摘要
为提高水泥-粉煤灰体系的早期性能,将二乙醇-单异丙醇胺(DEIPA)和水化硅酸钙晶核(C‑S‑H‑PCEs)这2种早强剂进行复掺,研究其对水泥-粉煤灰体系凝结时间、流动度和抗压强度的影响规律,同时结合X射线衍射仪(XRD)、热重-差示扫描量热(TG‑DSC)分析和扫描电镜(SEM)探讨其作用机理. 结果表明:DEIPA和C‑S‑H‑PCEs复掺可缩短水泥-粉煤灰净浆的凝结时间,增加其流动度,提高砂浆抗压强度;0.03% DEIPA和2.00% C‑S‑H‑PCEs复掺效果最优,净浆流动度增加217.5 mm,初凝和终凝时间分别缩短120、127 min,砂浆1、3 d抗压强度分别提高6.6、6.1 MPa.
2020年度中国建筑材料工业碳排放报告显示,水泥工业CO2排放量高达12.3亿t,约占建材行业CO2总排放量的83
水泥采用抚顺水泥股份有限公司产P∙Ⅰ42.5基准水泥,比表面积为357.5
Material | SiO2 | Al2O3 | Fe2O3 | CaO | MgO | SO3 | Other |
---|---|---|---|---|---|---|---|
Cement | 21.1 | 4.4 | 3.2 | 63.4 | 2.9 | 0.6 | 4.4 |
Fly ash | 43.0 | 23.0 | 2.5 | 5.6 | 1.0 | 0.8 | 24.1 |
醇胺类早强剂二乙醇-异丙醇胺(DEIPA)来自优索化工科技有限公司,试剂级,有效含量为85%,结构式如

图1 DEIPA的结构式
Fig.1 Structural formula of DEIPA

图2 C‑S‑H‑PCEs的TEM照片
Fig.2 TEM image of C‑S‑H‑PCEs
为探究DEIPA和C‑S‑H‑PCEs复掺对水泥-粉煤灰体系早期性能的影响,设计了试验配合比,如
Sample | w(DEIPA)/% | w(C‑S‑H‑ PCEs)/% | Cement/g | FA/g | Water/g | Sand/g | Sample | w(DEIPA)/% | w(C‑S‑H‑ PCEs)/% | Cement/g | FA/g | Water/g | Sand/g |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A0 | 0 | 0 | 315 | 135 | 225 | 1 350 | A5 | 0.02 | 1.00 | 315 | 135 | 225 | 1 350 |
A1 | 0.01 | 0.50 | 315 | 135 | 225 | 1 350 | A6 | 0.02 | 2.00 | 315 | 135 | 225 | 1 350 |
A2 | 0.01 | 1.00 | 315 | 135 | 225 | 1 350 | A7 | 0.03 | 0.50 | 315 | 135 | 225 | 1 350 |
A3 | 0.01 | 2.00 | 315 | 135 | 225 | 1 350 | A8 | 0.03 | 1.00 | 315 | 135 | 225 | 1 350 |
A4 | 0.02 | 0.50 | 315 | 135 | 225 | 1 350 | A9 | 0.03 | 2.00 | 315 | 135 | 225 | 1 350 |
根据GB/T 8077—2012《混凝土外加剂均质性试验方法》测定净浆流动性;根据GB/T 17671—2021《水泥砂浆强度检验方法(IOS法)》测定砂浆强度;根据GB/T 1346—2011《水泥标准稠度用水量、凝结时间、安定性检验方法》测定净浆凝结时间.采用Rigaku Ultima IV X射线衍射仪(XRD)表征水化试样的物相组成,其中靶材为Cu,扫描速率为10 (°)/min,扫描范围为10°~70°;采用日本HITACHI STA200型同步热分析仪(温度范围为室温~1 000 ℃;测试气体为氮气)对水化产物进行热重-差示扫描量热(TG‑DSC)分析;采用日本HITACHI S‑2360N型扫描电镜(SEM)进行微观形貌观察.
不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰净浆的流动度如

图3 不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰净浆的流动度
Fig.3 Fluidity of cement‑fly ash slurry under different use levels of DEIPA and C‑S‑H‑PCEs
不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰净浆的凝结时间如

