+----------+-----------------------------+-----------------------------+
| Slide 1  | ![](media/image1.wmf)       | This block of instruction   |
|          |                             | will cover the tests,       |
|          |                             | concepts and use of the new |
|          |                             | Superpave binder            |
|          |                             | specifications. At the end  |
|          |                             | of this block the student   |
|          |                             | will be familiar with the : |
|          |                             |                             |
|          |                             | \* Concepts behind the PG   |
|          |                             | binder grading system.      |
|          |                             |                             |
|          |                             | \* Tests used for           |
|          |                             | determining                 |
|          |                             | performance-related binder  |
|          |                             | properties.                 |
|          |                             |                             |
|          |                             | \* Selection of an          |
|          |                             | appropriate PG binder       |
|          |                             | grade.                      |
+----------+-----------------------------+-----------------------------+
| Slide 2  | ![](media/image2.wmf)       | The PG grading system was   |
|          |                             | developed to address the    |
|          |                             | short comings seen in the   |
|          |                             | traditional asphalt cement  |
|          |                             | specifications.             |
|          |                             |                             |
|          |                             | This specification is       |
|          |                             | referred to as a binder     |
|          |                             | rather than an asphalt      |
|          |                             | cement specification. The   |
|          |                             | difference is that a binder |
|          |                             | can be either a neat        |
|          |                             | (unmodified) or modified    |
|          |                             | asphalt cement. The term    |
|          |                             | "asphalt cement" usually    |
|          |                             | refers to an unmodified     |
|          |                             | asphalt cement.             |
+----------+-----------------------------+-----------------------------+
| Slide 3  | ![](media/image3.wmf)       | This specification uses     |
|          |                             | tests which evaluate the    |
|          |                             | fundamental material        |
|          |                             | properties (stress, strain, |
|          |                             | and strain rate). Changes   |
|          |                             | in asphalt properties due   |
|          |                             | to temperature, rate of     |
|          |                             | loading and the effect of   |
|          |                             | aging are considered.       |
|          |                             |                             |
|          |                             | Asphalt is a viscoelastic   |
|          |                             | material. That is, it can   |
|          |                             | both exhibit elastic and    |
|          |                             | viscous properties at the   |
|          |                             | same time. To demonstrate,  |
|          |                             | take a penetration tin of   |
|          |                             | asphalt cement at room      |
|          |                             | temperature. Press your     |
|          |                             | thumb into the asphalt;     |
|          |                             | this will leave a large     |
|          |                             | depression in the surface.  |
|          |                             | Then use a hammer to hit    |
|          |                             | the a remaining flat        |
|          |                             | section of the asphalt;     |
|          |                             | this will not leave much of |
|          |                             | an impression. Under light  |
|          |                             | but long term loads, the    |
|          |                             | asphalt has a noticeable    |
|          |                             | viscous behavior (it flows  |
|          |                             | out from under the load).   |
|          |                             | Higher, but much shorter    |
|          |                             | duration loads result in a  |
|          |                             | primarily elastic response. |
+----------+-----------------------------+-----------------------------+
| Slide 4  | ![](media/image4.wmf)       | The viscous component of    |
|          |                             | the binder response         |
|          |                             | dominates its warm          |
|          |                             | temperature behavior and is |
|          |                             | seen as permanent           |
|          |                             | deformation. The magnitude  |
|          |                             | of this deformation is      |
|          |                             | increased with the time     |
|          |                             | that the load is applied.   |
+----------+-----------------------------+-----------------------------+
| Slide 5  | ![](media/image5.wmf)       | Permanent deformation or    |
|          |                             | rutting of the pavement is  |
|          |                             | the result of               |
|          |                             | non-recoverable or plastic  |
|          |                             | deformation due to traffic  |
|          |                             | loads. At the warmer        |
|          |                             | temperatures, the aggregate |
|          |                             | structure carries a major   |
|          |                             | portion of the loads.       |
