稀硫酸侵蚀水泥砂浆的附面层效应试验研究

硫酸侵蚀水泥砂浆的产物会附着在试件表面形成附面层并对侵蚀带来阻滞效应.为研究附面层效应对反应速度的影响,用稀硫酸分2批对水泥砂浆进行为期2300 h的长期浸泡试验,为尽量消除附面层的积累,对其中一批试件采取定期轻刷表层去除附着层并更换浸泡液的长期浸泡方式,对另一批采取不去除附着层也不更换浸泡液的常规浸泡方式.试验获得了按硫酸消耗量计算的不同时间的腐蚀量,在此基础上结合溶解反应模型推算了不同时间砂浆材料的表观扩散系数,获得了不同批次表观扩散系数随浸泡时间的变化规律.结果表明,受附面层效应的影响,表观扩散系数按时间的幂函数规律降低,而且无论是否更换浸泡液,均会产生附面层效应并导致表观扩散系数降低,通过更换浸泡液和去除附着层的方式,可降低附面层效应的影响.     

硫酸盐浸泡环境下CaO-Na2CO3激发矿渣砂浆性能退化及机理研究

以Na₂SO₄和MgSO₄溶液为侵蚀介质,研究了在浸泡环境下CaO-Na₂CO₃激发矿渣(CNS)砂浆和普通硅酸盐水泥(OPC)砂浆经硫酸盐侵蚀前后的抗折强度、抗压强度及不同深度处的SO^2-₄浓度,结合X射线衍射(XRD)、扫描电子显微镜(SEM)、压汞法(MIP)等测试方法分析了CNS砂浆和OPC砂浆的侵蚀产物及孔结构,对比讨论了Na₂SO₄和MgSO₄对CNS砂浆和OPC砂浆的侵蚀机理。结果表明:CNS砂浆的水化产物主要是低Ca/Si比的水化硅铝酸钙(C-A-S-H),不存在氢氧化钙,碳酸钙的填充作用使其孔结构优于OPC砂浆,并且在相同侵蚀环境下,CNS砂浆的抗硫酸盐侵蚀能力大于OPC砂浆;MgSO₄侵蚀环境下CNS砂浆的侵蚀产物主要是水镁石(腐蚀后期会带动试件表面的砂浆一起剥落)和无黏聚力的水化硅铝酸镁(M-A-S-H);与Na₂SO₄相比,MgSO₄对CNS砂浆的腐蚀性更强。     

Corrosion monitoring of reinforcing steel in cement mortar by EIS and ENA

Health degradation by corrosion of steel in civil engineering, especially in rough environment, is a persistent problem. Environment pollution and global warming will exacerbate this problem. The assessment of whole-life costing and residual service life prediction of structures is very important. Pitting corrosion is the most important factor which influences the service life of the reinforced concrete structures in many chloride included environments. Electrochemical impedance spectroscopy (EIS) method is used to study the corrosion process of reinforcing steel in cement mortar. According to the results of the experiments, dispersion and diffusing effect control the electrochemical process of carbon steel corrosion in the cement mortar. By fitting the results with EC, the parameters about CPE and Warburg impedance are calculated. The pitting corrosion behavior of reinforcing steel in cement mortar has been studied by electrochemical noise analysis (ENA) method, the wavelet transform has been employed to analyze the EN data of reinforcing steel in mortar, and the energy distribution plot (EDP) is plotted. The experimental results show that the change of EDP during the corrosion process can qualitatively reveal useful information on corrosion mechanisms.     

苯丙乳液改性砂浆的优化配比及其性能研究

针对工程渗漏、混凝土修补问题,研究了苯丙乳液对水泥砂浆的改性效果.结果表明:砂浆中加入苯丙乳液能够提高抗折强度、抗拉强度和粘结强度,分别提高最大为42.8%、61.8%和1.91 MPa;苯丙乳液对砂浆吸水率影响十分显著,乳液掺量越大,吸水率越小;苯丙乳液能够改善砂浆的抗冻性、抗渗性、抗碳化性、耐腐蚀性和收缩率;龄期42 d,改性砂浆的收缩量减少13.6%;改性砂浆的透水压力为2.4 MPa,提高0.9 MPa;改性砂浆的氯离子渗透高度减少13.6%,且乳液掺量越大,氯离子的渗透高度越小.     

