Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed

153 a common brick of very sandy material size and number of ca- vities will very likely be very much the same as in the sand-lime- bricks, but there is however this principal difference, that in sandy, common bricks there are not only cavities between the grains but the latter consist of sand-grains imbedded in a very porous material. In such a material as sand-lime-bricks it is easily conceivable that it is of rather great importance whether the cavities are filled with water or not on the frost setting in. If full of water it will be very difficult for the ice, owing to the narrow outlets of the cavities, to expand without the surrounding sand-grains, in themselves quite impenetrable to the ice, getting displaced. For the common brick the case differs somewhat. Supposing that the structure of the brick is quite homogeneous, the water on freezing and then expanding will easily find its way through the porous material of the brick. But the homogeneity being deficient, the supposition for the water (the ice) dispersing all over the brick is broken, and conditions are thus quite changed. But of this an account will be rendered below. The Laboratory has, for the rest, not examined thoroughly the shape of the cavities in sand-lime-bricks or of the pores irt bricks, so that the above named is more particularly based on considerations, which seem apparent according to the general knowledge of the producing of the named materials. The natural conclusion from these considerations is, that the capillary attraction must b e considerably greater in bricks than in sand-lime-bricks and this conclusion has been strengthened by the experiments, which follow below1). For these experiments were taken 2 sorts of red bricks A and B and 2 sorts of sand-lime-bricks C and D2), 3 pieces of each sort. The bricks were dried till their weight was constant, and then weighed. They were thereafter placed in a *) A few months after these experiments had been made the Laboratory learned that under a discussion in Transact, of Americ. Cer. Soc. IX 07, 693 it was maintained by Prof. Wheeler that regular pores are of decisive im- portance to the resistance to frost in bricks, and that the rapidity with which water is absorbed by the bricks on these being partly immersed is thought to give a measure for the resistance to frost (Tonindustrie-Zeitung 1908, p. 873). 2) The designations of C and D employed here have no connection with those employed in Section II. 11 • •// ja/’ <