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A Study on the Mechanisms of Acceleration of Alkali-silica Reaction in Reinforced Concrete Structure Subjected to Cathodic Protection

阴极保护钢筋混凝土结构碱硅反应加速机理研究

基本信息

批准号：
09555134
负责人：
TORII Kazuyuki
金额：
$ 3.46万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Reinforced concrete beams with different water : cement ratios, 0.2 m by 0.3 m by 2 m, were made from the non-reactive river sand and the reactive andesitic coarse aggregate. After 28 days of the curing time, reinforced concrete beams were exposed outdoors, and the cathodic protection current of 50 mA/m^2 was applied to the steel reinforcement of RC beams. The expansion and cracking were monitored for about 3 years in order to investigate whether or not the cathodic protection may really accelerate the alkali-silica reaction of concrete around the steel cathode. After 3 years of the exposure time, the flexural loading test was carried out for ASR damaged RC beams.The main results obtained in this study are as follows ;(1) The concrete cylinders deteriorated due to the occurrence of ASR cracks in spite of the total alkali content of less than 3 kg/m^3 when they were exposed to a natural environment.(2) The cathodic protection current significantly increased the expansion and cracking of the RC beams containing alkali-reactive aggregates.(3) The surface treatment by the epoxy-type coating was not effective in controlling the expansion due to ASR especially when the cathodic protection was applied.(4) The load-bearing capacity in bending of the RC beams did not change independently of the degree of deterioration due to ASR cracks when the cathodic protection was not applied.(5) The load-bearing capacity in bending of the RC beams was 10 to 20 % lower due to the decrease in the bond strength around the steel cathode when the cathodic protection was applied for a long period.

用非活性河砂和活性安山质粗骨料制成不同水灰比的钢筋混凝土梁，0.2 m × 0.3 m × 2 m。养护时间28 d后，将钢筋混凝土梁暴露于室外，对钢筋混凝土梁的钢筋施加50 mA/m^2的阴极保护电流。为了研究阴极保护是否真的会加速钢阴极周围混凝土的碱-硅反应，对膨胀和开裂进行了约3年的监测。经过3年的暴露时间后，对混凝土柱进行了抗弯荷载试验，主要研究结果如下：（1）当混凝土柱暴露于自然环境中时，尽管总碱含量小于3 kg/m^3，但混凝土柱仍会因ASR裂缝而劣化。(2)阴极保护电流显着增加的钢筋混凝土梁的膨胀和开裂含有碱反应性骨料。(3)环氧型涂层的表面处理不能有效地控制由于ASR引起的膨胀，特别是当施加阴极保护时。(4)当不施加阴极保护时，由于ASR裂缝，RC梁的弯曲承载能力没有独立于恶化程度而改变。(5)钢筋混凝土梁的抗弯承载力降低了10%至20%，这是由于长期施加阴极保护时钢阴极周围的粘结强度降低。