活性复合掺合料对水泥胶砂抗侵蚀性能影响

以防腐阻锈成分、粉煤灰、矿渣粉等量取代部分水泥,研究单掺防腐阻锈成分、双掺粉煤灰和矿渣粉以及复掺三者时对水泥胶砂抗蚀系数、电极电位的影响,并利用扫描电子显微镜(SEM)对不同复合掺合料水化产物和表面特征进行分析.试验结果表明:单掺FZJ的水泥胶砂,当掺量为6%时,其初始抗蚀系数比未掺的基准水泥胶砂高20%;双掺粉煤灰与矿渣粉的水泥胶砂,当两者掺量为65%时,100次循环后抗蚀系数远高于基准水泥胶砂,抗蚀效果显著;三者复掺最佳替代水泥量为71%时,56 d电极电位曲线趋向钝化,水泥胶砂的抗氯盐锈蚀效果最显著.电镜分析表明:防腐阻锈成分对粉煤灰、矿渣粉实现了碱改性,增加其二次水化活性,使三者复合掺合料的砂浆试块抗侵蚀性能随养护龄期的增长更加显著,为在氯盐、硫酸盐环境下矿物掺合料砂浆或混凝土耐久性研究提供应用技术.     

阻锈剂对海水拌和再生胶砂力学性能和钢筋腐蚀行为的影响研究

针对海水拌和再生骨料混凝土的耐久性问题,对比分析了两种阻锈剂在单掺和复掺下对海水拌和再生胶砂力学性能和钢筋腐蚀行为的影响,并通过X射线衍射(XRD)、压汞(MIP)等测试手段分析其影响机理。结果表明:海水拌和再生胶砂在不掺阻锈剂的情况下前期腐蚀速度较快,7 d后腐蚀速度较慢,逐渐趋于钝化;氨甲基丙醇对海水拌和再生胶砂力学性能和钢筋锈蚀性能起不利影响,主要原因是其抑制了水泥水化进程,增加了孔隙数量;五水偏硅酸钠能使海水拌和再生胶砂中的钢筋发生钝化,具有显著阻锈作用,同时可促进C-S-H的形成,优化孔结构,对海水拌和再生胶砂力学性能影响较小。该试验可对海水拌合再生骨料混凝土耐久性的改善和服役安全性的提升提供参考。     

On the limitations of predicting the ohmic resistance in a macro-cell in mortar from bulk resistivity measurements

An experimental setup was designed to simulate the conditions for chloride-induced macro-cell corrosion, in which small anodes are located in a large network of cathodes. The overall aim of the present study was to assess whether measuring the bulk resistivity of reinforced concrete/mortar can give sufficient information about the resistance between anode and cathode inside a macro-cell. Measurements were executed in mortar specimens with high and low resistivities. Both the resistance in the simulated corrosion cells and the bulk resistivity of the mortar mixtures were determined. A comparison of the results showed no direct correlation. This indicates that the common practice of comparing bulk resistivity with corrosion rate may not be sufficient to characterize the corrosion process of chloride induced macro-cell corrosion.     

新型耐酸耐碱胶泥的研制

本文设计了一种新型呋喃树脂。经过试验确定了新型树脂的合成工艺。并用该树脂与固化剂、惰性添料配制了胶泥,测试了其常温、热处理及腐蚀后的胶泥的力学性能、腐蚀率及焦化时间。测试结果表明:该树脂胶泥具有优良的耐酸耐碱性能。     

无皂乳液VAC/DMC/VHE-水泥基复合材料的性能研究

研究了无皂乳液醋酸乙烯酯(VAC)/甲基丙烯酰氧乙基三甲基氯化铵(DMC)/乙烯基羟丁基醚与水泥共混所形成的水泥基复合材料的性能。研究发现,聚灰比为5%或10%时,该复合材料的抗折强度都有相应的提高,而抗压强度变化不大。与较早研究的2种无皂乳液与水泥共混所形成的复合材料比较,有更好的性能。     