|          |                             | Stiffer binders help to     |
|          |                             | keep the aggregate          |
|          |                             | structure intact as well as |
|          |                             | help resist deformation in  |
|          |                             | the binder matrix.          |
+----------+-----------------------------+-----------------------------+
| Slide 6  | ![](media/image6.wmf)       | Ruts can be very visible in |
|          |                             | extreme cases such as the   |
|          |                             | one shown in this photo.    |
|          |                             | Other places where rutting  |
|          |                             | can be observed are at stop |
|          |                             | lights. In many cases, the  |
|          |                             | crosswalk lines can         |
|          |                             | highlight this type of      |
|          |                             | distress.                   |
+----------+-----------------------------+-----------------------------+
| Slide 7  | ![](media/image7.wmf)       | At cold temperatures, or    |
|          |                             | under very quick loads, the |
|          |                             | binder response is          |
|          |                             | predominately elastic.      |
+----------+-----------------------------+-----------------------------+
| Slide 8  | ![](media/image8.wmf)       | A length of pavement can be |
|          |                             | considered to be a          |
|          |                             | semi-infinite constrained   |
|          |                             | beam. As the temperature    |
|          |                             | drops the asphalt concrete  |
|          |                             | wants to contract but is    |
|          |                             | restrained. This results in |
|          |                             | internal stresses building  |
|          |                             | up as the temperature       |
|          |                             | drops. Thermal cracks occur |
|          |                             | when the                    |
|          |                             | contraction-induced         |
|          |                             | stresses exceed the tensile |
|          |                             | strength of the mixture.    |
|          |                             |                             |
|          |                             | A number of researchers     |
|          |                             | have shown that the low     |
|          |                             | temperature behavior of the |
|          |                             | asphalt concrete pavement   |
|          |                             | is highly dependent upon    |
|          |                             | the properties of the       |
|          |                             | binder.                     |
+----------+-----------------------------+-----------------------------+
| Slide 9  | ![](media/image9.wmf)       | Thermal cracks are          |
|          |                             | transverse cracks, usually  |
|          |                             | at relatively evenly spaced |
|          |                             | intervals. The spacing gets |
|          |                             | closer together with        |
|          |                             | increasing binder stiffness |
|          |                             | the colder the              |
|          |                             | temperatures.               |
+----------+-----------------------------+-----------------------------+
| Slide 10 | ![](media/image10.wmf)      | Aging also needs to be      |
|          |                             | considered in the           |
|          |                             | specification as oxidation  |
|          |                             | and heat hardening during   |
|          |                             | tank storage, mixing and    |
|          |                             | placement (short term       |
|          |                             | aging) of the asphalt       |
|          |                             | concrete change the         |
|          |                             | properties of the original  |
|          |                             | binder.                     |
|          |                             |                             |
|          |                             | Long term aging refers to   |
|          |                             | the changes in binder       |
|          |                             | property after 7 to 10      |
|          |                             | years of exposure to        |
|          |                             | environmental factors.      |
+----------+-----------------------------+-----------------------------+
| Slide 11 | ![](media/image11.wmf)      | The binder designation is   |
|          |                             | based on expected extremes  |
|          |                             | of hot and cold pavement    |
|          |                             | temperatures.               |
+----------+-----------------------------+-----------------------------+
| Slide 12 | ![](media/image12.wmf)      |                             |
+----------+-----------------------------+-----------------------------+
| Slide 13 | ![](media/image13.wmf)      | A series of four test       |
|          |                             | methods are used to assess  |
|          |                             | key performance-related     |
|          |                             | properties of binders. The  |
|          |                             | first, the rotational       |
|          |                             | viscometer, evaluates the   |
|          |                             | viscosity of the binder at  |
|          |                             | temperatures similar to     |
|          |                             | those commonly used during  |
|          |                             | production.                 |
+----------+-----------------------------+-----------------------------+
| Slide 14 | ![](media/image14.wmf)      | The rotational viscosmeter  |
|          |                             | (also referred to at a      |
|          |                             | Brookfield viscometer) is a |
