MXPA05013129A - A method and apparatus of curing concrete structures - Google Patents

Abstract

A method of controlling the cure of concrete structures using intralaminar heat generated by applying electrical energy to electrically conductive members disposed within the structures. These conductive members include carbon fibers. The method further incorporates the electrically conductive, members as internal reinforcement in the cured, finished structure reducing or obviating the need for reinforcing steel. The electrically conductive, members are provided in various forms including but not limited to, pliable forms impregnated with a polymer resin matrix capable of being rigidified and completely rigidified forms. The invention may be used in conjunction with heat responsive agents to activate curing. A preferred embodiment of the method according to the invention is a controlled (expedited or heat activated) cure of a concrete structure. Concrete structures containing the electrical heating capability taught herein are also included within the invention.

Description

A METHOD AND APPARATUS FOR CURING CONCRETE STRUCTURES CROSS REFERENCE WITH RELATED REQUESTS This application claims the benefit and priority of the Application Provisional of E. U. No. 60 / 475,757 entitled "A Method for Curing Concrete Structures" filed June 4, 2003. BACKGROUND OF THE INVENTION FIELD OF USE The invention pertains to a novel method for curing concrete mixtures using electrically conductive components placed within Concrete, such as wires or conductive fibers, in a circuit path and using electrical current to create resistivity or impedance heating to control concrete curing. This invention pertains to hydraulic cements such as Portland cement, pozzolan ("Roman cement") and calcium aluminate, as well as resinous cements such as heat curing, moisture and catalytic cements, refractory clays, kaolin, low alumina clays and gypsum . Resinous cement materials can be covered in hydraulic cement or plaster coverings. The method taught by this invention can selectively raise the temperature of the concrete during setting and hardening to achieve an optimum force gain of the material or accelerate the curing (percent hydration) of the concrete structures using intra-laminar heat generated by the application of electrical energy to electrically conductive members arranged within the structures. The method can also be used in conjunction with concrete containing polymers, wherein the polymer is a catalyst that retards curing until it is induced by a specific temperature that is reached. This avoids the initiation of self-accelerated curing in a large mass concrete dump, such as in large foundations, plinths, retaining walls, etc. The method also incorporates the electrically conductive members as internal reinforcement in the cured structure, finished by reducing or obviating the need for reinforcing steel. The heat-conducting and electrically conductive members are provided in various ways including, but not limited to, collapsible forms impregnated with a polymer resin matrix capable of becoming rigid during curing and in completely rigid forms installed prior to pouring the mixture of cement. The electrically conductive members can also be fixed to reinforcing steel before pouring concrete. One application of the invention method is the expeditious curing of concrete for use in preformed fabricated structures and in the inclined construction ("inclined wall"). The invention also pertains to novel concrete products containing electrically conductive fibers, which can be heated by resistivity, such as foundations, plinths, floors, pillars, retaining walls and slab structures, slanted wall structures, and concrete structures. manufactured pre-formed. The electrically conductive fibers can be used in post-curing to heat the structure or for radiant heating of the space. This capacity could be used to defrost paved surfaces with concrete such as roads, roads, bridges and tracks. BACKGROUND OF THE INVENTION Concrete consists of a mixture of cement, sand and an aggregate of small stones. When water is added to a dry concrete mix, the cement paste formed must completely cover all the sand and particles of the aggregate, and fill the empty spaces between the aggregate particles. The cement paste hardens, due to the hydration reactions, and sticks inert sand and aggregate together. Cement materials such as Portland cement are cheap, of excellent durability, resistant to fire and other physical properties such as resistance to compression and rigidity. These materials have been widely used as a material for buildings and constructions. Nevertheless, the