Evaluation of the reliability and life span for cement materials by electric property measurements

通过电性能测量评估水泥材料的可靠性和寿命

• 批准号: 05650628
• 负责人: NAKAMURA Yoshinobu
• 金额: $ 1.09万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650628/
• 关键词: Portland Cement; Alkali aggregate reaction; Electric Conductivity; Weibull plot; Alternative method; Dielectric failure; Mechanical failure; Three-points bending strength; セッコウ; 機械強度; 絶縁強度; ワイブル統計; 破壊試験; 電気抵抗

Hardened gypsum and portland cement are chosen as a simple model of concrete and analogy beween the mechanical and dielectric strength distributions are found out. Both strength is evaluated in terms of Weibull statistics and the two-parameter Weibull function was adopted for both strength distribution. Both plots shows good coincidence independent of the water content during shaking of hemihydrate powder for hardening. At the hardened gypsum sheets which are made by shaking with 70wt% of water, both plots for mechanical and dielectric strength distribution show two straight lines with different slopes, however, both plots shows in good agreement. From the results, it is concluded that the mechanical strength distribution of hardened gypsum or Portland cement can be evaluated by using the dielectric strength distribution, which is casily obtained by breakdown testing.The low frequency impedance of Portland cement paste or mortal increased with an increasc in curing time and it is strongly affected by the addition of NaCl. The contamination of NaCl would induce the alkaliaggregate reaction ane it induces a sudden fracture of concrete or mortal. When small amount of NaCl is added to cement paste with reactive aggregate (Pyrex glass), the impedance in anomalous increases after 3 days curing. After 365 days curing, the evidence of alkali aggregate reaction is found out at NaCl added mortal with reactive aggregate. By the continuous monitoring of impedance of mortal, the alkali aggregate reaction can be foresee and if the anomalous increase in impedance is observed in early times, the alkali aggregated reaction is apprehensive.An alternative method to obtain a strength distribution of many test pieces at one time is proposed. In this method, bending stress of all subjected samples is simultaneously increased utilizing their elastic modules constancy and the fractured sample number is monitored by the change in electric conductance.

选用硬化石膏和波特兰水泥作为混凝土的简单模型，找出了力学强度分布和介电强度分布之间的相似性。两种强度均采用威布尔统计量进行评价，两种强度分布均采用双参数威布尔函数。两个图都显示出在摇动半水合物粉末以进行硬化期间与水含量无关的良好一致性。在通过用70wt%的水摇动制成的硬化石膏板处，机械强度和介电强度分布的两个曲线都显示出具有不同斜率的两条直线，然而，两个曲线都显示出良好的一致性。结果表明，可以用击穿测试得到的介电强度分布来评价硬化石膏或波特兰水泥的机械强度分布，波特兰水泥浆体或砂浆的低频阻抗随养护时间的延长而增大，NaCl的加入对低频阻抗有很大的影响。NaCl的污染会引起碱-骨料反应，引起混凝土或砂浆的突然断裂。在掺活性骨料（Pyrex玻璃）的水泥浆体中加入少量NaCl，养护3天后，电阻抗出现异常增大。经过365天的养护，在掺NaCl的活性骨料中发现了碱集料反应的迹象。通过对混凝土阻抗的连续监测，可以预见碱骨料反应的发生，如果在早期观察到阻抗的异常增加，则碱骨料反应是令人担忧的，提出了一种同时获得多个试件强度分布的替代方法。在该方法中，弯曲应力的所有受试者的同时增加利用其弹性模量恒定和断裂的样品的数量监测电导的变化。

项目成果

K.Sugai: "A Simultaneous Loading System to Evaluate the Structural Reliability for Brittle Materials" J.Amer.Ceram.Soc.(印刷中).

K. Sugai：“评估脆性材料结构可靠性的同步加载系统”J. Amer。

K.Sugai: "A Simultaneous Loading System to Evaluate the Structural Reliability forBrittle Materials" J.Amer.Ceram.Soc.(印刷中).

K. Sugai：“评估脆性材料结构可靠性的同步加载系统”J. Amer。

K.sugai: "A Simultaneous Loading System to Evaluate the Structural Reliability for Brittle Metcrials" J.Amer.Ceram.Soc.(in press).

K.sugai：“用于评估脆性金属结构可靠性的同步加载系统”J.Amer.Ceram.Soc.（印刷中）。

K.Sugai: "A Systematic Strength Distributin Evaluation through Simultaneously Loading" 日本セラミックス協会学術論文誌. (印刷中).

K.Sugai：“通过同时加载进行系统强度分布评估”日本陶瓷学会学术期刊（出版中）。

K.Sugai: "A Systematic Strength Distribution Evaluation through Simultaneously Loading" J.Ceram.Soc.Jpn. (in press).

K.Sugai：“通过同时加载进行系统强度分布评估”J.Ceram.Soc.Jpn。