Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed
År: 1909
Sted: Kjøbenhavn
Sider: 185
UDK: 6201(09)
Emne: Trykt hos J. Jørgensen & Co. (M. A. Hannover)
On the development of testing of materials in the north and on the work of the danish states testing laboratory in Copenhagen (english translation)
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158
be termed a theory by some people, but is, however, effectively
borne out by the experiments made with the bricks from Chri-
stiansborg, it will appear comprehensible that the Labora-
tory does not see any reason for changing the
test of resistance to frost for common bricks
(or at any rate only for changing it thus far that the bricks
will be placed alternately with the header-sides or stretcher-sides
resting on the bottom of the freezing-case), and the less so as
this test has never called forth any complaint neither on the pari
of the brick-manufactories nor from master-masons and ar-
chitects.
Every impartial looker-on will admit that for sand-lime-bricks
no great risk is run of finding these sorts of heterogeneity. But
one might, perhaps, be inclined to believe that as the capillary
attraction is less in sand-lime-bricks than in common bricks, the
evaporation from the surface must also be essentially less.
On making, however, comparative experiments in
drying common bricks and sand-lime-bricks,
this was not proved to be the case during the first four
days and nights of the drying. The determination of the capa-
city of drying of the bricks was made in the following way:
The bricks employed for the determination of the faculty of
absorbing water were saturated with water and laid up in two
rows in the laboratory, the bricks being placed on lists. The
spaces between the individual bricks were everywhere the same.
To equalize matters as much as possible for all the bricks, a brick
saturated with water of the same sort as those being examined
was placed at the ends of each row, without being, of course,
weighed. At proper intervals the bricks were weighed. After
being air-dried till their weight was constant, they were at last
dried at a temperature of about 100° Centrigade till their weight
was constant.
As it appears from Table VI an average increase of weight
of 0,5 per cent takes place for the sand-lime-bricks while being
saturated with water and dried, but for the bricks an average
decrease of weight of 0,1 per cent. In the graphical sketch of
the drying, no regard has, however, been taken of this; see fig.
23, p. 66.
The evaporation from the surface of the
brick saturated with water or at any rate very wet