EFFECT OF WATER ABSORPTION OF AGGREGATE AND SURFACE FINISHING OF CONCRETE ON RESISTANCE AGAINST ACID RAIN

摘要

Deterioration of concrete by acid rain may be related to the amount of the rain remaining on the concrete surface and its absorption into the concrete. For example, concrete consisting of recycled aggregate whose water absorption is extremely high absorbs much acid rain, and the amount of the rain remaining on the concrete surface will be affected by the degree of surface finishing on the concrete. At the first stage in this study, the resistance of recycled aggregate concrete against acid rain was investigated by an accelerated test. At the next stage, the resistances of concretes placed in forms made of several different materials were investigated. The main conclusions are as follows. (1) The neutralization velocity of recycled aggregate concrete by acid rain was faster than that of natural aggregate concrete. However, when cement clinker particles whose sizes were almost as the same as fine aggregate were added into recycled aggregate concrete, the neutralization velocity can be slow. The reason is considered that the cement clinker particles can supply Ca(OH)_2 much longer than ordinal cement. (2) When surface finishing on concrete was rougher, area where pH of the concrete was lower was deeper. The reason is that the rougher the surface of concrete is, the amount of rain remaining on the concrete surface increases.