Abstract:
A method of determining liquid absorption of an aggregate comprises providing a shaker apparatus, a vacuum source and a container; placing a sample of the aggregate in the container; adding liquid to the container sufficient to reach a calibration mark on the container; weighing the sample and liquid; mounting the container to the shaker apparatus; connecting the vacuum source to the container; agitating the sample and liquid with the shaker apparatus; applying a vacuum to the sample and liquid with the vacuum source; after the agitation and vacuum steps, adding liquid to the container sufficient to again reach the calibration mark on the container; again weighing the sample and liquid; and subtracting the initial weight of the sample and liquid from the final weight of the sample and liquid in order to determine the liquid absorption of the aggregate.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of application Ser. No. 10/294,856, hereby incorporated by reference herein. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates generally to paving material, and more particularly to a method and apparatus for determining liquid absorption of aggregate. Specifically this invention is for determining the saturated, surface-dry state of aggregate and for determining the amount of water and hence binder absorbed by an aggregate in order to determine the proper amount of binder to be added to a given amount of aggregate to produce paving material or other construction materials of acceptable mechanical qualities.  
         BACKGROUND OF THE INVENTION  
         [0003]    To design an asphalt paving mix, the proper amount of asphalt binder must be added to a given amount of aggregate material to maintain the right matrix of aggregate and binder in order to produce a paving material which will yield a strong and durable road. If there is too much binder in the mix, the road will be soft and rutting will occur. If there is not enough binder in the mix, the road will be brittle and will crumble or break apart.  
           [0004]    Aggregates used in the preparation of asphalt for road construction are tested to determine the amount of asphalt binder that will be absorbed internally into the aggregate when a batch is prepared. When binder is absorbed internally into the porous aggregate, that absorbed binder does not contribute to the effective volume of the asphalt mix. In order to account for this, additional binder must be added, which essentially disappears in the mix. The measurement of the binder absorbed by the aggregate which does not contribute to the volume of the asphalt mix is the percent absorption, by weight, of water absorbed into the aggregate to the weight of the aggregate itself (“PA”).  
           [0005]    The procedure for testing aggregate for PA is as follows. A sample of the dry aggregate is prepared to a condition where the internal voids are saturated with water, and the surface of the aggregate is dry. This condition is known as the saturated surface dry (“SSD”) state. The SSD sample is then weighed. The sample is then dried completely in an oven, and weighed again (dry). The difference between the SSD and dry weights, divided by the dry weight, and multiplied by 100, yields the PA.  
           [0006]    The current method for determining whether aggregate is at SSD is what is known as the “slump” test. In this test, a sample of aggregate is prepared with excess water so that it is wetter than the SSD state. The aggregate is placed into a metal cone, the metal cone is placed atop a non-absorbent surface of a table or bench and the aggregate is tamped down into the cone, through an opening in the tip of the cone, with a metal tamper. With aggregate pieces having water on the surface, i.e. with the aggregate sample being wetter than the SSD state, the cone of aggregate will remain standing when the metal cone is removed. The water between the particles of aggregate holds the aggregate together, due to surface tension. The SSD point is reached when there is a “slight slump” of the aggregate when the metal cone is removed. Once the aggregate sample has been initially prepared to wetter than the SSD state the aggregate is progressively agitated and subjected to warm air flowing over it, repacked into the metal cone and the metal cone removed, until this slight slump occurs. A 500 gram sample is then taken from the SSD aggregate and weighed. The 500 gram sample is then completely dried in an oven and is weighed again. The PA is then computed from the two weights.  
           [0007]    There are a number of problems with the slump test. First, the test is subjective. The definition of a “slight slump” will vary from technician testing the aggregate to the next. In addition, while the slump test works fairly well with natural sand, for which the test was originally developed, the test does not work as well for jagged material such as crushed granite and limestone. The crushed materials have a higher angularity (jaggedness) and a higher content of fine material, which packs better in the cone, holding the packed material together better. This requires the material to dry more before exhibiting a “slight slump”, making for an artificially dryer SSD point. On the other hand, a method which could actually measure the presence or absence of water on the surface of the aggregate would give a much more accurate measurement of whether the aggregate was in the SSD state or not and hence produce a much more accurate PA measurement.  
           [0008]    Second, when the sample is at a temperature above room ambient, it will continue to lose water weight by evaporation as long as the sample remains on the table or bench. This produces an artificially low PA. Also, the time between reaching SSD and weighing the sample will not be consistent from batch to batch and technician to technician. If the sample could maintain its SSD condition/moisture content from the time that that condition is reached until the sample is weighed then the measurement would be more accurate and repeatable from batch to batch and technician to technician.  
