Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed

 155 tions of the shell were, in fact, only observed on the header-side turning downwards, in so far as the bricks were, on the whole, damaged. It must then be supposed, that the damage is due to a prevention of the free evaporation from the surface combined with a small capil- lary attraction. This is also confirmed by the fact, that bricks which have not at all touched the bottom of the freezing case, but only been lying on the other bricks may suffer rather much. The Laboratory has later on made a great many similar ex- periments as regards the capillary attraction in common bricks and sand-lime-bricks. For the former accordance with the above named experiments was constantly substantiated. But among the sand-lime-bricks a few bricks were now and then found where the capillary attraction was rather considerable. In a single case 3 bricks of the same sort displayed a strong capillary attrac- tion. These bricks then were subjected to the usual test of resistance to frost of the Laboratory. This latter did not produce any dis- ruptions of the shell in the planes themselves, but in all bricks the corners were more or less damaged. The said bricks dis- played, for the rest, a resistance to fracture which is rather low for sand-lime-bricks, namely 124 kg pr. sq. cm. Probably the corners were specially fragile (besides, only 7 of 10 bricks were able to stand the changed test of resistance to frost of the La- boratory) . The corners seem, on the whole, to be a specially weak point in the sand-lime-bricks. This cannot seem strange, however, when it is borne in mind that it is claimed here that a brick with sharp corners shall be pushed out from the mould in a state, where the mass of the brick is not only quite soft but also practically unplastic. The great friction at the cor- ners quite naturally causes a weakening of the coherence between the outer shell of the cor- ners and the other part of the brick which un- der normal conditions is only the case to a very slight degree in bricks. The Laboratory does not maintain that a great capillary attrac- tion yields a guarantee for the resistance to frost in a brick or sand-lime-brick. With reference to what has just been said, it can especially very well be imagined that a brick loses its cor- 11*