|          |                             | concentric cylinder         |
|          |                             | rheometer. This means that  |
|          |                             | one cylinder rotates inside |
|          |                             | of another. Viscosity is    |
|          |                             | determined from the amount  |
|          |                             | of torque needed to rotate  |
|          |                             | a cylinder (called a        |
|          |                             | spindle) with a known       |
|          |                             | geometry. Viscosity, as     |
|          |                             | defined earlier, is the     |
|          |                             | ratio of the shear stress   |
|          |                             | to the strain rate. This    |
|          |                             | viscometer uses information |
|          |                             | about the torque, speed,    |
|          |                             | and geometry to obtain      |
|          |                             | these measurements.         |
+----------+-----------------------------+-----------------------------+
| Slide 15 | ![](media/image15.wmf)      | This photograph shows a     |
|          |                             | typical rotational          |
|          |                             | viscometer set-up.          |
+----------+-----------------------------+-----------------------------+
| Slide 16 | ![](media/image16.wmf)      | The second test method used |
|          |                             | to characterize the binder  |
|          |                             | is the dynamic shear        |
|          |                             | rheometer. This test method |
|          |                             | is used to evaluate the     |
|          |                             | original and short term     |
|          |                             | aged binder properties at   |
|          |                             | the warmest expected        |
|          |                             | pavement temperature. By    |
|          |                             | changing the geometry       |
|          |                             | (i.e., using smaller        |
|          |                             | diameter plates), the same  |
|          |                             | test method and equipment   |
|          |                             | can be used to determine    |
|          |                             | binder properties after     |
|          |                             | long term aging and at      |
|          |                             | intermediate in-service     |
|          |                             | temperatures.               |
+----------+-----------------------------+-----------------------------+
| Slide 17 | ![](media/image17.wmf)      | This type of rheometer has  |
|          |                             | a parallel plate            |
|          |                             | configuration. The stress   |
|          |                             | and strain measurements are |
|          |                             | based on the assumption of  |
|          |                             | a cylindrical geometry.     |
|          |                             | This is why a great deal of |
|          |                             | effort is expended in       |
|          |                             | preparing and trimming the  |
|          |                             | specimen prior to starting  |
|          |                             | the test.                   |
+----------+-----------------------------+-----------------------------+
| Slide 18 | ![](media/image18.wmf)      | The main advantage to this  |
|          |                             | test is that it can be run  |
|          |                             | using a sinusoidal wave     |
|          |                             | form. The elastic and       |
|          |                             | viscous component of the    |
|          |                             | material response can then  |
|          |                             | be determined by evaluating |
|          |                             | the strain response to an   |
|          |                             | applied stress (see next    |
|          |                             | two slides).                |
|          |                             |                             |
|          |                             | The time for one cycle has  |
|          |                             | been set at 10 rad/sec      |
|          |                             | (1.59 cycles per second).   |
|          |                             | This is generally           |
|          |                             | representative of the time  |
|          |                             | for one cycle of loading    |
|          |                             | due to 55 mph traffic.      |
+----------+-----------------------------+-----------------------------+
| Slide 19 | ![](media/image19.wmf)      | If a material is elastic,   |
|          |                             | then the strain response    |
|          |                             | will be in-phase with the   |
|          |                             | applied stress. If a        |
|          |                             | material is viscous, then   |
|          |                             | the response will be 90^o^  |
|          |                             | out of phase.               |
+----------+-----------------------------+-----------------------------+
| Slide 20 | ![](media/image20.wmf)      | When a material has both an |
|          |                             | elastic and viscous         |
|          |                             | component to its behavior,  |
|          |                             | this type of testing can    |
|          |                             | sort out the contribution   |
|          |                             | of each to the total        |
|          |                             | response. Delta is the      |
|          |                             | phase angle, that is, the   |
|          |                             | degrees that the strain     |
|          |                             | response is out of phase    |
|          |                             | with the applied stress.    |
|          |                             |                             |
|          |                             | The complex modulus, G\*,   |
