Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed

130 strength are given in kg pr. sq. cm. In the next column is given the number of cements for which the results are means, and in the following columns the 5 highest and 5 lowest results obtained in the course of the year for the various tensile and compres- sion-tests; In Table II are stated results of all the examinations of cement of 1908, by which the strength of the same cement has been determined both after 3, 7 and 28 days and (except in 4 cases) after 3 months; high-pressure-steam tests have also been made. By the above mentioned E r d m e n g e r high-pressure- steam test test-pieces for tensile and compression-tests are moulded in the usual way of the cement, and after being left 24 hours in moist air, they are laid in water in further 2 days and then boiled in a small boiler at a pressure of 10 atmospheres for 6 hours and tested for tension and compression. To institute a comparison 3 days tensile and compression-tests are also, as a rule, made in the usual way. The tests invented by Dr. Erd- menger in Hannover is an accelerated test for constancy of vo- lume, which as far as our knowledge goes is used no more else- where, but to a rather great extent in Denmark. It is thus pre- scribed in the specifications of delivery of The Hydraulic En- gineering Department. The Laboratory having also made a great many accelerated tests by the method of Le Chatelier, the results obtained by the two methods will be given here for those cements, for which both tests have been made until the 1. of January 1907, — see Table III. As it seems to appear from the comparison of the results of the Erdmenger test and the le Chatelier test, that these results differ very much, a graphical sketch is given of them at page 30 in fig. 9 in order to obtain a better view. The results of the former tests are given in making a notch in the sloping straight line for each test, namely in that point of the line whose ordinate counted by the statements on the left side of the figure represents the compression strength according to the lest. For each cement a cross in the same ordinate points out the result of Le Chatelier’s test, the increase of distance between the needles being marked out from above downwards according to the statement on the right side of the figure. 4 results, where Ihe distance between the needles was less than 1 mm or ex- ceeded 11 mm, are left out. At discretion a curve has then been