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Elucidation of Mechnisms of Deterioration of Concrete Caused by Chemical Attack of De-icing Salts and its Preventive Measures

除冰盐化学侵蚀引起混凝土劣化的机理及其预防措施的阐明

基本信息

批准号：
07555134
负责人：
KAWAMURA Mitsunori
金额：
$ 12.16万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

With regard to the deterioration of concrete due to the chemical attack caused by de-icing salts, it was found that a high-concentration CaCl_2 was very aggressive towards Portland cement concrete, and its aggressivity became more severe at a low temperature than at a high temperature, while no sign of deterioration was observed in NaCl solution idependent of both the temperature and the concentration of solution. The deterioration caused by the ingress of CaCl_2 solution seemed to be attributed to the dissolution of calcium hydroxide and the formation of complex salts. In the mortars incorp orating mineral admixtures such as fly ash, blast-furnace slag and silica fume, the combined effect of a decrease in the content of calcium hydroxide and a reduced chloride ion permeability on the process of hydration of mineral admixtures effectively improved the resistance to calcium chloride attack. Furthermore, it was confirmed that the entrained air in concrete improved the resistance to the calcium chloride attack, but the reduced water : cement ratio had little influence at later stages of exposure time in a high-concentration CaCl_2 solution. Interestingly, a further deterioration accompanied by cracking was found to be caused by the repetitive drying and wetting in CaCl_2 solution.With the regard to the deterioration of concrete due to alkali-silica reaction, in a reactive aggregate-bearing mortars with relatively low alkali contents, the promotion of their expansions in 1N NaCl solution was caused by a rise of OH^- ion concentration in pore solution. The increase in OH^- ion concentration in the pore solution was responsible for the intrusion of NaCl into the mortars containing a reactive aggregate.

关于混凝土由于除冰盐的化学侵蚀而劣化的问题，发现高浓度的CaCl_2对波特兰水泥混凝土具有很强的侵蚀性，低温时侵蚀性比高温时更严重，而NaCl溶液则不受温度和溶液浓度的影响。CaCl_2溶液的进入引起的劣化似乎是由于氢氧化钙的溶解和复盐的形成。在掺粉煤灰、矿渣和硅灰等矿物掺合料的砂浆中，降低氢氧化钙含量和降低氯离子渗透性对矿物掺合料水化过程的综合影响，有效地提高了砂浆的抗氯化钙侵蚀能力。此外，它被证实，在混凝土中的夹带空气提高抵抗氯化钙的攻击，但降低水灰比的影响不大，在后期阶段的暴露时间在高浓度的CaCl_2溶液。在碱-硅反应引起的混凝土劣化方面，对于碱含量相对较低的活性骨料砂浆，其在1 N NaCl溶液中的膨胀促进作用是由于孔隙溶液中OH^-离子浓度的升高引起的。孔隙溶液中OH^-离子浓度的增加是NaCl侵入含有活性骨料的砂浆的原因。