Objective To determine the penetration value of an asphalt cement sample.

Transcription

1 2 Transportation Laboratory The grades of the asphalt cement depending on the penetration in 1/10 mm are: AC ( hard & not effect with temperature ) used for inclined planes due to its high viscosity. AC used for filling isolation cracks & joints. AC [(60 70 ) hot weather, ( & ) cold weather ] used for highway pavement. AC for emulsions because his flexibility, Objective To determine the penetration value of an asphalt cement sample. Standard ASTM D5-78. Apparatus 1- Penetration device 2- Standard penetration needle 3- Water path 4- Stop watch 5- Thermometer Procedure 1- Heat the sample carefully. Temperature should not be more than 90 c above the expected softening point of the bitumen. The heating and pouring should be accomplished within a period of thirty minutes. 2- Pour the sample into sample container (penetration cup). Pour tow sample for each test condition variation. 3- Cover the samples with lipped beakers and cool them to a temperature of 25c. Place them in the transfer dish which should be placed in the water path at a temperature of 25 c for 1.5 to 2 hours. 4- Place the dish and the contents on the stand of the penetrometer. 5- Adjust the needle height so that it is just touching the surface of the sample.

2 3 6- Set the penetrometer dial to zero and then release the needle holder for the specified time. 7- Measure the depth of penetration by the needle position on the scale (tenth of millimeter). 8- Carry out at least 3 determinations at points on the surface at least 10 mm apart, gently clean the needle after each test. If the penetration is greater than 350. It's necessary to left 50 g only and multiplies the dial gage reading by 2 or increase the depth of the sample. Correct penetration on 100 g load = 2 X penetration on 50 g load. The Test Conditions : 1. 25C O g Load second. Results : Trial No Penetration (1/10 mm) Average Then the asphalt is classified within AC (60 70 ). The penetration = (1/10) x ( ) = 6.78 mm. Discussion and conclusion: 1- High penetration grades are used in cold climates : 2- Low penetration grades are used in summer to avoid softening under high temperature. 3- As the penetration decreases the hardness increases. 4- As the penetration increases the viscosity decreases. 5- In cold countries this test is performed with load 200 g, time 60 sec & temperature 5 degrees. 6- The sample must be returned to the water bath as soon as the trial is completed (within 2 minutes)to keep their temperature the same. Always clean the needle after each trial and try to penetrate as far as possible from the previous trials.

3 4 (نقطة الطراوة). liquid Softening point: is the temperature in which bitumen change from solid to Objective: To determine the softening point of a bitumen sample using the ring and the ball apparatus. Standard: ASTM D36-76 Ring and ball apparatus We first heat the sample 110 degrees above the expected softening point = 160 C O it becomes liquid and then we pour it into the oil painted rings and wait half an hour then cut the excess and put the balls in the centering rings. Then we put the apparatus in water with a thermometer in and we start to increase constant rate of 5 degrees per minute and record the which the balls penetrate the sample rings. Results: T 1 = 54 degrees Discussion & conclusion: The lower the softening point of asphalt the lower the temperature in which asphalt can be used in. Ductility: The which bitumen elongates before it a constant temperature. Objective: To determine the ductility of a bitumen sample. Standard: AASHTO T51 ASTM D ductility mold 2- ductilometer 3- thermometer

4 We prepare the sample and pour it in the previous way then we cool the sample to room temperature for 30 minutes and then we keep it in a water path for another degrees. We prepare the ductiliometer water to have 25 degrees temperature for minutes and then we place and fix the sample in it from its ends so then the test is started and we start pulling the sample with observing the temperature we read the value at which the sample was cut. Results The ductility was = 1 + m. Discussion and conclusion Coating of aggregate is better with high ductility material so the binder will be better. It is quite easier to mix material with high ductility than mixing with low ductility. It is easier to move high ductility material from plan than the one with low ductility. The high ductility asphalt cement loss some of it temperature so, we cover it while transportation. When the AC have high ductility it loss of temperature is slowly so, it is easier to roll it, but it affected by temperature quickly. The lower the ductility the probably of segregation problem presence which leads to low durability because of unsuitable coating and high permeability. If the thread in the test was sagging down i.e. the material has higher density than water so, we rise water density by adding salt, and if the thread was floating i.e. it s density less than water density so, we decrease water density by adding Methyl-Alcohol. In our test the source of error was due to personnel errors of not keeping the water temperature always 25 degrees and not monitoring if the thread was sagging or floating in which lead to cutting the thread before it elongates 1 meter. Object: To determine the Flash and Fire Points of bitumen sample using Cleveland Open Cup Apparatus. Theory: The Flash Point test is used to determine the temperature to which asphalt materials may be safely heated without danger of instantaneous flash in the presence of open flame. It s the temperature at which the vapor pressure is high enough to give off sufficient hydrocarbon vapors to form an explosive mixture with air when contacted with an open flame. The Fire Point is the temperature at the material will burn. In British standards, the expected Flash Points are as follows: Type of Bitumen Expected Flash Point, C AC RC < 40 Cutbacks MC SC > 110 5

