Preparation of graphene oxide/recycled cement-based composite materials
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摘要: 基于建筑垃圾再生细骨料替代天然砂，进行氧化石墨烯(GO)改性再生水泥基复合材料的综合物理性能和水化机制研究。采用超声分散GO及振动搅拌制备再生水泥基复合材料，综合耐久性能测试结果表明：和不掺GO再生水泥基复合材料相比，添加0.03% GO改性7 d龄期强度的GO/再生水泥基复合材料抗折和抗压强度分别提高了16%和21%；添加0.02% GO改性的28 d龄期强度的GO/再生水泥基复合材料抗折和抗压分别提高了13.7%和13.6%。GO/再生水泥基复合材料龄期7 d耐候、50次冻融循环后力学性能均良好；氯离子含量皆小于0.06%。放射性检测结果表明：GO/再生水泥基复合材料内照射指数IRa和外照射指数Ir均属于A类建筑材料。通过XRD、TG-DTA、SEM等手段对GO/再生水泥基复合材料水化机制研究表明：GO促进了钙矾石(AFt)晶体的大量生成及胶凝孔中存在更多的自由水，且对后期氢氧化钙(CH)的产生有抑制作用，进而提高了GO/再生水泥基复合材料综合物理性能。Abstract: Based on the replacement of natural sand by recycled fine aggregate from construction waste, the comprehensive physical properties and hydration mechanism of graphene oxide (GO) modified recycled cement-based composites were studied. The recycled cement-based composites were prepared by ultrasonic dispersion GO and vibration stirring. The comprehensive durability test results show that compared with recycled cement-based materials without GO, the flexural and compressive strength of the GO/recycled cement-based composites modified with 0.03% GO at 7 d age increase by 16% and 21%, respectively. The flexural strength and compressive strength of GO/recycled cement-based composites modified by 0.02% GO at 28 d age increase by 13.7% and 13.6%, respectively. The GO/recycled cement-based composite has a 7 d weather resistance and good mechanical properties after 50 freeze-thaw cycles; the chloride ion content is less than 0.06%. The radioactivity test results show that internal exposure index IRa and external exposure index Ir of GO/recycled cement-based composites belong to Class A building materials. The hydration mechanism of the GO/recycled cement-based composites was studied by XRD, TG-DTA, SEM and other means, the results show that GO promotes the large-scale formation of ettringite (AFt) crystals, and the presence of more free water in the gel pores, and has an inhibitory effect on the later generation of calcium hydroxide (CH), thereby improving the synthesis of GO/recycled cement-based composites physical properties.
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Key words:
- aggregates recycling /
- graphene oxide /
- cement-based composites /
- microstructure /
- cement hydration
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图 1 GO的TEM图像((a), (b))、XRD图谱(c)和FTIR图谱(d)
Figure 1. TEM images ((a), (b)), XRD pattern (c) and FTIR spectra (d) of GO
图 2 龄期水化GO/再生水泥基复合材料的强度变化: (a) 7 d；(b) 28 d
Figure 2. Intensity change of aged hydrated GO/recycled cement-based composites: (a) 7 d; (b) 28 d
图 3 GO/再生水泥基复合材料耐候抗冻融性能: (a)抗冻融试验；(b)耐候试验
Figure 3. Weather resistance, freeze-thaw resistance of GO/recycled cement-based composites: (a) Freeze-thaw resistance test; (b) Weather resistance test
图 4 龄期水化GO/再生水泥基复合材料XRD图谱: (a) 7 d; (b) 28 d
Figure 4. XRD patterns of aged hydrated GO/recycled cement-based composites: (a) 7 d; (b) 28 d
图 5 龄期水化GO/再生水泥基复合材料的TG和DTA曲线: (a) 7 d; (b) 28 d
Figure 5. TG-DTA curve of aged hydrated GO/recycled cement-based composites: (a) 7 d; (b) 28 d
图 6 龄期水化GO/再生水泥基复合材料的SEM图像
Figure 6. SEM images of aged hydrated GO/recycled cement-based composites
表 1 建筑垃圾的组成成分
Table 1. Composition of construction waste
Compsition Abandoned concrete Tile Sand Wood Others Content/% 67 16 9 3 5 
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表 2 再生细骨料的物理性能
Table 2. Physical properties of recycled fine aggregate
Apparent density/(kg·m−2) Bulk density/(kg·m−2) Water absorption rate/% 2334.8 1204.7 5.6
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表 3 标准砂的技术指标
Table 3. Technical Specifications of Standard Sand
Quality/g Silica content/% Loss on ignition/% Mud content/% 1350±5 98 0.3 0.01
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表 4 水泥的化学成分和矿物组成
Table 4. Chemical composition and mineral composition of cement
Clinker chemical composition/% Clinker mineral composition/% SiO2 Al2O3 CaO MgO SO3 f-CaO C3S C2S C3A C4AF 24.58 6.45 67.8 3.39 0.38 0.73 51.99 23.88 9.20 13.81
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表 5 氧化石墨烯(GO)的物理化学性能
Table 5. Physical and chemical properties of graphene oxide (GO)
Colour Thickness/μm Single layer/μm Peelable rate/% Tap density/(g·L−1) Graininess/mesh Oxygen content/wt% Brownish yellow ~1 0.2−10 >95 ~500 <80 ~51.6
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表 6 GO/再生水泥基复合材料的配比
Table 6. Experimental ratio of GO/recycled cement-based composites
Number Cement/g Sand/g Reclaimed sand/g Water/mL GO/% Fluidity/mm GO/recycled cement-0 450 945 405 252 0 187 GO/recycled cement-1 450 945 405 252 0.01 194 GO/recycled cement-2 450 945 405 252 0.02 189 GO/recycled cement-3 450 945 405 252 0.03 185 GO/recycled cement-4 450 945 405 252 0.04 182
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表 7 GO/再生水泥基复合材料中氯离子含量
Table 7. Chloride content in GO/recycled cement-based composites
Parameter GO/recycled
cement-0GO/recycled
cement-1GO/recycled
cement-2GO/recycled
cement-3GO/recycled
cement-4Cl− concentration/(mol·L−1) 0.00016839 0.00012556 0.00019146 0.00014859 0.00020216 Cl− mass percentage/% 0.005818 0.004457 0.006797 0.005277 0.007177
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表 8 GO/再生水泥基复合材料的内照射指数IRa和外照射指数Ir
Table 8. Internal exposure index IRa and external exposure index Ir of GO/recycled cement-based composites
Parameter GO/recycled
cement-0GO/recycled
cement-1GO/recycled
cement-2GO/recycled
cement-3GO/recycled
cement-4IRa 0.07 0.08 0.08 0.06 0.09 Ir 0.15 0.14 0.15 0.14 0.16 Grade A A A A A
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