摘要
以煤制天然气残渣(CSNGS)为辅助胶凝材料,采用旋转流变仪、抗折与抗压试验、X射线衍射仪(XRD)、扫描电镜-能谱仪(SEM‑EDS)、傅里叶变换红外光谱(FTIR)、热重分析(TG)等测试技术及方法,系统研究CSNGS对水泥复合胶凝材料流变性能、力学性能及微观结构的影响规律和作用机理.结果表明:掺入适量CSNGS可改善复合胶凝材料净浆的流变性能,当CSNGS掺量为10.0%时,净浆的屈服应力和塑性黏度分别降低27.2%和35.0%;掺入CSNGS有助于提升复合胶凝材料砂浆的抗折强度,当CSNGS掺量为20.0%时,复合胶凝材料砂浆28 d抗折强度为8.9 MPa,较水泥砂浆提高13.8%;当CSNG掺量为0%~30.0%时,复合胶凝材料砂浆28 d抗压强度可达水泥砂浆的88%以上.掺入CSNGS后反应产物中的凝胶和Ca(OH)2含量减少,凝胶中n(Ca)/n(Al+Si)、n(Ca)/n(Si)及n(Si)/n(Al)降低,钙矾石(AFt)含量增加,反应产物中有水化硅铝酸钙(C‑A‑S‑H)凝胶生成.
在“双碳”目标下,利用辅助胶凝材料替代部分硅酸盐水泥,降低混凝土中的水泥含量是建筑行业实现节能减排的有效途
部分工业废渣因具有较高的反应活性、良好的经济及环境效益成为辅助胶凝材料的主要来源.常用的辅助胶凝材料为粉煤
鉴于此,本文采用机械球磨方式对CSNGS进行活化,研究CSNGS掺量(质量分数,文中涉及的掺量、水胶比等均为质量分数或质量比)对CSNGS‑水泥复合胶凝材料流变性能、力学性能及微观结构的影响规律和作用机理.
CSNGS来源于内蒙古大唐国际克什克腾旗煤制天然气公司,经机械球磨45 min后备用(球料比为1.00∶0.25、球磨机转速为350 r/min、球磨45 min的CSNGS反应活性最
Material | SiO2 | Al2O3 | Fe2O3 | CaO | Na2O | MgO | K2O | SO3 | Other |
---|---|---|---|---|---|---|---|---|---|
Cement | 20.6 | 7.1 | 3.7 | 60.8 | 0.2 | 1.9 | 0.7 | 4.2 | 0.8 |
CSNGS | 52.0 | 20.1 | 11.6 | 6.5 | 3.1 | 2.8 | 1.5 | 0.2 | 2.2 |

图1 水泥和CSNGS的XRD图谱
Fig.1 XRD patterns of cement and CSNGS
Setting time/min | Flexural strength/MPa | Compressive strength/MPa | |||||
---|---|---|---|---|---|---|---|
Initial | Final | 3 d | 28 d | 3 d | 28 d | ||
168 | 229 | 5.5 | 7.7 | 28.1 | 51.7 |

图2 水泥和CSNGS的粒径分布
Fig.2 Particle size distributions of cement and CSNGS
Specimen code | w(cement)/% | w(CSNGS)/% | mW/mB |
---|---|---|---|
Cement | 100.0 | 0 | 0.5 |
CSNGS2.5% | 97.5 | 2.5 | 0.5 |
CSNGS5% | 95.0 | 5.0 | 0.5 |
CSNGS10% | 90.0 | 10.0 | 0.5 |
CSNGS20% | 80.0 | 20.0 | 0.5 |
CSNGS30% | 70.0 | 30.0 | 0.5 |
CSNGS40% | 60.0 | 40.0 | 0.5 |
CSNGS50% | 50.0 | 50.0 | 0.5 |
CSNGS75% | 25.0 | 75.0 | 0.5 |
本研究制备尺寸为的砂浆试件,先置于(20±2) ℃、相对湿度不小于90%的养护箱内养护24 h后脱模,再在室温下水养护至7、28、90 d,用于抗折、抗压强度试验;制备尺寸为的净浆试样,养护至28 d,用于微观分析.采用Brookfield RST‑SST型旋转流变仪测试净浆的流变特性;采用D/Max 2400型XRD分析反应产物组成;采用Nova NanoSEM 450型场发射扫描电镜-能谱仪(SEM‑ESD)研究反应产物的微观形貌和元素组成;采用EQUINOX55型傅里叶变换红外光谱(FTIR)测试仪分析产物的官能团与化学键;采用SDTA851E型热重/差热同步热分析仪分析产物受热后的质量损失.
Bingham流体模型是水泥等胶凝材料最常用的流变模
(1) |
式中:τ 为剪切应力,Pa;τ0 为屈服应力,Pa;η 为塑性黏度,Pa·s;为剪切速率,

图3 CSNGS‑水泥复合胶凝材料净浆的流变曲线
Fig.3 Rheological curves of CSNGS‑cement composite cementitious material slurry

图4 CSNGS‑水泥复合胶凝材料砂浆的抗折强度和抗压强度
Fig.4 Flexural strength and compressive strength of CSNGS‑cement composite cementitious material mortar
由
由

图5 CSNGS‑水泥复合胶凝材料净浆的XRD图谱
Fig.5 XRD patterns of CSNGS‑cement composite cementitious material slurry

图6 CSNGS‑水泥复合胶凝材料净浆的FTIR光谱
Fig.6 FTIR spectra of CSNGS‑cement composite cementitious material slurry

图7 CSNGS‑水泥复合胶凝材料净浆SEM照片和EDS分析
Fig.7 SEM images and EDS analysis of CSNGS‑cement composite cementitious material slurry
由

图8 CSNGS‑水泥复合胶凝材料净浆的TG‑DTG曲线
Fig.8 TG‑DTG curves of CSNGS‑cement composite cementitious material slurry
(1)煤制天然气残渣(CSNGS)-水泥复合胶凝材料净浆的流变曲线与水泥净浆流变曲线相似,均符合Bingham流体模型.掺入适量CSNGS有助于改善复合胶凝材料的流变性能.随着CSNGS掺量的增加,复合胶凝材料净浆的屈服应力和塑性黏度先减小后增大.0%~20.0% CSNGS掺量对复合胶凝材料净浆的流变性能具有正效应.
(2)掺入适量CSNGS有助于提升复合胶凝材料砂浆的抗折强度.当CSNGS掺量为20.0%时,复合胶凝材料砂浆的28 d抗折强度为8.9 MPa,较未掺CSNGS的水泥砂浆增加13.8%;当CSNGS掺量为0%~30.0%时,复合胶凝材料砂浆的28 d抗压强度可达未掺CSNGS水泥砂浆的88%以上.
(3)随着CSNGS掺量的增加,复合胶凝材料反应产物中的凝胶和Ca(OH)2含量逐渐减少,凝胶中n(Ca)/n(Al+Si)、n(Ca)/n(Si)、n(Si)/n(Al)降低,钙矾石(AFt)含量显著增加,反应产物中有水化硅铝酸钙(C‑A‑S‑H)凝胶生成.AFt对凝胶的连接作用及水化硅酸钙(C‑S‑H)凝胶与C‑A‑S‑H凝胶的相互填充作用使复合胶凝材料强度得到一定保障.
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