materials / is made of cement have a low tensile strength and impact resistance compared to the compressive strength. Concrete materials also have low heat transfer or heat dispersion capabilities. The material also has little energy absorption. Therefore, cement materials are considered as brittle or brittle. Energy absorption, impact resistance and tensile strength are improved by the introduction of reinforcing steel; typically steel rods made from mild steel and commonly referred to as "rebar". The mild steel contains 0.08 to 0.15% carbon with a tensile strength in the range of 300 to 900 MN / m2. As a general background, Portland Powder cement is made by burning a mixture of limestone with schistose clay or clay in a rotary kiln. The maximum temperature in the cement kiln is approximately 950 ° C, and at this temperature the limestone and clay are partially fused together as a hard slag. The cement slag is ground until pulverized and mixed with a small amount of gypsum (calcium sulfate) to produce dry cement powder. The function of plaster is to control the setting characteristics of cement. When the cement powder is mixed with water, a series of complex chemical reactions ("curing") occurs, which form hydrated silicates and calcium aluminates. (Curing is sometimes referred to as treatment or protection of concrete during the hardening period, however, it is actually used as the hydration process). It is this curing process that causes the wet cement to set and harden like a rigid material. The conditions under which this curing occurs can impact the resulting properties of the cement structure. Some of the hydration reactions take place very slowly and, although the cement will set up properly fast, the large hardness and hardness will not develop for several days, or weeks, depending on the cement composition, moisture content and temperature. The final properties of a concrete will depend on a number of factors, including the relative proportions of water, cement, polymer, sand and aggregate in the material, the average particle size of the aggregate, the type of aggregate stone used and the texture surface of the aggregate. (Uncured concrete is sometimes referred to as "green concrete"). The speed at which this curing occurs (hydration reaction) depends on the temperature. At a minimum ambient temperature of 23 ° C, a waiting period of between 5 and 10 days (120 to 240 hours) should be observed to allow the concrete to reach at least 75% of the design resistance (usually a resistance to the compression of 176 kg / cm2). This process becomes considerably slow at temperatures below 23 ° C resulting in cost increases and programming delays. The moisture content of the cement during curing is important. If there is insufficient water (moisture), the complete hydration of the cement particles will not occur. For complete hydration and the development of maximum strength, a water / cement ratio of approximately 0.4 / 1 is necessary. If the water / cement ratio is at a large excess of this value, the strength of the hardened cement will be reduced. Recently published studies have reported the effects of temperature on the final compressive strength of the cured concrete. If the temperature is either too low or too high, less than the optimum resistance to compression is achieved. For example, in a document published in 2004 and titled "Effect of Temperature on Hydration of Cement Materials", Antón K. Schindler of the University of Auburn, reports that the compressive strength for a mortar mixture cured at 50 ° C can be 17% lower than the compressive strength achieved by the same mixture of mortar cured at room temperature (20 ° C). This document adopts the work of Kjellsen and Detwiler, 1993. The published documents also declare that although increasing the temperature of the concrete during curing accelerates the reaction regime, the hydration reaction finally takes place until the substantial completion regardless of the temperature during the cured. Compression strengths of pure concrete can be up to 65 MN / m2, compared to a compressive strength of approximately 100 WIN / m2 for hardened cement. Other published sources assert that concrete for pavement typically has a compressive strength of between 21 1 kg / cm2 (20.7 MN / m2) and 352 kg / cm2 (34.5 MN / m2). High strength concrete is also defined as having a compressive strength of at t 422 kg / cm2 (41.4 MN / m2) and a concrete having a compressive strength of 1407 has been used in construction applications. kg / cm2 (137.9 MN / m2). The strength of the concrete to the stress, however, is only about one tenth of the value of the compressive strength.

