Ling Gang, Shui Zhonghe, Sun Tao, Gao Xu, Wang Yunyao, Sun Yu, Wang Guiming, Li Zhiwei
School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China.
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel). 2018 Dec 18;11(12):2576. doi: 10.3390/ma11122576.
This study explores the effects of metakaolin (MK) and silica fume (SF) on rheological behaviors and microstructure of self-compacting concrete (SCC). The rheology, slump flow, V-funnel, segregation degree (SA), and compressive strength of SCC are investigated. Microstructure characteristics, including hydration product and pore structure, are also studied. The results show that adding MK and SF instead of 4%, 6% and 8% fly ash (FA) reduces flowability of SCC; this is due to the fact that the specific surface area of MK and SF is larger than FA, and the total water demand increases as a result. However, the flowability increases when replacement ratio is 2%, as the small MK and SF particles will fill in the interstitial space of mixture and more free water is released. The fluidity, slump flow, and SA decrease linearly with the increase of yield stress. The total amount of SF and MK should be no more than 6% to meet the requirement of self-compacting. Adding MK or SF to SCC results in more hydration products, less Ca(OH)₂ and refinement of pore structure, leading to obvious strength and durability improvements. When the total dosage of MK and SF admixture is 6%, these beneficial effects on workability, mechanical performance, and microstructure are more significant when SF and MK are applied together.
本研究探讨偏高岭土（MK）和硅灰（SF）对自密实混凝土（SCC）流变行为和微观结构的影响。研究了SCC的流变学、坍落流动度（扩展度）、V型漏斗试验、离析度（SA）和抗压强度。还研究了包括水化产物和孔隙结构在内的微观结构特征。结果表明，用MK和SF替代4%、6%和8%的粉煤灰（FA）会降低SCC的流动性；这是因为MK和SF的比表面积大于FA，导致总需水量增加。然而，当替代率为2%时流动性增加，因为小颗粒的MK和SF会填充混合料的间隙空间并释放出更多自由水。随着屈服应力的增加，流动性、坍落流动度和SA呈线性下降。为满足自密实要求，SF和MK的总量不应超过6%。向SCC中添加MK或SF会产生更多水化产物，减少Ca(OH)₂并细化孔隙结构，从而显著提高强度和耐久性。当MK和SF外加剂的总用量为6%时，SF和MK一起使用时对工作性、力学性能和微观结构的这些有益影响更为显著。
