Abstract:
A method of repairing concrete slabs that have become uneven and dangerous is provided that employs lime sludge that is injected under pressure into the space between the lower surface of the damaged concrete slab and the underlying ground to raise that slab back into a level orientation. Once this has been accomplished, any remaining space below the slab is filled in with well dried sand blown in under pressure.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a method of repairing an existing section of concrete slab which has had portions settle into the ground so as to become uneven over time. More specifically, to a method of carefully raising a section of settled cement slab so as not to damage the section and allow for the injection of pressurized mason&#39;s sand into the cavity created between the bottom of the uneven cement slab and the settled ground. 
   Regardless of the care and skill used in the initial construction, concrete slabs tend to become misaligned over time due to different rates of settlement of the earth. Uplift from freeze/thaw cycles or tree root lifting are also common causes of slab misalignment. These problems cause cracks in the cement slab to develop and can also cause step-like structures to occur between sections of the slab. The end result of this condition is the creation of hazards to its users and liability for those who are responsible for their care. Additionally, the uneven cement slabs are extremely difficult to clear of snow and ice during the winter months in the northern areas of the United States, thus creating further hazards and liabilities for their users and owners. 
   In the past, there was a number of ways these problems were solved. One of these was to completely remove the damaged section of cement slab and then re-pour it. The problem with this method is that although it works very well, it is time consuming and very expensive. The re-pour method also results in a checkerboard looking cement slab as the new portions are often a very different color from the older weathered sections. Another method that has been used with the step formation problem is to construct concrete or tar ramps from the lower section of the cement slab to the upper. The problem with this method is that it still leaves uneven slab surfaces that are hazardous and difficult to maintain. 
   Finally, another method that is often used is mud jacking. In this repair method a hole is drilled through the uneven slab and wet mud is pumped under the slab until the slab becomes level. The first problem with this method is that the mud commonly used in this process is not viscous enough to provide an adequate amount of force to the cement slab to lift it enough to effectuate the repair. Another problem with the mud jacking method is that it requires that there be a substantial open area, or settle cavity, between the lower surface of the concrete slab on the underlying ground. Finally, the use of wet mud makes for an ineffectual repair as it tends to settle over time while drying resulting in a cement slab surface that retains the uneven condition that was intended to be repaired. 
   More recently, a number of patents have issued that attempt to deal with this problem in an effective and cost efficient manner. In U.S. Pat. No. 4,962,913, Stewart, Oct. 16, 1990, a method of lifting and repairing such damaged sidewalks is provided. The problem with this device is that by nature of its construction, a heavy frame supported by four wheels, it is large and cumbersome in operation. Further, this device requires the even lifting of a given slab in only small sections at a time, as one portion of the device rests on an un-lifted portion of the sidewalk. In U.S. Pat. No. 4,982,930, Stewart, Jan. 8, 1991, the same inventor attempted to resolve the short comings of his prior art by lightening the frame and removing the wheels. However, the resulting apparatus is still large and cumbersome in its operation. Additionally, these solutions are not capable of raising large sections of cement slabs and are therefore limited in their applications. 
   Therefore, from the foregoing discussion it can be seen that it would be desirable to provide a means of leveling existing cement slabs in an inexpensive manner that is highly portable, easily used and which also results in repaired slabs that are not subject to the settling problems that affect other repair methods. Furthermore, it can also be seen that it would be desirable to provide a method of repairing uneven sections of existing concrete slabs that would be capable of lifting large sections of the slabs in a manner that does not require mechanical heavy lifting apparatuses and that would be highly portable and capable of operating independently from outside power sources. 
   SUMMARY OF THE INVENTION 
   It is the primary objective of the present invention to provide a method of repairing existing concrete slabs that have become uneven and damaged due to settling or other changes in the elevation of the earth upon which they are built. 
   It is an additional objective of the present invention to provide a means of repairing damaged sections of concrete slabs which utilizes lime sludge as a fill material that is not susceptible to the settling propensities that are common in the materials used in the prior art. 
   It is an further objective of the present invention to provide such a method of repairing concrete slabs which is highly portable and capable of operating independently from all external power sources and which is economical and efficient in its operation. 
   It is a still further objective of the present invention to provide such a method of repairing slabs which is capable of operation in conjunction with concrete slabs varying in size from the relatively small section of concrete sidewalks to the huge concrete slabs that are commonly used in such things as freeways and airport runways. 
