摘要
采用硫铝酸盐水泥-硅酸盐水泥-石膏三元复合体系制备了低收缩早强型灌浆料,探究了其微观结构形成机理.结果表明:根据最优配合比制备的灌浆料1、3 d抗压强度分别为60.1、75.5 MPa,3 d自收缩率为351.39×1
水泥基灌浆料加水拌和后具有流动性好、黏聚性强、承载力高和微膨胀等特性,是一种优异的结构修补填充材
探索降低灌浆料收缩变形并保证其早期强度的途径已迫在眉睫.卢佳林
由此可见,低收缩和早强、高强难以兼顾的问题在传统灌浆料中仍比较突出.鉴于此,本文采用硫铝酸盐水泥(CSA)-硅酸盐水泥(P·Ⅱ)-石膏(G)三元复合体系,制备低收缩早强型灌浆料,探索水泥复配比例mCSA/mP·Ⅱ(质量分数,文中涉及的掺量、含量、比值等除特别说明外均为质量分数或质量比)、复合掺合料(COAD)细度(以比表面积表示)和石膏掺量等参数对灌浆料性能的影响规律,并对其配合比进行优化.采用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等探究灌浆料的微观结构形成机理,以期为低收缩早强型灌浆料的制备提供一定的理论依据和技术支持.
水泥采用42.5级硫铝酸盐水泥和P·Ⅱ 42.5级硅酸盐水泥.石膏中CaSO4含量不低于90%.复合掺合料由优质粉煤灰(比表面积820
Material | CaO | SiO2 | Al2O3 | Fe2O3 | MgO | K2O | SO3 | TiO2 |
---|---|---|---|---|---|---|---|---|
CSA | 39.70 | 13.80 | 27.30 | 3.51 | 2.23 | 0.64 | 10.90 | 1.08 |
P·Ⅱ | 62.80 | 21.70 | 5.45 | 3.41 | 2.19 | 1.50 | 2.29 | 0.28 |
G | 46.40 | 1.32 | 1.83 | 2.27 | 0.62 | 0.12 | 46.52 | 0.27 |
COAD | 12.60 | 44.81 | 30.51 | 4.83 | 1.84 | 1.68 | 1.38 | 1.40 |
SF | 0.77 | 97.00 | 0.36 | 0.65 | 0.42 | 0.48 | 0.15 | 0.16 |
根据前期探索性试验,确定水胶比0.2,胶砂比1.1,复合掺合料总掺量45.0%,石膏掺入形式为外掺.依据密实堆积理论并通过试验优化途径确定灌浆料的基准配合比,如
Sample No. | Mix proportion% | mCSA/mP·Ⅱ | Specific surface area of COAD/( | |||||
---|---|---|---|---|---|---|---|---|
CSA | P·Ⅱ | G | SF | WRA | DE | |||
A0 | 0 | 55.0 | 0 | 0 | 4.0 | 0.1 | 0∶10 | 790 |
A1 | 5.5 | 49.5 | 0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
A2 | 11.0 | 44.0 | 0 | 0 | 4.0 | 0.1 | 2∶8 | 790 |
A3 | 16.5 | 38.5 | 0 | 0 | 4.0 | 0.1 | 3∶7 | 790 |
B1 | 5.5 | 49.5 | 0 | 0 | 4.0 | 0.1 | 1∶9 | 730 |
B2 | 5.5 | 49.5 | 0 | 0 | 4.0 | 0.1 | 1∶9 | 760 |
B3 | 5.5 | 49.5 | 0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
B4 | 5.5 | 49.5 | 0 | 0 | 4.0 | 0.1 | 1∶9 | 820 |
C1 | 5.5 | 49.5 | 1.0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
C2 | 5.5 | 49.5 | 3.0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
C3 | 5.5 | 49.5 | 5.0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
C4 | 5.5 | 49.5 | 7.0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
C5 | 5.5 | 49.5 | 9.0 | 0 | 4.0 | 0.1 | 1∶9 | 790 |
D0 | 5.5 | 49.5 | 0 | 5.0 | 4.0 | 0.1 | 1∶9 | 790 |
首先以硫铝酸盐水泥和硅酸盐水泥构建CSA+P·Ⅱ二元体系,分析水泥复配比例对灌浆料性能的影响,以此为基础确定复合掺合料的最优细度;再掺入石膏,形成CSA+P·Ⅱ+G三元复合体系,分析石膏掺量对灌浆料性能的影响;最后确定灌浆料的最优配合比.硅灰具有较高的活性,对提高灌浆料的早期强度有
灌浆料的各项性能测试依据JG/T 408—2019《钢筋连接用套筒灌浆料》进行.对最优配合比灌浆料取样进行SEM‑EDS和XRD测试,以分析灌浆料的微观结构形成机理.
凝结时间是灌浆料能否成功应用的前提条件,
Sample No. | Setting time/min | Sample No. | Setting time/min | ||
---|---|---|---|---|---|
Initial | Final | Initial | Final | ||
A0 | 450 | 540 | B4 | 93 | 117 |
A1 | 99 | 124 | C1 | 102 | 129 |
A2 | 28 | 44 | C2 | 97 | 126 |
A3 | 19 | 32 | C3 | 96 | 123 |
B1 | 88 | 115 | C4 | 89 | 121 |
B2 | 90 | 119 | C5 | 84 | 115 |
B3 | 99 | 124 | D0 | 70 | 100 |
(1)掺入硫铝酸盐水泥使灌浆料的凝结时间大幅缩短,尤其当水泥复配比例为2∶8(试样A2)和3∶7(试样A3)时,其初凝时间、终凝时间均分别低于30、50 min.表明随着硫铝酸盐水泥占比的提高,复配水泥水化逐渐加快,因此凝结时间均低于未掺硫铝酸盐水泥的灌浆料.
(2)复合掺合料细度对灌浆料初凝时间和终凝时间的影响较小;随着石膏掺量的增大,灌浆料的凝结时间逐渐缩短;试样C3的初凝时间和终凝时间分别为96、123 min,而以相同掺量的硅灰替代石膏(试样D0)后,灌浆料的初凝时间和终凝时间缩短至70、100 min,其原因在于硅灰的颗粒极细,火山灰活性较高,水化迅速,从而导致灌浆料的凝结时间缩短.