When the concrete is subjected to tension (defined as the internal force in a material in equilibrium with an externally applied load), the fault probably begins at the interface between the aggregate and the cement. Aggregate particles with rough surfaces give concrete a greater strength than with aggregate with smooth surfaces. The tensile strength (maximum extension load sustained by the concrete before destruction) is low (up to 5 MN / m2) and, to overcome this disadvantage, the concrete conclusions are reinforced very often with steel, typically mild steel in the form of rods ("rebar"). In simple reinforced concrete, a network of steel rods or bars is assembled and the concrete is allowed to set around this frame or barbed wire. The steel reinforcement is placed on the portion of the concrete member that will be subjected to stresses. For example, in a life simply supported, the steel falls along the lower portion of the beam. There is a purely mechanical bond between the concrete and the steel, and the reinforcing bars are often twisted, or have surface projections (these can be formed by rolling the bars by pattern rollers) in order to increase the adhesion between the steel and the steel. the concrete. Another form of reinforced concrete is known as pre-stressed concrete. The concrete is placed in a state of compression by means of highly tensioned steel wires. When a pre-stressed concrete beam is in service, the initial compression stresses must be overcome before tension stresses can develop within the material. The concrete can be pre-tensioned by pre-tensioning, or by post-tensioning. In the initial method the steel wires are placed in tension before being surrounded by concrete. The tension that acts externally on the steel is removed when the concrete has set. In post-tensioning, the concrete is allowed to set and harden around a tube, or tubes. Then steel wires are put through the tubes and these wires are stretched and anchored in the concrete. The reinforcement of concrete with carbon or other fibers has been studied at least since 1994. U.S. Patent No. 5,308,696 teaches the dispersion of short carbon fibers (from 1.0 to 6.0 mm) in an uncured concrete mixture. The concentration of the fibers in the mixture can be 20% by volume. U.S. Patent No. 5,685,902 teaches the use of dispersed carbon fibers within a concrete mixture that is cured for 4 weeks (approximately 650 hours) at 20 ° C. U.S. Patent No. 6,612,085 teaches the use of composite materials fibrous formed in the traditional rebar shape. The patent claims the use of glass and carbon fibers within the "composite rebar". The present invention generally relates to a method for accelerating the curing of concrete structures while achieving the final resistance to optimal compression. One embodiment of the invention pertains particularly to the curing of large concrete wall panels used in tilt or tilt construction practices. One of the advantages of the tilting process is shortened construction times; frequently requiring only 4 to 6 weeks for completion. There are certain disadvantages, however, in the limitations in geometry due to the inherent properties of steel-reinforced concrete. In the tilting or tilting construction, panels with relatively thin walls (7.62 to 20.32 cm) are emptied or cast horizontally at ground level and raised to the vertical position by tilting the panel at one end by lifting the opposite end. The structure is then raised to a final position to form a structural wall or wall element. Typically, this procedure will be performed on the building site with the shapes and molding surfaces built on top of the floor slab, which has been cast first in a prepared sub-grade. With the molding shapes in place, the steel reinforcement members are placed within the panel area and the concrete is poured or emptied into the area defined by the shapes. Before the wall elements can be erected, sufficient time must be allowed for the concrete to have sufficient strength to withstand the stresses of the lift. Another method of construction to produce large concrete structures involves the casting or molding of structures in a central location. Once a satisfactory level of resistance is reached, the structures are removed from their molds and transported to the site of erection. This process lends itself to a somewhat more controlled environment, but does not provide ideal conditions for curing. Large, irregularly shaped concrete structures that comprise concrete must still observe the basic hydration reaction programs and, typically, are more economical due to transportation costs. The construction of concrete structures during extreme cold may still become impossible because the water, necessary for curing, can be frozen at low ambient temperatures. In order to accelerate the curing of concrete structures, it has become customary to incorporate additives into the concrete mix to prevent or retard freezing and alternatively provide a heating medium so that the concrete will heal more rapidly and thus facilitate a increase in productivity. Other methods simply use blankets or thermally insulated covers to contain some of the heat naturally generated by the hydration reaction process. The heating means have historically been the medium for the introduction of steam or hot water, pressurized in an enclosure that surrounds the curing forms containing the cast or cast concrete, the use of tubes or conduits carrying a