水泥净浆力电机敏性的试验研究

研究了水泥净浆从小载荷直至破坏时的力电效应，研究表明：水泥净浆在单向压应力作用下产生电流，电流强度随应力的增加而增加，电流强度与应力之间存在一一对应关系。载荷保持时，电流逐渐减小，随着水灰比的增加，敏感性也增加。力电机敏性随含水量的增加而增加，从而进一步验证了力电效应的机理。这一研究对开发多功能的混凝土机敏材料有重要的意义。     

CFRC中碳纤维长度分布规律研究

以羧甲基纤维素钠(CMC)和硅灰为碳纤维分散剂配制了碳纤维水泥基复合材料(CFRC),通过酸洗、多次过滤等从新拌CFRC料浆中将碳纤维分离出来,以分析碳纤维在CFRC中的长度分布规律。研究表明,碳纤维完全以单根纤维形式分散在水泥基体中,碳纤维在CFRC中以2 mm以下的短小纤维数量最多,而且在全部碳纤维中所占的体积分数为45%。这些短小碳纤维的长度低于纤维从水泥中拔出的临界长度,使得CFRC的电阻随载荷而变化。CMC的表面润滑作用、分散剂体系的粘性、硅灰填充效应和特别的湿拌-干湿拌-湿拌工艺有利于碳纤维在水泥基体中的分散。     

碱木素改性及其减水分散性能的研究

针对碱木素的结构特性，采用预氧化磺化反应对碱木素进行化学改性。研究了改性碱木素作为混凝土减水剂的减水分散生能，结果表明，改性后碱木素的物化性能和应用性能得到较大改善。掺入改性产品的水泥净浆具有流动度损失小的优点，2h内的流动度损失率率只有36％；在低掺量下，磺化碱木素初凝时间比空白水泥略长，终凝时间延缓3.5h。当掺入水泥质量0．2％（绝干量）的减水剂，水泥净浆的28天抗压强度比为115％，作为废物排放的碱木素可以改性为一种具有低流动度损失，缓凝，能提高混凝土后期强度等特点的低成本普通混凝土减水剂。     

C3A对水泥净浆结粒的影响

对水泥净浆结粒研究发现，熟料中C3A含量的波动，带来结粒量较大的变化，配制5种不同C3A含量的水泥，进行结粒研究。结果表明：C3A是影响水泥净浆结粒的主要因素，水泥结粒量随着水泥矿物成分中C3A的含量的增加而增大；随着净浆结粒程度的加大，体系更倾向于形成颗粒体积较大的结粒；C3A对水泥净浆结粒的作用要远大于水化温度对结粒的影响。     

硅灰对水泥净浆抗硫酸盐侵蚀性能的改善作用

将水泥净浆试件在5%Na2SO4溶液中长期浸泡,用试件强度随浸泡时间的变化和试件中物相的XRD分析,研究了硅灰对水泥净浆抗硫酸盐侵蚀性能的影响.在Na2SO4溶液侵蚀下,普通硅酸盐水泥净浆试件强度随浸泡时间先增长,然后急剧降低;外观和XRD相分析表明,其原因是由于形成了膨胀性钙矾石,造成试件开裂破坏;加入硅灰的水泥净浆试件强度损失明显减小,尤其是抗折强度没有降低,其抵抗强度下降系数还略有增加;原因是由于硅灰的稀释作用和火山灰效应减少了水泥净浆中Ca(OH)2的量,从而降低了水泥净浆试件在硫酸盐溶液侵蚀下形成的膨胀性钙矾石的量.因而,硅灰对水泥混凝土抗硫酸盐侵蚀性能有改善作用.     

木素磺酸钙对水泥净浆的缓凝机理研究

研究了掺加木素磺酸钙(简称木钙)后水泥净浆液相中钙离子、硫酸根离子和氢氧根离子浓度随水化时间的变化,以及除糖后木素磺酸钙对水泥净浆凝结时间的影响．结果表明,掺加木钙后在水化初期水泥净浆中S042-浓度大幅度上升,OH-浓度变化不大．木钙掺量越大,水泥净浆中游离Ca2 浓度的峰值出现越迟,浆体的初凝时间越长．进一步研究发现木钙的掺加能促进熟料矿物的水解,当木钙掺量为0．5％(质量分数)时,水泥净浆中的总Ca2 浓度峰值比未掺加木钙时增加48％,被络合的Ca2 量峰值较水化开始时增加2倍．在水泥净浆强碱性溶液中木钙的络合能力增强导致Ca(OH)2不能达到过饱和,是造成水泥净浆缓凝的重要原因,木钙对水泥净浆的缓凝机理为“吸附-络合”机理．     

水泥净浆结粒水筛检测方法研究

由水筛法得到启示，提出了一套水泥净浆结粒的检测方法。通过研究水泥称量、水化温度、水泥细度、水灰比、石膏掺量和水化时间对结粒量的影响，探讨了该检测方法的可行性，并计算了结粒量的标准偏差。结果表明：该净浆结粒检测方法可靠性高，检测结果具有很好的稳定性和重现性；同时对于不同条件下的变化，能够充分反映水泥净浆结粒的变化规律，是研究净浆结粒的有效方法。     