图1 水泥复配比例对灌浆料工作性的影响
Fig.1 Effect of cement compounding ratio on workability of grouting materials

图2 复合掺合料细度对灌浆料工作性的影响
Fig.2 Effect of fineness of composite admixture on workability of grouting materials

图3 石膏和硅灰掺量对灌浆料工作性的影响
Fig.3 Effect of gypsum and silica fume content on workability of grouting materials

图4 水泥复配比例对灌浆料力学性能的影响
Fig.4 Effect of cement compounding ratio on mechanical property of grouting materials
(1)随着硫铝酸盐水泥占比的增加,灌浆料各龄期的抗折强度与抗压强度均呈先上升后降低的趋势;当水泥复配比例为1∶9(试样A1)时,其1、3、28 d抗折强度与抗压强度均高于试样A0,且满足JG/T 408—2019的指标值.
(2)与试样A1相比,当水泥复配比例超过1:9时,试样A2和试样A3的抗折强度与抗压强度骤降,表明水泥复配比例对灌浆料各龄期的力学性能影响显著.其原因在于硫铝酸盐水泥的掺入提高了浆体早期的水化速率,形成了大量的钙矾石(AFt).同时,由于水化反应及所生成的胶体物质吸水,导致体系的耗水速率加快.当硫铝酸盐水泥占比过大时,由于体系失水较快,原水占据的空间未能被固相物质及时填充,形成了较多的孔隙.此外,体系的pH值也会因为硫铝酸盐水泥的掺入而降低,对粉煤灰的二次水化反应不

图5 复合掺合料细度和硅灰对灌浆料力学性能的影响
Fig.5 Effect of fineness of composite admixture and silica fume on mechanical property of grouting materials
(1)随着复合掺合料比表面积的增大,灌浆料各龄期的抗折强度先升高后降低,早期抗压强度呈下降趋势,后期抗压强度则先升高后降低;随着龄期的增长,复合掺合料的火山灰效应得以充分发挥,灌浆料的后期强度逐渐提高.
(2)以5.0%硅灰替代石膏降低了灌浆料的强度,试样D0的28 d抗压强度较试样B3降低约10 MPa.研究表

