2of 11 2. Materials and Methods The BFS used in this study was the experimental raw material provided by China Steel in Taiwan, with the label S6000, packed in 20 kg sealed bags. The papermaking wastes were provided by the Chung Hwa Paper Corporation in eastern Taiwan. Among them, lime mud was collected from the caustic kiln, paper sludge was collected during the sewage treatment process, and the bottom ash was collected from the recovery boilers. All the papermaking wastes were directly collected from the same batch of paper, with 150 kg samples of each material packed in six sealed bags. The sample of raw materials is shown in Figure 1. Those four materials were dried to constant weight at 110 ◦ C and sieved with a mesh size of 0.282 mm. The main chemical components provided by the manufacturer are shown in Table 1. Alkali-activated cementitious materials are formed by mixing aluminosilicate mate- rials with alkali metal silicate solutions and alkali activators [17,18]. Among them, alkali- activated slag has received wide attention for its low CO2 emission, high compressive strength, durability, and fire resistance [19]. Recently, more emphasis has been placed on the potential for solidifying waste from alkali-activated blast furnace slag [20–24]. This study aimed to analyze the possibility of alkali-activating the mixture of wastes and blast furnace slag (BFS) in papermaking. Moreover, the effects of different wastes on the physical and mechanical properties of the slurry are discussed. In this study, different single-type papermaking wastes (SPW) were mixed with BFS and alkali-activated at am- bient conditions. The compressive strengths and stress-time curves were used to analyze the optimized component and proportion of waste replacement BFS. On this basis, differ- ent types of wastes were selected as paper waste mixture (PWM) for further analysis to ensure a balance between the proportion of wastes in the mixtures, compressive strengths, and flexibilities. The effect of organic materials, such as wood chips, was also discussed. This study provided an appropriate alkali equivalent (AE) for the alkali activators. Alkali-activated cementitious materials are formed by mixing aluminosilicate materials with alkali metal silicate solutions and alkali activators [17,18]. Among them, alkali- activated slag has received wide attention for its low CO 2 emission, high compressive strength, durability, and fire resistance [19]. Recently, more emphasis has been placed on the potential for solidifying waste from alkali-activated blast furnace slag [20–24]. This study aimed to analyze the possibility of alkali-activating the mixture of wastes and blast furnace slag (BFS) in papermaking. Moreover, the effects of different wastes on the physical and mechanical properties of the slurry are discussed. In this study, different single- type papermaking wastes (SPW) were mixed with BFS and alkali-activated at ambient conditions. The compressive strengths and stress-time curves were used to analyze the optimized component and proportion of waste replacement BFS. On this basis, different types of wastes were selected as paper waste mixture (PWM) for further analysis to ensure a balance between the proportion of wastes in the mixtures, compressive strengths, and flexibilities. The effect of organic materials, such as wood chips, was also discussed. This study provided an appropriate alkali equivalent (AE) for the alkali activators. 2. Materials and Methods The BFS used in this study was the experimental raw material provided by China Steel in Taiwan, with the label S6000, packed in 20 kg sealed bags. The papermaking wastes were provided by the Chung Hwa Paper Corporation in eastern Taiwan. Among them, lime mud was collected from the caustic kiln, paper sludge was collected during the sewage treatment process, and the bottom ash was collected from the recovery boilers. All the papermaking wastes were directly collected from the same batch of paper, with 150 kg samples of each material packed in six sealed bags. The sample of raw materials is shown in Figure 1. Those four materials were dried to constant weight at 110 °C and sieved with a mesh size of 0.282 mm. The main chemical components provided by the manufacturer are shown in Table 1. Considering the simplification of the alkali-activated cementitious material produc- tion and the convenience of storage and transportation, sodium silicate powder was used to prepare activators. The composition of sodium silicate powder was 46.07% of SiO 2 and 51.35% of Na 2 O. The AE of the activators was 10%, the silicate modulus (Ms) of the acti- vators was 0.93, and the water-binder ratio (W/B) was 0.5. some energy consumption and environmental impact [15]. In addition, some studies in- vestigated the use of bottom ashes as aggregates [16].
Sustainability 2022 , 14 , 13536
Figure 1. The material diagram. ( a ) BFS. ( b ) Lime mud. ( c ) Paper sludge. ( d ) Bottom ash. Figure1. The material diagram. ( a ) BFS. ( b ) Lime mud. ( c ) Paper sludge. ( d ) Bottom ash.
Table1. Chemical composition of paper industrial wastes and BFS.
SiO 2 (wt. %)
CaO (wt. %)
Al 2 O 3 (wt. %)
SO 3 (wt. %)
Fe 2 O 3 (wt. %)
L.O.I (wt. %)
Other (wt. %)
Item
BFS
28.1
53.7 71.6 18.2 16.7
13.2
–
0.5 3.4 0.5 7.9
–
4.5 1.5 2.1
limemud
– –
– –
16.2
3.2
paper sludge bottomash
3.7 5.2
74.2 18.2
33.5 4.4 Legend: SiO 2 —Silicon dioxide; CaO—Calcium oxide; Al 2 O 3 —Aluminum oxide; SO 3 —Sulphur trioxide; Fe 2 O 3 —Ferric oxide; L.O.I—Loss on ignition; wt.%—weight percentage. 14.1
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