Abstract:
A concrete test cylinder mold formed of expandable polystyrene and which is used to form geometrically uniform concrete test cylinders that accurately reflect the structural properties of the concrete mix used to form the test cylinders despite fluctuations in temperature to which the test cylinder may be exposed during formation within the mold. The mold is constructed and configured such that compression testing of the concrete test cylinder may be conducted while the cylinder is still in the mold. A specially designed heat shield may be used in unison with the concrete test mold to form, at least in part, a system by which heat further may be retained within the system during formation of the concrete test cylinder.

Description:
BACKGROUND TO THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to concrete testing methods and systems and, more particularly, provides a method and system for producing reproducible concrete test cylinders. 
     2. Background of the Invention 
     In the construction of highways, buildings, and other structures utilizing concrete, it is necessary from time to time to test the strength of a sample of the poured concrete to ensure that it has sufficient structural strength required for a particular installation. The most common method of testing concrete has been to take a sample of fresh concrete from a mix at a construction site. 
     Specifically, fresh concrete is poured into a concrete test cylinder mold to form a cylindrical concrete test cylinder. Upon completion of the cylinder fabrication process, the poured concrete extends above the top of the concrete test cylinder mold. At this point, the concrete that extends above the top of the concrete test cylinder is manually struck off with a tamping rod. The concrete remaining in the test cylinder mold is then left to set. The following day the concrete test cylinder molds may be picked up and delivered to a laboratory where the concrete test cylinders are cured under laboratory conditions. 
     After curing, the concrete is removed from the cylinder and is tested for compressive strength. The compressive strength of the concrete test cylinders is a representation of the strength of the concrete placed in the structure. 
     The problem with the prior art concrete test cylinders that are produced in conventional concrete test cylinder molds is that the concrete test cylinders produced are subjected to fluctuating temperatures during their formation and cure and/or to temperature ranges that adversely affect the overall structural integrity of the concrete test cylinder. Additionally, the strength of conventionally formed concrete test cylinders is compromised due to the change in the specimen&#39;s water content, as some traditionally used molds may absorb water from the concrete test mix. 
     Another problem encountered by prior art molds used in the formation of concrete test cylinders is that such molds do not offer regularity and/or standardization in height, diameter, and smoothness. Accordingly, the prior art does not ensure that every sample is of the same height, diameter, and level. As a result, some concrete test cylinders are non-planar or have an oval diameter at the top of the mold. Accordingly, the accuracy of the test of the concrete test cylinder is reduced since the overall compressive strength of the concrete test cylinder can be erratic due to distribution caused by handling or transportation of the concrete test cylinder. Therefore, there exists a need in the art to improve the uniformity of a concrete test cylinder through the use of an efficient and cost effective product. 
     Nothing in the prior art provides the benefits attendant with the present invention. Therefore, it is an object of the present invention to provide an improvement which overcomes the inadequacies of the prior art devices and which is a significant contribution to the advancement of the art. 
     SUMMARY OF THE INVENTION 
     The above mentioned disadvantages and draw-backs of the prior art are alleviated or greatly overcome by a concrete test cylinder mold which is especially designed and adapted to produce reliable concrete test cylinders. The concrete test cylinder molds of the present disclosure are made from expandable polystyrene, and are formed of sufficient thickness on the top, side and bottom to hold the concrete cylinder test mix to a specific size while the mix cures. The expandable polystyrene is a natural insulator and can maintain the curing temperature far better than presently known molds. Additionally, as the expandable polystyrene has a minimal compressive strength, as compared to the compressive strength of the concrete, there is no need to remove the concrete test cylinder from the mold during compressive strength testing. The density of the expandable polystyrene is also selected to prevent the mold from absorbing water from the concrete test sample. The mold is configured to prevent tipping and to prevent injury to the concrete test cylinder during fabrication, handling, transport, and testing of the cylinder. In an exemplary embodiment, a release agent may be used to coat the mold to prevent the concrete from bonding to the mold during cure time; alternatively or additionally, a thin plastic sheet may be disposed on the inside surface of the mold to prevent such bonding. 
