基于碳酸盐定量分析的水泥石抗碳化性能测试方法

针对目前各种碳化深度测量方法的弊端,结合所发明的检测装置,形成了一套新型抗碳化性能测试方法一碳酸盐含量法.试验结果表明,这是一种更加精确的碳化测试方法,不仅能划分完全碳化区和碳化进行区,还不会因受到其它水泥石中性化因素的干扰而影响测量结果.基于试验结果,对比酚酞喷涂法,说明该方法更具有优势,不但原理简单,而且可以测得试...     

电沉积处理后带裂缝混凝土的抗碳化性能研究

选用ZnSO4和MgSO4两种电沉积溶液,对带裂缝的砂浆试件进行修复,测定了7天、14天、21天、28天、35天龄期带裂缝砂浆试件无裂缝处及裂缝处的碳化深度,研究了带裂缝的砂浆试件经过电沉积处理后碳化深度的变化情况.结果表明:利用ZnSO4和MgSO4两种电沉积溶液,对带裂缝的砂浆试件进行电沉积处理后,其抗碳化能力均有所提高,而且采用MgSO4溶液,抗碳化能力的提高程度要高于采用ZnSO4溶液的.     

石灰石粉和含铝相辅助性胶凝材料的协同作用对混凝土抗碳化性能的影响

为了研究石灰石粉和含铝相辅助性胶凝材料的协同作用对混凝土抗碳化性能的影响,选取了两种含铝相辅助性胶凝材料和石灰石粉以不同比例取代水泥,并采用差热分析、XRD和压汞法测试了其水化产物和微观结构。研究结果表明,单掺石灰石粉降低了混凝土的抗碳化性能,当石灰石粉掺量约为10%时,混凝土的碳化深度最低。当复掺石灰石粉和含铝相辅助性胶凝材料时,两者反应生成了碳铝酸钙,增大了固相体积,优化了孔结构,它们的协同作用提高了混凝土的抗碳化性能。当石灰石粉掺量为5%~15%,粉煤灰掺量小于10%,或者矿粉掺量为10%~30%时,混凝土的碳化深度最低。     

基于饱和面干骨料的粉煤灰混凝土配合比设计及碳化性能研究

本文以设计试验研究基于饱和面干骨料的粉煤灰混凝土为主,并通过试验数据分析得出结论：相同水胶比的情况下,随着粉煤灰掺量的增加,混凝土7d、28d强度逐渐下降,拌和物坍落度也平稳下降;自然养护条件和标准养护条件对碳化深度有一定的影响;饱和面干骨料粉煤灰混凝土的强度测定期应当延迟。     

玄武岩纤维对再生混凝土抗碳化性能的影响

采用快速碳化的方法研究了玄武岩纤维(BF)掺量和再生粗骨料(RCA)取代率对再生混凝土(RAC)抗碳化性能的影响,实测了3天、7天、14天、28天的碳化深度,对随碳化天数的增加,碳化深度与BF掺量、RCA取代率之间的关系进行了分析.结果表明,RAC的碳化与天然混凝土(NAC)类似,其碳化深度均随碳化天数的增加而增加,随...     

碳化混凝土再碱化后钢筋混凝土粘结性能研究

碳化混凝土再碱化过程中,由于物理和化学作用,对钢筋与混凝土的粘结性能有影响。采用拉拔试验,考虑到电流密度、再碱化时间、碳酸钠溶液浓度等因素研究了再碱化后钢筋混凝土的粘结强度。采用扫描电镜(SEM)分析了混凝土的微观结构,结果表明,再碱化后,钢筋混凝土的粘结强度得到明显提高;电流、碳酸钠溶液浓度以及再碱化时间对再碱化后的粘结强度有显著影响;混凝土的微观结构发生了改变,孔隙率减小,有利于粘结强度的增加。     

浅谈混凝土的碳化及防止措施

混凝土的碳化是指混凝土中原呈碱性的氢氧化钙,在大气中受到二氧化碳和水分的作用,逐渐变成呈中性的碳酸钙的过程,混凝土碳化对混凝土结构破坏影响很大。混凝土碳化机理水泥中的矿物以硅酸三钙和硅酸二钙含量较多,约占总重的75％,水泥完全水化后,生成的水化硅酸钙凝胶约占总体积的50%,氢氧化钙约占25％,水泥石的强度主…混凝土的碳化是指混凝土中原呈碱隍的氢氧化钙,在大气中受到二氧化碳和水分的作用,逐渐变成呈中性的碳酸钙的过程,混凝土碳化对混凝土结构破坏影响很大。     

高比表面积碳化钼/碳复合体的电化学性能研究

采用直接碳化法,羟丙基纤维素(HPC)、聚乙烯醇(PVA)、钼酸钾(K2MoO4)和碳酸钾(K2CO3)的混合物于900℃氢气氛围下碳化,制备了高比表面积碳化钼/碳复合体(MCCs).应用XRD、TG、SEM和电化学方法对其进行了表征和性能研究.XRD图谱表明,碳基上合成了α-Mo2C及微量Mo3C2.加入K2CO3增...     

