不同水灰比、砂灰比下碳酸钙晶须对水泥砂浆流变性的影响

采用旋转流变仪研究碳酸钙晶须增强水泥砂浆拌合物的流变性能。分析不同水灰比、砂灰比及碳酸钙晶须掺量下,新拌砂浆的屈服应力、塑性黏度和滞回环面积的变化。结果表明:碳酸钙晶须增强水泥砂浆拌合物的流变性符合Bingham模型;水灰比从0.35减小至0.30时,新拌碳酸钙晶须水泥砂浆的屈服应力、塑性黏度均增大,最大增幅分别为92.0倍和4.8倍;碳酸钙晶须掺量从0增大至2.5%时,新拌碳酸钙晶须水泥砂浆的屈服应力、塑性黏度均呈增大趋势,最大增幅分别为24.5倍和1.6倍。分析滞回环面积的变化表明,随着水灰比的减少和晶须掺量的增加,浆体内部阻碍流动的絮凝结构和网状结构的数量增大,这也是导致拌合物流动性差、流变参数大的主要原因。     

高地温环境下水泥基注浆材料性能研究及配比优化

为探明高地温地下工程中注浆材料的适宜配比,采用L₁₆(4⁵)正交试验,选取水灰比/膨润土掺量、减水剂含量、粉煤灰和矿粉掺量4个因素进行试验,测试了浆液在模拟地温(60℃和80℃)环境中的性能指标。研究结果表明：温度由60℃升至80℃,水泥基浆液析水率降低,黏度增加,凝结时间变短;60℃和80℃环境下结石体抗压强度分别在7 d和3 d达到最大值;水灰比/膨润土掺量对水泥基浆液析水率、黏度和抗压强度起主控作用,粉煤灰掺量对凝结时间影响最大,对抗压强度的影响顺序为水灰比/膨润土掺量>粉煤灰掺量>矿粉掺量>减水剂含量;采用矩阵分析方法,得出60℃和80℃环境浆液的最优配比均为水灰比0.6/膨润土掺量0、减水剂含量0.15%、粉煤灰掺量0、矿粉掺量30%。     

新拌石灰石粉-偏高岭土-水泥系统流变特性研究

石灰石粉和偏高岭土复掺可以替代部分水泥,有效降低水泥制品的碳排放。采用安东帕MCR 302旋转流变仪测试了新拌石灰石粉-偏高岭土-水泥浆体系统的流变特性。通过单纯形重心法对石灰石粉-偏高岭土-水泥砂浆系统进行了试验设计,利用Viscometer 5型混凝土流变仪对不同配比砂浆的流变特性进行了测试。结果表明：随着偏高岭土掺量的增加,水泥浆体的屈服应力和塑性黏度显著增大;随着石灰石粉掺量的增加,水泥浆体的屈服应力和塑性黏度呈先增大后减小的趋势;改变砂浆胶凝材料的配比能够显著影响砂浆的流动性以及流变参数。     

水泥-白云石粉浆体流变性能研究

试验采用旋转黏度计测定了水泥-白云石粉浆体剪切应力和塑性黏度随剪切速率变化的规律,对所测浆体T-γ曲线采用Bingham流体模型进行拟合,得到浆体屈服应力和塑性黏度,采用Power Law流体模型拟合出浆体的流变指数,并用触变环面积表征浆体的触变性.研究结果表明:在0 ～ 30％掺量范围内,随白云石粉掺量的增大,水泥浆体的屈服应力、塑性黏度和触变性均逐渐增加;白云石粉细度对浆体屈服应力和塑性黏度影响较小.     

陶粒泡沫混凝土配合比对抗压强度的影响研究

采用正交试验的方法,对陶粒掺量、水灰比和粉煤灰掺量对陶粒泡沫混凝土抗压强度的影响进行研究,以实现优化配合比、提高强度的目的。试验结果表明：粉煤灰掺量对陶粒泡沫混凝土抗压强度影响最大,陶粒掺量次之,水灰比最小;推荐配合比为：陶粒掺量为10%～20%,粉煤灰掺量为10%～15%,水灰比为0.4～0.5,其抗压强度最高。     