5 The Civil Engineering Center 6 Visit for more lecture notes and E-book! For AC and SC Cutback, the sample is heated at a high rate of C. When we reach 56 C below the expected Flash Point we reduce the rate to 5-6 C and we start passing the flame at 28 C below the expected Flash Point. For Rc and MC this is impossible, i.e. to heat it at a high rate, because the sample will burn within 2-3min, so we start at a low rate. This test is done on any type of bitumen. We will perform it on a Medium Curing Cutback and will pass the flame on the sample at 35 C (see Procedure). The Cleveland Cup Flash Point tester is widely used. The material in the cup is directly heated by a Bunsen Burner with the temperature rising at a slow constant rate. A small test flame is passed across the cup at specified intervals. The lowest temperature at which application of the test flame causes vapors above the surface of the liquid to ignite is taken as Flash Point. If the Flash Point test is continued until the test flame causes the liquid to ignite and burn for at least 5sec then this temperature is taken as Fire Point. The apparatus shall consists of the following: 1- Cleveland Open Cup apparatus, this consists of a test cup, heating plate, test flame applicator, heater and supports 2- A shield to protect the apparatus from drafts 3- A thermometer with a range of 6 to +400 C 1. Set up the apparatus in a draft free area and fill the cup to the filling mark with the sample. 2. Heat the sample at a rate of 5-6 C 3. When temperature reaches 35 C apply the test flame every 2 C on the thermometer. Pass the test flame across the center of the cup in a smooth motion in one direction in approximately 1 sec. Pass the flame in the opposite direction in the next test application. 4. Keep on this procedure until you observe the flash. Record Flash Point. 5. Continue the passing until the flash becomes flame for at least 5sec. Record Fire Point. Conclusions: If the flame last for 4sec then extinguished, then we are still in the Flash Point range. The Fire Point must last for 5sec at least. The Atmospheric Pressure will effect the vaporizing rate and so the Flash Point, so we use a Corrected Flash\Fire Point Equation : Corrected Flash\Fire Point = C ( 760 P ) Where: C: Observed Fire\Flash Point P: Pressure in testing room 760: 760mm Hg, the atom. Pressure at sea level Note that this equation is used only with Celsius temperatures. The flash point has an inverse relation with penetration.

6 7 Data Sheet & Calculations: Pressure in the lab = 690mm Hg Observed Flash Point = 89 C Corrected Flash Point = ( ) = 91.4 C the sample is : MC Observed Fire Point = 104 C Corrected Fire Point = ( ) = C Introduction : Viscosity is the resistance to different temperature degrees. The purpose of the Viscosity test is to determine the flow characteristics of asphalt in the range of temperatures used during application. The Viscosity or Consistency of Asphalt Cement is measured by either the Saybolt Fural Viscosity Test or the Kinematic Viscosity Test. Viscosity : the time that we needed to fill a standard flask ( 60 mm volume suitable temperature as ( 60 C ). Object: To determine the viscosity of bitumen by: A- The Saybolt-Furol viscosity test. B- The Kinematic Capillary viscosity test Theory: Here a specified volume of Asphalt Cement is placed in a standard tube closed with a cork stopper. Since the temperature of Viscosity determination for the Asphalt Cement is often above 100 C, oil is used as a medium for the constant temperature bath of viscometer. After the asphalt reaches a specified temperature the stopper is withdrawn and the time in seconds is measured for the flow of 60mL of the material through the Furol orifice. Standard: Saybolt-furol viscosity test ASTM D88 Kinematic viscosity test ASTM D2170 Viscosity Units : m 2 /sec. = 10-6 stocks ( st. ) = 10-4 centi-stoke ( cst ). Viscosity Asphalt standard temperature = 60 C : The classification : The viscosity range : ( cst. ) The Using : RC, MC & SC Prime coat RC, MC & SC Prime coat RC, MC & SC Tack coat RC, MC & SC Seal coat RC, MC & SC Use in cold mixture A- Saybolt-fural viscosity test :