   These objectives are accomplished by the use of a concrete slab leveling system that employs lime sludge as a fill material which is a mixture of calcium, magnesium, and water that is a common byproduct of water softening processes. Additionally, the chemical makeup of the lime sludge is similar to that of mortar and cement and provides similar structural integrity properties when dried. The use of the lime sludge imparts these cement-like qualities to the fill when dried while retaining the fluid qualities when fully hydrated that allows for its easy pumping through hoses and other components used in these operations. Additionally, the use of the lime sludge improves the lift characteristics of the fill material due to its viscous nature allowing a concrete slab to be easily lifted even when there is little or no settle cavity between the concrete slab and the underlying ground. 
   The delivery of the fill material to the targeted area beneath a damaged concrete slab is accomplished by the use of an apparatus that is built upon a vehicle such as a flatbed truck or trailer which makes it highly transportable enabling the invention to move from site to site quickly and easily. The flatbed platform of the vehicle provides the point of attachment for the material bin which is a relatively large opened topped rectangular box which holds the fill material that is to be pumped under the targeted concrete slab. The material bin has an interior that is constructed with downward diagonally oriented sides that form a V-shape. This manner of construction directs fill material towards the auger channel located at the bottom center of the bin&#39;s interior. 
   The auger channel is an open top box that extends the length of the lower surface of the bin&#39;s interior and which contains the auger itself. The auger is a screw-like device which is rotationally driven by the bidirectional auger motor on the most forward surface of the exterior of the bin. The auger serves to move the fill material contained within the bin towards the front of the auger channel during operations so that it can be moved efficiently into the pump assembly. The pump assembly draws the provided fill material from the bin and delivers it under pressure to the tool hose which in turn is employed to deliver the fill material to the desired location. 
   The pump assembly performs this function by the use of a plurality of hydraulic type cylinders that are tied together through the use of a pump cap attached to the upper ends of the cylinder&#39;s rams. One of these cylinders is hydraulically activated and operated by an independent hydraulic system that is contained within the body of the flatbed transport vehicle. The operation of the pump is accomplished by the expansion of the hydraulic cylinder through the activation of the hydraulic manifold controls which forces its ram upwards thereby pushing the pump rod cap upwards. By virtue of the cap&#39;s tie to the plurality of operational cylinder rams, the operational cylinders are also expanded. 
   The expansion of the operational cylinders draws the fill material from their interiors from the pump manifold which ties the pump assembly to the material bin. The pump manifold is equipped with two one-way valves which control the flow of the fill material within the pump assembly. The first of these valves, the forward one-way valve, lies between the interior of the bin and the pump manifold and functions to allow the flow of fill material into the manifold as the cylinders are expanded. Conversely in this operation the rearward one-way valve lies between the pump manifold and its outlet the manifold pipe and functions to keep fill in the manifold pipe from being drawn back into the pump manifold. 
   Once the expansion of the hydraulic cylinder is complete and the operational cylinders are full, the hydraulic cylinder is then contracted which forces the fill within the operational cylinders back into the pump manifold. This reversal of flow closes the forward one-way valve thereby blocking the flow of the fill back into the bin and opens the rearward one-way valve allowing the fill to be forced into the manifold pipe and to a delivery mechanism to be forced under a settled section of concrete slab. Additionally, the use of the pump assembly in conjunction with the fill material provides enough pressure at the point of delivery to elevate even the largest concrete slab in common use today. 
   These components of the pump apparatus function together to facilitate the repair of a damaged concrete slab in the following manner. First, once the targeted section of cement slab has been identified, dried mason&#39;s sand is blown under the slab under high pressure. This process serves to fill in any existing settle cavities in preparation for the slab raising procedure. With this complete, an operator drills a hole through the slab in a position that is roughly in its center. Once this has been accomplished, the nozzle portion of the injector gun is forced into this hole which forms a seal between the gun nozzle and the concrete slab. The operator then opens and closes the control handles which sends a flow of the lime sludge under pressure through the gun nozzle. The pressurized lime sludge is thus forced between the concrete slab and underlying ground. The continual build up of the lime sludge beneath the concrete slab places upward pressure on the lower surface of the damaged concrete slab. This upwards pressure slowly raises the concrete slab until it reaches a point at which it is level with the remaining neighboring slab. 