图4 不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰净浆的凝结时间
Fig.4 Setting time of cement‑fly ash slurry under different use levels of DEIPA and C‑S‑H‑PCEs
不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰砂浆的抗压强度如

图5 不同DEIPA和C‑S‑H‑PCEs掺量下水泥-粉煤灰砂浆的抗压强度
Fig.5 Compressive strength of cement‑fly ash mortar under different use levels of DEIPA and C‑S‑H‑PCEs
为探究DEIPA和C‑S‑H‑PCEs复掺对水泥-粉煤灰体系水化产物的影响,采用XRD对掺入DEIPA和C‑S‑H‑PCEs的水泥-粉煤灰净浆进行物相分析,1 d龄期净浆的XRD图谱如

图6 不同DEIPA和C‑S‑H‑PCEs掺量下1 d龄期水泥-粉煤灰净浆的XRD图谱
Fig.6 XRD patterns of cement‑fly ash slurry cured for 1 d under different use level of DEIPA and C‑S‑H‑PCEs
不同DEIPA和C‑S‑H‑PCEs掺量下1 d龄期水泥-粉煤灰净浆的TG‑DSC曲线如

图7 不同DEIPA和C‑S‑H‑PCEs掺量下1 d龄期水泥-粉煤灰净浆的TG‑DSC曲线
Fig.7 TG‑DSC curves of cement‑fly ash slurry cured for 1 d under different use levels of DEIPA and C‑S‑H‑PCEs
水泥浆体中Ca(OH)2的含量通常反映水泥的水化程度.根据
(1) |
式中:w()为Ca(OH)2的含量,%;w()为Ca(OH)2损失水的质量分数,%;w() 为CaCO3的热损失质量分数, %;M()为Ca(OH)2的摩尔质量,g/moL;为Ca(OH)2损失水的摩尔质量,g/moL;为CO2的摩尔质量,g/moL.
A0 | A1 | A2 | A5 | A8 |
---|---|---|---|---|
11.5 | 15.4 | 15.9 | 14.7 | 14.9 |
1 d龄期水泥-粉煤灰净浆试样A0、A1和A8 的 SEM照片如

图8 1 d龄期水泥-粉煤灰净浆试样A0、A1和A8的SEM照片
Fig.8 SEM images of cement‑fly ash slurry samples A0、A1and A8 cured for 1d
水泥-粉煤灰体系的水化是一个非常复杂的过程,包括水泥熟料的水化与粉煤灰的二次水化.水泥熟料的水化主要为硅酸盐相和铝酸盐相的水化.粉煤灰的二次水化主要是其中活性SiO2、Al2O3与Ca(OH)2反应生成C‑S‑H凝胶、C‑A‑S‑H凝胶、AFt和单硫型硫铝酸钙(AFm)

图9 DEIPA和C‑S‑H‑PCEs促进水泥-粉煤灰体系水化过程的机理
Fig.9 Mechanism of promotion of cement‑fly ash hydration process by addtion of DEIPA and C‑S‑H‑PCEs
(1)DEIPA和C‑S‑H‑PCEs复掺可显著改善水泥-粉煤灰净浆的流动度,缩短其凝结时间.复掺0.03% DEIPA和2.00% C‑S‑H‑PCEs后,水泥-粉煤灰净浆流动度达到最大值299.0 mm,较空白组增大217.5 mm;且净浆凝结时间明显缩短,初凝和终凝时间分别为103、183 min,较空白组缩短120、127 min.
(2)复掺DEIPA和C‑S‑H‑PCEs可提高水泥-粉煤灰砂浆的早期强度,复掺0.03% DEIPA和2.00% C‑S‑H‑PCEs后,水泥-粉煤灰砂浆的1、3 d抗压强度达到最大值16.8、23.8 MPa,较空白组提高6.6、6.1 MPa.
(3)DEIPA和C‑S‑H‑PCEs复掺能够促进水泥熟料的水化和粉煤灰的二次水化,改善水泥-粉煤灰体系的早期性能,且在本文研究范围内,随着DEIPA和C‑S‑H‑PCEs掺量的增加,水泥-粉煤灰体系的早期性能改善愈加显著.
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