heat transfer medium. from a central boiler unit to the surfaces of the structure or its mold or surrounding form, and still molds and electrically heated forms. See, for example, paragraphs 64 to 85 of the application for EU 2003/0168164 by Blackmore et al., Published on September 1, 2003. All these methods, while addressing the problems with novel and in some way effective means, are laborious and do not provide an economic, timely cure mechanism for concrete structures. A heat transfer must still take place from the external heat source through a transport apparatus and finally through the cross-sectional area of the concrete structure in order to accelerate the curing. This process suffers from an exorbitant loss of heat to the atmosphere. There is an apparent need for a concrete heating method that is energy efficient and economical to implement; that ultimately reduces cycle times, labor costs and construction finishing. There is also a need for concrete structures that can be heated internally and in a controlled manner. The main objective of the present invention is to demonstrate an efficient means to controllably introduce heat to concrete structures during curing. Another objective is to accelerate the time required to cure the concrete. Another object is to provide a heating means that can also provide the internal reinforcement of the finished structure. Another object of the invention is to form an improved concrete structure. BRIEF DESCRIPTION OF THE INVENTION The present invention relates generally to a method for accelerating the curing of concrete structures and, more particularly, to the curing of large wall or concrete wall panels used in tilting or tilting construction practices. The method refers to in situ heating during the curing of concrete structures. By strategically placing electrically conductive components that can be heated by resistivity in a conductor circuit path through the thickness of a concrete structure and that can be connected to an external power source, it is possible to exploit the electrical resistivity of these components and use them as heating members. By having the heating components positioned internally within the concrete, the energy requirement can be significantly reduced. The internal placement of the heating members also offers a synergistic result because these members remain as reinforcement in the finished structure The invention also pertains to the control of the concrete curing regime beginning with an initial curing regime at an elevated temperature, and then removing the heat of the resistivity in a controlled manner to maintain a desired curing regime, consistent with maximizing the compressive strength of the final concrete.In addition, the invention can be used in conjunction with known additives for concrete that retard the auto -acceleration of the hydration reaction (curing) in a large mass of cast concrete until a required high activation energy is reached.Such catalytic additives are used in conjunction with mixtures of concrete and polymer.The polymer blends can be used in castings or heavy castings of dough, such as plinths, floors, pillars, m ureas and retaining slabs, where it is desired that the heat of reaction does not drive the curing to a regime detrimental to the strength of the concrete. An electrical component subject of the invention is a rod, wire or fiber containing carbon or graphite (collectively "carbon"), such as carbon fiber fabric in a braid, cloth or ribbon. The carbon fibers are electrically conductive and can be heated without loss of material properties, have a low coefficient of thermal expansion and have a high resistance. Carbon fibers having a filament diameter of 7.5 μm (1 0"e) typically have a tensile strength of 1750 MN / m2, in contrast to the tensile strength of mild steel of between 300 and 900 MN / When the used heating members are made of carbon fibers, the resulting reinforcing properties may be equal to or greater than those of the steel reinforcement In the construction of a wall or wall element, such as in the tilting construction, the carbon fibers are presented in the form of a three-dimensional profile impregnated with a polymer resin matrix compatible with the alkaline environment of the concrete and capable of becoming rigid with the addition of the heat produced in the described curing operation. of the members allows quick and easy distribution within the forming mold.The heating members are arranged in a continuous sequence or are placed individually idually throughout the structure. In an embodiment of the invention, the outer conductive contact members are removably attached to the internal surfaces of the forming mold at selected locations before the heating members are placed and the concrete is emptied. These contact members serve as connection points for the malleable members as they are arranged in the structure to ensure correct placement and to communicate the electrical power from an external source of power supply to the heating members. Other forms of connection may be used, depending on the geometry of the structure, including continuous bus bars and a roller system placed outside the shape of walls or walls that accumulate the malleable heating members and provide tension to ensure that the stratum heating remains in place during concrete casting. The heating members discussed can also be provided in a rigid manner. In this scenario, fos members can be