碳纤维水泥石压敏传感器电极的实验研究

电极的设计是制作碳纤维水泥石压敏传感器的重要环节之一。本文首次提出了埋入式网状电极的概念,同时综合分析了网状电极的特点。本文的研究表明埋入式铜质网状电极具有相容性和耐久性好、极化作用和接触电阻小等优点,是碳纤维水泥石压敏传感器的理想电极;在电阻测试中,四极法较两极法具有更高的准确性。此外,本文还研究了电极的结构参数对四极法测试结果准确性的影响。     

高浓度盐环境下偏高岭土对水泥石抗盐冻性能的影响

为研究高浓度盐环境下偏高岭土对提高水泥石抗冻性的使用效能,本工作通过探究偏高岭土掺量对冻融循环后水泥石强度损失率、水化产物含量、盐侵蚀产物含量的影响规律,建立了水化及侵蚀产物含量与抗压强度损失率间的线性回归方程,并计算出偏高岭土对提升水泥石抗盐冻性能的最佳掺入范围。结果表明：偏高岭土可有效提高水泥石的抗盐冻性能,且材料的强度损失率随掺量的增加呈线性降低趋势;高浓度盐环境下水泥石表层氢氧化钙会与钙离子和氯离子反应生成膨胀型晶体水合氯氧化钙;氢氧化钙和水合氯氧化钙的含量随偏高岭土掺量的增加呈下降趋势,且线性相关;以强度损失率作为评价标准拟合出水泥石免受破坏的氢氧化钙和水合氯氧化钙临界值分别为9.2%和7.1%。     

水泥石的结构、组成与干缩性能的关系

通过干缩测定、IR分析、TG-DSC综合热分析、孔结构测定(MIP法)等方法研究了水泥石的结构、组成与干缩性能的关系.水泥石的结构、组成(孔结构、水化产物的组成和数量、C-S-H的表面性能及化学结构)的改变通过采用矿物掺合料等量取代水泥、干燥前养护温度改变(20℃和60℃)来实现.结果表明,可逆收缩取决于水化产物的数量与C-S-H凝胶的表面性能与化学结构,随压汞法测得的小于30nm的孔体积增加而线性增加;不可逆收缩则与C-S-H凝胶的化学结构及其表面性能有关,C-S-H凝胶的聚合度增加,表面积下降,不可逆收缩减小;总干缩中部分不可逆收缩是由C-S-H的硅酸盐聚合度增加而造成的.     

纤维素醚改性水泥浆的粘度变化研究

增稠是纤维素醚对水泥基材料的重要改性效果。研究了纤维素醚掺量、粘度仪旋转速度和温度对纤维素醚改性水泥浆粘度变化的影响。结果表明:纤维素醚掺量增加,水泥浆的粘度不断增加,纤维素醚溶液和水泥浆的粘度具有"复合叠加效应";纤维素醚改性水泥浆的假塑性低于纯水泥浆,粘度仪的旋转速度越低,或纤维素醚改性水泥浆的粘度越低,或纤维素醚掺量越低,纤维素醚改性水泥浆的假塑性越明显;温度升高,由于温度和水泥水化的共同作用,纤维素醚改性水泥浆的粘度会增加或降低。纤维素醚的种类不同,其改性水泥浆的粘度变化规律存在差异。     

Flow Behavior of Fresh Portland Cement Pastes

Portland cement pastes prepared at various water/cement ratios were studied using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory measuring device MV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. In this article, experimental shear stress and shear rate data were fitted very satisfactorily with a model proposed by the authors. Excellent results were achieved also by applying the Quemada equation. Oscillatory flow data gave further information on the workability of the pastes investigated. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the first based on polycyclic copolymers with modified structures carrying hydroxylated side chains, the second on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage. In the case of Ergomix 1000, agreement between the optimum dosage determined rheologically and that recommended by the producer was obtained.     

Flow Behavior of Fresh Portland Cement Pastes

Portland cement pastes prepared at various water/cement ratios were studied using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory measuring device MV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. In this article, experimental shear stress and shear rate data were fitted very satisfactorily with a model proposed by the authors. Excellent results were achieved also by applying the Quemada equation. Oscillatory flow data gave further information on the workability of the pastes investigated. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the first based on polycyclic copolymers with modified structures carrying hydroxylated side chains, the second on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage. In the case of Ergomix 1000, agreement between the optimum dosage determined rheologically and that recommended by the producer was obtained.     

