2.1 Influence of pore structure on compressive strength
2.1.1 Effect of open and closed state of pores on compressive strength
The correlations between the AC total porosity ratio and compressive strength are shown in Figure 2.( represent F-1~F-8; represent C-10~C-30; represent C-x; represent Re-F.) There is a negative correlation between the compressive strength and the total porosity ratio, but the R2 of the linear fitting is only 0.6409. While, when the fresh AC and recycled AC are separately fitted, the R2 are up to 0.9798 and 0.9807 respectively, and the Re-F does not conform to the former two linear relationships. Accordingly, some pore characteristic index may be great different among the fresh ACs, recycled ACs and Re-F, which leads to AC compressive strength presents different relationships with characteristic index. As shown in Figure 3, there is a good negative correlation between the open porosity and compressive strength, regardless of whether the AC is recycled or not and whether the material is coal powder or AC powder. It can be seen that it is the open pores that lead to the decrease of the AC compressive strength, rather than the total pores including closed pores.
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FIGURE 2 Correlation between total porosity and compressive strength
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FIGURE 3 Correlation between open porosity and compressive strength