Laboratory investigation of reinforcement corrosion initiation and chloride threshold content for self-compacting concrete

Time-to-corrosion (T_i) of reinforcement in concrete and chloride threshold content (C_th) are important service life determinants for reinforced concrete structures in chloride-laden environments. In this study, the two determinants of a series of self-compacting concretes (SCC) and regular concretes were experimentally investigated. A new sampling approach for C_th determination (milling powder from corrosion active site at the rebar/concrete interface) was adopted to accurately express chloride content resulting in corrosion occurrence. It is found that the T_i and C_th follow the 3-parameter Weibull distribution. The results indicate that the corrosion initiation of rebar in concrete slabs depends upon both cement alkalinity and superplasticizer. Rebar, embedded in high alkalinity cement SCC, exhibits better corrosion resistance as indicated by the longer T_i, higher C_th and larger Weibull modulus, m. A larger Weibull modulus indicates that anti-corrosion performance of rebar in slabs is more stable and less scattered. The effects of specific superplasticizer on rebar corrosion resistance are discussed from the viewpoint of air void amount and size distribution at the rebar/concrete interface.     

AM／AMPS／DMDAAC／AMC16S共聚物的合成与性能

采用氧化还原引发体系合成了丙烯酰胺（ＡＭ）／２丙烯酰胺基－２－甲基丙磺酸（ＡＭＰＳ）／二甲基二烯丙然氯化铵（ＤＭＤＡＡＣ）／２－丙烯酰胺基十六烷磺酸（ＡＭＣ１６Ｓ）四元共聚物,借助红外光谱和差热分析研究了聚合物的结构和热稳定性,初步评价了共聚物的溶液性能,结果表明,ＡＭ／ＡＭＰＳ／ＤＭＤＡＡＣ／ＡＭＣ１６Ｓ共聚物具有较好的热稳定性和耐温抗盐能力。     

氯乙烯-醋酸乙烯酯共聚物的后功能化研究

通过将氯乙烯－醋酸乙烯酯－丙烯酸羟乙醋共聚物（VAGF）与马来酸酐酯化接枝，制得带羟基的氯醋三元共聚物。探索了原料配比、催化剂用量、反应时间及反应温度对酯化接枝反应的影响，并用红外光谱进行表征。得到酯化反应的最佳条件为：催化剂用量为VAGF质量的0．8％，VAGF质量分数为15％，温度100℃，时间9h。氯乙烯－醋酸乙烯酯－丙烯酸羟乙酯三元共聚物的马来酸酐酯化活性高于氯乙烯－醋酸乙烯酯－乙烯醇三元共聚物。     

持续荷载下混凝土的氯离子扩散性能研究

基于实际海洋环境暴露条件,研究了力学荷载作用下混凝土中的氯离子扩散性能.以Fick第二定律理论为基础,用误差函数对混凝土中随深度变化的氯离子含量分布进行了曲线拟合,从而得到氯离子表现扩散系数,并以此表征氯离子在混凝土中的传输性.分析了氯离子的扩散系数与原材料、配合比、暴露环境以及力学荷载间的关系.结果表明,力学荷载对海洋环境下混凝土中的氯离子传输性能有显著影响,在利用氯离子扩散模型预测暴露海洋环境下混凝土结构的使用寿命时,需要考虑荷载因素的影响.     

对叔丁基氯苄的合成工艺研究

以叔丁基苯、多聚甲醛和盐酸为原料,通过氯甲基化反应制备对叔丁基氯苄。研究了投料摩尔比、反应温度、反应时间以及催化剂对产物收率的影响,优惠工艺条件为:磷酸作催化剂,叔丁基苯∶甲醛∶氯化氢=1∶3∶3(mol/mol),反应温度80～85℃,反应时间15h。     

氯乙烯悬浮聚合釜搅拌工程的研究

以冷模方法对目前我国广泛采用的氯乙烯悬浮聚合ＬＦ３０－Ⅱ型３０ｍ￣３，７０ｍ￣３及１３０ｍ￣３聚合釜搅拌工程进行了研究。剖析了搅拌桨叶、挡板的设置；并对这几种聚合釜的搅拌功率准数、搅拌功率消耗、循环特性和湍流强度等特性进行了具体的比较。其结果为氯乙烯悬浮聚合釜的搅拌设计与工业釜的改造提供了技术数据。     

氯离子对硫铵结晶系统的影响及对策

研究了硫铵结晶系统中氯离子的来源以及对硫铵结晶系统的影响,并制定了控制氯离子含量的对策。硫铵结晶系统由于氯离子进出严重不平衡,导致母液中的氯离子含量高,造成设备腐蚀,影响产品质量和系统安全,因而必须控制氯离子的含量。     

乙炔氢氯化反应铜基催化剂研究进展

开发乙炔氢氯化无汞催化剂对我国聚氯乙烯(PVC)工业具有重要意义,目前以金为代表的贵金属催化剂已经接近工业化应用,但其生产成本高限制了其市场推广,因此相对价廉的铜基催化剂受到广泛关注。主要从配体和载体改性等方面综述了科研人员对金属铜基催化剂在乙炔氢氯化反应中性能提升所做的工作,并且总结了含铜多金属催化剂在乙炔氢氯化反应中的研究进展,最后对铜催化剂工业发展前景进行了展望。     

Electrochemical corrosion behavior of 300M ultra high strength steel in chloride containing environment

The electrochemical corrosion behavior of 300M ultra high strength steel in chloride containing environment was investigated by potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The results show that uniform corrosion occurs on 300M steel during the electrochemical measurements because no anodic passivation phenomenon is observed on polarization curves within the measurement range. The tests also show that 300M steel is highly susceptible to chloride containing solution, which is characterized by corrosion current density increasing with the addition of chlorides, and corrosion potential shifting towards positive direction and corrosion resistance decreasing, positively suggesting that chloride ions speed up the corrosion rate of 300M steel. Meanwhile corrosion products on the 300M steel surface formed during the salt spray test are too loose and porous to effectively slow down the corrosion rate. Additionally, a schematic structure of uniform corrosion mechanism can explain that 300M steel has better property of stress corrosion cracking (SCC) resistance than stainless steels.     

Irreversible dilation of NaCl contaminated lime-cement mortar due to crystallization cycles

The mechanism of damage occurring in NaCl contaminated materials has not been clarified yet. Apart from crystallization pressure, other hypotheses have been proposed to explain the cause of decay. Irreversible dilation has been observed in a few cases but has never been studied in a more systematic way. The aim of the research is to contribute to the modeling of this phenomenon.In the present paper the effect of NaCl on the hydric and hygric behavior of a lime-cement mortar is extensively studied. The results indicate that NaCl influences the hydric and hygric dilation behavior of the material. The material contaminated with NaCl shrinks during dissolution and dilates during crystallization of the salt. This dilation is irreversible and sufficient to damage the material after few dissolution/crystallization cycles. This behavior is not restricted to NaCl, but is observed in the presence of other salts as well (NaNO₃ and KCl). Outcomes of electron microscopy studies suggest that salts causing irreversible dilation tend to crystallize as layers on the pore wall.