再生微粉和石灰石粉对水泥浆体流变性能的影响

本文基于流变学原理研究了10%、20%和30%的再生微粉和石灰石粉对水泥浆体扩展度、屈服应力和塑性黏度等流变性能的影响,并进一步研究了不同体系的Zeta电位,阐明再生微粉和石灰石粉掺量对水泥浆体流变性能的影响机理。结果表明：再生微粉和石灰石粉对水泥浆体流变性能有着显著的影响;随着再生微粉掺量增加,浆体的屈服应力和塑性黏度先增加后减小,而石灰石粉体系则表现为随着掺量的增加,浆体的屈服应力和塑性黏度先减小后增加,这主要与再生微粉和石灰石粉体系的Zeta电位有关。     

水泥-粉煤灰-石灰石粉复合浆体的流变性能

采用Rheolab QC型旋转黏度计研究了水泥–粉煤灰–石灰石粉复合浆体的流变性能,分析了不同粉体含量以及石灰石粉颗粒粒径对复合浆体屈服应力、塑性黏度以及触变性的影响。结果表明:复合浆体中石灰石粉掺量增大或颗粒粒径减小,浆体屈服应力、塑性黏度和触变性均增大;随剪切速率增大,水泥–粉煤灰–石灰石粉复合浆体发生显著的剪切稀化现象,随后塑性黏度渐趋稳定,掺入石灰石粉后,提高了浆体由剪切稀化向塑性黏度逐渐稳定时需要的剪切速率;在水泥–粉煤灰体系浆体中掺入质量分数为20%～40%石灰石粉能够显著改善浆体的流变性能,提高浆体的稳定性。     

矿物掺合料对胶凝材料浆体流变性能和触变性的影响

基于大流态混凝土配合比,研究了各种矿物掺合料对胶凝材料浆体的流变性能和触变性的影响。结果表明:通过流变仪转速阶梯变化制度构建稳定的浆体流动状态,并利用转换方程可进行浆体流变性能参数的有效测量和计算。胶凝材料浆体的流变性能符合Bingham模型。粉煤灰和粉煤灰微珠均能降低浆体的屈服应力、塑性黏度和触变性,粉煤灰微珠作用效果更为明显;硅灰能增大浆体的屈服应力、塑性黏度和触变性;磨细矿渣粉会降低浆体的屈服应力和触变性,提高浆体的塑性黏度。在进行大流态混凝土配合比设计时应综合考虑矿物掺合料对新拌混凝土流变性能的影响。     

大掺量粉煤灰泡沫混凝土保温板的试验研究

采用H2O2作发泡剂,制备了大掺量粉煤灰泡沫混凝土保温板,分析了其结构形成机理;研究了粉煤灰掺量、激活剂、水灰比和发泡剂等因素对性能的影响.通过优化工艺参数,制备了粉煤灰掺量达到45％(质量百分数),性能优良的泡沫混凝土保温板.     

含不同形态硅灰的复合胶凝材料浆体的流变学特性（英文）

通过流变度和坍落度测试,研究了原状硅灰和加密硅灰对水灰比为0.25和0.30的复合胶凝材料的流变性能的影响。结果表明:初始测量中,加密硅灰(0~12%)使净浆屈服应力从0~5 Pa增加到20~60 Pa,塑性黏度从1 500 mPa·s增大到3 200 mPa·s;原状硅灰的掺加(0~12%)使净浆的屈服应力基本维持在0~8 Pa,塑性黏度在1 500~2 000 mPa·s。加密硅灰可以增大复合胶凝材料浆体的屈服应力和塑性黏度,原状硅灰则能在一定时间内使复合胶凝材料浆体保持相同的流变性。无论含有何种形态的硅灰,复合胶凝材料浆体的屈服应力和扩展度之间均呈线性关系,相关系数达到R~2=0.911 16。     

基于粉煤灰掺量的砂浆塑性收缩开裂本构关系的研究

研究了粉煤灰掺量对于砂浆塑性收缩性能和塑性粘度的影响。试验表明,随着粉煤灰掺量的增加,砂浆抗裂指数增大,开裂所需时间增加,塑性粘度降低;建立了粉煤灰掺量与砂浆抗裂指数、开裂时间的本构关系,及掺加粉煤灰后砂浆塑性粘度与抗裂指数的本构关系。     

环保型套筒灌浆料的配合比设计及性能研究

选用碱矿渣水泥作为胶凝材料,结合Dinger-Funk方程的最紧密堆积理论,用粉煤灰漂珠作为矿物掺合料,并用铜尾矿砂部分取代天然砂来提高粉体的堆积密度,制备套筒灌浆料.研究了塑性膨胀剂掺量、粉煤灰漂珠掺量、铜尾矿掺量、砂胶比对套筒灌浆料性能的影响,并对最紧密堆积设计配合比进行了验证.结果表明:随着塑性膨胀剂掺量的增加,...     