7 8 1- Saybolt viscometer with fural orifice and bath 2- Withdrawal tube 3- Thermometer support 4- Filter funnel 5- Receiving flask 6- Timer 7- Viscosity thermometer 1. Fill the bath at least 6mm above the overflow rim of the viscometer. 2. Calibrate the Saybolt Fural viscometer at 50 C using a viscosity standard with a min efflux time of 90sec. If the efflux time defers from the standard by more than 0.2%, calculate the correction factor from the eq: F = V / t Where: V: Certified Saybolt Fural viscosity of the standard t: Efflux time at 50 C in seconds. 3. Insert a tight fitting cork stopper with a cord attached into the air chamber at the bottom of the viscometer. 4. Filter the sample into the viscometer until the level is above the overflow rim. Stir the sample with a thermometer in circular horizontal motion at 30-50rpm until the temperature remains constant. 5. Position the receiving flask where the stream of oil will just strike the nick of flask 6. At the same time, pull the cork from the viscometer and start the timer. Stop the timer when the flowing sample reaches the graduation mark. Record time in seconds. 60 C : SFS = 2 x centi-stock = 2 x cst. Time =792 SFS Viscosity = 792*2 = 1584 centi stoke If the sample is MC Cutback (depending on results from flash Point test). so it's classified as MC 800 ( Range used as a seal coat). Discussion and conclusion: 1- In the experiment there was some kind of errors because the asphalt was not flowing continuously into the receiving flask which shows that there was some air preventing the flowing which lead to an over estimate of the time and the viscosity. 2- It is important to determine the flow of the asphalt at some temperature to know how to deal with it. 3- It is important that the flow of the asphalt is not too high so that you can control it in the area you want to use it in. 4- It is quite important that the flow is not too low so that it is easy pour it and deal with it. 5- The viscosity is the resistance to flow. That means that the more is viscosity the more resistance to flow, and so the more time to fill the flask. 6- Some times we need to find the viscosity of lighter oil. The time using Fural procedure will be very small. Thus, another viscosity test is done called Saybolt Universal Viscosity test. In this

8 9 test the tube through which the oil will flow is 1.75mm dia, compared with 3.15mm dia for Fural, and calibrated at 35 C. The less diameter means more resistance and thus more time. Universal viscosity is 10times more than Fural one. Viscosity Test Diameter of Std. Temp. Condition Use for : NOTE : Fural 3.15 mm large open 37.8 C Heavy ( Cutbacks ) T fural = (1/10)T universal = (1/10)SUS Universal 1.75 mm small open 50 C Light T universal = 10T fural = 10SFS 7- Not be sure that temperature remained constant after stirring the sample may cause some errors in the test. 1- Zeitfuchs cross-arm viscometer 2- Thermometer. 3- Water bath 4- Timer (stop watch). B- kinematics capillary viscosity test : Theory: Kinematic Viscosity of Asphalt Cement at higher temperatures such as 135 C is usually measured with gravity flow capillary viscometers. In this test, and because of the wide range of asphalt, several calibrated viscometers differing in the size of capillary are necessary. The basis of this test is the measure of time required for the constant volume of material to flow under rigidly controlled test conditions, such as temperature and the head of flowing liquid. Using the measured time in seconds and the viscometer calibration constant, it s possible to compute the viscosity of the material in the fundamental units, i.e. stokes (st) or centistokes (cst) as: V cst = V sec * C Where: V cst : Viscosity in centistokes V sec : Viscosity in seconds C : Viscometer Calibration Constant = Allowing sealed samples, as received, to reach room temperature. 2- Open the sample container and mix the sample thoroughly by stirring for 30 seconds taking care to avoid the entrapment of air. 3- Place the viscometer, with access vertical, in the water bath which has already been brought to required temperature (60 C to 135 C pour ) the sample to be tested into the large tube, being carefully not to wet the side walls, until it reaches appoint about 5 to 6 mm from the top to the siphon positioned beneath the horizontal tube. 4- Leave the set for about minutes. 5- Apply light suction to the small tube so that the sample fills the siphon. 6- Measure the time in seconds and tenth of second 7- Multiply this time by the constant 2.414of the viscometer to get the viscosity in centistokes (mm2/ sec).

9 10 Results: Time = 599 sec Viscosity = 599 x = centi 60 degrees If the sample is MC Cutback (depending on results from flash Point test). it is classified as MC 800 ( Range ) ( used as seal coat ). Discussion and conclusion: 1- As we have seen the results were quite reasonable since the values of the viscosity tends to make the sample appropriate for seal coat. 2- At 60 degrees 1SFS x Device Constant = centi stokes 3- Saybolt fural =1/10 saybolt universal due to difference in diameter. Objective: To study the change that could occur to the physical properties of the asphalt due to continuous heating of the asphalt and for a long time. Theory: Long time heating has a significant effect on the physical properties of the asphalt. The heating will increase the Viscosity, kinematic viscosity, softening point, Density and Flash Point. It will decrease the Ductility and Penetration. In our test we will noticed the change in its weight and Penetration due to long term heating. Result and Conclusion: Weight of sample before heating = g Weight of sample before heating = g Loss on heat = The deference in weight before and after heating = g The decrease in weight of the sample is due to vaporization of liquid inside the specimen, which leads to harder condensed asphalt. So the weight becomes less, due to lose of liquid, and Penetration becomes smaller, due to hardening of the sample (see Data Sheet) : Average = The penetration of sample before heating = 6.78 mm. The penetration of sample after heating = (1/10) x ( ) = General conclusions: heating decreasing the penetration and ductility. increasing the softening point,flash point,density,viscosity & kinematic viscosity.