Unit_Weight_&_Voids_in_Aggregate

Unit Weight & Voids in Aggregate Introduction This lab explores ASTM C29, Standard Test Method for Bulk Density (“Unit Weight”) & Voids in Aggregate. In the lab an analysis of a fine and course aggregate was conducted in order to determine the unit weight in a compacted and loose state. The lab also determined the voids in fine and coarse aggregate separately, along with the voids of a combined mixture of fine and coarse material. The main objective of the lab is to calculate the unit weight levels which are necessary for selecting proportions for concrete mixtures. A secondary objective was to have the ratio of coarse to fine aggregate in the mixture be as close to 50/50 as possible. Test Procedures Apparatus and Materials Requirements 1. (1) Digital scale that was readable to 0.1g. 2. (2) Flat pyrex 13”x9” dish 3. (1) tamping rod- a round, straight steel rod, 5/8 in. in diameter and approximately 24 in. in length, having one end rounded to a hemispherical tip of the same diameter as the rod. 4. (1) Measure- a cylindrical metal watertight measure ( nominal 1/3 ft3 for coarse aggregate and 1/10 ft3 for fine aggregate) 5. (1) drying oven capable of 250°F 6. (1) metal scoop 7. (1) Large metal tray 8. (1) large bulb dropper 9. (1) pair of oven protective gloves 10. (1)large metal spoon 11. (1) nylon brush 12. Coarse aggregate oven dried at 250°F and then cooled to room temperature 13. Fine aggregate oven dried at 250°F and then cooled to room temperature Note: The sample size of the two aggregates should be approximately 2 times the amount it would take to fill the measure. Procedure Measure Calibration 1. Determine the weight of the dry measure. 2. Fill the measure completely full with water and determine the weight of the measure plus water. 3. Calculate the weight of the water by taking the difference of (1) and (2) above. 4. Calculate the volume of the container. Loose Unit Weight (shoveling procedure) 1. Fill the measure to overflowing by means of a scoop, discharging the aggregate from a height not to exceed 2 in. (50mm) above the top of the measure. 2. Level the surface of the aggregate with straightedge. 3. Determine the weight of the measure plus content, and the weight of the measure alone, recording values to the nearest 0.1 lb (0.05kg) Compact Unit Weight (rodding procedure) 1. Fill the measure one-third full and level the surface with fingers. 2. Rod the aggregate with 25 strokes of the tamping rod evenly distrusted over the surface 3. Add additional aggregate to the measure to the two-third full level, level with fingers, and rod again with 25 strokes of the tamping rod. 4. Add additional aggregate to overflowing and rod again using 25 strokes of the tamping rod. 5. Level the surface of the aggregate with straightedge. 6. Determine the weight of the measure plus content, and weight of measure alone, recording values to the nearest 0.1 lb (0.05 kg) Note: When rodding the first layer, do not allow the rod to strike the bottom of the measure. When rodding the subsequent layers, do not force the rod into the previous layer of aggregate. Compact Unit Weights (rodding procedure) of sand and gravel mixture (coarse & fine aggregate mixture) 1. Determine the compact (dry-rodded) unit weight of an assigned sand-gravel mixture. 2. After you have weighed each respective component, mix the fine and coarse aggregate together and record a total weight. Calculate the percentages of each component in the mix. Thoroughly mix the fine and coarse aggregate together in a large mix pan before proceeding. 3. Determine the unit weight using the Compact Unit Weight Procedure (steps 1-6) above. Test Results and Discussion Formulas V=Wwγw Where: V= Volume Ww= weight of water γw= unit weight of water γbulk=(G-T)V Where: γbulk=unit weight of the aggregate, lb/ft3 (for both loose and compact unit weights) G= mass of aggregate plus the measure, lb T= mass of measure, lb V= volume of the measure, ft3 n(%)=Gs γw- γbulkGs γw100 Where: γbulk=unit weight of aggregate, lbft3 n(%)= void content for compact unit weights Gs= bulk specific gravity, dry basis (from ASTM C127 or C128) Based on lab reports recently completed it appears the coarse aggregate has a bulk specific gravity of 