     These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter, in which there is illustrated and described preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of these and other objects of the present invention, reference will be made to the detailed description of the present invention which is to be read in association with the accompanying drawings, wherein: 
         FIGS. 1 and 2  are schematics depicting an exemplary test cylinder mold; 
         FIG. 3  is a schematic depicting a longitudinal section of the test cylinder mold depicted in  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic depicting an elevational view of a portion of the test cylinder mold depicted in  FIGS. 1-3 ; 
         FIG. 5  is a schematic depicting an elevational view of a bottom side of the test cylinder mold depicted in  FIGS. 1-3 ; 
         FIG. 6  is a schematic depicting a longitudinal section of the test cylinder mold depicted in  FIGS. 1-3 ; 
         FIG. 7  is a schematic depicting an elevational view of a top side of an exemplary lid; 
         FIG. 8  is a schematic depicting an elevational view of a bottom side of the lid depicted in  FIG. 4 ; 
         FIGS. 9 and 10  are schematics depicting an exemplary heat shield; 
         FIG. 11  is a schematic depicting an elevational top view of a portion of the exemplary heat shield depicted in  FIGS. 9 and 10 ; 
         FIG. 12  is a schematic depicting an elevational bottom view of a portion of the heat shield depicted in  FIGS. 9 and 10 ; 
         FIG. 13  is a schematic depicting a longitudinal section of the heat shield depicted in  FIGS. 11 and 12 ; and 
         FIGS. 14-16  are schematics depicting an exemplary cap for the heat shield depicted in  FIGS. 11-13 ; 
         FIG. 17  is a schematic depicting a longitudinal section of an exemplary system; and 
         FIG. 18  is a schematic depicting an exploded view of the system depicted in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed herein is a concrete test cylinder mold that is specially configured to produce a concrete test cylinder that accurately and reliably reflects the properties of a concrete mix used at a work site for a particular construction. Further disclosed herein is a concrete test system comprising a concrete test cylinder mold and a concrete test cylinder, wherein the concrete test system may be subjected to compression testing useful in determining the compressive strength of the concrete test cylinder. Further disclosed herein is a concrete test assembly useful in forming the concrete test cylinder, wherein the assembly comprises the concrete test cylinder mold, the concrete test mix, and a heat shield. The heat shield is specially designed to further insulate the concrete test mix during cure of the concrete test mix. 
     The inventive concepts shall be more particularly described with reference to the drawings, wherein it is to be understood that the invention is not to be limited thereby, but shall include all modifications and variations thereto as would be evident to a person of ordinary skill in the art upon reading the present disclosure. 
     Referring to  FIGS. 1-6 , an exemplary concrete test cylinder mold  10  comprises a main body  12 . Main body  12  has a generally frusto-conical shaped side wall  14  having an exterior side  15  oppositely situated to an interior side  17 , and an anterior terminal end  21  oppositely situated to a posterior terminal end  25 . Side wall  14  tapers inwardly as it extends from posterior terminal end  25  to anterior terminal end  21 , and, therefore, posterior terminal end  25  has an outer diameter greater than an outer diameter of anterior terminal end  21 . Main body  12  further comprises a generally cylindrical-shaped chamber  27  surrounded by interior side  17  and which extends the length of interior side  17 . 
     Main body  12  further comprises a plurality of grooves  30 . Each of the grooves of plurality  30  is formed through an outer edge  22  of anterior terminal end  25  and extends longitudinally on exterior side  15  of side wall  14  short of extending through posterior terminal end  25 . In a preferred embodiment, the grooves of plurality  30  are radially and regularly spaced around exterior side  15  of main body  12 , and are formed parallel with one another. Plurality of grooves  30  assists in the removal of the concrete test cylinder from mold  10 , such as may be desired after the concrete test cylinder has been tested for compressive strength. 
     Concrete test cylinder mold  10  further comprises a base  32 . Base  32  comprises a substantially circular-shaped body having a top side  51  oppositely situated to a bottom side  53  and joined thereto via a side wall  55  that is contiguously formed with and substantially perpendicular to top and bottom sides  51  and  53 . Side wall  55  comprises an outer diameter greater than an outer diameter of side wall  14 . Top side  51  is contiguously and coaxially formed with posterior terminal end  25  of side wall  14 , such that side wall  14  is recessed relative to side wall  55 . 
     Main body  12  and base  32  are formed of expanded polystyrene. In an exemplary embodiment, the expandable polystyrene has a density of about 1.5 pounds per cubic foot. Furthermore, in an exemplary embodiment, the expandable polystyrene used to form mold  10  comprises beads having a range in diameter of about 0.063 inch to about 0.188 inch, wherein about 0.063 inch to about 0.125 inch is more preferred, and about 0.063 inch to about 0.100 inch is especially preferred. The expandable polystyrene is preferably formed of a modified grade of expandable polystyrene, and, hence, has fire retardant properties. 
