The paper "Experiment Details of the Penetration Values of Three Samples of Bitumen" is a great example of a lab report on engineering and construction. Bitumen is a viscous complex high molecular weight hydrocarbon derived from the process of petroleum refining. Newman (2004, pp120-122)It is incorporated into many substances which are termed bituminous materials. Asphalt and tar are used in numerous bituminous materials used in civil engineering. Penetration value is the measure of the consistency of bituminous material. It is the depth covered by the insertion of a standard needle in the bituminous specimen under a specific load, temperature and time conditions.
The depth is measured in tenths of a millimeter. These tests are a means of classification. it is used to check whether road-making materials have the correct bitumen grade, whether the bitumen has been hardened by overheating in storage or mixing or whether it has been stored in high temperatures for long periods. Introduction The purpose of the experiment was to assess the penetration values of the three samples of bitumen. Also, it was to help in the determination on which samples match with the used ring and ball test.
The penetration index of bitumen was also determined. The grading of bitumen entirely depends on the hardness or softness of bitumen. This is an important aspect as it aids to locate where bitumen can be used in different climatic regions. The method used for the experiment is the needle penetration test. Experiment details Various apparatus are used to carry out the experiment such as; a flat bottom dish, penetration needle holder, timing device, water bath maintained at 25.2oC, a transfer tray which supports the flat bottom dish, thermometer with a range of about 0-45 and a clock of the accuracy of about one second. The test sample is then heated to a constant temperature.
The needle is then cleaned before each test is carried out. The specimen is poured in the transfer dish to at least 16mm in excess. The specimen is covered with water from the temperature bath. The dish is then placed in the penetration apparatus. The needle is lowered till its tip comes in contact with the touch surface of the sample where its image is reflected from the specimen surface.
Zero position of the needle is noted and, the needle holder is released for the required time say after five seconds. The readings of the penetration are recorded in tenths of millimeters. Repeat the above procedure three times on each sample. They should not be less than 10mm from the side of the container, not less than 10mm apart. The needle should be cleaned between the determinations and each test should be completed after about two minutes from removing the sample. Figure 1 Results Sample/determination 1 2 3 average grade 2B21 17 18 20 18 A20 Discussions The experiment leads to a curve that has some concavity due to the soft nature of the top layer due to soaking.
Also, when the surface of the plunger is not horizontal this shape is likely to be obtained. The test is majorly influenced by the pouring temperature, size of the needle, the time taken to release the needle and the weight of the needle. Penetration value of 30/40 and 80/100 is mostly used. Newman (2004, pp120-121) A higher penetration value finds its importance in the colder region while the lower one is used in hot climatic regions.
In addition, lower penetration is difficult to bond, but when this is attained it stays for a longer time. Penetration level greater than 20 in most cases leads to cracking. Experiment 2 The softening point of Bitumen Abstract Bituminous materials have varying melting points. Their viscosity changes from being more viscous to less viscous making their determination of softening point difficult to determine. This calls for the use of ring and ball test in this experiment. This experiment gives the temperature at which viscosity takes place. Introduction Bitumen softens at a given specific point.
It is the point whereby bitumen changes its state from semi-solid to a liquid. This aids in determining the consistency of the bitumen that would be used in different climatic conditions on different types of constructions. The experiment is arbitrary and entails putting 9.50mm diameter ball specimen bitumen held in a brass ring. It is then placed in a water bath whereby it is heated until the sample gets soft to a point where the ball falls through the sample. The distance of the fall may be about 25 mm to the base plate the ring and the ball assembly.
This test has little practical impact and it is majorly used in analytical purposes. Experimental procedure. Various apparatus are used during the experiment which includes steel balls of about, 9.5mm and weighs approximately 3.50, brass rings which are square-shouldered, ball guides, water bath that is maintained at a constant temperature of about 25.2oC, ring holder, and bottom plate, a needle which is straight and highly polished and allows penetration without much friction. A cylindrical metallic dish which is flat and cylindrical of dimensions 55 mm in diameter and 35 mm in depth is required.
Penetration of order of 220 will require a dish of 70mm diameter and 45mm depth is required. Heat is applied to attain a temperature of the bath liquid of about 5oC or approximately -0.5oc per minute. This takes place as the stirrer operates. When the bitumen surrounding the ball reaches the base plate the temperature at that particular point is noted. Figure 2 Results Temperature(oc) mean Ball 1 56.0 55.6 Ball 2 55 Discussions Bitumen achieves softening under given conditions. It attains this at a given temperature when the bituminous material reaches a given viscosity level.
Gopi (2010, pp193-194). The results were affected by the rate at which the sample is being heated, the weight of the ball and the quality of the liquid. Lower softening points bituminous materials are used in colder regions while higher softening points are used in warmer places. The knowledge about softening assists in areas that have thick films such as the crack fillers and the joints to ensure that they do not flow. The occurrence of excessive brittleness. A high penetration grade is used in spray application works. Significance and Use Bitumen is viscous-elastic materials without sharply defined melting points; they gradually become softer and less viscous as the temperature rises.
Gopi (2010, pp193-196)The softening point is useful in the classification of bitumen’ s, as one element in establishing the uniformity of shipments or sources of supply, and is indicative of the tendency of the material to flow at elevated temperatures encountered in service. Errors There were systematic and random errors during the experiment. The major causes of error were systematic factors such as; Weather conditions, parallax error on reading, and error in the apparatus.
Also, the size of the apparatus such as the weight of the needle also altered the results.