|          |                             | is the vector sum           |
|          |                             | (Pathagorean's theorem). If |
|          |                             | delta is 0, the G\* equals  |
|          |                             | the storage modulus. In     |
|          |                             | other words, the response   |
|          |                             | is all elastic. If delta is |
|          |                             | 90^o^, then the response is |
|          |                             | all viscous (G\* = viscous  |
|          |                             | component).                 |
+----------+-----------------------------+-----------------------------+
| Slide 21 | ![](media/image21.wmf)      | This photograph shows a     |
|          |                             | typical dynamic shear       |
|          |                             | rheometer set-up. The       |
|          |                             | chiller which is used for   |
|          |                             | temperature control is not  |
|          |                             | shown.                      |
+----------+-----------------------------+-----------------------------+
| Slide 22 | ![](media/image22.wmf)      | This shows a close up of    |
|          |                             | the upper parallel plate    |
|          |                             | with a sample of asphalt    |
|          |                             | between it and the lower    |
|          |                             | (black hexagonal platform)  |
|          |                             | plates. Once the sample is  |
|          |                             | loaded, this chamber will   |
|          |                             | be covered and filled with  |
|          |                             | liquid at the desired       |
|          |                             | temperature.                |
+----------+-----------------------------+-----------------------------+
| Slide 23 | ![](media/image23.wmf)      | This photograph shows a     |
|          |                             | sample of asphalt cement    |
|          |                             | placed on the upper DSR     |
|          |                             | plate. This plate will be   |
|          |                             | mounted in the rheometer    |
|          |                             | and the plate moved         |
|          |                             | downward to achieve the     |
|          |                             | desired gap. The asphalt    |
|          |                             | will be squeezed out the    |
|          |                             | sides and the excess        |
|          |                             | trimmed off.                |
+----------+-----------------------------+-----------------------------+
| Slide 24 | ![](media/image24.wmf)      | When the DSR is run at warm |
|          |                             | test temperatures, the      |
|          |                             | results are used to         |
|          |                             | indicate the ability of the |
|          |                             | binder to resist rutting.   |
|          |                             | For this testing, a 25 mm   |
|          |                             | diameter parallel plate     |
|          |                             | configuration is used.      |
+----------+-----------------------------+-----------------------------+
| Slide 25 | ![](media/image25.wmf)      | The first DSR parameter     |
|          |                             | used in the PG grading      |
|          |                             | system is G\*/sin , based   |
|          |                             | on testing the original     |
|          |                             | asphalt at the average 7    |
|          |                             | day high pavement           |
|          |                             | temperature. At high        |
|          |                             | temperatures, the potential |
|          |                             | for permanent deformation   |
|          |                             | (rutting) is the major      |
|          |                             | pavement distress being     |
|          |                             | evaluated.                  |
|          |                             |                             |
|          |                             | G\* in Pascals at 10        |
|          |                             | rad/sec is numerically      |
|          |                             | equal to viscosity in       |
|          |                             | Poise:                      |
|          |                             |                             |
|          |                             | G\* (Pascal)/in s^-1^)\] \* |
|          |                             | (10 Poise/1 Pascal.s)       |
|          |                             |                             |
|          |                             | Since increasing the        |
|          |                             | viscosity of asphalt has    |
|          |                             | been historically used as   |
|          |                             | one means of helping to     |
|          |                             | reduce rutting, using G\*   |
|          |                             | in this specification       |
|          |                             | parameter makes sense.      |
|          |                             | Including the sin parameter |
|          |                             | allows a softer but more    |
|          |                             | elastic (less permanent     |
|          |                             | deformation per load cycle) |
|          |                             | to be used rather than      |
|          |                             | simply increasing the       |
|          |                             | viscosity.                  |
+----------+-----------------------------+-----------------------------+
| Slide 26 | ![](media/image26.wmf)      | Short term aging is         |
|          |                             | accomplished using the same |
|          |                             | RTFO oven as has been       |
|          |                             | traditionally used in the   |
|          |                             | AR viscosity graded         |
|          |                             | specification.              |