   Once the concrete slab has been lifted by the process described above, the nature of the lime sludge leaves some open space in the settle cavity between the lower surface of the concrete slab and the surface of the ground. This is a result of the viscous nature of the fill material as it does not need to fill the entire settle cavity before lifting the slab. This characteristic of the material fill allows the user to pack the remaining open space with dried mason&#39;s sand which, because of its stable nature, further solidifies the repair. The sand fill is accomplished by drilling more holes into the slab and injecting the sand into the openings. Once these processes have been completed, the open holes in the concrete slab are filled in with an appropriate material to complete the repair of the concrete slab. 
   For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the flatbed and pump apparatus used in conjunction with the present invention which illustrates the positioning of the pump on a flatbed truck and the relative positions of its major components in relation to the flatbed. 
       FIG. 2  is a side elevation view of the injector gun component used in conjunction with the present invention illustrating its manner of construction and the orientation of its major components. 
       FIG. 3  is a side elevation cutaway view of the material bin component used in conjunction with the present invention and illustrates the relationship between the material bin, the auger, and the pump assembly which are pivotal to the delivery of the fill material. 
       FIG. 4  is a side elevation cutaway view of the pump assembly component used in conjunction with the present invention illustrating the manner by which lime sludge is drawn from the bin into the pump assembly during its operation. 
       FIG. 5  is a is a side elevation cutaway view of the pump assembly component used in conjunction with the present invention illustrating the manner by which lime sludge is forced through the manifold and into the manifold pipe during the operation of the pump. 
       FIG. 6  is a side elevation cross sectional view of a section of typically damaged concrete slab in which one portion has settled into the underlying earth. 
       FIG. 7  is a side elevation cross sectional view of a section of typically damaged concrete slab illustrating a settled portion which has been prepared for repair by the addition of a plurality of the gun nozzle holes through its body. 
       FIG. 8  is side elevation cross sectional view of a section of concrete slab which is being raised by the introduction of lime sludge into the settle cavity by the use of the injector gun component. 
       FIG. 9  is side elevation cross sectional view of a section of concrete slab which has been raised by the introduction of lime sludge and illustrating the method used to inject mason&#39;s sand into the remaining portions of the settle cavity to complete the repair. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, and more specifically to  FIG. 1 , the present invention is employed to repair concrete slabs by making use of a plurality of devices to introduce lime sludge  17  in the desired location. The first of these is a slab lift pump apparatus  10  which is a self contained portable device that is employed to pump at pressure the lime sludge  17  through the connected tool hose  66 . The portable aspect of the slab lift pump apparatus  10  is accomplished by placing its components on a flatbed  14  vehicle that is equipped with a set of wheels  18  such as a truck or trailer. Additionally, all of the components of the slab lift pump apparatus  10  that are necessary for its operation are contained on the surface of the flatbed  14  which allows it to be quickly moved from site to site and to operate completely independently. 
   The slab lift pump apparatus  10  is made up of a large open topped fill container  16  within which the lime sludge  17  that is used to elevate the targeted concrete slabs is stored during operations. The fill container  16  has a bin interior  46  into which the lime sludge  17  is deposited. The rearward surface of the fill container  16  also serves as the mounting point for the pump assembly  12  which is the component of the slab lift pump apparatus  10  employed to move the lime sludge  17  from the bin interior  46  to the tool hose  66  and thus, to the targeted repair area. 
   The flatbed  14  also provides a place of securement for additional ancillary components of the slab lift pump apparatus  10  that are necessary for its operation and which allow it to be operated independently. The first of these is the generator unit  20  which is an electric generator that can be employed to power electrical tools such as hand held drills that may be necessary for the lift operation. Additionally, the power unit  22 , which is an internal combustion engine that primarily powers the hydraulic pump  30  to which it is attached, is also positioned along the fill container  16  and which draws hydraulic fluid from the fluid reservoir  28  and supplies the necessary hydraulic pressure to the remaining components of the slab lift pump apparatus  10  through the primary hydraulic pressure and return lines,  24  and  26 . 
   The hydraulic fluid necessary to operate the system is stored and supplied by the fluid reservoir  28  which is connected to the hydraulic pump  30 . The hydraulic motor  30  forces the hydraulic fluid under pressure through the primary hydraulic pressure line  24  which in turn is connected to the hydraulic control manifold  38  mounted on the exterior of the fill container  16 . The hydraulic control manifold  38  is used to control the flow of hydraulic pressure to the other operational components of the slab lift pump apparatus  10 . 
