摘要
以玄武岩粉末-电石渣固体废弃物凝胶体系为主料,掺入脱硫石膏,利用水热固化技术制备了人造石颗粒材料,分析了不同水热固化温度、水热固化时间、钙硅比对人造石颗粒强度及物相变化规律的影响.结果表明:人造石颗粒的抗压强度高于30 MPa,电石渣可替代消石灰;人造石颗粒的最佳制配方案为钙硅比0.9、温度200 ℃、时间12 h以及脱硫石膏添加量约5%.
中国建筑工程行业持续发展,石材需求量进一步增大.自2015年以来,中国一直位居世界石材进出口总量榜首.石材工业作为资源加工型产业,石粉废渣与成品的产出比约为3∶7,其造成的环境污染问题不容忽视,因此,开发石粉固废体系的综合利用方法迫在眉睫.
在工业生产中,石粉可用作二次工业原料、仿石涂料、建筑材料、混凝土和地聚物材料等.国内外学者针对玄武岩粉末的循环再利用已有大量研究.Dobiszewska
水热固化作为一种可在低温(<200 ℃)饱和蒸汽压环境下提高无机废弃物强度,实现固体废弃物再利用的方法,已被广泛应用于城市工业废弃物的再处
基于此,本文以玄武岩粉末为主要原料,利用水热固化技术,掺以一定比例的电石渣和脱硫石膏等固体废弃物,制备了人造石颗粒材料.通过无侧限抗压强度测试,分析了不同反应条件下人造石颗粒强度的变化规律;通过X射线衍射仪(XRD)、红外光谱(FTIR)和扫描电镜(SEM)、能谱分析(EDS)等,分析了人造石颗粒中的主要物相组成和具体形貌特征.研究成果以期为实现全固废凝胶体系再利用的批量化生产、为人造石颗粒在路基工程、混凝土粗骨料等领域的应用提供技术参考.
工业固体废弃物:电石渣(CS)取自湖北昌耀新材料股份有限公司;脱硫石膏(DG)取自浙江台州三门电厂;玄武岩粉末(BP)选自浙江嵊州.CS、DG和BP的SEM照片、XRD图谱分别见图

图1 CS、DG和BP的SEM照片
Fig.1 SEM images of CS, DG and BP

图2 CS、DG和BP的XRD图谱
Fig.2 XRD patterns of CS, DG and BP
Material | SiO2 | Al2O3 | CaO | Fe2O3 | MgO | SO3 | IL |
---|---|---|---|---|---|---|---|
CS | 3.765 | 94.443 | 0.195 | 0.333 | 15.500 | ||
DG | 2.269 | 0.516 | 49.328 | 0.442 | 0.539 | 45.422 | 21.300 |
BP | 48.228 | 14.282 | 9.186 | 14.952 | 4.485 | 1.275 |
人造石颗粒以玄武岩粉末为Si基材料,消石灰或电石渣为Ca基材料.设定钙硅比n(Ca)/n(Si)(BP与CS中所含CaO与SiO2的摩尔比)为0.4、0.6、0.7、0.8、0.9、1.0,并混合5%的脱硫石膏,用水量(以BP质量计)均为25%,且对玄武岩粉末进行筛分(74 μm).试验过程为:用JJ‑5水泥胶砂搅拌机将原料进行充分混合,水分批加入,选定低速档(140±5) r/min搅拌5 min后,改用高速档(285±5) r/min搅拌3 min;将混合料置于20×20 mm的模具中,通过BJ‑15型粉末压片机,在成型压力30 MPa下静压成型.将试件置于高压反应釜中,分别在水热固化温度T为80、120、160、200、240、260 ℃下,水热固化时间t为6、12、18、24 h,并于80 ℃下干燥10 h.对人造石颗粒进行无侧限抗压强度测试,并借助Bruker D8 Advance型XRD、Thermo Scientific Nicolet iS20型FTIR、Hitachi S4800型SEM、Micromeritics ASAP 2460型比表面积测试(BET)以及Hitachi SV8010型EDS对其进行表征.试验工况见
Material | n(Ca)/n(Si) | T/℃ | t/h |
---|---|---|---|
BP+SL+DG | 0.4, 0.6, 0.7, 0.8, 0.9, 1.0 | 200 | 12 |
BP+CS+DG | 0.4, 0.6, 0.7, 0.8, 0.9, 1.0 | 200 | 12 |
BP+SL+DG | 0.8 | 80, 120, 160, 200, 240, 260 | 12 |
BP+CS+DG | 0.8 | 80, 120, 160, 200, 240, 260 | 12 |
BP+SL+DG | 0.8 | 200 | 0, 6, 12, 18, 24 |
BP+CS+DG | 0.8 | 200 | 0, 6, 12, 18, 24 |
CaO‑SiO2‑H2O体系在水热反应条件下产物为不同的Ca、Si相,其中托勃莫来石(5CaO·6SiO2·5H2O)的产生可大幅提高混合体强

