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.

针对除冰盐化学侵蚀引起的混凝土劣化问题，发现高浓度CaCl_2对硅酸盐水泥混凝土的侵蚀性很强，且其侵蚀性在低温下比高温下更为严重。温度，而在 NaCl 溶液中没有观察到变质的迹象，与温度和溶液浓度无关。 CaCl_2溶液的进入引起的劣化似乎归因于氢氧化钙的溶解和络盐的形成。在掺入粉煤灰、高炉矿渣、硅灰等矿物掺合料的砂浆中，氢氧化钙含量的降低和氯离子渗透性的降低对矿物掺合料水化过程的综合作用，有效提高了抗渗性。对氯化钙的攻击。此外，已证实混凝土中夹带的空气提高了对氯化钙侵蚀的抵抗力，但在高浓度 CaCl_2 溶液中暴露时间的后期阶段，降低的水灰比几乎没有影响。有趣的是，发现伴随开裂的进一步劣化是由CaCl_2溶液中的反复干燥和润湿引起的。关于碱-硅反应引起的混凝土劣化，在碱含量相对较低的反应性骨料砂浆中，在1N NaCl溶液中促进它们的膨胀是由于孔溶液中OH^-离子浓度的升高引起的。孔隙溶液中 OH^- 离子浓度的增加是导致 NaCl 侵入含有反应性骨料的砂浆的原因。