2.60 and the fine aggregate has a bulk specific gravity of 2.54. γw= unit weight of water (62.3 lbft3 or 998 kgm3) n%=Gcom γw- γbulkGcom γw100 Where: Gcom=100CGc+FGf Gcom= the specific gravity of the combined sand-gravel mixture Gc= the bulk specific gravity of the coarse aggregate Gf= the bulk specific gravity of the fine aggregate C and F are fractions (%) of the coarse and fine aggregates comprising the sand-gravel mixture, respectively (the sum of C and F equal 100%) Calculations Volume of Measure V=2838g62.3 lbft3 V=45.554 ft3 Loose unit weight of fine aggregate γbulk=(4633.4g)45.554 ft3 γbulk=101.71 lbft3 Compacted unit weight of fine aggregate γbulk=(4919.8g)45.554 ft3 γbulk=108.0 lbft3 Loose unit weight of coarse aggregate γbulk=(4016.1g)45.554 ft3 γbulk=88.16 lbft3 Compacted unit weight of coarse aggregate γbulk=(4291.6g)45.554 ft3 γbulk=94.21 lbft3 Compacted unit weight of fine and coarse aggregate mixture γbulk=(5686.6g)45.554 ft3 γbulk=124.83 lbft3 Percent void content of compacted fine aggregate n(%)=2.54*62.3- 108.02.54*62.3100 n%=31.8% Percent void content of compacted coarse aggregate n(%)=2.51*62.3- 94.212.51*62.3100 n(%)=39.8% Percent void content of compacted fine and coarse aggregate mixture Gcom=10046.62.6+53.42.54 Gcom=2.57 n%=2.57*62.3- 124.832.57*62.3100 n%=22.0% Table 1- Data Collection Chart STANDARD TEST METHOD FOR WEIGHT & VOIDS IN AGGREGATE, ASTM C29  | GROUP NAME: | GROUP WTH | GROUP CAPTAIN: | JUSTIN HENRY | SCALE ID: | A & D COMPANY 5004 | SCALE SN: | 13002089 | OVEN TEMPERATURE: | 250 ° F | LOOSE UNIT WEIGHT  | COARSE AGGREGATE + TARE | 6616.2g | COARSE AGGREGATE | 4016.1g | FINE AGGREGATE + TARE | 7233.5g | FINE AGGREGATE | 4633.4g | COMPACTED UNIT WEIGHT  | COARSE AGGREGATE + TARE | 6891.6g | COARSE AGGREGATE | 4291.6g | FINE AGGREGATE + TARE | 7519.9g | FINE AGGREGATE | 4919.8g | COMPACTED UNIT WEIGHT OF MIXTURE | RATIO OF THE MIXTURE | 53.4% FINE; 46.6% COARSE | WEIGHT OF FINE AGGREGATE (COMPACTED) | 4919.8g | WEIGHT OF COARSE AGGREGATE (COMPACTED) | 4291.6g | MIXTURE + TARE | 8286.7g | MIXTURE | 5686.6g | WATER WEIGHT | TARE WEIGHT OF MEASURE | 2600.1g | TARE + WATER | 5438.1g | WATER | 2838g | WATER TEMPERATURE | 19°C | Results Discussion The results of this lab show the fine aggregate unit weight to be 101.71 lb/ft3 loose and 108.00 lb/ft3 compacted. For the coarse aggregate unit weight 88.16 lb/ft3 loose and 94.21 lb/ft3 compacted. The lab also found a unit weight for the compact course and fine mixture (46.6% coarse/53.4% fine) of 124.83 lb/ft3. The void content for the fine compact, coarse compact, and the mixture of fine and coarse were 31.8%, 39.8%, and 22.0% respectively. Questions 1.) Would you recommend measuring quantities of material by weight or volume' In order to create quality concrete the quantity of each ingredient must be measure accurately. Measuring in terms of weight and not volume, allows for adjustments in moisture conditions. Conclusion In conclusion the results of this lab show the fine aggregate unit weight to be 101.77 lb/ft3 loose and 108.06 lb/ft3 compacted. For the coarse aggregate unit weight 88.21 lb/ft3 loose and 94.26 lb/ft3 compacted. The lab also found a unit weight for the compact course (46.6%) and fine (53.4%) mixture of 124.9 lb/ft3. The void content for the fine compact, coarse compact, and the mixture of fine and coarse were 31.8%, 41.8%, and 21.9% respectively.  The primary objective of the lab was to calculate the unit weight levels which are necessary for selecting proportions for concrete mixtures was accomplished. The secondary objective was also accomplished; the ratio of coarse aggregate to fine aggregate in the mixture was within 3 % of a 50/50 mixture. The data provided in this lab could now be used to create a concrete mixture. References 1. ASTM C29 Bulk Density (unit Weight) and Voids in Aggregate. 2. ASTM C127 Specific gravity and absorption of coarse aggregate. 3. ASTM C128 Specific gravity and absorption of fine aggregate. 4. ASTM C125 Terminology Relating to Concrete and Concrete Aggregates 5. AASHTO T19 Unit Weight and Voids in Aggregate. Appendices Appendix A- Lab instruction sheet, Lab 6 - Unit Weight & Voids in Aggregate, ASTM C29 Appendix B- Construction Materials laboratory safety guidelines