氧化石墨烯分散液对水泥净浆水化和力学性能 影响机理分析

为研究氧化石墨烯(GO)掺量对水泥净浆水化和力学性能的影响,采用改进Hummers法和超声波分散法制备GO片层分散液,利用傅里叶红外光谱(FTIR)和X-射线衍射(XRD)表征GO;研究了GO掺量对水泥净浆抗压、抗折强度的影响规律,并从微观角度揭示了GO分散液对水泥净浆的调控机理。结果表明:与普通水泥净浆相比,掺入适量的GO能够促进水泥水化进程,提高水泥净浆中的化学水结合量,水化晶体互相缠绕、交织形成规整有序的多面体状微结构,使水泥净浆的早期力学性能显著提高,最佳GO掺量为水泥质量的0.03%。适量的GO能够提高水泥净浆的抗压和抗折强度,促进水泥净浆水化晶体的生长,改变晶体的尺寸和形状,实现对水泥净浆微结构的调控。     

可再分散胶硫铝酸盐水泥基耐海水材料研究

目的应用无机、有机材料复合理论，研究用于人工渔礁制作中木船表面处理的可再分散胶水泥基耐海水材料．方法通过5％以内的不同掺量聚合物乳液和可再分散聚合物粉末对水泥基材料改性效果的对比，掺有机硅防水剂对聚合物改性水泥净浆性能的影响、涂覆于木材表面的水泥净浆硬化后涂层的耐海水等性能的研究，特别对高性能可再分散胶水泥基耐海水材料于木材粘结后在海水中浸泡28d的粘结力、耐磨性、抗冲击性及开裂情况进行了测定和现场观察与评价．结果研究表明可再分散胶水泥基耐海水材料是一种高性能的水泥基复合材料，尤其是与木材的粘结性能十分优异；而在力学性能方面，可再分散胶水泥基复合材料也比聚合物乳液水泥基复合材料有所提高．结论掺占水泥质量5％的可再分散聚合物粉末、2％有机硅的水泥净浆涂覆于木材表面，硬化后会形成耐海水性能良好的涂层，可作为船体表面保护层，满足船只沉降后长期经海水浸泡的要求．     

偏高岭土对水泥净浆火山灰效应强度贡献率的影响

根据蒲心诚教授提出的偏高岭土火山灰效应定量分析方法,进行了偏高岭土对水泥净浆(以下简称净浆)火山灰效应强度贡献率(以下简称强度贡献率)的影响研究.结果表明:随着偏高岭土掺量的增加,其净浆强度贡献率增加;随着养护龄期的增加,其净浆强度贡献率呈现先减少后增加的趋势,且7,d时出现最低值;3、28,d时小粒径偏高岭土(2.5和3.75,μm)的净浆强度贡献率明显高于7,d时的值,这说明偏高岭土火山灰效应主要是发生在早期(3,d)和后期(28,d);而大粒径偏高岭土和补充激发剂则有利于提高其中期(7,d)净浆强度.     

Electrical resistance and microstructure of latex modified carbon fiber reinforced cement composites

The electrical resistance,flexural strength,and microstructure of carbon fiber reinforced cement composites(CFRC) were improved greatly by adding water-redispersible latex powder.The electrical resistance of CFRC was investigated by two-probe method.The input range of CFRC based strain sensors was therefore increased,whereas electrical resistance was increased and remained in the perfect range of CFRC sensors.The analysis of scanning electron microscopy indicated that elastic latex bridges and a latex layer existed among the interspaces of the adjacent cement hydration products which were responsible for the enhancement of the flexural strength and electrical resistance.The formation mechanism of the elastic latex bridges was also discussed in detail.The continuous moving of two opposite interfaces of the latex solution-air along the interspaces of the adjacent hydrated crystals or colloids was attributed to the formation of the elastic latex bridges.     

碳纤维增强水泥基复合材料的力学性能研究进展

碳纤维(Carbon Fibers, CFs)作为增强相运用在复合材料中一直是研究热点。综述了CFs的种类、分散方式及其在水泥基复合材料中分散性的评估方法、CFs表面涂层改性的制备工艺及其优缺点。通过改善CFs在水泥基体中的分散性和对CFs表面进行涂层改性处理,可以制备性能良好的碳纤维增强水泥基复合材料（CFRC）。同时,对CFRC力学性能的影响因素进行了系统的探讨及研究,包括水灰质量比、养护龄期、成型工艺、硅粉掺量、外加剂、CFs掺量和长度等。总结出进一步提高CFRC力学性能的关键在于改善CFs在水泥基体中的分散性和相容性,并为今后制备高性能CFRC提供参考。     

单向分布钢纤维增强水泥浆的制备与性能研究

研究了制备单向分布钢纤维增强水泥浆的方法及其性能.在成型阶段施加外部磁场,钢纤维可被磁化并受外部磁场作用,使水泥浆拌合物中的钢纤维形成定向分布,制备出单向分布钢纤维增强水泥浆.研究表明,这种方法制备的单向分布钢纤维增强水泥浆中,90%左右的钢纤维方向与磁场方向一致或接近;钢纤维方向系数达到0.95或更高;与乱向分布钢纤维增强水泥浆相比,单向分布钢纤维增强水泥浆抗折强度显著提高;抗折强度相同时,单向分布技术可节省钢纤维25%以上.     

