Hủy bỏ đúc từ khô hơn và diễn ra trong dessicator cho đến khi nó đạt đến nhiệt độ phòng. . Ghi lại trọng lượng của dàn diễn . Các tính toán Casting tỷ lệ: Đọc trực tiếp từ quy mô duy trì độ ẩm% ¼. | Appendix B 163 3b. Sample preparation . Approximately 700 g of sample is weighed in a 1000 ml beaker. . Mix sample for approximately 1 min. . Transfer sample to beaker and measure the Brookfield viscosity. . Record reading. . Return sample to 1000 ml beaker. . Add two drops of deflocculant. . Repeat steps 2-6 until minimum viscosity is reached. 3c. Procedure . Measure out 200 ml of sample. . Filter 200 ml of sample through a baroid filter press using Whatman 42 filter paper with a pressure of 90 psi filter slurries for 1 h . . After filtration period remove baroid and allow sample to drain for 5 min. . Remove cast from baroid and record weight. This is the casting rate. . Place cast into drier for a minimum of 18 h. . Remove cast from drier and place in dessicator until it reaches room temperature. . Record weight of cast. 3d. Calculations Casting rate Read directly from scale . . wet weight of cast dry weight of cast moisture retention ----------------- - ------ ----------X 100 dry weight of cast 4. Modulus of rupture MOR Purpose To determine the dry strength of a clay. 4a. Apparatus Plaster mold which forms bars 3 4 in. X 7 in. Low shear mixer Drying oven Dessicator Compression tester Calipers 4b. Sample preparation . Clay and slurry. . Clay and water are mixed together to form a slurry with a specific gravity of solids . . Water is added to a slurry so that a specific gravity of is achieved. . Mix in the weight of quartz which will give a 50 clay and 50 flint body. 4c. Procedure . Add deflocculant to sample until minimum Brookfield viscosity is reached. . Cast samples in plaster molds forming bars 3 4 in. diameter and 7 in. long. Allow bars to cast overnight. . Remove bars from mold and allow to air dry for 6 h. . Place bars in drier at 240 F overnight. . Place bars in dessicator and allow to cool to room temperature. . Remove bars one at a time .