图3 钙硅比对人造石颗粒抗压强度的影响
Fig.3 Effects of n(Ca)/n(Si) on compressive strength of artificial stone particles
不同钙硅比下人造石颗粒的XRD和FTIR图谱见

图4 不同钙硅比下人造石颗粒的XRD和FTIR图谱
Fig.4 XRD patterns and FTIR spectra of artificial stone particles under different n(Ca)/n(Si)
根据IUPAC分类,人造石颗粒N2吸附-脱附等温曲线与Ⅳ型曲线相似,中段出现H1型吸附回滞环,说明其孔径分布较均匀.不同钙硅比下人造石颗粒的N2吸附-脱附等温曲线见

图5 不同钙硅比下人造石颗粒的N2吸附-脱附等温曲线
Fig.5 N2 adsorption and desorption isotherm of artificial stone particles under different n(Ca)/n(Si)
水热固化温度对人造石颗粒抗压强度的影响见

图6 水热固化温度对人造石颗粒抗压强度的影响
Fig.6 Effects of hydrothermal curing temperatures on compressive strength of artificial stone particles
不同水热固化温度下人造石颗粒的XRD和FTIR图谱见

图7 不同水热固化温度下人造石颗粒的XRD和FTIR图谱
Fig.7 XRD patterns and FTIR spectra of artificial stone particles under different hydrothermal curing temperatures
对比不同水热固化温度下人造石颗粒的FTIR图谱,随着水热固化温度的升高,试件的特征峰位置发生轻微偏移,但强度差异明显.3 400~3 619 c
水热固化时间对人造石颗粒抗压强度及结晶度的影响见

图8 水热固化时间对人造石颗粒抗压强度及结晶度的影响
Fig.8 Effects of hydrothermal curing time on compressive strength and crystallinty of artificial stone particles
不同水热固化时间下人造石颗粒的XRD和FTIR图谱见

图9 不同水热固化时间下人造石颗粒的XRD和FTIR图谱
Fig.9 XRD patterns and FTIR spectra of artificial stone particles under different hydrothermal curing time
不同水热固化时间下人造石颗粒的SEM照片见

图10 不同水热固化时间下人造石颗粒的SEM照片
Fig.10 SEM images of artificial stone particles with different hydrothermal curing time
Spot | Microtopography | At/% | Phase | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
O | Si | Ca | Al | Na | Mg | Fe | C | S | |||
1 | Bulk | 56.19 | 13.17 | 9.34 | 12.84 | 2.77 | 1.96 | 0.62 | 1.68 | Anorthite | |
2 | Cocoon | 52.02 | 13.49 | 12.77 | 3.43 | 1.57 | 2.12 | 0.13 | 11.65 | 0.32 | Crystalline C‑S‑H |
3 | Bar | 53.68 | 15.97 | 13.35 | 3.89 | 0.68 | 1.27 | 0.52 | 8.43 | 0.88 | Tobermorite |
4 | Bar | 53.21 | 16.85 | 14.16 | 2.57 | 0.83 | 1.54 | 0.11 | 7.29 | 0.16 | Tobermorite |
脱硫石膏的主要成分是二水硫酸钙(CaSO4·2H2O),大部分工业废弃物和一些天然矿物材料的主要化学组成可用CaO‑SiO2‑Al2O3体系概括,玄武岩粉末属于高硅类天然矿物材料,其活性来源为活性SiO2,脱硫石膏与玄武岩粉末协同作用反应具有一定的可行性.脱硫石膏掺量wDG对人造石颗粒抗压强度的影响见

图11 脱硫石膏掺量对人造石颗粒抗压强度的影响
Fig.11 Effect of desulfurized gypsum contents on compressive strength of artificial stone particles
(1)利用水热固化技术可用电石渣完全代替消石灰,将玄武岩粉末-电石渣-脱硫石膏固体废弃物凝胶体系制备成人造石颗粒材料.
(2)玄武岩粉末和电石渣可快速合成托勃莫来石,其反应机理是:在高温高压条件下,玄武岩粉末中的Si—O键在O
(3)随着水化反应时间的延长,主要水化产物的演变顺序为:块状原料、茧状C‑S‑H晶体和条状托勃莫来石晶体.本文试验条件下,人造石颗粒水热固化最佳制配方案:原料钙硅比为0.9、水热固化温度为200 ℃、水热固化时间为12 h.
(4)脱硫石膏对水热反应起硫酸盐激发作用,可有效促进人造石颗粒强度的增长;脱硫石膏过量会在反应初期形成大量钙矾石,包覆在玄武岩粉末表面,阻碍水热反应的进;脱硫石膏添加量取5%左右为宜.
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