地下水强酸盐复合腐蚀环境下不同矿物掺合料对水泥砂浆耐腐蚀性能的影响

模拟了贵州地区地下水强酸盐复合腐蚀环境,系统研究了粉煤灰、矿渣粉和硅灰3种矿物掺合料单掺与复掺对水泥砂浆耐腐蚀性能,如耐蚀系数、质量变化率、氯离子相对扩散系数的影响规律,并探讨了地下水强酸盐复合腐蚀环境下水泥砂浆的腐蚀机理。结果表明,与基准砂浆相比,单掺与复掺矿物掺合料均提高了砂浆的耐蚀系数,降低了砂浆后期氯离子相对扩散系数,但增大了砂浆质量损失率。这3项指标从不同角度反映了地下水复合腐蚀环境下水泥砂浆的耐腐蚀性能。     

带裂缝混凝土氯离子扩散作用试验研究及数值模拟

为了准确评估带裂缝工作混凝土结构的耐久性能,针对氯离子在带裂缝混凝土中的扩散过程进行研究。提出了无损制备裂缝的方法,可高效易行地在混凝土侧面及内部产生裂缝。对带裂缝的水泥砂浆试件进行氯盐溶液浸泡试验,深入研究了单缝和双缝试件中氯离子的扩散作用,修正了氯离子的扩散系数,并对带裂缝混凝土的氯离子扩散过程进行了数值模拟。研究结果表明：氯离子会沿裂缝发展方向及垂直于裂缝发展方向扩散,随着水灰比的减小,砂浆试件的抗氯离子扩散性能明显提高,在一定范围内,当裂缝间距增大,双缝间的氯离子扩散交互影响作用明显减小,ANSYS软件的模拟结果与试验数据吻合良好。     

An electrochemical and microstructural characterization of steel-mortar admixed with corrosion inhibitors

The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion. The admixing of NaCl and the corrosion inhibitors in fresh mortar was found to alter the morphology and microstructure of the hardened mortar at the steel-mortar interfacial region. The admixing of the inhibitors increased the risk of carbonation of cement hydrates at the steel-mortar interfacial region, but partially displaced chloride ions. Chloride and the admixed inhibitors facilitated the formation of different cement hydrates and affected chloride binding at the steel-mortar interfacial region. The admixing of all three inhibitors was found to increase the polarization resistance of steel, indicating reduced corrosion rate of the steel over 48-day exposures to salt ponding.     

不同环境条件下混凝土构件氯离子侵蚀试验

为研究不同环境条件下混凝土构件氯离子侵蚀劣化规律,开展弯拉应力构件的氯离子浸泡侵蚀试验和无应力构件的盐雾侵蚀试验.基于氯离子质量分数、构件弯拉强度及弯拉应变等测试结果,研究了侵蚀时间、环境温度、应力水平、环境氯离子质量分数及侵蚀方式等因素对氯离子扩散特征和构件抗弯性能的影响.试验结果表明:浸泡环境中混凝土内部氯离子质量分数较盐雾环境高;试件内部氯离子质量分数随腐蚀时间、环境温度、环境氯离子质量分数及应力水平的增大而增大;氯离子扩散系数随应力水平和环境温度的提高而增大;在较低应力水平、较低环境温度和较短的侵蚀时间内,混凝土构件极限弯拉强度有小幅度上升趋势,然后随侵蚀时间的增长而衰减;混凝土构件的极限弯拉应变随各影响因素的增大而降低.研究结果可为钢筋混凝土构件在氯盐侵蚀环境下的耐久性评估及设计提供依据,具有一定工程实际意义.     

水泥砂浆外涂有机硅烷防护效果研究

为了研究外涂有机硅水泥砂浆材料的防护效果,用有机硅涂料对水泥砂浆进行表面涂层处理,并与未涂层水泥砂浆和涂丙烯酸的水泥砂浆相比较,系统研究了改性有机硅涂层对防水抗渗性能、抗碳化性能、抗氯离子渗透等性能的影响。试验结果表明：有机硅外涂水泥砂浆呈现出较好地疏水效果,使用有机硅外涂水泥砂浆的防水抗渗性能大大改善了;与空白组、丙烯酸组相比,涂有有机硅涂层的砂浆的氯离子扩散系数显著降低,约为空白组的1／4,约为丙烯酸组的1／3;随着养护时间的增加,涂有有机硅涂层的试块的碳化程度明显低于空白组和丙烯酸组,而且碳化深度增长速度明显变慢;空白样水泥砂浆密实性较差,表面粗糙多孔,试块结构疏松,而加了硅烷的试块涂料与水泥浆表面粘结紧密,界面区并不明显。为烷氧基有机硅烷作为水泥砂浆防护材料实际工程应用奠定一定的基础。     

