The study reported herein was conducted as part of the Research Project on the Development of New Formwork System for Reinforced Concrete Buildings and of the Research Project on the Development of Techniques for Improving Life Time of Buildings.

This paper shows the fundamental experimental results of accelerated carbonation test of concrete masonry structures using a special chamber with high concentration of carbondioxide gas.A possible approach of predicting physical service life of this type of structures is presented here. Firstly, the effect of concrete block face shells on the carbonation speed of grouted concrete within concrete blocks was examined experimentally.This experiment consists of various parameters of the properties of concrete masonry units and grouted concrete, and of grouting methods. Secondly, a theoretical method for predicting the carbonation depth of grouted concrete through the face shell of concrete blocks is proposed.

The total carbonation depth of concrete masonry including face shell could be predicted on the basis of the theoretical method using the ratio of the actual thickness (Dfo) of face shell to the carbonation coefficient (Af) of the same face shell,(Dfo/Af), that is, the carbonation resistance of the concrete block. Furthermore, the total depth could be practically predicted using the concept of "the effective thickness of face shell" (De). The ratio of De to Dfo is presended to be approximately equal to the ratio of the compressive strength of face shell to that of grouted concrete on the basis of the empirical examination of the test data. This empirical relationship can take a role in corresponding to the practical partial range of the theoretical approximation within the compressive strength of grouted concrete of 150-300kgf/cm ².

Finally, the various types of deteriorations in concrete masonry are disccussed in the relation of predicting service life. The possibility of prolonging service life is confirmed by improving the quality of concrete masonry units as an industrialized product.

^*1 Head of Construction Techniques Division, Building Research Institute, Ministry of Construction