     Referring to  FIGS. 7 and 8 , concrete test cylinder mold  10  may further comprise a lid  100  which may be secured over anterior terminal end  21  of main body  12 . Lid  100  comprises a generally circular shaped body  102  having a top face  104  oppositely situated to a bottom face  106 . Lid  100  further comprises an annular shaped side wall  108 . Side wall  108  comprises an interior side  110  contiguously formed with an outer perimeter of bottom face  106 , and an exterior side  112  contiguously formed with an outer perimeter of top face  104 . An annular-shaped bottom wall  114  is contiguously formed with and positioned transversely to side wall  108 . Bottom wall  114  comprises a sloped portion  115  contiguously formed with a substantially planar portion  117 , wherein sloped portion  115  is also contiguously formed with interior side  110  and slopes upwardly from interior side  110  towards substantially planar portion  117 . Substantially planar portion  117  is contiguously formed with exterior side  112  and is parallel to top and bottom faces  104  and  106 . A space  116  is formed between and extends from bottom face  106  and bottom wall  114 . 
     Referring to  FIG. 3 , lid  100  is configured and dimensioned such that when received by concrete test cylinder mold  10 , side wall  108  overhangs exterior side  15  of side wall  14  of mold  10 , interior side  110  of side wall  108  physically abuts exterior side  15  of side wall  14 , and bottom face  106  physically abuts anterior terminal end  125 . Bottom face  106  and top side  51  of base  32  are preferably in parallel alignment with one another to thereby ensure that the top and bottom sides of the concrete test cylinder formed within mold  10  are parallel with each other, thereby assisting in the creation of a uniformly shaped concrete test cylinder. 
     To form the concrete test cylinder, a concrete mix is poured into chamber  27  of mold  10 . The concrete mix may be evenly distributed within chamber  27  via a rod member as is conventionally known in the art. Lid  100  may be positioned on main body  12  of mold  10  as described above, and the concrete mix may be allowed to cure to form the concrete test cylinder. 
     In an exemplary embodiment, prior to placement of the concrete mix into mold  10 , at least one of main body  12 , base  32 , and lid  100 , and more preferably at least main body  12  of mold  10 , is coated with a release agent. The release agent serves to lubricate the expanded polystyrene. Additionally or alternatively, a thin plastic sheet may be placed on the inside surface of at least one of main body  12 , base  32 , and lid  100  of mold. Either or body of the release agent and the thin plastic sheet serves to prevent the concrete from sticking to mold  10  during the concrete&#39;s curing time within mold  10 . 
     The mold described herein protects the concrete mix inside the mold from temperature swings and from damage during handling. The density of the expandable polystyrene used to form the mold is high enough to prevent the expandable polystyrene from drawing water away from the concrete mix. Standard compressive tests can be performed on the mold and the concrete test cylinder formed therein using the same procedures as are done with traditionally used plastic or metal containers. The ability of the heat of hydration of the concrete while curing in the mold formed of expandable polystyrene allows the temperature of the concrete mix to cure at a more uniform temperature for a longer period of time as compared to the temperature of concrete cured in conventional molds, particularly when the molds are exposed to temperatures below 32 degrees Fahrenheit, as the expandable polystyrene maintains the heat of hydration within the mold during curing. 
     An outer protective heat shield formed of expandable polystyrene can provide an additional method to maintain the concrete cylinder at a temperature higher than current cylinder designs under cold weather conditions. Accordingly, further disclosed herein is a heat shield that is specially designed to be used in combination with the mold disclosed herein to further enhance the conditions under which the concrete test cylinder is formed, and to, thereby, protect the integrity of the concrete test cylinder during its formation. 
     Referring to  FIGS. 9-13 , an exemplary heat shield  200  comprises a generally cylindrical shaped body  202  having a side wall  204 . Side wall  204  has an anterior terminal end  203  oppositely situated to a posterior terminal end  205 . Side wall  204  further has an exterior side  206  oppositely situated to an interior side  208 , wherein interior side  208  surrounds a chamber  210 . Body  202  further comprises an open-ended top side  212  contiguously formed with anterior terminal end  203  and having an opening  209  coaxial with chamber  210 . Top side  212  has an outer edge  214  oppositely situated to an inner edge  216 , wherein inner edge  216  is contiguously formed with interior side  208  and outer edge  214  is contiguously formed with exterior side  206 . Posterior terminal end  205  turns substantially perpendicularly inwardly towards chamber  210  to form a bottom side  220  of bottom  202 . Bottom side  220  turns substantially perpendicularly away from top side  212  to form a footing  224 . 
