Patent Publication Number: US-2011048541-A1

Title: Vacuum Saturation Technique for Porous Aggregate Material

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
     This application claims priority benefits from U.S. Provisional Patent Application Ser. No. 61/239,064 filed Sep. 2, 2009, entitled “Vacuum Saturation Technique For Porous Aggregate Material”. The &#39;064 provisional application is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the manufacture of concrete. In particular, the present invention relates to the saturation of porous aggregate material employed in the manufacture of concrete. 
     BACKGROUND OF THE INVENTION 
     In the manufacture of concrete, the use of lightweight aggregate material is preferred because the resulting concrete will be lighter than conventional concrete (110-120 lbs/ft 3  versus 150 lbs/ft 3 ), thereby reducing trucking and transportation costs for building panels and other products formed from lighter weight concrete. 
     Expanded slag material available in the Midwestern U.S. is a source of porous aggregate material employable in the manufacture of concrete. The problem with porous aggregate material is its tendency to suck the water out of the cement paste, thereby preventing adequate hydration for curing. In that case, the final strength of the resulting concrete products is unacceptable. Other lightweight, porous aggregate materials, such as expanded shale, are also available and have similar bulk density characteristics. 
     In a concrete pump application, the high pressure during pumping can force water into the aggregate material. This results in the concrete drying before it is out of the pipeline, thereby increasing the probability that the dried concrete will clog the pipeline. 
     In the present technique, the porous aggregate material is pre-saturated so water fills the pores. Using pressure on a large scale to pre-saturate the porous aggregate material is not effective, however. Neither is soaking the porous aggregate material in a bin or spraying the surface with water. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present technology provide methods and systems for saturating porous aggregate material. In an embodiment, a method of saturating porous aggregate material includes: (a) filling an interior of a vacuum vessel with porous aggregate material; (b) applying a vacuum to said vessel interior until a desired vacuum level is reached; (c) drawing water into said vessel under vacuum until substantially all of said aggregate material is covered; and (d) pumping unabsorbed water from said vacuum vessel. 
     In an embodiment, the vacuum level is at least about 20 inHg. 
     In an embodiment, the vacuum vessel is filled to at least about 75% of a volume of the vacuum vessel. 
     In an embodiment, the water is provided to the vacuum vessel and pumped out of the vacuum vessel using a water conduit. 
     In an embodiment, the water conduit includes a slotted pipe extending from a lower portion of the vacuum vessel to an upper portion of the vacuum vessel. 
     In an embodiment, the unabsorbed water is pumped from the vacuum vessel after the aggregate material is saturated with water so as to have a bulk density of about 53-57 lbs/cu-ft. 
     In an embodiment, the unabsorbed water is pumped from the vacuum vessel after the aggregate material is covered by the water for at least about 60 seconds. 
     In an embodiment, the method further includes filtering the unabsorbed water to remove particulate matter. 
     In an embodiment, the method further includes delivering the porous aggregate material to the vacuum vessel using a conveyor. 
     In an embodiment, the method further includes moving porous aggregate material emptied from the vacuum vessel using a conveyor. 
     In an embodiment, a system for saturating porous aggregate materials includes: (a) a vacuum vessel having an aggregate material inlet at an upper portion thereof, said inlet having a valve associated therewith for permitting said vessel interior to be filled when said vessel inlet valve is in an open position, and an aggregate material outlet at a lower portion thereof, said outlet having a valve associated therewith for permitting said vessel interior to be emptied when said vessel outlet valve is in an open position; (b) a vacuum line fluidly connected to a top portion of said vessel, said vacuum line having a valve associated therewith for applying vacuum to said vessel interior when said vacuum line valve is in an open position; (c) a water delivery conduit fluidly connected at one end to a water source and at its other end to said vessel interior, said water delivery conduit having a valve associated therewith for permitting water flow to said vessel interior when said water delivery conduit valve is in an open position; (d) a water removal conduit fluidly connected at one end to said vessel interior and at its other end to a pump, said water removal conduit having a valve associated therewith for effecting removal of water from said vessel interior upon actuation of said pump, whereby opening said vacuum line valve when porous aggregate material is present in said vessel interior imparts negative pressure to said aggregate material such that upon closing said vacuum line valve and opening said water delivery conduit valve, water is drawn into said vessel interior to saturate said porous aggregate material, and actuating said pump thereafter removes unabsorbed water from said vessel. 
