Abstract
Compound properties of an alkali-free liquid accelerator are the mainstream of accelerator research and development in the present. Combined with the technical characteristics of wet-mix shotcrete in coal mines, organic high-polymer SWF is used to modify the accelerator because of improving the bond strength of the material and increasing the performance of antisagging. The mechanism of filling and thickening of SWF was analyzed from the aspects of pore characteristics and spatial structure of concrete. Through the determination of setting time, strength, and dispersibility, the optimum dose was determined, and a new style accelerator WIT-1 suitable for wet-mix shotcrete in coal mines was developed and applied on-site. The experimental results show that the addition of SWF increases the dispersibility of the accelerator product and the cohesiveness of concrete under the condition of ensuring strength and setting time, and the effect of modifying the accelerator to reduce the rebound of the wet-mix shotcrete is obvious.
Highlights
Advances in Materials Science and Engineering the study of compound modification of the accelerator, the comprehensive performance of the existing alkali-free liquid accelerator and the quality of shotcrete are improved and the application of the wet-mix shotcrete technology in the coal mining industry is promoted
Teng’s experiment [23] shows that the addition of a small volume of SWF in the mortar can significantly improve the mortar bond strength, bending strength, and compressive strength, and the flexibility of modified mortar is improved with the increase of SWF volume
From the consideration of improving the properties of wet-mix shotcrete, the polymer composition of SWF has good dispersibility and film-forming property so that it can form a film at the interface between the pores of the concrete and the matrix to form a small polymer phase to improve the bond strength. e internal organic adhesive composition of SWF can improve the antisagging property and instantaneous adhesion property of the concrete. e buffer layer can be formed as soon as possible by increasing the bond force between the cement slurry and the aggregate, thereby effectively promoting the mechanical energy conversion of the high-speed concrete slurry
Summary
The viscous degree of cement paste was observed by observation; during the test, we found that, with the increase of the volume of SWF, the cement paste becomes more viscous, which has good effect on increasing the cohesiveness of shotcrete, reducing the shotcrete rebound, and increasing the thickness of the primary spraying. Considering the influence of SWF on the setting time, compressive strength, and cohesiveness of the accelerator sample, the properties of the modified accelerator in group B are more balanced. E research shows that reducing the surface tension can increase the dispersibility of the accelerator. From the consideration of the construction technology of wet-mix shotcrete, reducing the surface tension of the accelerator can improve the sprayed dispersion of the accelerator and improve the ability of the liquid particles to capture the concrete particles, thereby enhancing the quick setting and bonding effect of concrete and improving the quality of shotcrete [21]. Table 4: 1 d and 28 d compressive strength of the modified accelerator and standard deviation of compressive strength
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