   In furtherance of this purpose, the hydraulic control manifold  38  is equipped with the hydraulic cylinder control handle  48  and the auger drive control handle  52  which are employed to control the flow of hydraulic pressure to their respective components by opening and closing valves contained within its casing. Therefore, the activation of the auger drive control handle  52  supplies hydraulic power to the auger drive motor  50  which in turn drives the auger  72  in a rotational manner (both of which will be described in greater detail below). The hydraulic cylinder control handle  48  in similar manner supplies hydraulic pressure to the primary hydraulic system to operate the hydraulic motor  30 . 
   The construction of the injector gun  11  is further detailed in  FIG. 2  which illustrates its relative components in relation to the present invention. The injection gun  11  is made up of a vertically oriented gun nozzle  58  which is the component which engages the concrete slab and delivers the lime sludge  17 . The gun nozzle  58  is connected at its upper end to the lower surface of the nozzle manifold  60  which is a T-like apparatus having connected to its forward end a pressure outlet valve  56  which can be used to relieve unneeded pressure contained within the injector gun  11 . The rearward side of the nozzle manifold  60  is connected to the gun pipe  70  which forms the majority of the horizontal portion of the injector gun  11 . The gun pipe  70  also contains the flow valve  62  which can be used to control the flow of lime sludge  17  to the gun nozzle  58  by the operation of the connected valve handle  64 . Finally, the gun pipe  70  is connected at its most rearward end to the hose connector  68  which is in turn connected to the lead edge of the tool hose  66  which supplies the lime sludge  17 . 
   The construction of the fill container  16  and its connection to the associated components of the slab lift pump apparatus  10  are further illustrated in  FIG. 3 . As previously stated, the fill container  16  is the component of the invention that is used to hold the lime sludge  17  during operations and is generally described as an open topped rectangular box having bin forward and rearward walls,  78  and  80 , and the two bin diagonal sides  76  defining the bin interior  46 . The bin diagonal sides  76  are both angled inwards from their upper edges at the top of the bin interior  46  to their terminus at the upper most edge of the vertical sides of the auger channel  74  located at the bottom center of the bin interior  46 . The auger channel  74  is a relatively square in cross-section component which houses the auger  72  and forms the bottom of the bin interior  46 . The primary purpose of the auger channel  74  is to ensure that the lime sludge  17  contained within the fill container  16  is always in contact with the auger  72  so that it can be moved to the pump assembly  12 . The auger  72  itself is a screw-like device which, by the rotational force applied through the auger drive motor  50 , is employed to move the fill to the pump assembly  12  and to keep the fill mixed. Additionally, the bin diagonal sides  76  and the auger channel  74  are also lined with a heavy gauge plastic bin liner  82  that helps keep the lime sludge  17  from sticking to the bin interior  46  and ensuring that it will move down into the auger channel  74 . 
   At the forward end of the fill container  16 , the auger channel  74  is connected to the pump manifold  36  of the pump assembly  12  through the manifold inlet  90 . This supplies lime sludge  17  to the interior of the pump manifold  36  through the forward one-way valve  84  which is employed to control the flow of lime sludge  17  and which will be discussed in greater detail below. At this point, the hydraulic action of the pump assembly  12  and its components operate to pump the fill to the desired location to effectuate the desired repair. 
   The manner in which the pump assembly  12  operates is further illustrated in  FIGS. 4 and 5 . The expansion of the primary hydraulic cylinder  32  through the hydraulic fluid forcing the internal primary cylinder piston  112  upwards, in turn forces the pump rod cap  40  in a mirroring upward motion defined by the cylinder movement arrow  110 . This upward motion of the pump rod cap  40  also pulls up the operational cylinder rams  44  which in turn pulls up the connected operational cylinder pistons  114  contained within the operation cylinders  34 . The upward motion of the operational cylinder pistons  114  creates a partial vacuum within the operational cylinders  34  which serves to act on the fill within the system imparting material flow  108  which acts to load up the operation cylinder interiors  118  through the cylinder ports  88 . The material flow  108  also places upward pressure on the forward one-way valve  84  allowing the lime sludge  17  to move into the pump manifold  36 . Additionally, the material flow  108  in this configuration places downward pressure on the rearward one-way valve  86  which effectively closes off the manifold outlet  92  which keeps any material rearward of it from being drawn back into the interior of the pump manifold. 