+----------+-----------------------------+-----------------------------+
| Slide 27 | ![](media/image27.wmf)      | This photograph shows a     |
|          |                             | close-up of the inside of   |
|          |                             | the oven. Glass jars (shown |
|          |                             | in the next photograph) fit |
|          |                             | snuggly in the circular     |
|          |                             | openings in the rotating    |
|          |                             | carriage. As the opening of |
|          |                             | each jar passes the air     |
|          |                             | line nozzle, air is blown   |
|          |                             | over the continually moving |
|          |                             | thin film of asphalt        |
|          |                             | inside. A fan in the oven   |
|          |                             | keeps the temperature even  |
|          |                             | throughout the chamber.     |
|          |                             |                             |
|          |                             | Once the jars are loaded    |
|          |                             | into the carriage, the door |
|          |                             | is shut, the temperature    |
|          |                             | stabilized at 163^o^C, and  |
|          |                             | the aging process continues |
|          |                             | for 80 minutes.             |
+----------+-----------------------------+-----------------------------+
| Slide 28 | ![](media/image28.wmf)      | This shows an example of a  |
|          |                             | clean jar before adding 35  |
|          |                             | g of asphalt. The other jar |
|          |                             | shows how it looks at the   |
|          |                             | end of the test.            |
+----------+-----------------------------+-----------------------------+
| Slide 29 | ![](media/image29.wmf)      | In addition to preparing    |
|          |                             | simulated short term aging  |
|          |                             | of binders for further      |
|          |                             | tests, the mass loss due to |
|          |                             | volatilization of the light |
|          |                             | fractions can be measured.  |
|          |                             | This is done by determining |
|          |                             | the mass of two jars with   |
|          |                             | asphalt at the beginning of |
|          |                             | the test, cooling these     |
|          |                             | jars at the end of the      |
|          |                             | aging, then determining the |
|          |                             | mass once again.            |
+----------+-----------------------------+-----------------------------+
| Slide 30 | ![](media/image30.wmf)      | This briefly summarizes the |
|          |                             | concepts behind this        |
|          |                             | specification parameter.    |
+----------+-----------------------------+-----------------------------+
| Slide 31 | ![](media/image31.wmf)      | Fatigue is addressed by     |
|          |                             | assessing G\* sin after     |
|          |                             | RTFO aging (simulating      |
|          |                             | aging during mixing and     |
|          |                             | construction) and PAV aging |
|          |                             | (simulating aging after 7   |
|          |                             | to 10 years of service).    |
|          |                             | This is because fatigue     |
|          |                             | cracking takes time,        |
|          |                             | exposure to environmental   |
|          |                             | factors, and traffic before |
|          |                             | it occurs. An intermediate  |
|          |                             | test temperature is used to |
|          |                             | simulate the appropriate    |
|          |                             | average field conditions.   |
|          |                             |                             |
|          |                             | The configuration is        |
|          |                             | changed from a 25 mm to a 8 |
|          |                             | mm diameter plate. This is  |
|          |                             | necessary to keep within    |
|          |                             | the torque limits of the    |
|          |                             | DSR equipment.              |
+----------+-----------------------------+-----------------------------+
| Slide 32 | ![](media/image32.wmf)      | Fatigue cracking shows up   |
|          |                             | in the wheel paths and is   |
|          |                             | the result of the tensile   |
|          |                             | strength at the bottom of   |
|          |                             | the asphalt concrete layer  |
|          |                             | being exceeded by the       |
|          |                             | flexing of the pavement due |
|          |                             | to traffic loads. Since the |
|          |                             | crack starts at the bottom  |
|          |                             | of the layer and works its  |
|          |                             | way up, the pavement is     |
|          |                             | thoroughly cracked once the |
|          |                             | they are visible.           |
|          |                             |                             |
|          |                             | Some limited examples of    |
|          |                             | fatigue cracks starting at  |
|          |                             | the pavement surface have   |
|          |                             | been noticed lately. This   |
|          |                             | type of fatigue cracking    |
|          |                             | has been linked to an       |
|          |                             | increase in tire pressures  |
|          |                             | in the newer truck tires.   |
