Pore distributive heterogeneity of cementitious materials by poker vibration: Quantification and modification

Vibration is a critical procedure in the production of cementitious materials to reduce porosity and improve compaction. However, the vibration energy of poker (inserted-type) vibrators exhibits spatial attenuation, which leads to pore distributive heterogeneity and results in uneven mechanical behavior of the material. The current study experimentally investigates the heterogeneity issue and quantifies the relevant efficient compaction zone (ECZ) for a single poker vibrator. Experimental results demonstrate that energy transmission of poker vibration becomes stable at 20 s and forms the ECZ with only 53.9% coverage. The study confirms that certain difference of insertion depths between two adjacent vibrators can effectively improve the ECZ coverage and solve the corresponding heterogeneity problem. Subsequently, it formulates equations to determine the optimal depth difference and to develop a modified vibration mode. Compared to the conventional operation modes, the presented mode reduces the vertical porosity deviation from 2.46% to 0.90% and decreases the overall specimen porosity from 4.27% to 2.47%. And it achieves over 95% ECZ coverage. The findings and the proposed method have applications in promoting the precise vibration control for the on-site cementitious material production.