Duration: Instructor: Trainees: CASIA, MA. CRISTINA B.
Bautista, John Michael Copones, Justin DR Cuartero, Chester James De guzman, Jacob Masa, Raymund
INTRODUCTION: Asphalt, also known as bitumen, is a sticky, black and highly viscous liquid or semi -solid form of petroleum. The primary use (70%) of asphalt/bitumen is in road r oad construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs. We performed different tests; specific gravity, penetration, softening point, viscosity and ductility, in different types of asphalt sample: 60/70, 115, 116 and 118.
LABORATORY TEST PERFORM 2.1 SPECIFIC GRAVITY
Specific gravity is defined as the ratio of the mass of a given volume of the bituminous material to the mass of an equal volume of water, the temperature of both being specified as 25 0C. First you should calibrate the pycnometer then dry the calibrated pycnometer. Pour heated sample about 34 ful, allow the asphalt to cool to roo m temperature for not less than 40 minutes. Weigh the pycnometer containing the sample with the stopper and record its mass. Fill the pycnometes with the distilled water from the beaker used in calibration, cool at a 25 0C for at least 30 minutes, take out the pycnometer from the beaker and wipe off the water from its surfaces and immediately take the weight and record he mass. The test method involves the measurement of the mass of the material tested and the mass of an equal volume of water.The mass of the sample is simply determined by subtracting the mass of the container from the mass of the container with the sample The mass of an equal volume of distilled water is determined by subtracting the mass of the container with the asphalt sample and the mass of the container filled with water alone. The specific gravity is calculated as the ration of the two results. This test is a fundamental property frequently required as an aid in classing binders for use in paving jobs. It is also used in identifying the source of bitumen binder and in case bitumen contains mineral impurities the specific gravity will be higher. Thus it is possible for a quantitative extraction of mineral impurity in bitumen. The experiment has been performed successfully and the specific gravity determined is 1.02. The specific gravity of the asphalt 60/70 is 1.02 while the other asphalt sample; 115 is 1.07, 116 is 1.13 and 118 is 1.17. I observed that the more solid the asphalt sample is, the higher the specific gravity is. We must assure that all precautions are taken in making the specific gravity bottles thoroughly cleaned and dried in the first weighting. The surface of the pycnometer must be cleaned and dried after filling with water before weight so it will not affects on its weight. There should be no bubbles in the pycnometer so the chance of error will be eliminated and thus the value is correct. We must follow all the listed methods to ensure that the chance of error will be eliminated.
2.2 PENETRATION TEST
Penetration is the consistency of a bituminous material measured at a controlled temperature. The penetration of a bituminous material provides a direct information as to how hard or soft it is. A bituminous material with high penetration value obviously means that it is soft. First heat the sample until it becomes fluid then fill the sample containers with the heated asphalt at least 25 mm. Allow it to cool to room temperature for 1 to 1.5 hours. Immerse the sample, transfer the dish and the tripod support into the water bath. Set the penetration apparatus over a flat surface with sufficient lightning then transfer the sample into the dish and take them out of the bath. Adjust the needle holder until the tip of the needle touches the asphalt sample Adjust t he rack of the dial until its bottom slightly touches the tip of the needle holder, record the initial reading and release the needle holder by pressing the ferrule or the specified time of penetration then lower the rack of the dial slowly until its bottom touches the tip of the holder and record the final reading. Loosen the needle screw and lift the holder, leaving the needle in the sample then bring back the transfer dish and the sample container into the water bath and maintain it for 5 minutes. Penetration test is used to measure the consistency of bitumen, so that they can be classified into standard grades. Greater value of penetration indicates softer consistency. Generally higher penetration bitumen is preferred for use in cold climate and smaller penetration bitumen is used in hot climate areas. It measures the hardness or softness of bitumen by measuring the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds. The bitumen is softened to a pouring consistency, stirred thoroughly and poured into containers at a depth at least 15 mm in excess of the expected penetration. It may be noted that penetration value is largely influenced by any inaccuracy with regards to size of the needle, weight placed o n the needle and the test temperature. In hot climates, a lower penetration grade is preferred. The result of the penetration test in asphalt sample 60/70 is 6 mm while the other asphalt sample; 115 is 15 mm, 116 is 2.33mm and 118 is 1.15mm. I observed that the harder or the more solid the asphalt sample is, the higher the result in penetration test is. The possible sources of the test are not using distilled water. There should be no movement of the container while needle penetrates it sample. We must follow all the listed methods to ensure that the chance of error will be eliminated. . Always follow what is said in the manual book, if there’s not clear instruction or clarifications kindly ask your instructor or professor about these things.