纳米高岭土颗粒改性水泥基复合材料的性能

研究了纳米高岭土颗粒对不同龄期水泥基材料微观结构（微孔结构、微观结构）及物理力学性能（工作性、抗弯强度、抗压强度、氯离子渗透性）的影响。结果表明,纳米高岭土颗粒的填充效应及其对水泥水化的促进作用改善了水泥基材料的微观孔结构,限制了氯离子在水泥基材料中的渗透扩散。当高岭土为水泥质量的1％时,水泥浆1、3、7、90 d抗弯强度分别提高30．41％、39．04％、36．27％和38．32％;当高岭土为水泥质量的5％时,水泥砂浆氯离子扩散系数降低53．03％;混凝土氯离子扩散系数随高岭土掺量增加呈指数递减;当高岭土为水泥质量的5％时,氯离子扩散系数降低18．87％;抗压强度分别提高28．4％;改性混凝土28 d抗压强度与混凝土氯离子扩散系数呈线性增加关系。     

Chloride Ion Critical Content in Reinforced Concrete

Chloride ion critical content was studied under soaking and cycle of dry and wet conditions, with three electrochemical nondestructive measuring techniques, i e, half-cell potential, A C impedance, and time potential. The experimental results show that chloride ion critical content is primarily determined by the water cement ratio, while for the same concrete mixture the chloride ion critical content in soaking conditions is larger than that in a cycle of dry and wet conditions.     

混合侵蚀与冻融环境下混凝土力学性能劣化试验

以质量分数为3%的NaCl和5%的Na2SO4混合溶液为侵蚀介质,采用快冻法,对设计强度等级为C30、水灰比分别为0.44、0.50、0.55的混凝土试件进行了0、50、100、150、200次冻融循环试验,测定了各组试件的质量损失、抗压强度、应力、应变等。试验结果表明,混凝土随着冻融循环次数的增多,其表观质量和力学性能均呈现出不同程度的下降趋势,且水灰比越大下降越快。建立了与冻融循环次数相关的力学性能劣化线性方程,为进一步开展混凝土结构在冻融和侵蚀离子共同作用下的劣化机理与计算模型的研究提供了依据。     

盐碱溶液对混凝土氯离子渗透性能的影响

基于盐碱寒冷地区的工程环境与混凝土的配制特点,模拟配制了SA溶液,对水灰比、含气量和粉煤灰掺量三个参数对混凝土氯离子渗透性能的影响进行了正交试验研究.结果表明:氯离子渗透深度x与渗透时间t之间的关系可以拟合成幂函数x=atb来描述,且在显著性水平α=0.01下其相关关系显著;SA溶液中SO42-和Mg2+的存在对于Cl-的渗透具有一定的抑制作用,冻融循环在混凝土本体结构未破坏之前对于氯离子的渗透也具有一定的抑制作用;水灰比、含气量和粉煤灰掺量三个参数对浸于4.0%NaCl溶液、SA溶液、SA溶液并受冻融循环三种情况下氯离子渗透深度影响的顺序不同;随着水灰比的增大,氯离子渗透深度增大;粉煤灰能够抑制氯离子的渗透,且20%掺量的效果优于35%;含气量对于抵抗氯离子渗透存在不利影响,且未受冻融作用时,3.0%的影响更大.     

Damage action of alkali-resistant glass fiber in cement-based material

The compressive strength and flexural strength with the same strength class cement mortar of the alkali-resistant glass fiber cement mortar were tested in standard and hot-water curing condition, and the damage mechanism of alkali-resistant glass fiber was studied. The interaction mechanisms of the chemical erosion and physical injury in different curing conditions were studied in order to summarize the damage mechanism of alkali-resistant glass fiber in cement-based materials, and chloride diffusivity coefficient and porosity of cement mortar were tested in the different curing conditions. The experimental results are that the strength of cement based materials and fiber cement slurry interface zone were closely related, and heat curing could accelerate the hydration of cement, but inevitably enlarge the defect.     