     Footing  224  has a lower substantially ring-shaped member  225 . Member  205  comprises a top side  226  oppositely situated to a bottom side  228 , and a substantially annular-shaped side wall  207  contiguously formed with top and bottom sides  226  and  228  and positioned transversely thereto. Top side  226  is coplanar with bottom side  220  of body  202 . Side wall  207  comprises an exterior side  234  oppositely situated to an interior side  232 . Exterior side  234  is directed to exterior side  206  and is recessed relative thereto, thereby forming an outer flange  236  between exterior side  206  and exterior side  234 . Member  205  further comprises an opening  230  formed through top and bottom sides  226  and  228  and immediately surrounded by interior side  232 , wherein opening  230  is coaxial with chamber  210  and has a diameter less than the diameter of chamber  210 . 
     Heat shield  200  further comprises an interior annular member  238  which is contiguously and continuously formed along a perimeter of interior side  208  of side wall  204 , and which is contiguously and continuously formed with top side  226  of footing  224 . Interior annular member  238  comprises an interior side wall  248  contiguously formed with top side  226  of footing  224  and which extends substantially perpendicularly therefrom towards top side  212  of heat shield  200 . Interior annular member  238  further comprises a top side  244  which is perpendicularly formed with interior side wall  248  and that is contiguously formed with interior side  208  of side wall  204 . 
     Referring to  FIGS. 14-16 , heat shield  200  may further comprise a cap  260  which may be secured to body  202  of heat shield  200 . Cap  260  comprises a generally circular shaped upper member  262  having a top side  264  oppositely situated to a bottom side  266  and joined thereto by a side wall  268 . Centrally disposed and contiguously formed on bottom side  266  is a lower member  270  having a generally annular shaped configuration. Lower member  270  has an annular shaped exterior side wall  272  oppositely situated to an annular shaped interior side wall  274 . 
     Cap  260  further comprises a generally annular shaped lip  278  contiguously formed with lower member  270  and positioned opposite to upper member  262 . Lip  278  comprises a face  280  that is directed opposite to upper member  262  and transversely to side walls  272  and  274  of lower member  270 , and which is recessed relative to exterior and interior side walls  272  and  274 . Cap  260  further comprises a space  276  immediately surrounded by interior side wall  274  and that extends from bottom side  266  of upper member  262  to face  280  of lip  278 . 
     Upper member  262  comprises an outer diameter greater than an outer diameter of lower member  270 . Accordingly, exterior side wall  272  of lower member  270  is recessed relative to side wall  268  of upper member  262 . 
     Cap  260  further comprises a plurality of channels  284 . Each channel of plurality  284  extends from top side  264  of upper member  262  to face  280  of lip  278 , and through lower member  270 . Plurality of channels  284  allows air to enter an air space between exterior side  15  of mold  10  and interior side  208  of heat shield  200 . This embodiment is particularly useful where air activated heat pads are used as an additional source for heat as will be described below in further detail. 
     In an exemplary embodiment, heat shield  200 , which includes body  202 , footing  224 , interior annular member  238 , and cap  260 , comprises expandable polystyrene, wherein an exemplary expandable polystyrene has a density of about 1.5 pounds per cubic foot, and has the same properties as was described above with reference to mold  10 . 
     Referring to  FIGS. 17 and 18 , an exemplary system  300  comprises concrete test cylinder mold  10  and heat shield  200 . Heat shield  200  receives mold  10  through chamber  210 . When properly disposed within body  202  of heat shield  200 , bottom side  53  of base  52  of mold  10  is disposed on top side  226  of footing  224  such that side wall  55  of base  52  physically abuts interior side wall  248  of interior annular member  238 . An air space  302  is created between interior side wall  208  of heat shield  200  and exterior side  15  of mold  10 . Cap  260  is positioned atop body  202  such that bottom side  266  of cap  260  physically abuts top side  212  of body  202  and anterior terminal end  21  of mold  10 , and such that lower member  270  of cap  260  extends within air space  302  such that exterior side wall  272  physically abuts interior side  208  of body  202  and interior side wall  274  physically abuts exterior side  15  of mold  10 . Plurality of channels  284  are in fluid communication with air space  302 . 
