6of 11 suggested that the samples were crushed and lost the stress intensity at the peak. Only the peak points of the curves differed between them, indicating that lime mud or bottom ash could not change the characteristics of brittle materials, resulting in the alkali activation of BFS. In the partial substitution of BFS with paper sludge or wood chips, the curves decreased slowly at the peak. This change indicated that the samples still exceeded the yield strength in some respects. Based on these results, paper sludge or wood chips could significantly change the properties of alkali-activated BFS from brittle to ductile [29].
Sustainability 2022 , 14 , 13536
Figure 5. The stress curve of the slurry with the 20% proportion of SPW substituted for BFS. Figure5. The stress curve of the slurry with the 20% proportion of SPW substituted for BFS. 3.2. Effect of Paper Waste Mixture (PWM) Proportion Due to the experimental results of the partial substitution of BFS with SPW, the lime mud and paper sludge were considered suitable materials for partial substitution. The experiment parameters of the PWM substitution are shown in Table 3. The effect of the proportion of various waste mixtures on compressive strength was discussed in this section. Based on the results, the proportion of BFS in the mixed powder can be further reduced. 3.2. Effect of Paper Waste Mixture (PWM) Proportion Due to the experimental results of the partial substitution of BFS with SPW, the lime mud and paper sludge were considered suitable materials for partial substitution. The experiment parameters of the PWM substitution are shown in Table 3. The effect of the proportion of various waste mixtures on compressive strength was discussed in this sec- tion. Based on the results, the proportion of BFS in the mixed powder can be further re- duced. As shown in Figure 6, the compressive strengths of BFS substituted with waste mix- tures showed a similar trend to that of BFS substituted with SPW. The compressive strength rapidly increased to a maximum around day 7 and fluctuated from 7 to 28 days. When the BFS was substituted by waste mixtures with a weight proportion of 50%, the highest compressive strength was 23.1 MPa. It was evident that the compressive strength decreased with decreasing proportion of lime mud in the waste mixtures. For every 5% reduction in the proportion of lime mud, the average compressive strength decreased by nearly 2.5 MPa. Table 3. Experimental parameters of PWM substitution proportion. PWM5-5 50 20 30 Legend: AE—Alkali equivalent; Ms—Silicate modulus; W/B—Water-binder ratio; wt.%—weight percentage. PWM4-1 PWM4-2 As shown in Figure 6, the compressive strengths of BFS substituted with waste mix- tures showed a similar trend to that of BFS substituted with SPW. The compressive strength rapidly increased to a maximum around day 7 and fluctuated from 7 to 28 days. When the BFS was substituted by waste mixtures with a weight proportion of 50%, the highest compressive strength was 23.1 MPa. It was evident that the compressive strength decreased with decreasing proportion of lime mud in the waste mixtures. For every 5% reduction in the proportion of lime mud, the average compressive strength decreased by nearly 2.5 MPa. 60 60 30 20 10 20 10% 0.93 0.5 PWM5-1 PWM5-2 50 50 40 35 10 15 Experiment No. Solid Materials wt.% AE Ms W/B BFS Lime Mud Paper Sludge Table3. Experimental parameters of PWM substitution proportion. Experiment No. Solid Materials wt.% AE Ms W/B BFS Lime Mud Paper Sludge PWM4-1 PWM4-2 PWM5-1 PWM5-2 PWM5-3 PWM5-4 60 60 50 50 50 50 30 20 40 35 30 25 10 20 10 15 20 25 10% 0.93 0.5
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