     In an embodiment, the water delivery conduit and said water removal conduit are connected at a bottom portion of said vessel. 
     In an embodiment, the water delivery conduit and said water removal conduit are one water conduit, said water delivery conduit valve and said water removal conduit valve are one water conduit valve, and said pump is interposed in said one water conduit. 
     In an embodiment, the one water conduit is connected at a bottom portion of said vessel. 
     In an embodiment, the pump has a strainer disposed upstream thereof such that particulate matter present in said water removal conduit is impeded from entering said pump. 
     In an embodiment, the water delivery conduit and said water removal conduit are in fluid communication with a slotted pipe extending from the lower portion of the vacuum vessel to the upper portion of the vacuum vessel, the slotted pipe configured to deliver and remove water from the vacuum vessel via the slots. 
     In an embodiment, the system further includes a conveyor configured to deliver porous aggregate material to the vacuum vessel. 
     In an embodiment, the system further includes a conveyor configured to move porous aggregate material that has been emptied from the vacuum vessel. 
     In an embodiment, the vacuum line is configured to impart negative pressure to said vacuum vessel until a vacuum level of at least about 20 inHg is achieved. 
     In an embodiment, the system further includes (e) a second vacuum vessel having an aggregate material inlet at an upper portion thereof, said second vessel inlet having a valve associated therewith for permitting said second vessel interior to be filled when said second vessel inlet valve is in an open position, and an aggregate material outlet at a lower portion thereof, said second vessel outlet having a valve associated therewith for permitting said second vessel interior to be emptied when said second vessel outlet valve is in an open position; (f) a second vacuum line fluidly connected to a top portion of said second vessel, said second vacuum line having a valve associated therewith for applying vacuum to said second vessel interior when said second vacuum line valve is in an open position; (c) a second water delivery conduit fluidly connected at one end to the water source and at its other end to said second vessel interior, said second water delivery conduit having a valve associated therewith for permitting water flow to said second vessel interior when said second water delivery conduit valve is in an open position; (d) a second water removal conduit fluidly connected at one end to said second vessel interior and at its other end to said pump, said second water removal conduit having a valve associated therewith for effecting removal of water from said second vessel interior upon actuation of said pump, whereby opening said second vacuum line valve when porous aggregate material is present in said second vessel interior imparts negative pressure to said aggregate material such that upon closing said second vacuum line valve and opening said second water delivery conduit valve, water is drawn into said second vessel interior to saturate said porous aggregate material, and actuating said pump thereafter removes unabsorbed water from said second vessel. 
     In an embodiment, the first vacuum vessel and the second vacuum vessel are configured such that they can be operated simultaneously. 
     In an embodiment, the first vacuum vessel and the second vacuum vessel are configured such that they can be operated one at a time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1  is a schematic diagram of a system for saturating porous aggregate material used in accordance with an embodiment of the present technology. 
         FIGS. 2-6  are schematic diagrams of steps involved in a technique for saturating porous aggregate material used in accordance with an embodiment of the present technology. 
         FIG. 7  is a schematic diagram of a system for saturating porous aggregate material used in accordance with an embodiment of the present technology. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) 
     The present invention relates to the manufacture of concrete. In particular, the present invention relates to the saturation of porous aggregate material employed in the manufacture of concrete. 
     It has been found that expanded slag aggregate used in the manufacture of concrete should preferably have an initial bulk density of about 53-57 lbs/cu-ft so that water added in batching for cement paste hydration is not overly absorbed by the aggregate. However, expanded slag material available in the Midwestern U.S. has a dry bulk density of about 47 lbs/cu-ft, and, in practice, expanded slag material delivered for use in the manufacture of concrete will have a bulk density between 47-50 lbs/cu-ft. Due to the porosity of the aggregate, if the aggregate is completely saturated, the aggregate will have a bulk density of about 57 lbs/cu-ft. This represents over 21% increase in weight due to moisture content. 