     In another exemplary embodiment, system  300  may further comprise one or more heating pads that may be disposed within air space  302  to input thermal energy into system  300  to maintain proper curing temperature within the system as the concrete poured within mold  10  cures. The heating pads may be activated by, e.g., at least one of electrical, mechanical means, and chemical means. Exemplary chemically-activated heating pads may comprise at least one of, e.g., iron powder, activated carbon, remiculite, a salt, and the like. When the one or more chemically-activated heating pads are exposed to air, which enters system  300  via holes  284 , a chemical reaction occurs which produces heat. Alternatively or additionally, the one or more chemically-activated heating pads may have one or more pouches that start the heating process when the materials within the one or more pouches are placed into air space  302 . 
     The concrete test cylinder mold of the present disclosure has several advantages over currently known molds. For example, the expandable polystyrene used to form the mold comprises a density which has been optimized to prevent the mold from absorbing water in the concrete test mix. 
     Additionally, use of expandable polystyrene in the formation of the mold provides an insulating effect, thereby insulating the concrete test mix from dramatic fluctuations in temperature, thereby maintaining the integrity of the concrete test mix during its formation into the concrete test cylinder. Additionally, ASTM standards require that the concrete test cylinder formed within a mold be allowed to cure for up to 48 hours at an exterior temperature range of between about 60 degrees Fahrenheit to about 80 degrees Fahrenheit. Therefore, as expandable polystyrene has strong insulating properties, the molds disclosed herein may be used to cure the concrete test cylinders at any time of the calendar year as they readily can meet the ASTM&#39;s temperature range. 
     In addition to the benefits derived from the use of expandable polystyrene, the mold of the present disclosure has certain advantages based upon its physical design. For example, the mold of the present disclosure comprises a base that is configured to rest firmly on the ground when in use and to resist tipping over when the concrete test mix is poured into the mold. Additionally, the mold is constructed to survive rough handling during consolidation of the poured concrete mix into the mold, e.g., when the concrete mix is subjected to blows from a rod used to mix and consolidate the concrete test mix in the mold, and during the removal, transport, and delivery of the mold and concrete mix to the testing facility, and to protect the concrete test cylinder from damage. Nonetheless, in an exemplary embodiment, the mold may include a support member disposed within the chamber of the mold and positioned on the top side of the base. The support member is designed to protect the mold from forces sustained by the mold when the tamping rod is used with excessive force. In an exemplary embodiment, the support member comprises a generally disc-shaped configuration and is formed of a plastic material. 
     The mold is further designed to facilitate the placement and visibility of a label thereon, wherein the label bears information relevant to the testing and/or identification of the concrete test cylinder. Additionally, the lid and the base of the mold are configured to assure that the surfaces are parallel to one another once the cover is placed on the cylinder thereby ensuring that the concrete test cylinder has a uniform configuration. Additionally, the lid is designed to fit firmly on the mold to prevent accidental dislodgement. 
     As the compressive strength of the mold formed out of expandable polystyrene is minimal and insignificant compared to the compressive strength of the concrete test cylinder (i.e., the compressive strength of the concrete test cylinder is at a minimum of about 281 times stronger than the compressive strength of the mold), when the concrete test cylinder is ready for testing, the complete system, e.g., the mold and the concrete test cylinder, may be placed in a conventionally known and used compression testing machine and the compressive strength may be tested by conventional means. For example, an exemplary method for testing the compressive strength of the concrete test cylinder includes providing a compression testing machine having rings located at the top and bottom of the machine, wherein, during compression, the rings applies a uniform load to the concrete test cylinder. The compression testing machine may be hydraulic and may gradually add weight to the top of the concrete test cylinder and the gauge measures the weight that the concrete test cylinder is bearing. The gauge then measures the weight at which the concrete test cylinder fails, which is the weight at which the concrete test cylinder cracks and breaks. Different compositions of concrete made for different applications have different weight requirements, which may range from about 1,000 pounds per square foot to about 10,000 pounds per square foot. 
     The foregoing description of the preferred embodiment of the invention is to be considered as illustrative and not as limiting. Various other changes and modifications will occur to those skilled in the art for performing substantially the same function, in substantially the same way, to achieve substantially the same result without departing from the true scope of the invention as defined in the appended claims.