摘要
采用赫切尔-巴尔克模型拟合流变曲线,研究了含水率、外加剂(聚羧酸减水剂和季铵盐型表面活性剂)对建筑渣土泥浆在不同静置时间下流变性能的影响,并阐明了外加剂的作用机理.结果表明:随着含水率的增大,建筑渣土泥浆的流变性能参数均减小;随着2种外加剂掺量的增大,建筑渣土泥浆的初始表观黏度和塑性黏度先增大后减小;建筑渣土泥浆的屈服应力随着季铵盐型表面活性剂掺量的增加而一直增大,随着聚羧酸减水剂掺量的增大先增大后减小,相同掺量下聚羧酸减水剂的作用效果更好;外加剂分子间的排斥力与黏土对外加剂的吸附力两者之间的主导作用决定建筑渣土泥浆的流变性能.
随着中国城市基建设施的加快建设,大量建筑渣土和废弃泥浆堆积已严重影响施工安全和城市绿色发
灌浆材料和浇筑式材料是常见的高附加值材料,具有初始流动性能好、经时损失小和后期强度高等性能.对渣土泥浆的流变行为进行研究,在不改变浆体水固比的情况下实现浆体流变性能的可调节,使其具有低含水率、高流态的施工性能,具有重要的现实意义.泥浆是典型的非牛顿流体,可采用宾汉姆流变模型拟合其流变曲
浆体中黏土颗粒易吸附外加
建筑渣土泥浆(后文简称渣土泥浆)为宁波市海曙区施工开挖的砂土质渣土,其含水

图1 渣土泥浆的粒径分布和XRD图
Fig.1 Particle size distribution and XRD pattern of waste mud
采用NJ‑160水泥净浆搅拌机,按
采用Brookfield DVNext流变仪测试渣土泥浆的流变性能,剪切速率为0~60

图2 动态剪切测试中剪切速率随时间的变化
Fig.2 Change of shear rate with time in dynamic shear test
不同含水率渣土泥浆的表观黏度见

图3 不同含水率渣土泥浆的表观黏度
Fig.3 Apparent viscosity of waste mud with different water contents
不同含水率对渣土泥浆流变性能的影响见

图4 不同含水率对渣土泥浆流变性能的影响
Fig.4 Effects of different water contents on rheological properties of waste mud
在0~60
由

图5 不同含水率渣土泥浆的屈服应力和塑性黏度
Fig.5 Yield stress and plastic viscosity of waste mud with different ww
不同聚羧酸减水剂掺量对WS50表观黏度的影响见

图6 不同聚羧酸减水剂掺量对WS50表观黏度的影响
Fig.6 Effects of different contents of SP on apparent viscosity of WS50
不同聚羧酸减水剂掺量下的WS50流变性能见

图7 不同聚羧酸减水剂掺量下的WS50流变性能
Fig.7 Rheological properties of WS50 with different contents of SP
由

图8 不同聚羧酸减水剂掺量下的WS50屈服应力和塑性黏度
Fig.8 Yield stress and plastic viscosity of WS50 with different SP contents
不同季铵盐型表面活性剂掺量对渣土泥浆表观黏度和初始流变性能的影响见

图9 不同季铵盐型表面活性剂掺量对渣土泥浆表观黏度和初始流变性能的影响
Fig.9 Effect of different YZ contents on apparent viscosity and initial rheological properties of waste mud
通过赫切尔-巴尔克流变模型拟合,可得到不同季铵盐型表面活性剂掺量下的渣土泥浆屈服应力和塑性黏度,结果见

图10 不同外加剂掺量下的渣土泥浆屈服应力和塑性黏度
Fig.10 Yield stress and plastic viscosity of waste mud with different additive contents
当w≤0.2%时,由于外加剂掺量低,其排斥力不足以破坏原有的结构,聚羧酸减水剂和季铵盐型表面活性剂均对渣土泥浆流变性能起到负面效果,泥浆的屈服应力和塑性黏度均增大.当w=0.3%时,由于季铵盐型表面活性剂的电荷密度较低、排斥力较小,不足以在渣土泥浆静止时破坏其“卡片屋”结构,导致泥浆的屈服应力继续增大,但当渣土泥浆发生流动后,在剪切力的作用下其“卡片屋”结构被破坏,内部颗粒间存在季铵盐型表面活性剂之间的排斥力,使得维持流动所需的力减小,渣土泥浆塑性黏度减小.聚羧酸减水剂电荷密度大,在渣土泥浆静止时产生的排斥力足以直接破坏其“卡片屋”结
内部自由水是影响渣土泥浆流变性能的关键.在不改变含水率的情况下,调节渣土泥浆流变性能只能通过增大颗粒间距,同时释放被黏土包裹的自由水.外加剂分子与黏土颗粒的作用机理主要是黏土颗粒吸附和分子间的排斥作用,其分子结构示意图见

图11 外加剂的分子结构示意图
Fig.11 Molecular structure diagrams of additives

图12 外加剂与黏土的层间吸附作用
Fig.12 Interlayer absorption between additive and clay

图13 不同掺量下外加剂对黏土的作用示意图
Fig.13 Schematic diagrams of the effect of additives on clay under different contents
(1)随着建筑渣土泥浆含水率从40%增加至60%,建筑渣土泥浆的表观黏度、屈服应力、塑性黏度均减小,但其流变经时损失减小,流变保持性更好;建筑渣土泥浆的屈服应力和塑性黏度均随着静置时间的增加而增大.
(2)建筑渣土泥浆的表观黏度、屈服应力、塑性黏度和流变经时损失随聚羧酸减水剂掺量增加先增大后减小;随着季铵盐型表面活性剂掺量的增加,渣土泥浆屈服应力增大,表观黏度和塑性黏度先增大后减小;当聚羧酸减水剂掺量达到0.3%时,建筑渣土泥浆塑性黏度减小至0.82 Pa·s,其效果明显优于相同掺量下的季铵盐型表面活性剂(2.38 Pa·s).
(3)在外加剂掺量较低的情况下,外加剂主要起到吸附黏土、团聚泥浆的作用,使建筑渣土泥浆屈服应力、塑性黏度和表观黏度均增大;在外加剂掺量较高的情况下,外加剂主要起静电排斥作用,使建筑渣土泥浆中的颗粒结构破坏,减小其塑性黏度和表观黏度;具有更高电荷密度的聚羧酸减水剂静电排斥力更大,对建筑渣土泥浆的流变性能改善效果更好.
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