     It has been found that placing aggregate in a vacuum vessel at a pressure of about 20-27 inches of mercury (in Hg) and then filling the vessel with water, can satisfactorily saturate aggregate for use in concrete manufacturing. For example, in certain embodiments, aggregate and water can be retained in a vacuum vessel for 5 minutes at a vacuum pressure of about 20 inHg in order to saturate the aggregate to a bulk density of about 53-57 lbs/cu-ft. For example, in certain embodiments, aggregate and water can be retained in a vacuum vessel for 1 minute at a vacuum pressure of about 27 inHg in order to saturate the aggregate to a bulk density of about 53-57 lbs/cu-ft. For example, in certain embodiments, pressure and time can be varied linearly (for example, such that a pressure of 23.5 inHg corresponds to a saturation time of 3 minutes) in order to saturate the aggregate to a bulk density of about 53-57 lbs/cu-ft. 
     Embodiments of the present technology further describe systems and methods for saturation of porous aggregate material employed in the manufacture of concrete. In the figures, like elements have like identifiers. 
       FIG. 1  is a schematic diagram of a system  100  for saturating porous aggregate material used in accordance with an embodiment of the present technology. System  100  includes a vacuum vessel  102 , a vacuum  104 , a water supply  106 , a water delivery/removal conduit  108 , a pump  109 , a strainer  110 , and a plurality of valves  111 ,  112 ,  113 ,  114 ,  115 ,  116 ,  117 ,  118 ,  119  and  120 . 
     Vacuum vessel  102  includes an interior  121 , an inlet  122 , and an outlet  124 . In certain embodiments, the vessel interior  121  can have a volume that is about 2000 cubic feet, and can be filled with up to about 50 tons of aggregate. Vessel inlet  122  has a valve  118  associated therewith and is configured to allow aggregate material to be provided to the vessel interior  121  when valve  118  is in an open position. Aggregate material can be supplied, for example, from a hopper  126  and a conveyor  128 , where conveyor  128  delivers aggregate to hopper  126 , and the aggregate passes thorough hopper  126  prior to passing through vessel inlet  122 . Vessel outlet  124  has a valve  119  associated therewith and is configured to allow aggregate material to be emptied from the vessel interior  121  when valve  119  is in an open position. Aggregate material can be emptied through a clamshell gate  130  into a weigh conveyor  132 , for example. In certain embodiments, valves  118  and  119  can be knife gate valves. 
     Vessel interior  121  is operably connected to vacuum  104  such that vacuum  104  can be applied to vessel interior  121  until a desired vacuum level within vessel interior  121  is achieved. Valve  117  is a shut-off valve disposed between vacuum  104  and vessel interior  121 . Valve  117  can allow vacuum  104  to be applied to vessel interior  121  when in an open position and stop vacuum  104  from being applied to vessel interior  121  when in a closed position. In certain embodiments, vacuum  104  can be applied to vessel interior  121  until a vacuum level of about 20-27 inHg is achieved. 
     Vessel interior  121  is in fluid communication with water supply  106  via water delivery/removal conduit  108 . Pump  109  and strainer  110  are also in fluid communication with water supply  106  via water delivery/removal conduit  108 . Water delivery/removal conduit  108  has parallel paths and a plurality of valves ( 111 ,  112 ,  113 ,  114 ,  115 ,  117  and  120 ) that are configured such that water being delivered to vessel interior  121  does not pass through pump  109 , and water being removed from vessel interior  121  does pass through strainer  110  and pump  109 . Valves  111 ,  112 ,  113 ,  114 ,  115  and  120  are shut off valves that can allow water to pass through when in an open position and stop water from passing through when in a closed position. Valve  117  is a check valve that can allow water to pass through in one direction only. In system  100 , check valve  117  only allows water to pass through toward water supply  106  and away from pump  109 . That is, check valve  117  only allows water to pass through in the direction X. Operation of the valves when using system  100  will be described in more detail in connection with  FIGS. 2-6 . While a single water delivery/removal conduit  108  with parallel paths is depicted in system  100 , in certain embodiments, a water delivery conduit can be completely separate from a water removal conduit. In certain embodiments, water supply  106  can be elevated relative to vacuum vessel such that gravity and the pull of vacuum  104  can cause water to flow from water supply  106  to vessel interior  121  when the water valves are open. In certain embodiments, water supply  106  can be a pressurized water supply such that gravity, the pull of vacuum  104  and the pressure from the water supply cause water to flow from water supply  106  to vessel interior  121  when the water valves are open. 
