Twelve years have passed (at the time of writing) since the mine was closed in 1974 and maintenance of the buildings ceased. As we indicated in Table 3-1. The kind of damage referred to occurred during these twelve years has been devastating and the deterioration accelerates year by year. For example, the effects of weathering on the reinforced concrete frame of the Nikkyu company flats and building No. 30 are as indicated in Table 3-1. The kind of damage referred to here is such that lumps of concrete have broken off or are badly cracked. In many places where the concrete has fallen off, terribly rusty reinforcing bars are exposed. On the other hand, in undamaged area the phenolphthalein test proved that the concrete was not neutralised and, when struck with a concrete testing hammer, it proved to be physically unweakened. As described above, a number of factors account for these differences between damaged and undamaged area's and it is hard to access the precise role of each factor in quantitative terms.