矿渣水泥中自由氯化物及可溶性氯化物的定量评价

通过细孔溶液测定在水泥浆中自由氯化物含量和通过ASTM测定可溶性氯化物含量,在氯化物掺用量相同的条件下,BSC细孔溶液中的氯离子浓度比OPC低43%~71%,表明在水泥中掺用高炉矿渣将大大降低氯离子浓度。     

机场道面除冰液作用下大掺量粉煤灰混凝土的抗冻性

通过大掺量粉煤灰混凝土（HFCC）试件在质量分数为3．59／6,12．5％,25％机场道面除冰液（CMA溶液）、质量分数为3．5％的NaC1溶液、质量分数为3．5％的飞机除冰液（AD溶液）、质量分数为25％的商品飞机除冰液与水中快速冻融试验,获得了冻融过程中HFCC的质量损失率和相对弹性模量的变化规律。结果表明：在质量分数为3．5％的介质中,HFCC在NaCl溶液中的冻融破坏以表面剥落为主,在AD,CMA溶液中以内部冻融损伤为主;与水中冻融条件相比,质量分数为3．5％的CMA溶液延缓了HFCC的冻融破坏作用;HFCC在CMA溶液作用下的冻融破坏与其质量分数密切相关,CMA溶液质量分数越高,HFCC的冻融破坏作用越小,当CMA溶液的质量分数在12．5％以上时,即使经受600次快速冻融循环,其质量损失率和相对动弹性模量损失均很小;在质量分数为25％的冻融介质中,HFCC在商品飞机除冰液中的抗冻性较差,在机场道面除冰液中抗冻性较好;HFCC完全能够应用于较高质量分数CMA溶液进行冬季除冰雪作业的水泥混凝土机场跑道。     

钢筋在混凝土模拟孔溶液中的腐蚀研究

钢筋锈蚀是影响混凝土结构耐久性的主要因素.研究了模拟孔溶液pH值、Cl-浓度、SO42-浓度以及空气等对钢筋锈蚀的影响.试验结果表明：随溶液pH值降低,钢筋锈蚀程度增加.随孔溶液中Cl-浓度增加,锈蚀钢筋增重率线性增加.依据钢筋增重率判断,Cl-导致钢筋锈蚀临界值为0.065%.氯盐溶液中SO42-存在使钢筋锈蚀速度变为原来的2~3倍.将腐蚀溶液中钢筋与空气隔绝将延缓钢筋锈蚀.     

毛细作用下硫酸钠半浸泡水泥基材料抗氯离子渗透性研究

硫酸盐和氯盐复杂盐蚀环境中的服役结构会受到两者产生的耦合作用。研究毛细作用下硫酸钠半浸泡混凝土试样的抗氯离子渗透性能,设计不同水灰比、不同硫酸钠溶液浓度的砂浆毛细上升试验,测试硫酸钠半浸泡混凝土试样的扫描电镜（SEM）、X射线衍射（XRD）和氯离子电通量。结果表明：硫酸钠半浸泡混凝土抗氯离子渗透性能劣化,前期劣化严重,随着半浸泡时间的延长,抗氯离子渗透性能有所回升,但依然比未浸泡试样的差。结合微观测试结果可知,混凝土抗氯离子渗透性能劣化的主要原因是：前期,在毛细作用下硫酸钠溶液填充了混凝土孔隙,减弱了固化氯离子的结合能力,释放了较多自由氯离子,从而增大了氯离子的扩散量;后期,随着浸泡时间的延长和环境湿度的变化,孔隙中的硫酸钠溶液过饱和后,形成无水Na₂SO₄和Na₂SO₄·10H₂O结晶体的混合物,结晶混合物沉淀于孔壁,部分阻碍了氯离子的扩散,从而减缓了抗氯离子渗透性能的劣化。硫酸钠溶液浓度超过5%以后,随着硫酸钠溶液浓度的升高,毛细上升速度减缓,混凝土抗氯离子渗透性能相应提高。硫酸钠溶液半浸泡下,水泥基材料毛细上升快慢可作为衡量混凝土抗氯离子渗透性能好坏的指标。硫酸钠和氯化钠的复合溶液对硫酸钠毛细上升有延缓作用,会改善混凝土的抗氯离子渗透性能。     

Temperature-induced deformation of CRTS II slab track and its effect on track dynamical properties