+----------+-----------------------------+-----------------------------+
| Slide 33 | ![](media/image33.wmf)      | This summarizes the testing |
|          |                             | required for this           |
|          |                             | specification requirement.  |
+----------+-----------------------------+-----------------------------+
| Slide 34 | ![](media/image34.wmf)      | A pressure aging vessel     |
|          |                             | (PAV) treatment of the RTFO |
|          |                             | binder is used to further   |
|          |                             | age the binder. This        |
|          |                             | simulates long term aging   |
|          |                             | changes.                    |
+----------+-----------------------------+-----------------------------+
| Slide 35 | ![](media/image35.wmf)      | This photograph provides an |
|          |                             | example of an older type of |
|          |                             | pressure aging vessel       |
|          |                             | equipment. There are        |
|          |                             | currently several makes and |
|          |                             | models of PAV ovens         |
|          |                             | available.                  |
+----------+-----------------------------+-----------------------------+
| Slide 36 | ![](media/image36.wmf)      | This shows the vessel       |
|          |                             | inside an oven. The pans    |
|          |                             | with the binder are in the  |
|          |                             | rack inside the vessel.     |
+----------+-----------------------------+-----------------------------+
| Slide 37 | ![](media/image37.wmf)      | Note that G\* is now        |
|          |                             | multiplied by sin instead   |
|          |                             | of divided by it. Going     |
|          |                             | back to the vector          |
|          |                             | representation, it can be   |
|          |                             | seen that G\* sin is simply |
|          |                             | viscous component of G\*.   |
|          |                             | Since the specification     |
|          |                             | places a maximum on G\* sin |
|          |                             | , it is essentially         |
|          |                             | limiting the viscous        |
|          |                             | component of the asphalt.   |
|          |                             |                             |
|          |                             | A maximum on this parameter |
|          |                             | is set to ensure that the   |
|          |                             | binder is soft enough to    |
|          |                             | flex under traffic loads    |
|          |                             | without cracking.           |
+----------+-----------------------------+-----------------------------+
| Slide 38 | ![](media/image38.wmf)      | This summarizes the         |
|          |                             | concepts for this           |
|          |                             | specification requirement.  |
+----------+-----------------------------+-----------------------------+
| Slide 39 | ![](media/image39.wmf)      | Low temperature binder      |
|          |                             | properties are determined   |
|          |                             | using the bending beam      |
|          |                             | rheometer (BBR).            |
+----------+-----------------------------+-----------------------------+
| Slide 40 | ![](media/image40.wmf)      | This test applies a static  |
|          |                             | load to a simply supported  |
|          |                             | beam of asphalt cement.     |
|          |                             | Temperature is held         |
|          |                             | constant using a liquid     |
|          |                             | bath. A computer provides   |
|          |                             | both equipment control and  |
|          |                             | data acquisition.           |
+----------+-----------------------------+-----------------------------+
| Slide 41 | ![](media/image41.wmf)      | This is what the asphalt    |
|          |                             | beam looks like immediately |
|          |                             | after removing the mold     |
|          |                             | (not shown). Care should be |
|          |                             | taken in handling the       |
|          |                             | sample as just the heat     |
|          |                             | from a hand can soften the  |
|          |                             | beam sufficiently, allowing |
|          |                             | it to deform considerably.  |
+----------+-----------------------------+-----------------------------+
| Slide 42 | ![](media/image42.wmf)      | The entire system is        |
|          |                             | comprised of the computer   |
|          |                             | hardware, BBR,and chiller   |
|          |                             | system located under the    |
|          |                             | counter (liquid circulates  |
|          |                             | from the chiller through    |
|          |                             | the BBR fluid bath).        |
+----------+-----------------------------+-----------------------------+
| Slide 43 | ![](media/image43.wmf)      | The equation used to        |
|          |                             | determine the change in     |
|          |                             | stiffness with time is that |
|          |                             | for a simply supported      |
|          |                             | beam. The geometry          |
|          |                             | parameters remain constant  |
|          |                             | throughout the test. The    |
|          |                             | only values that change are |
|          |                             | the deformation of the beam |
|          |                             | due to the static load and  |
|          |                             | the stiffness calculated    |