不同龄期钢纤维增强水泥砂浆纤维拉拔试验与模拟研究

钢纤维增强水泥基复合材料作为一种多相复合材料,其增强增韧效果的发挥依赖于钢纤维与基体之间的界面粘结性能。通过开展不同龄期的钢纤维增强水泥基复合材料单根纤维拉拔试验及数值模拟研究,分析了龄期对钢纤维增强水泥砂浆界面粘结性能的影响,建立了不同龄期的单根纤维拉拔细观模型,通过将模拟结果与试验结果进行对比验证模型的有效性。根据所建立的细观模型分别对不同龄期钢纤维增强水泥砂浆纤维-基体间的界面粘结作用机理及纤维-基体间粘结表面在纤维拔出过程中的应力变化进行了分析。结果表明:所建立细观模型模拟得到的纤维最大拉拔力及荷载-滑移曲线与试验结果吻合较好,钢纤维的最大拉拔力及钢纤维-水泥砂浆基体的界面粘结强度均随着龄期的增加而增加;在7 d龄期内界面粘结强度的增长速度较快,7 d龄期后增长速度放缓;随着龄期的增加,不同龄期段的界面粘结强度的增长率逐渐减小并趋于稳定。采用拟合得到的粘结表面材料参数能够有效模拟各龄期下单根钢纤维从水泥砂浆中的拔出过程。     

Electrical emission in mortar under low compressive loading

Electrical emission in mortar under low compressive loading was investigated in this paper. Electrical emission in mortar is apparent even under the compressive stress less than 30% of compressive strength. Under uniaxial trapezoid load, there are two sinesoids associated with the loading and unloading phases, respectively. With the loading rate increasing, the amplitude of electrical emission increases. The mechanisms of the electrical emission in mortar under low compressive stress include the opening of microcrack, the flow of liquid in mortar, and the charge leakage. The electrical emission under cyclic loading was also studied. An understanding of the electrical emissions may lead to practical applications such as the nondestructive testing of concrete.     

碳纤维增强轻质砂浆的力学与电学性能

采用煤发电厂废料－－飘珠为轻集料，代替一般砂浆中砂子，并探讨这种轻南砂浆进行碳纤维增强的成型工艺，使用这种工艺可制备包含不同品种、不同掺量的碳纤维增强水泥复合材料。对材料的波折、抗拉、抗压、抗冲击性能、导电性能等进行了研究，并从实验测试的结果讨论碳纤维的品种、一对以上性能的影响。     

Effect of strain rate and temperature on the performance of epoxy mortar

The behavior of epoxy mortar was studied under various curing conditions, temperature and strain rate. The effect of aggregate size and distribution on the mechanical properties of epoxy mortar was also studied. Epoxy mortar with a uniform fine sand was cured at various temperatures to determine the optimum curing condition. The strain rate was varied between 0.01 to 6 percent strain per minute and the testing temperature between 22°C and 80°C. The strength, modulus, and compressive strain-strain relationship of polymer mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of epoxy mortar are quantified. Compared to the uniformly graded fine aggregate fillers the gap-graded aggregates produced polymer mortar with better mechanical properties. The compressive modulus and splitting tensile strength of epoxy mortar are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress-strain behavior of epoxy mortar. The constitutive relationship parameters are also related to the testing temperature and logarithmic strain rate.     

纳米SiO2-CSA-OPC复合修补砂浆的抗盐渍土侵蚀性能研究

为了研究纳米SiO2-硫铝酸盐水泥-普通硅酸盐水泥(NS-CSA-OPC)复合修补砂浆的抗盐渍土侵蚀性能,采用在NaCl溶液、Na2 SO4溶液及NaCl-Na2 SO4复合溶液下的长期半浸泡试验模拟盐渍土侵蚀环境,以加速侵蚀NS-CSA-OPC砂浆试件.试验测试了3种侵蚀环境下,NS-CSA-OPC修补砂浆质量、相对...     

5℃环境下水泥砂浆抗硫酸盐侵蚀性能试验研究

研究了不同水泥品种、矿物掺合料对水泥基材料在5℃下抗硫酸盐侵蚀的性能的影响,分别采用普通硅酸盐水泥、中抗硫水泥以及加入矿粉与硅灰的水泥砂浆试件,测试各试样在(5±1)℃的3%Na2 SO4溶液浸泡后的强度变化情况,综合考虑砂浆强度与抗蚀系数对砂浆抗硫酸盐侵蚀性能进行评价,并运用SEM、EDS、XRD分析方法对腐蚀机理进行了分析.结果表明:在5℃环境下,砂浆试样的强度普遍低于常温环境下,砂浆抗硫酸盐侵蚀能力15%矿粉+3%硅灰>中抗硫水泥>15%矿粉+1%硅灰>普通硅酸盐水泥;加入矿物掺合料明显改善了水泥砂浆抗硫酸盐侵蚀性能,并且硅灰的含量越高效果越明显;低温下腐蚀产物不仅有石膏,还有碳硫硅钙石的生成.     