2.3 SOFTENING POINT TEST
Softening point of material as determined by the ring and ball test is often used to characterize asphalts of the harder types, especially those used as sealants, high softening point indicates that the material would flow/melt only at a relatively high temperature. Heat the asphalt sample, should not exceed 15 minutes then set the rings upon a plate and pour the heated sample into the rings then allow it to cool for 30 minutes. Cut-off the level the excess material using spatula, place the samples and the balls into a bath and maintain the temperature to 5 0C for 15 minutes, pour cold, freshly boiled distilled water into the container then place the ball over the sample in the mold using the ball-centering guide, slightly pressing it into sample and assemble the mold with the sample and the ball on the ring and thermometer support. Insert a thermometer and set it up in the container with cooled distilled power, place this assembly upon the heater then start the heater and increase the temperature at the r ate of 50C per min until the sample reaches it softening point. Bitumens/ Asphalts are viscoelastic materials without sharply defined melting points; they gradually become softer and less viscous as the temperature rises. For this reason, softening points must be determined by an arbitrary and closely defined method if results are to be reproducible. The softening point is useful in the cl assification of bitumens, 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. The Softening Point test has been performed and the softening point value has been calculated as 62 0C for asphalt sample grade: 60/70 while the other sample is; 115 is 720C, 116 is 79 0C and 118 is 95 0C. I observed that the harder/ more solid the asphalt sample indicates that the material would flow/melt only at a relatively high temperature. When setting the rings upon a plate rubbed with a detergent bar or wiped with glue to prevent the asphalt from sticking. Always follow what is said in the manual book, if there’s not clear instruction or clarifications kindly ask your instructor or professor about these things.
2.4 VISCOSITY TEST
The viscosity of the material is a measure of its ability to resist flow. The more viscous the binder, the more stable the pavement will be. Prepare the viscometer and insert the cork stopper at the bottom of the tube. Insert the displacement ring in the gallery and pour the heated sample into the cylindrical tube through a funnel with No. 20 si eve, until it slightly overflows over the rim. Insert a thermometer into the tube and stir the asphalt sample in a rotary motion until it reaches the testing temperature then place the receiving flask directly under the efflux tube, snap off the cork stopper and record the time of efflux of 60 ml. of the sample. This test method is useful in characterizing the consistency of tar and tar distillates by measuring, their flow properties. It is applicable to materials that are readily liquid at temperature up to 100°C. Viscosity in Engler’s degrees ≈ 1/4 th of say bolt furol viscosity (seconds). The degree of fluidity at application temperature greatly influences the strength characteristics of resulting paving mixes. High or low fluidity at mixing and compaction has been observed to result in lower stability values. There is an optimum value of fluidity or viscosity for mixing and compaction for each aggregate grading of the mix and bitumen grade. At low Viscosity, the binder simply lubricates the aggregate particles instead of providing a uniform film thickness for binding action. Similarly high viscosity also resists the comp active effort and the resulting mix will be heterogeneous in character exhibiting low stability values. Liquid asphalt is used to save large amount of energy required to melt or make the asphalt workable. The Viscosity test has been performed and the viscosity value has been calculated as 165 seconds for asphalt sample grade: 60/70. The viscosity ratio of the 60/70 asphalt in given temperatures 120°C, 130°C, 140°C and 150°C are 283s, 180s, 165s and 104s respectively. Make sure that the timing when you click the timer is right to ensure that there’s small possibility of errors. Always follow what is said in the manual book, if there’s not clear instruction or clarifications kindly ask your instructor or professor about these things.
2.5 DUCTILITY TEST
Ductility is the ability of the material to elongate when subjected to tension. In this test, a sample of the asphalt material is heated then poured into a special mold to form a briquette specimen. This specimen is subjected to tension, using the ductility machine, at a controlled rate of 5 cm/min at a temperature of 25 0C until the specimen breaks apart. The ductility of the material is the distance through which the specimen is stretched until breaks. This test method provides measure of tensile properties of bituminous materials and may be used to measure ductility for specification requirements. Bituminous materials used in pavement construction should possess sufficient ductility otherwise the pavement would crack due to temperature or traffic stresses and may render the pavement pervious and damage the pavement structure. Several agencies have specified minimum ductility values for various types of bitumen pavements. However a ductility of 100 cm’s is specified generally for bituminous construction. Roads expand at daytime while they contract at night. So, if the bitumen is not adequately duc tile cracking will occur. More than one grade may be used in the same project. For example; we may use grade 80/100 on the main traffic lane and lower grades on the arteries. The Ductility test has been performed and the ductility value has been calculated as 100+ cm for asphalt sample grade: 60/70 while the other sample is 115 is 4.5 cm, 116 is 2.9 cm and 118 is 0.75cm. I observed that the more liquid or the softer the asphalt sample is the longer it takes to break. Temperature was not maintained in the lab so the value may differ at 25 o C as we performed at the Lab temperature. The plate assembly upon which the mold is placed shall be perfectly flat and level so that the bottom surface of the mold touches it throughout. In filling the mold, care should be taken not to distort the briquette and to see that no air pocket is within the molded sample. Always follow what is said in the manual book, if there’s not clear instruction or clarifications kindly ask your instructor or professor about these things.
ASPHALT SAMPLE
SPECIFIC GRAVITY
PENETRATION
SOFTENING POINT
VISCOSITY
DUCTILITY
60/70
1.02
6mm
62 0C
165 seconds
100+cm
115
1.07
15mm
790C
283 seconds
4.5 cm
116
1.13
2.33 mm
790C
180 seconds
2.9 cm
118
1.17
1.15 mm
950C
104 seconds
0.75cm