Influence of particle size distributions on yield stress and viscosity of cement–fly ash pastes

The rheological properties of blended cement-based materials depend strongly on mixture proportions and the characteristics of the components. In this study, design of experiments is used to investigate the influence of three variables (cement particle size distribution (PSD), fly ash PSD, and ratio of fly ash to cement) at each of four levels on the yield stress and viscosity of blended pastes. Both rheological parameters are seen to vary over several orders of magnitude for the evaluated design space. Physical characteristics of the powders, such as cement and total particle densities and total particle surface area, are computed for each mixture. A percolation-type relationship is observed between yield stress and cement particle (number) density. While neither apparent nor plastic viscosities were particularly well described by the commonly employed Kreiger–Dougherty equation, plastic viscosities were found to be linear functions of either total (cement + fly ash) particle surface area or total particle density.     

Rheological properties of cementitious materials containing mineral admixtures

The rheological properties of cementitious materials containing fine particles, such as mineral admixtures (MA), were investigated using a Rotovisco RT 20 rheometer (Haake) with a cylindrical spindle. The mineral admixtures were finely ground blast furnace slag, fly ash and silica fume. The cementitious materials were designed as one, two and three components systems by replacement of ordinary portland cement (OPC) with these mineral admixtures. The rheological properties of one-component system (OPC) were improved with increasing the dosage of PNS-based superplasticizer. For two-components systems, yield stress and plastic viscosity decreased with replacing OPC with blast furnace slag (BFS) and fly ash (FA). In the case of OPC-silica fume (SF) system, yield stress and plastic viscosity steeply increased with increasing SF. For three components systems, both OPC-BFS-SF and OPC-FA-SF systems, the rheological properties improved, compared with the sample with SF. In the two and three components systems, the rheological properties of samples containing BFS improved much more than with FA replacement alone.     

Rheological properties of grouts with viscosity modifying agents as diutan gum and welan gum incorporating pulverised fly ash

This investigation was undertaken to evaluate the influence of the dosage of the second generation of viscosity modifying agent (diutan gum) on fluidity and rheological parameters of cement-based materials grout compared to welan gum. All grouts were made with 0.40 water-to-binder ratio (W/B). The fresh properties of control grouts made without any viscosity modifying agent (VMA) and with superplasticizer (SP) were compared to those of grouts made with 0.02, 0.04, 0.06 and 0.08% diutan gum by mass of binder. Similar mixes made with welan gum were compared to those containing diutan gums. The effect of admixtures on fluidity and rheological parameters are discussed in this paper. The effect of the replacement of cement by pulverised fly ash (PFA) was also investigated. Grouts with replacements of PFA of 5, 13 and 20% by mass were used with the same W/B. Similar control grouts and mixes incorporated different dosages of PFA made with welan gum were made in order to compare the fluidity and the rheological parameters to the previous grouts made with diutan gum.The results show that the increase of the dosage of diutan gum and welan gum for a given dosage of SP increases significantly the yield value, the apparent and plastic viscosity and reduces the fluidity. With an increase in dosage of SP, the apparent viscosity at low shear rate decreases dramatically than that at high rate of shear rate due to the pseudo-plastic rheology of the grouts containing VMA. Both VMAs exhibited high apparent viscosity values at low shear rates which were attributed to the entanglement and intertwining of VMA polymer chains at low shear rate and association of water between adjacent chains. For a given dosage of VMA, diutan gum showed a high apparent viscosity than welan which could be attributed to the molecular weight and to the long-side chain of diutan gum leading to greater entanglement and intertwining. For any given dosage of SP, the diutan gum exhibited higher yield value and plastic viscosity than welan gum. Diutan gum grouts demonstrate a greater yield value and apparent and plastic viscosity than welan gum for control and PFA grouts. The replacement of cement by PFA resulted in a reduction of yield value and an increase in plastic viscosity.     