图6 石膏掺量对灌浆料力学性能的影响
Fig.6 Effect of gypsum content on mechanical property of grouting materials
(1)随着石膏掺量的增加,灌浆料的抗折强度与抗压强度先升高后降低.当石膏掺量为5.0%(试样C3)时,灌浆料的1、3 d抗折强度分别达到12.5、20.9 MPa,1、3 d抗压强度分别达到60.1、75.5 MPa,均满足JG/T 408—2019的指标值.表明适量石膏的掺入加速了复合体系的早期水化反
(2)当石膏掺量超过5.0%(试样C4和试样C5)时,灌浆料的28 d强度明显下降.这是因为过量石膏的掺入会导致AFt的生成量增加并迅速积聚在一起,所形成的浆体结构不利于灌浆料强度的发展.尤其当石膏在早期不能完全反应时,后期还会生成延迟AFt及二次石膏,使得灌浆料的抗压强度降

图7 水泥复配比例对灌浆料收缩性能的影响
Fig.7 Effect of cement compoumding ratio on shrinkage characteristics of grouting materials

图8 复合掺合料细度对灌浆料收缩性能的影响
Fig.8 Effect of fineness of composite admixture on shrinkage characteristics of grouting materials

图9 石膏和硅灰掺量对灌浆料收缩性能的影响
Fig.9 Effect of gypsum and silica fume content on shrinkage characteristics of grouting materials
(1)随着石膏掺量的增加,灌浆料的自收缩率先降低后升高,石膏掺量为5.0%(试样C3)时灌浆料的自收缩率最小,3 d自收缩率仅为351.39×1
(2)试样D0的自收缩率和干燥收缩率较大,其3 d的自收缩率和28 d的干燥收缩率分别为855.36×1
综合以上各因素对灌浆料凝结时间、工作性、力学性能和收缩性能的影响,确定试样C3的配合比为三元复合体系制备低收缩早强型灌浆料的最优配合比.
最优配合比灌浆料的SEM图像如

图10 最优配合比灌浆料的SEM图像
Fig.10 SEM images of grouting material with optimal mix proportion
硫铝酸盐水泥水化较快,在适量石膏作用下生成大量的AFt晶体,提供了灌浆料的早期强度.此外,本试验采用较低的水胶比,胶凝材料在最优颗粒级配的条件下可达到物理填充的均匀密实状态,水化生成的C‑S‑H凝胶填充于AFt晶体骨架中,使灌浆料的结构更加致密,促进并保证了后期强度的增长.AFt作为硫铝酸盐水泥主要的水化产物,具有一定的微膨胀性,其在很大程度上抑制了灌浆料的收缩变形.
对
Spot | At/% | n(Ca)/n(Si) | ||||
---|---|---|---|---|---|---|
O | Al | Si | S | Ca | ||
1 | 63.72 | 6.46 | 4.99 | 4.71 | 16.76 | 3.34 |
2 | 69.13 | 2.79 | 9.20 | 2.23 | 14.51 | 1.58 |
3 | 75.58 | 0 | 0 | 0 | 23.34 | 0 |

图11 水化28 d时最优配合比灌浆料的XRD图谱
Fig.11 XRD pattern of grouting material with optimal mix proportion hydrated for 28 d
(1)灌浆料的最优配合比:水胶比0.2、胶砂比1.1、硫铝酸盐水泥掺量5.5%、硅酸盐水泥掺量49.5%、石膏掺量5.0%(外掺)、复合掺合料掺量45.0%(比表面积790
(2)根据最优配合比制备的灌浆料1、3 d抗压强度为60.1、75.5 MPa,3 d自收缩率为351.39×1
(3)钙矾石(AFt)和水化硅酸钙(C‑S‑H)凝胶的稳定生长使灌浆料具有较高的早期强度,C‑S‑H凝胶还能促进灌浆料后期强度的发展.针棒状的AFt与片状Ca(OH)2晶体紧密结合,AFt的微膨胀作用使灌浆料的收缩变形逐渐变小,进一步保障了其早强、高强和低收缩特性.
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