Abstract
Polyurethane (PU) grouting material has been widely utilized to control water inrush in mining fields. However, the application has been limited by its high cost and poor flame retardancy. Here, we use the fly ash (FA), a waste from coal of the iron-making industry and power plants, as a partial replacement of conventional filler in PU grouting materials to reduce the production cost and the environmental pollution of FA. The surface-modified FA-filled PU (PU/FA) composites were prepared by room-temperature curing. The effects of FA contents (φ) on the structure, foaming behavior, thermal stability, mechanical properties, hydrophobic properties, and flammability of PU grouting materials were examined. Results showed that the higher the φ, the more porous the PU/FA composites are, resulting in a lower density and lower mechanical properties. The relationship between the compression modulus E and the density ρ of the PU/FA composites was E ∝ ρ1.3. In addition, the surface-modified FA improved the compatibility between the hard and soft segment of PU in the PU/FA composite, giving the composites enhanced thermal stability, high hydrophobicity, and flammability resistance.
Highlights
Owing to the complex underground geological conditions of coal mines, accidents such as coal slippage, gas protrusion, and mine water inrush in fractured rock mass occur and seriously affect the safety of underground operators and the efficiency of this process
The peak of fly ash (FA) at 1097 cm−1 corresponds to the Si-O-Si bond’s stretching vibration, and that at 798 cm−1 corresponds to the Si-CH3 bond. These results indicated that the peak strength of FA at 1097 and 798 cm−1 was enhanced possibly due to the increased or stable presence of Si-O-Si bonds and Si-CH3 bonds after the modification by silane coupling agents
This indicates that many polymers adhered to the surface of the FA particles after being modified by a silane coupling agent This phenomenon is consistent with the results reported by
Summary
Owing to the complex underground geological conditions of coal mines, accidents such as coal slippage, gas protrusion, and mine water inrush in fractured rock mass occur and seriously affect the safety of underground operators and the efficiency of this process. A widely used and time-proven technique to prevent such mine accidents is to reinforce broken coal and rock by grouting, which can effectively connect and support weak structures. Traditional inorganic materials are easy to dilute and hard to coagulate under the influence of water inrush, while the high reactive exotherm, flammability, and high cost of organic materials violate the original purpose of disaster management. Organic materials tend to foam in wet fractures greatly reducing their strength. Research on grouting materials for coal mines has become an important research direction for the safety of coal mining
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