(_With acknowledgements to "The Spectator"_)
Through the courtesy of Messrs. Alban Richards & Co. we are able to
publish the results of certain very instructive tests that have been
carried out on Pise during the past winter. Messrs. Richard's experience
and Report bring out two points with especial clearness, (1) That Pise
work, though not impossible under winter conditions, is not ordinarily
desirable unless some means of artificially drying the earth be resorted
to. (2) That the strength of Pise increases with surprising rapidity as
the work dries out. It should be remarked that none of the samples
tested were made from really good Pise soil, such for instance as the
red marls or brick earths. With such materials or anything approaching
them, the results would have been even better, as the Report points
out:--
"In conjunction with Mr. Williams-Ellis, we have made certain tests with
a view to satisfying ourselves as to the practicability of _pise de
terre_ for house construction. In order to obtain what we might term the
minimum or 'worst' tests, we decided to erect walls for this purpose in
the winter. This we have done for the last three months, which has been
a very wet period, and the following is a short description of the tests
we have made:--
"1. Two walls were erected measuring 14 ft. long, 9 ft. high and 18
in. thick, spaced 20 ft. apart, with short return ends to each wall.
Wall plates were placed centrally along the top of each wall, on
which were placed 9 in. by 3 in. wood joists, at 16 in. centres,
across the 20 ft span. In order to obtain the minimum results we
allowed the shutters to remain until the test was ready to be
applied, so that walls did not have an opportunity of drying or
hardening. This condition was thought necessary, as it is quite
reasonable to expect that if _pise de terre_ cottages are erected,
considerable weight might be placed on the walls immediately the
shuttering is struck. We then proceeded to test the walls to
destruction. The floor space provided for by the joists referred to
above measure 220 super. feet, the load was then applied gradually.
The load applied totalled 16-1/2 tons, which is equivalent of 168 lbs.
per super. foot of floor space, under which the wall collapsed,
which, in our opinion, provides a factor of safety of three to the
normal load which a cottage floor would have to bear.
"We are convinced that very much better results can be obtained in this
method of construction with walls which were first dried before the load
was applied. Further experiments are to be made to procure further data
on this subject. In addition to the above tests, we have submitted to
the National Physical Laboratory, blocks made of _pise de terre_, from
poor to medium soil, for testing purposes, and the following are the
results which have been obtained:--
"The following Report shows results of Tests made by the National
Physical Laboratory.
[Headnote: Pise Tests]
"REPORT ON TESTS OF BUILDING BLOCKS OF PISE DE TERRE SENT FOR TEST
BY MESSRS. W. ALBAN RICHARDS & CO., LTD.
"_Tests made on January 14, 1920._
"First set of three blocks sent in November 1919.
"These blocks were composed of a fine gravel containing very few and
very small stones. The material was said to be similar to that used at
Merrow Down, near Guildford, Surrey. It appeared to be very similar to
Farnham gravel.
"The blocks were tested in compression, one within twenty-four hours of
arrival at the laboratory, and the others after drying for a time in the
laboratory. For results of tests see Table I.