           [0009]    Third, as the sample is agitated and dried, the sample will begin to generate dust, which leaves the sample, and thus alters the aggregate constitution. Dust can also adversely effect mechanical parts such as bearings, motors, couplings etc. of the equipment used in the SSD/PA testing, thus contributing to premature failure of same. The dust is also a nuisance to the technicians operating the equipment. It would be desirable to somehow contain the dust generated by the sample during the SSD/PA determination.  
           [0010]    Knowing the liquid absorption of a material is valuable for a variety of reasons. First, the liquid absorption relates to the optimum amount of time the material should be processed in the preparation of asphalt mixes and concrete mixes. Second, from the liquid absorption one can calculate the film coefficient, which relates to the V ssd , one of the parameters disclosed in the assignee&#39;s own U.S. Pat. No. 6,486,475, hereby incorporated by reference herein, which determines the SSD of the material.  
           [0011]    Bulk specific gravity of an aggregate is defined as the weight of dry aggregate to the weight of weight having a volume equal to that of the aggregate including both its permeable and impermeable voids. Apparent specific gravity is defined as the ratio of dry aggregate to the weight of water having a volume equal to the solid volume of the aggregate excluding its permeable voids. One current method of determining the apparent specific gravity of a material sample involves soaking the material with water while manually hand agitating the material to remove air from the sample allowing water to displace the trapped air. Another current method of determining apparent specific gravity combines the step of pulling a partial vacuum on the vessel containing the specimen under test with manual hand agitation. Yet another current method has the technician pulling a vacuum on a pouch containing the sample to determine the apparent specific gravity, then puncturing the pouch under water to allow water into the sample to determine the liquid absorption. These methods are time consuming and prone to variation from one technician to the next.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention solves the noted problems of the slump test, while providing for the liquid absorbing characteristics of aggregate to be determined. The invention is both method and apparatus for determining liquid absorption of aggregate, for determining the SSD state of an aggregate, and for determining the PA of an aggregate.  
           [0013]    The method of determining SSD condition and related liquid absorption of an aggregate comprises providing a sample of the aggregate, adding liquid to the sample, subjecting the sample to a light source signal, monitoring a light reflected signal reflected from the sample and controlling either addition of liquid to the sample or removal of liquid from the sample as a function of the light reflected signal. Preferably the controlling step is controlling addition of liquid to the sample.  
           [0014]    The liquid is preferably water. The light source signal is preferably an infrared source signal and the light reflected signal is preferably an infrared reflected signal.  
           [0015]    The method further comprises agitating the sample. One manner of agitation comprises moving the sample in an orbital motion. Another manner of agitation comprises moving the sample in a wobbling motion. A third manner of agitation comprises stirring the sample. Preferably the agitating step comprises a combination of the three, namely moving the sample in an orbital motion, moving the sample in a wobbling motion and stirring the sample.  
           [0016]    Preferably liquid is added to the sample only until the reflected light signal reaches a predetermined value indicative of the sample being at the SSD state. The predetermined value of the reflected light signal is determined by averaging the reflected light signal reflected from the dry sample with the reflected light signal reflected from the sample when wetter than the SSD state. The reflected light signal reflected from the dry sample, which can vary from aggregate to aggregate, is measured with the apparatus of the present invention and the value of the reflected light signal reflected from the sample wetter than SSD is approximately a constant 0.08 Volts for all aggregate.  
           [0017]    Weighing the sample in the dry state and in the SSD state enables the technician to additionally determine the PA of the aggregate.  
           [0018]    The method may further comprise heating the sample to remove liquid from the sample, with the controlling step controlling removal of liquid from the sample as a function of the reflected light signal by controlling the heating of the sample.  
           [0019]    The apparatus of the present invention comprises a support for supporting a sample of the aggregate, a liquid source for adding liquid to the sample, a light source which subjects the sample to a light source signal, a light sensor which senses a reflected light signal reflected from the sample and a processor/controller which controls either addition of liquid from the liquid source to the sample or removal of liquid from the sample as a function of the reflected light signal. Preferably the processor/controller controls addition of liquid from the liquid source to the sample.  
           [0020]    The liquid source is preferably a water source, the light source is preferably an infrared source and the light sensor is preferably an infrared detector.  