Flow Behavior of Fresh Very High Strength Portland Cement Pastes

Flow behavior of fresh very high strength portland cement pastes prepared at various water/cement ratios was studied by using a rate-controlled coaxial cylinder viscometer (Rotovisko-Haake 20, system M5-osc., measuring device MV2P with serrated surfaces). The tests were performed under continuous flow conditions. Experimental shear stress and shear rate data were fitted very satisfactorily with various models, one of which has already been proposed by the authors. Excellent results were achieved also by applying the Quemada equation. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the former based on polycyclic copolymers with modified structures, carrying hydroxylated side chains, and the latter on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage and verifying the effectiveness by comparing rheological results with those obtained in a previous work on an ordinary portland cement. The use of superplasticizers modified rheological behavior of the pastes; however, no value of optimum dosage was found for any additive, but only a superplasticizer concentration range within which pastes presented very low values of viscosity. Moreover, both superplasticizers showed a greater effectiveness when added to HSPC pastes rather then the OPC ones formulated with the same water/cement ratio.     

碳化对玻璃纤维增强氯氧镁水泥性能的影响规律及其机理

利用快速碳化试验方法,测定了普通和改性玻璃纤维增强氯氧镁水泥(GRMC)在碳化前后的弯曲应力-挠度曲线,运用XRD分析其碳化产物组成,用SEM观察其显微结构特征与玻璃纤维的腐蚀状况。结果表明:在快速碳化28d后,普通GRMC的水化产物5Mg(OH)2.MgCl2.8H2O(简称5.1.8)碳化为Mg(OH)2.MgCl2.2MgCO3.6H2O(简称1.1.2.6),Mg(OH)2碳化为MgCO3,碳化后的部分MgCl2溶出和流失导致材料基体孔洞较多,结构松散,从而引起普通GRMC的初裂强度降低,极限挠度变大,极易变形;而改性GRMC的水化产物5.1.8在快速碳化条件下保持基本稳定,微观结构未发生显著变化,显示出较强的抗碳化能力,其初裂强度增大,初裂挠度和极限挠度几乎不降低,不易开裂。此外,碳化作用不会导致玻璃纤维的腐蚀,纤维与水泥基体粘结良好,结构致密。     

缓凝剂硼砂对磷酸镁水泥水化硬化特性的影响

为了探讨缓凝剂硼砂(B)对磷酸镁水泥(MPC)的作用机理,测试和分析了不同掺量硼砂(B)的磷酸镁水泥(MPC)浆体的凝结时间、pH值、体系温度以及硬化体的强度和微观结构。结果表明:硼砂在一定掺量范围内对磷酸镁水泥(MPC)浆体有较明显的吸热降温促进作用和调节pH值作用,两种作用均可减慢浆体的水化反应速度且进一步影响硬化体的微观结构形貌和强度。由此推论硼砂在磷酸镁水泥(MPC)浆体中,除在MgO表面形成保护膜外,还通过降低体系温度和调节浆体pH值进而减慢水化反应速度来延缓浆体的凝结,随着硼砂(B)掺量的变化,不同因素起主导作用。     

水泥材料成型过程对硬化体结构与性能的影响

新拌水泥混凝土浆体常被抽象为含水的颗粒悬浮结构,这种抽象将复杂的成型过程过于简化,存在许多难以预知和不可量化的因素,给水泥基材料科学体系的架构造成技术障碍。分别综述了混凝土成型、水泥净浆成型共同存在的组分材料离析、泌水和夹杂气泡等缺陷,分析了组分分散效果对水泥水化硬化体结构与性能的影响。将水泥颗粒堆积体与其水化硬化体制备结合起来,通过压制绝干水泥颗粒堆积结构,再毛细吸水成型水泥水化硬化体,可以最大程度避免微观层面的离析、泌水及夹杂气泡等不易量化的因素对成型的影响,有利于模型化研究非均质、多层次复杂结构的演变与性能调控。     

弯曲荷载对硬化水泥浆体和砂浆碳化过程的影响

研究了弯曲荷载对硬化水泥净浆和砂浆试体碳化过程的影响.结果表明:弯曲荷载会加速水泥浆体和砂浆的碳化过程,在弯曲荷载作用下水泥浆体和砂浆的碳化动力学过程可用式x=C0eaηtb描述,其中b值均接近1/2;碳化时间对砂浆碳化深度的影响略小于对水泥浆体的影响,而应力水平对水泥浆体和砂浆碳化的影响大致相同.