Mechano-electric Effect of Hardened Cement Paste During Quasi-static Loading

Mechano- electric effect of cement paste was investigated in this paper. As compressive stress was applied on the specimen, an electrical current was observed. The intensity of the electrical current increased with stress increasing, and decreased with stress decreasing. Different measurement methods were also discussed in this paper. This phenomenon was related to the electrokinetic phenomenon of solid/liquid interface in cement paste. The study on mechano-electric effect of hardened cement paste provides a new method for making smart concrete structures .     

不同电参数对CFRC应变敏感性的响应

CFRC具有压敏性，测试方法和测试参数的选择对CFRC的压敏性有一定的影响。采用直流电阻测试法、交流阻抗测试法和电容测试法研究了不同电参数(直流电阻、交流阻抗、电容)对CFRC应变敏感性的响应。实验结果表明：直流电阻和交流阻抗随压力的变化都能反映试样受载变形的全过程：弹性阶段、损伤阶段、破坏阶段；电容随压力的增大而增大；交流阻抗和电容随应变的变化比直流电阻随应变的变化灵敏且稳定。最后对这3种测试方法作了综合评价。     

电阻率法研究早期水泥净浆孔结构的演变过程

采用无电极电阻率法原位连续监测3种水灰比（0.23、0.35和0.53）水泥净浆早期水化过程中电阻率的变化全过程,同时结合等温量热仪测试的水化程度,建立水泥净浆随时间发展过程中浆体电阻率与孔结构发展的定量关系。结果表明：根据电阻率及其微分曲线的变化规律可以把水泥水化过程分为4个阶段：溶解期、诱导期、加速期和减速期。水灰比越低,毛细孔隙率和收缩因子变小,曲折因子变大,致使浆体电阻率升高,而孔溶液电阻率却下降。     

Compression sensibility of magnetic-concentrated fly ash mortar under uniaxial loading

The electrical conductivity, compression sensibility, workability and cost are factors that affect the application of conductive smart materials in civil structures. Consequently, the resistance and compression sensibility of magnetic-concentrated fly ash (MCFA) mortar were investigated using two electrode method, and the difference of compression sensibility between MCFA mortar and carbon fiber reinforced cement (CFRC) under uniaxial loading was studied. Factors affecting the compression sensibility of MCFA mortar, such as MCFA content, loading rate and stress cycles, were analyzed. Results show that fly ash with high content of Fe3O4 can be used to prepare conductive mortar since Fe3O4 is a kind of nonstoichiometric oxide and usually acts as semiconductor. MCFA mortar exhibits the same electrical conductivity to that of CFRC when the content of MCFA is more than 40% by weight of sample. The compression sensibility of mortar is improved with the increase of MCFA content and loading rate. The compression sensibility of MCFA mortar is reversible with the circling of loading. Results show that the application of MCFA in concrete not only provides excellent performances of electrical-functionality and workability, but also reduces the cost of conductive concrete.     

Investigation of the Interfacial Transition Zone between Aggregate-Cement Paste by AC Impedance Spectroscopy

Three different types and sizes of coarse aggregate were chosen,and the alternating current(AC) impedance of cement paste samples with and without aggregate was measured at different curing ages.Based on Song's equivalent circuit model,the electrical properties from the AC impedance results were obtained,and the resistance of connected pores RCCP was used to characterize the microstructure of the interfacial transition zone(ITZ).The results show that the RCCP of concrete sample with aggregate is lower than that of cement paste sample,which indicates that the introduction of aggregate in cement paste makes the ITZ porous.Furthermore,for the same type of aggregate,an increase in particle size leads to a more porous ITZ,which accounts for the "water effect" and a larger aggregate would accumulate a thicker water film around it.In addition,for the same size of aggregate,the physical interaction between aggregate and cement paste is dominant in early age,and the microstructure of the ITZ around limestone aggregate is denser,which mainly depends on its rough surface and high water absorption.However,the microstructures of the ITZ around granite and basalt aggregates are denser in later age,which may be due to their higher chemical activity,and the chemical interaction between them and cement paste resulting in the generation of more hydrates.AC impedance spectroscopy thus proves to be powerful for evaluation of the microstructure of the ITZ.     

SEM-backscattered electron imaging and image processing for evaluation of unhydrated cement volume fraction in slag blended Portland cement pastes

Proper parameters for image taking and minimum field number for image processing were investigated to evaluate volume fraction of unhydrated cement(UHC) in both neat cement paste and slag blended cement paste. Our research suggested that magnification 250× was sufficient for the two pastes, and accelerating voltage should be set as 15 kV and 20 kV for BSE image taking of neat cement paste and slag blended cement paste respectively; the minimum field number increased while the total imaging area stayed the same as the magnification increased within certain statistical bias.