高钙粉煤灰在小石峡水电站中的应用研究

研究了高钙粉煤灰不同掺量情况下混凝土的体积安定性及高钙粉煤灰的最大掺量情况下,在不同水胶比、不同掺量情况下混凝土的力学性能及耐久性性能。研究发现：掺高钙粉煤灰混凝土的安定性可通过测定其胶凝材料的安定性来评定,掺加25%左右的高钙灰,所配制的混凝土的强度性能和体积稳定性都较好,随着水胶比的降低,掺高钙粉煤灰混凝土同龄期的抗压强度逐渐增大：掺高钙粉煤灰灰混凝土具有良好的抗渗性能及良好的抗冻性能。     

Ⅰ级粉煤灰对水泥净浆开裂的影响

采用环约束法,试验研究了Ⅰ级粉煤灰对不同水胶比下水泥净浆开裂的影响。试验研究发现：Ⅰ级粉煤灰在低水胶比（0.24）情况下对净浆开裂几乎没有影响,当水胶比为0.32和0.40时抗裂作用明显;较高水胶比（0.32、0.40）情况下,Ⅰ级粉煤灰对净浆的抗裂性能有较好的改善作用,在20%～65%掺量范围内,随着掺量的增大,净浆的开裂龄期延长,抗裂性能提高。     

外加剂对半柔性路面用早强型水泥基灌浆料工作性能的调控

针对大孔隙沥青混合料路面对灌浆材料工作性能要求较高的特点,本文开发了一种半柔性路面用早强型水泥基灌浆料。采用快硬硫铝酸盐水泥与普通硅酸盐水泥在不同比例下进行复掺,确定了水泥体系的基础配比;通过正交试验,确定了粉煤灰、硅灰、赤泥等矿物掺合料最佳配比。通过在灌浆料体系中复掺减水剂、胶粉、缓凝剂及早强剂外加剂,对灌浆料的工作性能进行了优化调控,最终获得满足性能要求的半柔性路面用水泥基灌浆料。结果表明,灌浆料体系的最优配比为m(快硬硫铝酸盐水泥)∶m(普通硅酸盐水泥)=7∶3,外掺粉煤灰、硅灰、赤泥的量分别为硫铝酸盐-普通硅酸盐复合水泥质量分数的9%、6%、3%,水胶比为0.40,砂胶比为0.25,早强剂、胶粉、减水剂、缓凝剂的掺量分别为0.08%、2.5%、0.35%、0.20%(质量分数),其初始和20 min流动度分别为13 s和19 s,初凝和终凝时间分别为62 min和65 min,3 h、1 d、7 d和28 d的抗压强度分别为17.08 MPa、18.13 MPa、24.59 MPa和26.19 MPa,7 d干缩率为0.18%。     

掺Ⅱ级粉煤灰高性能混凝土抗冻性试验研究

以Ⅱ级粉煤灰作为超细掺合料掺入到混凝土中,研究在不同水胶比、不同掺量情况下混凝土的抗冻性能。通过试验研究发现：在水胶比0.35以上时,当混凝土中不掺加引气剂,掺粉煤灰的混凝土均不能抵抗200次的冻融循环作用;当水胶比低于0.30及其以下时,粉煤灰掺量在30%以下,混凝土具有良好的抗冻性能,可抵抗200次的冻融循环作用。当混凝土中掺加引气剂,水胶比在0.40及其以下,粉煤灰掺量在50%以下时,混凝土具有良好的抗冻性能,可抵抗200次的冻融循环作用。     

掺Ⅱ级粉煤灰混凝土的抗硫酸盐侵蚀性能研究

对掺Ⅱ级粉煤灰的混凝土,改变其水胶比和粉煤灰掺量,进行抗硫酸盐侵蚀试验,结果表明：水灰比为0．40的普通混凝土,无法抵抗硫酸根离子浓度2500-20250mg／L硫酸盐溶液侵蚀,其水泥石孔隙中侵蚀产物以石膏为主,侵蚀现象主要发生在试件的表层,具体形态表现为试件表层逐渐疏松、剥落。水胶比为0．40以下、粉煤灰掺量30％及其以上的混凝土能够抵抗硫酸根离子浓度为20250mg／L的硫酸盐侵蚀。