After the test the specimen was removed and its moisture content determined. The specimen of soil, after being dried, is shown in Figure 5; it is in the middle foreground. The screen, made of perforated brass, is at the left. The lower plunger is not shown in the photograph. Figure 5. Apparatus and test specimen used to determine ex pansive force of adobe soil. Moisture Content The moisture content of air-dry adobe soil was obtained by drying to a constant weight in an oven maintained at 100 degrees Centigrade. The details are given in Table II. The small lumps are shown at the right in Figure 6. One of the large lumps is in the middle background in the same figure. A 500-gram sample of each soil was used. It was placed on a 200-mesh sieve and washed with water. The soil passing the sieve was rejected and that remaining on it was dried and screened through coarser sieves as indicated in Table III. The relative amounts of the original sample (the two jars to the left in the photograph) and the material retained on a 200-mesh sieve are shown in Figure 7. The grain size of the material passing a 200-mesh sieve was not determined for lack of time. Specific Weight The weights of adobe soils in lbs. per cu. ft. are given in Table IV. The volumes of separate pieces were determined and the specific weights computed. The 2 cu. in. lumps. were coated with paraffin and weighed in water; they are shown in the middle foreground in Figure 6. The other weights were computed from the volumetric-shrinkage data with the exception of the average material which was shoveled into a 1⁄2 cu. ft. measuring box and jarred so as to completely fill the box. Strength Four briquettes were molded with different soil-pastes taken at random when the volumeshrinkage test specimens were being prepared. They were tested after being thoroughly airdried. A mixture of different soils made into a paste was used to try out the gun shown in Figure 8 (page 40): Several specimens were prepared; the one to the left in the photograph was cut to a length of 1.2 in. so that the ends were plane and parallel to each other. Its diameter was 0.9 in. The specimen was thoroughly air-dry when tested in compression. RESULTS The results are given in the following tables and plates in the order indicated in the Table of Contents. in. Average material was a mixture of dust and lumps, none of which were larger than 2 cu. Table III. Sieve Analyses of Adobe Soils Cumulative weights of soil retained on given sieve, expressed in percentage of total weight of sample. *Soil Survey of Porterville Area, 1908 Field Operations of Bureau of Soils, page 1324. |