           [0021]    The apparatus further preferably includes an agitator for agitating the sample. The agitator may be a turntable which moves the sample in an orbital motion, a turntable which moves the sample in a wobbling motion or a stirrer which stirs the sample. Preferably the agitator is a combination of all three, namely a turntable which moves the sample in an orbital motion and in a wobbling motion and a stirrer which stirs the sample.  
           [0022]    The support is preferably a bowl which contains the sample. The bowl preferably includes an island in the center thereof to direct the sample radially outwardly. The bowl preferably concludes a lid thereon. The lid preferably includes a dome offset from the center of the lid. The light source and light sensor are preferably positioned such that the light source signal and light reflected signal pass through the dome normal to a surface of the dome. The light source is preferably an infrared source and the light sensor is preferably an infrared detector. The apparatus preferably includes a cabinet containing the support, the liquid source, the light source and the light sensor. The cabinet preferably includes a door providing access to an interior thereof. A bracket is preferably mounted to an underside of the door, and the light source and light sensor are preferably mounted to this bracket.  
           [0023]    The processor/controller preferably processes the reflected light signal as a function of time and controls addition of liquid to the sample such that liquid is added to the sample only until the reflected light signal reaches a predetermined value indicative of the sample being at the SSD state. The reflected light signal reflected from the dry sample, which can vary from aggregate to aggregate, is measured with the apparatus of the present invention and the value of the reflected light signal reflected from the sample wetter than SSD is approximately a constant 0.08 Volts for all aggregate.  
           [0024]    The apparatus may further preferably include a weight indicating device for weighing the sample in the dry state and in the SSD state to thereby additionally determine the PA of the aggregate.  
           [0025]    The apparatus may further include a heater for removing liquid from the sample, in which case the processor/controller controls removal of liquid from the sample as a function of the reflected light signal by controlling the heater.  
           [0026]    The present invention thus avoids the subjectivity of the slump test, replacing it with a much more scientific empirical test which actually measures the presence or absence of water on the surface of the aggregate. The present invention also avoids the problem of the slump test wherein continual water evaporation, after reaching SSD, produces an artificially low PA, since the moistened aggregate is maintained in a bowl sealed with a lid thereby preventing moisture escape. Further, the bowl with lid sealed thereon eliminates the generation of dust as the initially dry sample is begun to be agitated during initial addition of water to the sample.  
           [0027]    In another aspect, the invention is a method of determining liquid absorption of an aggregate, comprising providing a shaker apparatus, a vacuum source and a container; placing a sample of the aggregate in the container; adding liquid to the container sufficient to reach a calibration mark on the container; weighing the sample and liquid; mounting the container to the shaker apparatus; connecting the vacuum source to the container; agitating the sample and liquid with the shaker apparatus; applying a vacuum to the sample and liquid with the vacuum source; after the agitation and vacuum steps, adding liquid to the container sufficient to again reach the calibration mark on the container; again weighing the sample and liquid; and subtracting the initial weight of the sample and liquid from the final weight of the sample and liquid in order to determine the liquid absorption of the aggregate.  
           [0028]    The method can further comprise the steps of dividing the difference between the initial and final weights of the sample and liquid by the dry weight of the sample and liquid; and multiplying the quotient by a constant and by 100 to determine the percent liquid absorption of the aggregate. The constant is preferably about 0.5.  
           [0029]    adding the dry sample weight to the weight of the container, sample and liquid with the liquid at the calibration mark on the container;  
           [0030]    subtracting from that sum the final weight; and  
           [0031]    dividing that difference into the dry sample weight to determine the apparent specific gravity of the aggregate.  
           [0032]    The agitation and vacuum steps can be performed simultaneously or sequentially. Preferably the agitation step is performed first and the vacuum step is performed second. Preferably a series of agitation steps are alternated with a series of vacuum steps. Preferably the agitation step is performed for about 5 minutes and then the vacuum step is performed for 5 about minutes. Preferably the vacuum step preferably applies a vacuum of about 22 inches of Hg. Preferably the vacuum step applies an initial vacuum of about 22 inches of Hg and a final vacuum of about 28 inches of Hg. Preferably agitation is performed for about 3 minutes, agitation and about 22 inches Hg vacuum is performed for about 3 minutes and agitation and about 28 inches Hg vacuum is performed for about 5 minutes.  