     Water delivery/removal conduit  108  extends into vessel interior  121  and, inside vessel interior  121 , comprises a pipe  134  with a plurality of slots  136  through which water is delivered from pipe  134  to vessel interior  121  and through which water is removed from vessel interior  121  by pipe  134 . In certain embodiments, pipe  134  can be a 5 inch diameter, schedule  80  pipe. In certain embodiments, each slot  136  can be ⅛ of an inch wide and 12 inches long, extending lengthwise about pipe  134 . 
       FIGS. 2-6  are schematic diagrams of steps involved in a technique for saturating porous aggregate material used in accordance with an embodiment of the present technology. 
       FIG. 2  depicts system  100  while aggregate  202  is being delivered to vessel interior  121 . At this stage, valves  111 ,  112 ,  113 ,  114 ,  115  and  120  are closed such that water is not being delivered to or removed from vessel interior  121 . Valve  117  is closed such that vacuum  104  is not being applied to vessel interior  121 . Valve  119  is closed such that aggregate  202  will not pass through vessel outlet  124  and will be retained in vessel interior  121 . Valve  118  is open such that aggregate  202  can be delivered to vessel interior  121  through vessel inlet  122 . Conveyor  128  is aligned with hopper  126  and run such that aggregate  202  can be delivered to vessel interior  121 . Conveyor  128  can continue to deliver aggregate  202  until a desired fill level is achieved. In certain embodiments, the aggregate fill level can be no greater than about 75% of the total capacity of vessel interior  121 . 
       FIG. 3  depicts system  100  after aggregate  202  has been delivered to vessel interior  121 , and while vacuum  104  is being applied to vessel interior  121 . At this stage, valves  111 ,  112 ,  113 ,  114 ,  115  and  120  are closed such that water is not being delivered to or removed from vessel interior  121 . Conveyor  128  is no longer delivering aggregate  202 . Valve  118  is closed such that aggregate cannot be delivered to vessel interior  121  through vessel inlet  122 . Valve  119  remains closed such that aggregate will not pass through vessel outlet  124  and will be retained in vessel interior  121 . Valve  117  is opened to allow vacuum  104  to be applied to vessel interior  121 . Vacuum  104  is turned on such that air is removed from vessel interior  121  (in the direction Y) until a desired vacuum level inside vessel interior  121  is achieved. Air inside the vessel interior  121  at a desired vacuum level is indicated by  302 . In certain embodiments, the vacuum level can be about 20-27 inches of mercury (inHg). 
       FIG. 4  depicts system  100  after vacuum  104  has been applied to vessel interior  121 , and while water is being delivered to vessel interior  121  from water supply  106 . At this stage, valve  117  is closed such that vacuum  104  is not being further applied to vessel interior  121 . Valve  118  remains closed such that aggregate cannot be delivered to vessel interior  121  through vessel inlet  122 . Valve  119  remains closed such that aggregate will not pass through vessel outlet  124  and will be retained in vessel interior  121 . Valves  111 ,  112 ,  113  and  120  are open and valves  114  and  115  are closed such that water  401  is being delivered to vessel interior  121  from water supply  106  via water conduit  108  without passing through pump  109 . Water  401  flows in direction M and is delivered to vessel interior  121  via slots  136  in pipe  134 . Water  401  can be delivered to vessel interior  121  until a desired fill level is achieved. The water fill level should be sufficient to cover the aggregate  202  in vessel interior  121 , as depicted, for example, by water fill level  402 . Aggregate  202  can be saturated by water  401  provided in vessel interior  121  at the desired vacuum level. In certain embodiments, the aggregate and water can be held in this state for about 1-5 minutes depending on the vacuum level (for example, 20-27 inHg) to promote full saturation of the aggregate. 