|          |                             | using this time-dependent   |
|          |                             | deformation.                |
+----------+-----------------------------+-----------------------------+
| Slide 44 | ![](media/image44.wmf)      | The software collects       |
|          |                             | deformation measurements at |
|          |                             | 8, 15, 30, 60, 20,and 240   |
|          |                             | seconds and the             |
|          |                             | corresponding stiffness is  |
|          |                             | calculated. The stiffness   |
|          |                             | is then plotted versus the  |
|          |                             | log of time. Since          |
|          |                             | deformation increases the   |
|          |                             | longer the load is left on  |
|          |                             | the sample (and deformation |
|          |                             | is in the denominator of    |
|          |                             | the preceding equation),    |
|          |                             | stiffness decreases with    |
|          |                             | time.                       |
|          |                             |                             |
|          |                             | The parameters used in the  |
|          |                             | specification are the creep |
|          |                             | stiffness at 60 seconds and |
|          |                             | the slope of the tangent    |
|          |                             | line at this point (called  |
|          |                             | m-value). There is a        |
|          |                             | maximum requirement on the  |
|          |                             | binder stiffness to ensure  |
|          |                             | that the binder is          |
|          |                             | sufficiently soft at cold   |
|          |                             | temperatures.               |
|          |                             |                             |
|          |                             | There is a minimum set on   |
|          |                             | the slope requirement. This |
|          |                             | is to ensure that the       |
|          |                             | material can relax (deform) |
|          |                             | quickly enough to prevent   |
|          |                             | cracking.                   |
+----------+-----------------------------+-----------------------------+
| Slide 45 | ![](media/image45.wmf)      | If the binder fails the BBR |
|          |                             | stiffness requirement, it   |
|          |                             | is not necessarily an       |
|          |                             | unacceptable material. In   |
|          |                             | this case, the direct       |
|          |                             | tension test (DTT) is used  |
|          |                             | to determine if the binder  |
|          |                             | can stretch a given         |
|          |                             | distance without failing    |
|          |                             | (breaking).                 |
|          |                             |                             |
|          |                             | The original testing device |
|          |                             | mounted and pulled a sample |
|          |                             | vertically. Because of      |
|          |                             | problems with sensors       |
|          |                             | mounted outside the         |
|          |                             | chamber, sample molding,    |
|          |                             | and alignment problems, the |
|          |                             | equipment has been          |
|          |                             | redesigned.                 |
+----------+-----------------------------+-----------------------------+
| Slide 46 | ![](media/image46.wmf)      | Regardless of the type of   |
|          |                             | equipment used, a sample of |
|          |                             | binder is molded into a     |
|          |                             | "dog bone" shape with a     |
|          |                             | uniform center cross        |
|          |                             | section. The sample is      |
|          |                             | pulled until the it breaks  |
|          |                             | in the middle. The stress   |
|          |                             | and strain at failure are   |
|          |                             | recorded. This test         |
|          |                             | requires a minimum strain   |
|          |                             | before the sample fails.    |
+----------+-----------------------------+-----------------------------+
| Slide 47 | ![](media/image47.wmf)      | This is the new direct      |
|          |                             | tension test equipment. In  |
|          |                             | this unit, a set of four    |
|          |                             | samples are pulled          |
|          |                             | horizontally. Temperature   |
|          |                             | is controlled by using a    |
|          |                             | liquid bath rather than     |
|          |                             | air-cooled. As with all of  |
|          |                             | the other equipment, this   |
|          |                             | one is also computer        |
|          |                             | controlled.                 |
+----------+-----------------------------+-----------------------------+
| Slide 48 | ![](media/image48.wmf)      |                             |
+----------+-----------------------------+-----------------------------+
| Slide 49 | ![](media/image49.wmf)      | This figure summarizes the  |
|          |                             | testing required for the PG |
|          |                             | binder specification.       |
+----------+-----------------------------+-----------------------------+
| Slide 50 | ![](media/image50.wmf)      |                             |
+----------+-----------------------------+-----------------------------+