           [0033]    In yet another aspect, apparatus for determining liquid absorption of an aggregate comprising a shaker apparatus for supporting and agitating a container containing a sample of the aggregate and liquid; a vacuum source for applying a vacuum to the sample and liquid; and a processor/controller operably associated with the shaker apparatus and vacuum source which controls operation of the shaker apparatus and vacuum source in response to inputs received from an operator of the apparatus.  
           [0034]    The processor/controller preferably controls the vibration frequency, amplitude and duration of said shaker apparatus. The processor/controller preferably also controls the vacuum pressure and duration of said vacuum source. The apparatus can further comprising a weighing device; the processor/controller operably associated with the weighing device; the processor/controller operable to cause the weighing device to weigh the sample and liquid before and after operation of the shaker apparatus and vacuum source, to compute a percent liquid absorption of the sample from the weights of the weighing device and to display the percent liquid absorption of the sample.  
           [0035]    These and other advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION  
       [0036]    [0036]FIG. 1 is a perspective view of the apparatus of the present invention;  
         [0037]    [0037]FIG. 2 is a view taken along line  2 - 2  of FIG. 1;  
         [0038]    [0038]FIG. 3 is a front view of the apparatus, partially broken away;  
         [0039]    [0039]FIG. 4 is a plot of actual voltage of the infrared detector as a function of time as the sample goes from a dry state to an SSD state;  
         [0040]    [0040]FIG. 5 is an average of the voltage plot of FIG. 4 illustrating the SSD point; and  
         [0041]    [0041]FIG. 6 is a perspective view of an apparatus for determining liquid absorption of an aggregate. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]    Referring first to FIG. 1, there is illustrated apparatus  10  embodying the principles of the present invention for determining liquid absorption of aggregate, for determining the SSD state of an aggregate and for determining the PA of an aggregate.  
         [0043]    The apparatus  10  comprises a cabinet  12  having a base  14 , a pair of opposed side walls  16 ,  18  and a back wall  20 . An openable and closeable door  22  is pivoted to a partial top wall  24  via hinge  26  and forms the remainder of the top and front of the cabinet  12 . Mounted to the underneath side of the door  22  is a bracket  30  to which are mounted an infrared source  32  and an infrared detector  34 , the operation of which will be described below.  
         [0044]    Referring now to FIGS. 2 and 3, the apparatus  10  is shown in more detail. A support in the form of a bowl  40  is provided for containing a sample  42  of aggregate. The bowl  40  includes an island  44  in the center thereof to direct the aggregate  42  radially outwardly during motion of the bowl  40 , which will be described below. A horizontal wall  46  interconnects the front, side and back walls  14 ,  16 ,  18  and  20  and provides structure upon which the bowl  40  is mounted.  
         [0045]    A motor  48  is mounted to the horizontal wall  46  and includes an output drive shaft  50 . Output drive shaft  50  has fixedly secured thereto a plate  52  and an eccentric shaft  54 . The axes of rotation of the shafts  50 ,  54  are angled just off of parallel by approximately 0.75°. The axis of rotation of the shaft  54  is offset from that of shaft  50  a distance d. Preferably, d is approximately 0.078″ on average. A bearing  56  encircles eccentric shaft  54 . The inner race of the bearing  56  is fixedly secured to the eccentric shaft  54 . A counterweight  58  is mounted to the plate  52  to offset or counterbalance the effects of the shaft  54  being offset from the shaft  50  the amount d. The outer race of the bearing  56  is fixedly secured to an inverted flanged cylinder  60 . A Z bracket mounts stop a plate  65 . A ¼ turn thumb nut  63  removably secures the bowl  40  onto the top of the Z bracket. A rubber boot  64  has an upper end sandwiched between the flanged cylinders  60  and plate  61 , and a lower end secured to the horizontal wall  46  via screws  66  or the like. Screws  62  pass through plate Z bracket  61 , plate  65 , boot  64  and screw into cylinder  60 . Boot  64  protects bearing  56 , etc. from contamination and also serves to prevent bowl  40  from rotating about its own axis.  
         [0046]    Due to the offset d, rotation of motor output shaft  50  causes bowl  40  to move in an “orbital” motion having a radius equal to d. The 0.75° deviation from parallel between the axes of shafts  50 ,  54  imparts a “wobbling” motion to the bowl  40  and hence sample of aggregate  42 .  
