*Article* **Study on Foamed Concrete Used as Gas Isolation Material in the Coal Mine Goaf**

**Changyu Xu 1,2, Lijun Han 1,2,\*, Maolin Tian 1,2, Yajie Wang <sup>1</sup> and Yuhao Jin 1,2**


Received: 25 July 2020; Accepted: 22 August 2020; Published: 25 August 2020

**Abstract:** In view of the serious threat of gas accumulation in the coal mine goaf and the limitations of the existing gas sealing materials, the orthogonal experiment was developed to study a new type of foamed concrete for mine gas sealing. Dry density, gas permeability, and compressive strength were studied as the material indicators according to the demands of the gas isolation material in the coal mine goaf, and the experimental results showed that foam content was the most important factor. Meanwhile, the optimum mix was selected according to the influence of foam content as well as the engineering requirement. Then two application modes of this foamed concrete for goaf gas isolation were put forward, after which the convection-diffusion model of gas was built by COMSOL Multiphysics (COMSOL Inc., Stockholm, Sweden) to reveal the mechanism of different application modes using the parameters of the new foamed concrete. Simulation results showed that this foamed concrete used as isolating material for goaf gas could significantly decrease the gas concentration in workface, which can provide a reference for similar engineering.

**Keywords:** foamed concrete; orthogonal experiment; optimum mix; coal mine goaf; gas isolation
