizer at 5 min after mixing. a) Low Sp/C, 100×; b); Low Sp/C, 400×; c) High Sp/C, 100×; d) High Sp/C, 400×
4 Images of microstructure of fresh cement pastes with superplasticizer at 5 min after mixing. a) Low Sp/C, 100×; b); Low Sp/C, 400×; c) High Sp/C, 100×; d) High Sp/C, 400×
5 The variation of initial flowability of fresh cement pastes with Sp/C at varied W/Cs
5 The variation of initial flowability of fresh cement pastes with Sp/C at varied W/Cs
6 Schematic drawing of fresh cement paste (Structures see Fig. 2)
6 Schematic drawing of fresh cement paste (Structures see Fig. 2)
7 The multi-scale microstructure model of FCP at W/C ≤ 0.15 (Structures see Fig. 2)
7 The multi-scale microstructure model of FCP at W/C ≤ 0.15 (Structures see Fig. 2)
8 The multi-scale microstructure model of FCP at W/C > 0.15 (Structures see Fig. 2)
8 The multi-scale microstructure model of FCP at W/C > 0.15 (Structures see Fig. 2)
9 Comparison between the experimental data and calculated results for the yield stress versus W/C of fresh ­cement pastes at different dosage of superplasticizer
9 Comparison between the experimental data and calculated results for the yield stress versus W/C of fresh ­cement pastes at different dosage of superplasticizer
The flowability of cementitous materials like concrete can be improved by adding superplasticizers ZKG
The flowability of cementitous materials like concrete can be improved by adding superplasticizers
ZKG

The microstructure of fresh cement paste (FCP) in the presence of superplasticizer was investigated in this study. A Morphologi G3 microscope was applied to directly observe the microstructure of the FCP with the emphasis of the real organization structure of cement particles in the paste. Based on the microstructure characterization, the working mechanism of superplasticizer on the flowability of FCP was analyzed. Combined with the real microstructure of multi-sized cement particle suspension and the working mechanism of superplasticizer, the contents of different types of water in cement suspension and the volume fraction of solid phase were calculated. Finally, a generalized multi-scale microstructure model of FCPs at varied superplasticizer dosages and water to cement ratios was established, which was verified by the experimental results of yield stress of the FCPs.

1 Introduction

Flowability has been considered one of the important properties of fresh cement-based materials due to their essential roles in the construction process as well as their effects on the mechanical properties and durability of hardened ones. Basically speaking, the macroscopic flowability is primarily determined by the microstructure of the materials, e.g. the packing state and the contents of solid phase in the cementitious suspension systems etc. [1-3]. In the fresh cement paste (FCP), the agglomeration of cement particles immediately takes places upon the contact of cement to...

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ZKG 10/2015

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ZKG 10/2015

Ressort:  Materials
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TEXT Zhang Yanrong1,2,3, Kong Xiangming2*, Gao Liang1,3,4*, Chen Feng1, Xing Feng5
1 State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing/China
2 Department of Civil Engineering, Tsinghua University, Beijing/China
3 Beijing Key Laboratory of Track Engineering, School of Civil Engineering, Beijing Jiaotong University, Beijing/China
4 Beijing Engineering and Technology Research Center of Rail Transit Line Safety and Disaster Prevention, Beijing ­Jiaotong University, Beijing/China
5 College of Civil Engineering, Shenzhen University, Shenzhen/China
* Corresponding ­addresses: kxm@mail.tsinghua.edu.cn; lgao@bjtu.edu.cn

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