         [0047]    Referring now to FIGS.  1 - 3 , a water reservoir  80  is mounted to rear wall  20  and includes flexible tubing or a hose  82  connected thereto. Hose  82  preferably has a 0.01 inch diameter nozzle or output end. A pump  84  pumps water from reservoir  80  through hose  82  into bowl  40  at a preferred rate of approximately 8 micro liters per minute. A removable lid  86  seals the sample  42  within the bowl  40 , and includes a small hole  88  through which the tube  82  passes. The lid  86  includes a domed region  90 . The domed region  90  allows signals from the infrared source  32  and to the infrared detector  34  to pass through the lid  86  normal thereto. Wire fingers  92  are mounted within the bowl  40  and extend downwardly into contact with the sample  42  of aggregate and serve to further break apart particles of the sample  42  by stirring during injection of water into bowl  40 . A processor/controller  94  is operably connected to the infrared source  32 , infrared detector  34  and to a display panel  96  on front wall  14  of cabinet  12 . An on/off switch  98  is also mounted on front wall  14  of cabinet  12 .  
         [0048]    Referring now to FIGS. 4 and 5, the processor/controller  94  preferably processes the reflected infrared signal reflected from the moistened aggregate  42  as a function of time, and controls addition of water to the sample  42  via the pump  84  such that liquid is added to the sample  42  only until the reflected light signal reaches a predetermined value indicative of the sample being at the SSD state, which will be described in more detail below. As is illustrated in FIG. 4, the actual or “raw” infrared reflected voltage indicated by infrared detector  34  as a function of time decreases during addition of water to the sample  42  and during mixing or agitation of the sample  42  therewith. The infrared source  32  and infrared detector  34  are mounted in an isosceles triangle configuration, wherein the IR source and detector define two points and the surface to be measured, i.e. the surface of the aggregate sample  42 , defines the third point. Light travels from the infrared source  32  to the aggregate  42 , scatters back off the aggregate  42 , and then travels to the infrared detector  34 . Because water is very optically absorbing at wave lengths above 1.8 micrometers, the signal of the infrared detector  34  will decrease as the voids in the aggregate fill with water. The signal will show a saturating effect when the voids become completely filled with water. At the point where the aggregate  42  becomes wetter than SSD, the slope of the curve shown in FIG. 4 asymptotically approaches zero. The SSD point occurs at a point in time prior thereto, as will be described below in more detail. The processor/controller  94  monitors the infrared reflected signal via an analog to digital converter (not shown). To isolate the reflected infrared signal from any thermal effect noise of the thermopile infrared detector  34 , the infrared source  32  is modulated at approximately one Hz. The electrical circuit (not shown) associated with the IR source  32  and detector  34  preferably includes an electronic high pass filter and a signal rectifier to provide a dc output signal for the processor/controller  94 .  
         [0049]    Referring now specifically to FIG. 5, FIG. 5 illustrates the average of the voltage signal versus time curve of FIG. 4 as averaged by the processor/controller  94 . The voltage signal V 0  at time t 0  is the voltage representative of the IR reflectance of the dry aggregate. The voltage signal V wet  at time t wet  is the voltage representative of the IR reflectance of the aggregate wetter than SSD. It has been empirically determined that the voltage signal V ssd  at time t ssd  is approximately equal to the average of V 0  and V wet . In other words, it has been empirically determined that V ssd  is approximately equal to (V 0 +V wet )/2. It has also been determined empirically that V wet  for most aggregates is approximately a constant 0.08 Volts. Thus, once V 0  has been measured for a particular aggregate, V ssd  can be readily calculated with the above formula and the processor/controller can then be programmed with the calculated V ssd  value. The processor/controller monitors the voltage and controls addition of water to the sample  42  such that water is added only until the voltage reaches the predetermined V ssd  value.  
         [0050]    To automatically determine the PA of an aggregate, the apparatus  10  could advantageously incorporate a weighing scale  100  to record the weight of the sample  42  dry and at the SSD point, in real time.  
         [0051]    To determine the SSD state of an aggregate going from wet to dry, the apparatus would include a heater  102  controlled by the processor/controller  94  to perform the reverse of the above, i.e. to remove liquid from the sample  42  by heating it.  
         [0052]    Cabinet  12  may be fabricated of aluminum sheet. A suitable material from which to fabricate the bowl  40  is polypropylene. The thickness of the polypropylene in the area of the domed region  90  is preferably 0.02 inches or less. A suitable infrared source or emitter  32  is ReflectIR available from Ion Optics of Waltham, Mass. A suitable infrared detector or receiver  34  is DZMHS005 available from Dexter Research of Dexter, Mich. A suitable motor  48  is Type 04 available from Faseo Motors of Ozark, Mo. A suitable pump  84  is 090SP-24-8 available from Bio-Chem Valve, Inc. of Benton, N.J.  
