PIS) DE TERRE.
PEPROUGH the courtesy of Messrs. Alban Richards 1. and Co. we are able to publish the results of certain very instructive tests that have been carried out on Flee during the past winter. Messrs. Richards's experience and Report bring out two points with especial clearness. (1) That Pits!: 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 Bilotti& be remarked that none of the samples tested were made front 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 :— " Tn conjunction with Mr. Williams-Ellis, we have made certain tests with a view to satisfying ourselves as to the prac- ticability cf piee 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 snort description of the tests we have made :— 1. Two walls were erected measuring 14 feet long, 9 feet high and 18 in. thick, spaced 20 feet 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 joiat., 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 waits did not have an opportunity of drying or hardening. This condition was thought necessary, as it is quite meonable to expect that if pise de terre cottages are emoted. considerable weight might be placed on the walls immediately the shuttering is struck. We then pro- eeeded to test the walls to destruction. The floor space provided for by the joists referred to above measure 220 eager feet. The load was then applied gradually. The load at. vsied totalled 161 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 Labora- tory blocks made of piee de terre, from poor to medium soil, for testing purposes, and the following are the results which have been obtained :— REPORT On Tests of Building Blocks of Pis e de Terre sent for Test by Messrs. W. Alban Richards and Co., Ltd.
Tests made on January 14th, 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 ap- peared to be very similar to Farnham gravel.
The blocks were tested in compression, one within 24 hours of arrival at the Laboratory, and the others after drying for a time in the Laboratory. For results of tests see Table I.
Second set of blocks sent in December, 1919.
This set consisted of six blocks in three pairs, each pair having been rammed with a different quantity of water.
One of each pair was tested within 24 hours of arrival at the Laboratory, and the others after drying in the Laboratory for 26 days.
The material used was not homogeneous, and the mixture consisted of a very clayey loam, a fibrous loam, sand and large stones. The clayey material gave rise to Surface cracks as the blocks dried.
For results of tests see Table U.
From the second set of blocks it would appear that it is better to ram with too much moisture than with too little. It will be noted that the density of the wet block was 30% more than that of the dry block, so that a wall could be carried higher with the dry material than with the wet, although such a wall would never gain the strength which a wet one would upon drying.
Dimensions In inches. Age in days. Area In sq. ft. Den- sity lba. per c.ft. LOAD. REMARKS
4-23 Intone per sq. ft.
UT1 UT2 UT3
2 flx 9X 9 89X 81X 81
995' 8-91X 815
9 18 162 '550 556 131 125 117 166 247
517 1010 Cracked Collapsed Collapsed Small cracks appeared
Dimensions. In Inches.
Area in sq. ft.
Den- ally lbs. per
in tons In tons Per
1 dry 8-9X 9 X81
1 155 106 045
Cracked at one corner
011 012 Collapsed VW2
9X9X 9 26 '562 105
314 Collapsed. Material quite dry
In interior VW3
3 wet 91:: 9-1:: 8-9
1 *570 131 015
4 wet 8-8>: 81 X 81
110 3-20 516 Collapsed. Material quite dry
In interior VW5
9:•.81X 9 1 158 126
Bulged and cracked
019 124 Collapsed 1W6
6 medium 81 x 88 X 7
26 '546 109 313 610
Collapsed. Material slightly
damp in the interior • Age after arrival at Laboratory.
Seal of NATIONAL PHYSICAL LABORATORY. Signature of Director.
We are of opinion that, having regard to the fact that the house at Newlands Corner (Guildford 4 miles) has weathered the winter, without showing any signs of dampness, pieS de (errs will make a thoroughly dry house.
We consider that the testa roads are satisfactory, and prove that this form of construction is of a sufficiently sound nature to be employed in the building of houses. With really suitable material, such as a light brick-earth or marl, it is considered that the results already obtained might well be 100 per cent. bettor."
We are informed that additional tests are now pro- ceeding with regard to the water-proof and weather- resisting qualities of Pise, the results of which will be duly published.