       FIG. 5  depicts system  100  after aggregate  202  has been saturated, and while water is being removed from vessel interior  121 . At this stage, valve  117  remains closed such that vacuum  104  is not being further applied to vessel interior  121 . Valve  119  remains closed such that aggregate will not pass through vessel outlet  124  and will be retained in vessel interior  121 . Valve  118  is open such that ambient air can flow into vessel interior  121  through vessel inlet  122 . Valves  112 ,  113  are closed and valves  111 ,  114 ,  115  and  120  are open such that water  401  is being removed from vessel interior  121  by pump  109  via water conduit  108 . Pump  109  is turned on such that water is drawn in direction N from vessel interior  121  via slots  136  in pipe  134 . Water  401  continues to be drawn until excess water  401  is removed from vessel interior  121 . Although slots  136  in pipe  134  act as a filter that does not allow large particles to enter water conduit  108 , some smaller particulate matter may still enter water conduit  108 . Thus, strainer  110  is disposed upstream from pump  109  such that strainer  110  can filter particulate matter from water  401  prior to water  401  passing through pump  109 . In certain embodiments, slots  136  in pipe  134  can be configured to filter particulate matter larger than ⅛ of an inch in diameter from water  401 . In certain embodiments, strainer  110  can be configured to filter particulate matter larger than 1/32 of an inch in diameter from water  401 . 
     The amount of water  401  that returns to water supply  106  is less than the amount originally delivered because aggregate  202  has been saturated and retains some water. Thus, after remaining water  401  has been returned to water supply  106 , water supply  106  can be topped off from a separate water supply in order to replenish the water that remained in the aggregate  202 . 
       FIG. 6  depicts system  100  after water has been removed from vessel interior  121 , and while aggregate is being removed from vessel interior  121 . At this stage, valve  117  remains closed such that vacuum  104  is not being further applied to vessel interior  121 . Valve  118  remains open such that ambient air can flow into vessel interior  121  through vessel inlet  122 . Valves  111 ,  112 ,  113 ,  114 ,  115  and  120  are closed such that water is not being delivered to or removed from vessel interior  121 . Valve  119  is open such that aggregate  202  can pass through vessel outlet  124  and will be emptied from vessel interior  121 . Aggregate  202  can be emptied onto weigh conveyor  132  via clamshell gate  130 , which can be used to regulate the flow of aggregate onto weigh conveyor  132 . In certain embodiments, clamshell gate  130  can be configured to allow 6000 lbs/min of aggregate to flow onto weigh conveyor  132 . 
       FIG. 7  is a schematic diagram of a system  700  for saturating porous aggregate material used in accordance with an embodiment of the present technology. The system  700  includes two water supplies  106  in fluid communication with four vacuum vessels  102  via water conduit  108 . In certain embodiments, water conduit  108  can comprise pipe of different diameters. For example, in the embodiment shown, water conduit  108  includes 5 inch diameter pipe  702 , 3 inch diameter pipe  704  and 2.5 inch diameter pipe  706 . Vacuum  104  is operably connected to the four vacuum vessels  102 , for example, using 1.5 inch diameter pipe  708 . In the manner shown, or in other similar fashion, any number of water supplies can be paired with any number of vacuum vessels, and a vacuum can be paired with any number of vacuum vessels. The piping and valves can allow the vacuum vessels to be utilized one at time or simultaneously as desired for concrete production purposes. 
     In certain embodiments, operating the systems and/or applying the methods described herein can provide for improved manufacture of lightweight concrete with acceptable strength and reduced probability that dried concrete will clog the pipeline during manufacture. 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.