水泥混凝土专业外文翻译5

《水泥混凝土专业外文翻译5》由会员分享，可在线阅读，更多相关《水泥混凝土专业外文翻译5（10页珍藏版）》请在毕设资料网上搜索。

1、附录 （一）外文原文 4.2.1.1 C ement Test by Sieve No. 170 The fineness of cement affects the quality of the concrete industry in general. A big cement particle cannot completely react with water as water cannot reach a remaining core in the cement particle. The water propagates through the cement particles a

2、nd they start to dehydrate, which causes an increase in temperature, which is the main reason for the forming of hair cracks and preventing stabilization of cement volume. As a result, an increase in the cement particle size reduces the strength of the same cement content and increasing the fineness

3、 of the cement will improve the workability, cohesion, and durability with time and decrease the water moving upward to the concrete surface. Figure 4.1, from Neville s book (1983), presents the relation between concrete strength and the concrete fineness at different ages. To perform this test, tak

4、e a sample of 50 g of cement and shake it in a closed glass bottle for two minutes and then revolve the sample gently using dry bar. Put the sample in a closed bottle and leave it for two minutes. Put the sample in 170 sieve (90 microns) and move it, shaking the sieve horizontally and rotationally,

5、then confirm finishing the sieve test when the rate of passing cement particles is not more than 0.5 g/min during the sieve process. Remove the fines carefully from the bottom of the sieve using a smooth brush. Then, collect and weigh the remaining particles on the sieve (W1). Repeat the same test w

6、ith another sample. Then the residual weight for the second test is obtained (W2). Calculate the values of the remaining samples through R1 = (W1/50) 100 R2 = (W2/50) 100 The ratio (R) is calculated by taking the average of R1 and R2 to the nearest 0.1% and, in the case of deviating results of the t

7、wo samples, more than 1%. Do the test a third time and take the average of the three results. You can accept or refuse the cement based on the following condition: For Portland cement t he R must not exceed than 10%. For rapid hardening Portland cement the R must not exceed 5%. 4.2.1.2 Initial and F

8、inal Setting Times of Cement Paste Using Vicat Apparatus The objective of this test is to define the time for initial and final setting of the paste of water and cement with standard consistency by using a Vicat apparatus and determine whether the cement is expired or can be used. The initial settin

9、g is the required time to set and after that concrete cannot be poured or formed； the final setting time is the time required for the concrete to be hardened. Vicat apparatus (Figure 4.2) consists of a carrier with needle acting under a prescribed weight. The parts move vertically without friction a

10、nd are not subject to erosion or corrosion. The paste mold is made from a metal or hard rubber or plastic like a cut cone with depth of 40 2 mm and the internal diameter of the upper face 70 5 mm and lower face 80 5 mm and provides a template of glass or similar materials in the softer surface. Its

11、dimensions are greater than the dimensions of the mold. The needle is used to determine the initial setting time in a steel cylinder with effective length 50 1 mm and diameter 1.13 0.5 mm. The needle measuring time is in the form of a cylinder with length of 30 1 mm and diameter 1.13 0.5 mm and held

12、 by a 5 mm diameter ring at the free end to achieve distance between the end of the needle and the ring of 0.5 mm. The test starts by taking a sample weighing about 400 g and placing it on an impermeable surface and then adding 100 ml of water and recording zero measurement from the time of adding w

13、ater to the cement and then mixing for 240 + 5 seconds on the impermeable surface. To determine the initial setting time and calibrate the device until the needle reaches the base of the mold, then adjust the measuring device to zero and return needle to its original place. Fill the mold with cement

14、 paste with standard consistency and troll the surface, then put the mold for a short time in a place that has the the temperature and humidity required for the test. Specific Surface (Wagner)-m2/kg 365 days 90 days 28 days 7 days 20 150 200 250 300 30 40 50 Compressive Strength, Mpa Transfer the mo

15、ld to the apparatus under the needle, and then make the needle slowly approach the surface until it touches the paste s surface, stop it in place for a second or two seconds to avoid impact of primary speed, then allow the moving parts to implement the needle vertically in the paste. Grading depends

16、 on when the needle stops penetrating or after 30 seconds, whichever is earlier, and indicates the distance between the mold base and the end of the needle, as well as the time start from the zero level measurement. Repeat the process of immersing the needle in the same paste in different locations

17、with the distance between the immersing point and the edge of the mold or between two immersing points not less 10 mm after about 10 minutes, and clean the needle immediately after each test. Record time is measured from zero up to 5 1 mm from the base of the mold as the initial setting time to the

18、nearest 5 minutes. Ensuring the accuracy of measurement of time between tests reduces embedment and the fluctuation of successive tests. The needle is used to identify the final time of setting； follow the same steps as in determining time of initial setting and increase the period between embedment

19、 tests to 30 minutes. Record the time from zero measurement until embedment of the needle to a distance of 0.5 mm, which will be the final setting time. Control the impact of the needle on the surface of the sample so the final setting time presents the effect of the needle. To enhance the test s ac

20、curacy reduce the time between embedment tests and examine the fluctuation of these successive tests. Record the final setting time to the nearest 5 mm. According to the Egyptian specifications the initial setting time must not be less than 45 minutes for all types of cement except the low heat ceme

21、nt, for which the initial setting time must not be less 60 minutes. The final setting time must be shorter than 10 hours for all types of cement. 4.2.1.3 D ensity of Cement The purpose of this test is to determine the density of cement by identifying the weight and unit volume of the material by usi

22、ng the Le Chatelier density bottle. The determination of the cement density is essential for concrete mix design and to control its quality. This test follows specifications of the American Society for Testing and Materials, ASTM C188-84. The Le Chatelier device is a standard round bottle. Its shape

23、 and dimensions are shown in Figure 4.3. This bottle must have all the required dimensions, lengths, and uniform degradation and accuracy. The glass that is used in the Le Chatelier bottle must be of high quality and free from any defects. It should not interact with chemicals and have high resistan

24、ce to heat and appropriate thickness to have a high resistance to crushing. Measurements start at the bottle s neck and go from zero to 1 mL and from 18 to 24 mL with accuracy to 0.1 mL. Each bottle must have a number to distinguish it from any other. Write on the bottle the standard temperature and

25、 the capacity in millimeters over the highest point of grading. Processed sample cement weighing about 64 g to the nearest 0.05 g must be tested. Fill the bottle with kerosene free from water and oil whose density is at least 62 API. Up to point gradations between zero and 1 mL, dry the inner surface of the bottle at the highest level of kerosene if necessary, and use rubber on the surface of the table used for the test when filling the bottle. The bottle, which is filled with kerosene, is placed in a water bath and the first