PVAc改性水泥砂浆耐化学腐蚀性能

采用聚醋酸乙烯酯(PVAc)乳液制备改性水泥砂浆,研究了PVAc改性砂浆经硫酸、硝酸、氢氧化钠、硫酸钠和汽油腐蚀后的强度残留比,并通过扫描电镜(SEM)观测了砂浆的微观形貌,采用X射线衍射仪(XRD)分析了经腐蚀后砂浆的物质组成.结果表明:水泥砂浆耐硫酸、硝酸腐蚀性能较差,但PVAc乳液可有效改善砂浆的耐酸腐蚀性能;PVAc乳液可一定程度改善水泥砂浆的耐硫酸盐酸腐蚀性能;高含量PVAc改性砂浆可应用于碱性环境;油污对普通水泥砂浆和聚合物水泥砂浆腐蚀效果均不明显;PVAc乳液胶膜可填充水泥砂浆的内部孔隙,有效阻塞了腐蚀介质进入,同时,PVAc胶膜具有弹性,可吸收膨胀应力,降低了膨胀破坏发生,从而改善砂浆的耐腐蚀性能.     

水泥浆体—集料界面的结构特性与砂浆抗蚀性的关系

本文从界面出发对以石英砂、硅酸盐水泥熟料和高铝水泥熟料作集料的砂浆的抗蚀性进行了对比实验。结果表明两种水泥熟料砂浆均具有比石英砂浆好得多的抗硫酸盐腐蚀和硫酸腐蚀性能。从扫描电镜和能谱及砂浆的氯离子扩散系数的测定结果对上述砂浆的抗蚀性差异的原因、界面结构特性在砂浆腐蚀过程中的作用机理进行了详细的论述。据此给出了界面的结构特性与砂浆的抗蚀性之间的明确关系。     

Corrosion of steel bars in OPC mortar exposed to NaCl, MgCl2 and CaCl2: Macro- and micro-cell corrosion perspective

In North America, corrosion of the steel rebar commonly occurs due to chloride attack from deicing salts. In Canada, based on the severity and temperature of the ambient environment, three different deicing salts, or combination of them, are used: NaCl, MgCl₂ and CaCl₂. In this paper, the effect of each of these salts on the corrosion of steel rebar and their impact on the durability of the mortar have been investigated. The results show that CaCl₂ has the most negative effect on the steel and, in high concentrations, on the integrity of the mortar. MgCl₂ also deteriorates the mortar if used in high concentration, while NaCl has no apparent effect on mortar durability even in high concentration.     

Chloride-induced corrosion behavior of reinforcing steel in spent fluid cracking catalyst modified mortars

Concrete properties can be improved by various additives. Nowadays there is a strong interest concerning the use of spent fluid catalytic cracking catalyst (SFCC) as an admixture to improve mechanical properties of concrete. This work aims at studying the corrosion resistance of steel rebars in SFCC modified mortar specimens. Results of physicochemical characterization indicate the acceleration of cement hydration due to pozzolanic activity of SFCC. Electrochemical measurements show that the addition of the SFCC enhances corrosion resistance by delaying its corrosion onset and decreasing the corrosion rate. These benefits can be attributed to the reduction of the mortar permeability.     

Influence of impressed current on the initiation of damage in reinforced mortar due to corrosion of embedded steel

Corrosion of steel in cementitious material is a slow process. Therefore in this study, accelerated corrosion tests were carried out by impressing current between steel embedded in mortar and a counter-electrode to study the process of corrosion leading to cracking in mortar. The specimens, which were made of mortar reinforced with steel, were immersed in solutions which contained or did not contain chlorides.

Critical times with respect to the onset of corrosion can be defined in various ways by using either steel half-cell potential, or potential drop between embedded steel and a counter-electrode, or expansion of the mortar specimen. These parameters give quite similar critical times and are related to the development of corrosion products and microcracking. The results obtained provide information on corrosion kinetics of embedded steel when corrosion is accelerated by impressed current and show the similarities to natural corrosion pattern when solutions contain chlorides.