         [0053]    Referring now to FIG. 6 there is illustrated apparatus  200  for determining liquid absorption of a material. The apparatus  200  comprises a shaker apparatus  202  for supporting and agitating a container  204  containing a material specimen  206 . Shaker apparatus  202  can be, for example, a Vortex Maxi Mix III, model number M65820-33, available from the assignee. Container  204  can be, for example, a 500 ml volumetric flask. Container  204  can be loosely or hard mounted to a support  208  to prevent vortexing. A vacuum source  210  is connected to the container  204  via hose  212  and stopper  214 . A processor/controller  216  is operably associated with the shaker apparatus  202  and the vacuum source  210  and controls operation of the shaker  202  and vacuum  210  in response to inputs received from a technician. The processor/controller  216  preferably controls the vibration frequency, amplitude and duration of the shaker  202  and the vacuum pressure and duration of the vacuum  210 . Optionally a weighing device  218  can be included. The processor/controller  216  would also be in operable association with the weighing device  218  such that the processor/controller  216  causes the weighing device  218  to weight the sample  204  and liquid before and after operation of the shaker  202  and vacuum  210 . The processor/controller  216  would then determine the difference in the two weights and from the difference compute the liquid absorption and/or apparent specific gravity which would then be displayed on a display.  
         [0054]    In use of the apparatus  200 , 250 ml of water is poured into the container  204 , a sample of material  206  is placed into the container  204  and a period of time is allowed to pass, for example 5 minutes. Then, additional water is added up to a calibration mark on the container  204 . The container  204 , sample  206  and water are then weighed and the initial weight is recorded. The container  204  and its contents are then subjected to a series of agitation and vacuum steps. After the series of agitation and vacuum steps water is again added up to the calibration mark. The container  204 , sample  206  and water are again weighed and the final weight is recorded. The difference in the initial and final weights is directly related to the liquid absorption of the sample  206 . By dividing the difference by the dry weight of the sample, and by multiplying the quotient by a constant, about 0.5, and by 100, the percent liquid absorption is obtained. The initial and final weights can also be used to calculate apparent specific gravity, and a film coefficient, the latter being a parameter which relates to the V ssd , one of the parameters disclosed in the assignee&#39;s own U.S. Pat. No. 6,486,475. By adding the dry sample weight to the weight of the container, sample and liquid with the liquid at the calibration mark on the container, subtracting from that sum the final weight, and dividing that difference into the dry sample weight, one can determine the apparent specific gravity of the aggregate.  
         [0055]    The agitation and vacuum steps can be performed simultaneously or sequentially. Preferably the agitation step is performed first and the vacuum step is performed second. Several agitation steps can be alternated with several vacuum steps. The length of the agitation and vacuum steps is preferably about 3 to 5 minutes. A vacuum of from about 22 inches of Hg to about 28 inches of Hg is preferred. One particular routine is to perform agitation for about 3 minutes, perform agitation and apply a vacuum of about 22 inches of Hg for about 3 minutes, and perform agitation and apply a vacuum of about 28 inches of Hg for about 5 minutes. Such a routine can be selected as inputs to the processor/controller  216  which then controls the magnitude and duration of the vibration of the shaker  202  and of the pressure of the vacuum  210 .  
         [0056]    The invention thus permits a technician to determine a material&#39;s liquid absorption, percent liquid absorption, apparent specific gravity and film coefficient in about ten to twenty minutes, as apposed to about twelve hours for the current manual hand method.  
         [0057]    Those skilled in the art will readily recognize numerous adaptations and modifications which can be made to the present invention which will result in an improved method and apparatus for determining liquid absorption of aggregate, yet all of which will fall within the spirit and scope of the present invention as defined in the following claims. For example, while the invention has been described in connection with determining the SSD state of an aggregate in going from a dry condition of the aggregate to a wet condition, the invention can also be practiced in the reverse, i.e. going from an overly saturated condition of the aggregate to a SSD condition of the aggregate. However, the SSD state of the aggregate, as determined by infrared reflection, is more readily obtained for the dry to wet process than for the wet to dry process. Additionally, the wet to dry process requires a heating means be incorporated into the apparatus. Accordingly, the invention is to be limited only by the scope of the following claims and their equivalents.