复碱化混凝土孔溶液的pH值(英文)

Evolution of pH Value of the Pore Solution after Realkalisation of Carbonated Concrete

碳化混凝土的复碱化是用碳酸钙缓冲溶液浸渍混凝土的电化学过程,目的是使混凝土孔溶液的pH值稳定在10以上,从而防止混凝土的进一步碳化.然而,该方法的实际应用表明:虽然孔溶液中已明显含有足量的碱(Na+,K+,Li+),但pH值仍降到10以下.本文通过试验提出了一个用以解释pH值随时间降低的假说,结果表明:由于混凝土孔溶液中存在溶解的硫酸盐,因此单纯提高孔溶液的碱离子(碳酸盐)相对含量,不能确保其pH值高于10.用提出的化学机理可解释混凝土电化学复碱化技术实际应用中观察到的现象,但是,由于混凝土孔溶液中溶解离子相互作用十分复杂,目前还不能在复碱化技术中对其加以考虑,因此复碱化技术尚不能被进一步推荐应用.

Method for realkalisation of carbonated concrete is based on the electrochemical processes. In order to increase the pH value of pore solution the concrete is impregnated with alkali carbonates solutions. These buffer solutions should stabilize the pH value of pore solution at a level higher than 10. However, analyses of impregnated concrete in practice show that the pH value drops to values below 10 although sufficient alkali (Na+, K+, Li+) concentration was available in pore solution. Experiments were carried out to confirm a hypothesis to explain the timedependent decrease of the pH value. It is concluded that in the presence of dissolved sulfates even a comparatively high content of alkali carbonates is not sufficient to maintain pH value higher than 10. The chemical mechanisms suggested in this paper are used to explain observations of practical applications. The complex interactions of dissolved ions in pore solution have hardly been taken into consideration of the development of new technologies for realkalisation up to now. For this reason, the methods for realkalisation of carbonated concrete as discussed in this paper cannot be recommended.