Trade-Off Between Permeability and Compressive Strength for Aerated Concrete-Based Material with Fly-Ash Under High Pressure

Coal seam gas will seriously threaten the safety of mining. The stability of drainage borehole determines the safety of both mining and utilization of coal seam gas. However, the borehole will collapse, leading to the failure of gas drainage. A porous and firm low-cost aerated concrete-based material for borehole protection is proposed as a solution. Under high confining pressure, the mechanism of pore distribution of aerated concrete-based material on its properties is still unclear. In this work, the experiment and molecular dynamics simulation are combined to analyze how pore distribution determines its permeability and compressive strength. The effect of water-to-cement ratio on aerated concrete is first investigated by pore distribution, compressive strength, and permeability measures. The experimental results of optimal water-to-cement ratio of 0.6 agree with the existing experimental results of 0.54–0.64. Further, the orthogonal experiment is used to investigate the relationship between pore distribution and its permeability by doping fly-ash. It is found that under the same water-to-cement ratio, the doped fly-ash shows a limited effect on the permeability of aerated concrete. The pore in the range from 500 to 1500 μ m mainly contributes to the flow rate. The optimal mixture of doped aerated concrete is water-to-cement ratio of 0.6 and mass fraction of doped fly-ash of 40%. Moreover, the absorption/desorption effects of methane molecules are illustrated by molecular dynamics simulation. It is found that the flow rate of aerated concrete will be enhanced by hydrophobic fly-ash nanoparticles. The present work can inspire further mixture design and pave the way for the development of aerated concrete-based material with high porosity and compressive strength at high confining pressure.