Normal_Consistency_Normal_Consistency_of_Hydraulic_Portland_Cement

Statement of Objectives Determine normal consistency of hydraulic Portland cement in accordance with ASTM C 187 standard specifications. Materials Used A provided sample of dry Portland Type II Cement was used. Distilled water was also used. Apparatus Used 1. Vicat Apparatus adhering to ASTM C 187, see Figure 1. 2. Graduated Cylinders. 3. Mixers adhering to ASTM C 305. Procedure 1. Figure 1: Vicat Apparatus To make the first mix, 650 grams of Portland cement and 155 ml of water were measured out. 2. The water was placed in the mixer, and then the cement was added to the water. The mixture sat for 30 seconds to allow the cement to absorb the water. 3. After the 30 seconds, the mixer was turned on a low speed for 30 seconds. 4. Once the 30 seconds of mixing finished, the mixer was shut off and the cement paste was scraped off the sides of bowl. The mix rested for 15 seconds. 5. Once rested, the mixer was turned on medium speed for 60 seconds. 6. After the 60 seconds of mixing, the mix was ready to test. Our group made a ball of cement in the palms of our hands. Once the ball was shaped, it was tossed between hands about 6 times. 7. The ball was inserted in the Vicat ring with a constant pressure. The bottom and top were leveled off to make flat, stable surfaces. 8. We placed the cement and Vicat ring under the rod to test. The rod was placed just above the cement and the indicator needle was set to zero. 9. The rod was released to sink into the cement and the timer was started. After 30 seconds, the distance the rod had sunk was measured. 10. Steps 1 through 9 were repeated with the other mixes. The second mix was 650 grams of Portland cement and 165 ml of water. The third mix was 650 grams of Portland cement and 175 ml of water. The final mix was 650 grams of Portland cement and 185 ml of water. All results were recorded. Results Water Content(ml) | Amount of Portland Cement (g) | Rod Drop(mm) | 155 | 650 | 1 | 165 | 650 | 6.5 | 175 | 650 | 14 | 185 | 650 | 24 | Table 1: Results from experiment Figure 2: Rod Drop vs Water Content with graphical line showing amount of water for a 10 mm drop Class Comparison of Normal Consistency As can be seen in Table 2, below, our test results fall within one standard deviation of the class average. Group | Calculated Water Content at 10 mm | Normal Consistency (%) | Group 1 | 166.7 | 25.6 | Group 2 | 165.6 | 25.5 | Group 3 | 171.8 | 26.4 | Group 4 | 169.9 | 26.1 | Group 5 | 168.8 | 26.0 | Group 6 | 168.2 | 25.9 | Group 7 | 171.7 | 26.4 | Group 8 | 174.0 | 26.8 | Group 9 | 172.5 | 26.5 | Group 10 | 167.7 | 25.8 | *Group 11 | 186.4 | 28.7 | Group 12 | 173.9 | 26.8 | Group 13 | 170.3 | 26.2 | Average | 170.1 | 26.2 | Standard Deviation | 2.8 | 0.4 | *Not counted since group results appear to be an outlier. | Table 2: Class Comparison Discussion and Summary According to the test results for our group, our findings are within one standard deviation of the class average. According to the textbook (Mindness, 48), the water to cement ratio, in percent, should be between 24 to 33%. Our calculated percentage, at 25.9%, falls within this range as well as the class average at 26.2%. Therefore, the results can be considered satisfactory for standard hydraulic Portland cement. The “normal consistency” test performed does not help determine the quality of the cement in use. However, the test does analyze the performance of the cement. Since water to cement ratio is in direct correlation to the final strength of the cement, it is important that this ratio is within a normal & predictable range. The workability is also affected by this ratio and therefore must also be within a normal & predictable range. Conclusion Based upon our calculated results, the hydraulic Portland cement tested appears to be of a normal consistency of 25.9%, which is within the standard range of 24 to 33%. Our conclusion is, therefore, the test material will perform as predicted for standard Portland cement. In other words, the strength and workability should perform as expected, if the water to cement ratio is maintained as specified by the designer. References 1. ASTM Standards C187-04. 2. ASTM Standards C305-06. 3. Mindness, Sydney, Concrete Second Edition, 2003 Pearson Education, Inc. NJ.