Two finite-element models of the CRTS II slab track are presented to simulate temperature-induced deformations of the concrete track slab with no deterioration or with a deteriorated cement asphalt mortar(CAM).One model,which considers the fully bonding interface between the slab and the CAM layer,could applied to a track that is in good condition;the other model uses cohesive zone elements to simulate the deteriorated CAM with some possible interfacial separation and slip.Utilizing both of the models,temperature-induced warp deformations of track under various temperature loads are investigated.The influence of temperature deformation on the dynamic properties of the track is analyzed based on the train-track coupled dynamics.Numerical results show that the deteriorated CAM layer can significantly increase temperature deformations of a CRTS II track slab,which would produce tiny rail irregularities.There are clear differences between the deformation shapes of the track slabs that have an inseparable mortar layer and those have a separable mortar layer.The track slab with a deteriorated mortar layer showed more open curl distortion than the track slab in good condition.The dynamical response index of the slab track is intensified to a certain level due to the temperature deformation;with an increase of the train speed,the track dynamical responses increased linearly.However,rail irregularities due to the temperature deformations are very tiny.Even if a track is exposed to extreme temperature loads and the mortar layer is deteriorated,temperature deformation can have a negligible effect on the track’s dynamical properties.     

超缓凝剂对硅酸盐水泥砂浆性能的影响

目的为配制一种新型有机复合超缓凝剂，研究不同掺量及养护条件下其缓凝效果和硬化机理．使之可有效地应用于大体积混凝土及缓黏接预应力混凝土工程中．方法利用XRD和SEM等微观手段，对掺入超缓凝剂水泥砂浆的缓凝性能进行了测试和表征．结果超缓凝剂在不同养护条件下，可使水泥水化“休眠”20～40d，“休眠”结束后能迅速水化而结构不发生变化．XRD图谱表明并未发现异常水化物产生；SEM图像表明，掺超缓凝剂的水泥硬化结构更加致密．结论在标准养护条件下，掺量0．035％的超缓凝剂可使水泥水化“休眠”34d，“休眠”结束后59d可达空白试件28d强度．随养护温度增加和超缓凝剂掺量的降低，水化“休眠”期降低．超缓凝剂并未使水化产物发生本质变化，其耐久性应是可靠的．     

The adsorbing effect of calcined layered double hydroxide for chloride ions in simulated concrete pore solutions

The adsorbing effect of calcined layered double hydroxide （CLDH） for chloride ions in simulated concrete pore （SCP） solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl^- and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio （[C1^-]/[OH^-]） of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with CI-, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.     

Investigation of stress corrosion cracking initiation of 7A52 aluminum alloy

The stress corrosion cracking(SCC) behaviour of 7A52 aluminum alloy in air and in 3.5% NaCl solution was researched by slow strain rate test(SSRT) and SEM-EDS. The SCC susceptibility was estimated with the loss of the reduction in area. The experimental results indicate that the SCC susceptibility of 7A52 aluminum alloy in 3.5% chloride solution is the highest at strain rate of 1×10-6 s-1. The lowest one is under the condition of 1×10-5 s-1. Stress concentration and anode dissolving around Al-Fe-Mn intermetallics initiate micropores which will result in microcracks. The existence of intermetallics in the microstructure may play an important role in understanding the SCC initiation mechanisms of 7A52 aluminum alloy.     

Degradation of bond between steel bar and freeze-thaw concrete after electrochemical chloride extraction

The effect of electrochemical chloride extraction(ECE) on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 mm×100 mm×400 mm.During the experiment,3% NaCl(vs mass of cement,mass fraction) was mixed into concrete to simulate chloride contamination,and the specimens experienced 0,25,50,75 freeze-thaw cycles before ECE.In the process of ECE,different current densities and durations were adopted.It is indic...     

混凝土表面氯离子浓度时变规律试验研究

采用氯盐浸泡试验,定期检测了混凝土表面处的氯离子浓度,并对数据进行了拟合分析,研究了混凝土表面氯离子浓度随时间的变化规律,分析了氯盐溶液浓度、水灰比和粉煤灰掺量对表面氯离子浓度大小及其累积速率的影响。结果表明,表面氯离子浓度随时间的增加逐渐增长并最终达到稳定状态。随着氯盐溶液浓度的增加,表面氯离子浓度将更快地达到稳定状态,表面氯离子浓度也相应增大;水灰比越大,表面氯离子浓度累积速率越快,表面氯离子浓度越大;掺入粉煤灰可加快表面氯离子浓度的累积速率,表面氯离子浓度随粉煤灰掺量的增加而增大。通过对现有模型的比较与修正,提出了一个更为完善的模型。