   Conversely, when the primary hydraulic cylinder  32  is contracted, it pulls the pump rod cap  40  in a downward motion indicated by the cylinder movement arrow  110  which in turn pushes the operational cylinder pistons  114  downward. This downward movement forces the lime sludge  17  contained within the operational cylinder interiors  118  back into the pump manifold  36  as illustrated again by the material flow  108  arrows. The reversal of the material flow  108  has the opposite effect on the forward and rearward one-way valves,  84  and  86 . That is to say, the material flow  108  in this configuration places downward pressure on the forward one-way valve  84  sealing off the manifold inlet  90  thereby keeping the lime sludge  17  from being forced back into the fill container  16 . Conversely, the material flow  108  opens the rearward one-way valve  86  allowing the lime sludge  17  to exit the pump manifold  36  and enter the manifold pipe  106  and repaired nozzle hole  116  to be delivered in the desired location. 
   The manner in which this equipment (or other similar equipment) is employed to deliver the lime sludge  17  to the desired location in the repair process is illustrated in  FIGS. 6 ,  7 ,  8 , and  9 .  FIG. 6  illustrates the typical situation in which a damaged slab  96  exists which has in whole or in part settled into the underlying ground  102  below the normal position of a level concrete slab  94 . This situation normally results in a centrally located slab crack  100  and slab gaps  98  located on damaged slab&#39;s  96  outer edges. This situation creates a potentially dangerous variance in the heights of neighboring concrete slabs  93  which must be repaired. 
   The repair process of the present invention is commenced by initially filling any existing settle cavities  105  between a damaged slab  96  and the underlying ground  102 . This operation can be accomplished by inserting a sand fill nozzle  119  in an existing gap between the damaged slab  96  and the surrounding ground  102  or by drilling a sand nozzle hole  124  through the damaged slab  96  in an appropriate location and inserting the sand fill nozzle  119  through the sand nozzle hole  124 , thus, gaining access to any existing settle cavity  105 . The fact the mason&#39;s sand is blown into the settle cavity at very high pressures ensures that it will be dispersed to fill in any such settle cavities even if they are located at a relatively great distance from the sand nozzle hole  124 . 
   Once the existing settle cavities have been filled by the above described manner, the operator proceeds with the repair process by drilling an appropriate number of a gun nozzle holes  104  thought the damaged slab  96  as illustrated in  FIG. 7 . The number of these gun nozzle holes  104  that are required to perform the desired repairs is determined by the severity of the existing damage and the size damage slab  96  that these repairs are being performed on. The drilling of the gun nozzle holes  104  provides the user with access to the slab/ground interface  107  between the damaged slab  96  and the ground  102 . Upon completion of this step, the gun nozzle  58  of the injector gun  11  is secured within the gun nozzle hole  104  and the operator engages the injector gun  11  by providing pressurized lime sludge  17  to the delivery components to force it between the lower surface of the damaged slab  96  and the ground  102 . 
   The effect of this injection of the lime sludge  17  is to lift the damaged slab  96  off of the underlying ground  102  which serves to open up additional settle cavities  105 . The settle cavities  105  are partially filled by the lime sludge  17  which also places an upward force on the lower surface of the damaged slab  96 . This upward force is a function of the nature of the lime sludge  17  as at some point in the pumping process, the tendency of the lime sludge  17  to spread in an outward manner is less than its tendency to spread upward. It is this tendency for the lime sludge  17  to spread upward that is exploited to provide the required lifting of the damaged slab  96 . 
   The lifting process described above is continued until the upper surface of the damaged slab  96  is raised to a point where it is level with the surrounding concrete slab  93  as illustrated in  FIG. 8 . Once this has been accomplished, the injector gun  11  is removed from the gun nozzle hole  104  which is then filled in to produce a repaired nozzle hole  116  which is formulated to match the surrounding surface of the damaged slab  96 . This process leaves some existing open space in the settle cavity  105  which is addressed in the final step of the process. 
   After the damaged slab  96  has been restored to its proper orientation, additional sand nozzle holes  124  are drilled through the body of the damaged slab  96  to allow for the insertion of a sand fill nozzle  119  which is employed to fill the remaining settle cavity  105 . The mason&#39;s sand  122  is delivered under air pressure by a device in common use in the industry through the sand fill nozzle  119  which is controlled by the use of the sand nozzle handle  120 . The mason&#39;s sand  122  is a perfect tool for this application as it is non-compatible and will therefore resist any further settling of the concrete slab  93 . Thus, the present invention provides a method of repairing damaged concrete slabs  93  in a manner that results in a long lasting repair that can be effectuated at lower cost and greater efficiency than was previously available. 
   Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.