manipulated in the same way as traditional steel reinforcement materials. The opposite ends of the rigid members are allowed to protrude through the shape walls for similar communication with the external source of electrical power or are connected to the contact members in a similar described configuration. The heating members are strategically placed to provide a consistent heat profile through the thickness of the structure and have a substantial surface area that offers adequate contact with the surrounding concrete where the thermal energy produced is conducted directly to the surrounding concrete. By introducing heat to a concrete structure using the aforementioned process, the curing cycles can be reduced up to as much as 66%. The design of the heating members is flexible because the carbon fiber content, the polymer content and the profile geometry can be calculated and modified to provide a specific surface area, meet the cost and electrical requirements and supply the resistance and rigidity necessary to the structure. For example, by introducing heat to the central portion of a panel or a concrete wall structure using the invention described above, thermal energy is efficiently transferred to the concrete without any loss to the atmosphere resulting in faster cycle times. curing and reduced energy requirements that translate into increased productivity and cost savings. A synergistic benefit of the invention is the ability to minimize or obviate the need for reinforcing steel by employing the structural properties of the heating members which again alleviate installation costs and offer a degree of flexibility in design. These and other novel aspects and advantages of the present invention will be apparent from the following description of the embodiments with reference to the accompanying drawings. Other benefits of the invention will become apparent also to those skilled in the art and such advantages and benefits are included within the scope of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate the preferred embodiments of the invention. These drawings, together with the general description of the invention given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. Figures 1A and 1B illustrate the reported results of compression resistance information at various temperatures at real ages and equivalent ages. Figure 2 illustrates the reported results of the compressive stress of mortar cured at different temperatures. Figure 2B illustrates a heating program taught by an embodiment of the invention. Figure 2C is a table of the Heating Properties of Carbon Fibers. Figure 2D illustrates the time for temperature of a 1K carbon fiber "wire" trailer. Figures 3A, 3B and 3C illustrate the reported results for the degree of hydration for concrete mixtures cured at different temperatures. Figure 4A illustrates the existing rebar placement practices within a cement block.

Figure 4 B illustrates the typical or simple application to form a prestressed concrete block. Figure 5 is an isometric view of a typical sloping wall or wall forming an arrangement representing the members forming the perimeter and the traditional steel reinforcement members in place. Figure 6 is an isometric view of an arrangement forming an inclined wall representing the use of the heating members described in the invention and a connection method, for communicating electrical energy from a power supply to the heating members. Figure 7 is an enlarged cross-sectional view of a forming wall and an electrical connection removably attached. Figure 8 is a cross-sectional view of a heating element formed in a three-dimensional profile. Figure 9 is a plan view of an arrangement of a typical heating member representing the heating members in a continuous circuit. Figure 9A illustrates a cross-sectional view along the axis AA illustrated in Figure 9. Figure 10A illustrates a side perspective for a sloped concrete wall structure using fibers as taught by the invention. Figure 10B illustrates a side perspective of another embodiment of the invention using a different orientation of the fibers. Figure 1 1 illustrates a perspective view of one embodiment of the invention wherein the fibers are oriented substantially in a region near the outer edge. Figure 1 1 B illustrates a cross-sectional view along the axis AA illustrated in Figure 1 1 A. Figures 1 1 C and 1 1 D illustrate another embodiment of the invention along the AA axis in Figure 1 1 A. Figure 12 illustrates the cross-sectional view "along the CC axis in Figure 11 A. Figures 13 and 13A illustrate the placement of fiber elements supported by the reinforcing rebar. Figure 14 illustrates a view of a braided reinforcement fiber with multiple layers. Figures 15 and 5A illustrate reinforcement and heating fibers in a vertical wall plan. DETAILED DESCRIPTION OF THE INVENTION The foregoing general description and the following detailed description are merely illustrative of the subject matter of the invention and additional modes, advantages and particulars of this invention will be readily suggested to those skilled in the art without departing from the spirit and scope of the invention. the invention. The invention generally provides a means for heating concrete structures employing electrically conductive components (also described herein as "fiber circuits") embedded within the concrete structure to provide heat by impedance or resistivity from an AC current source or CD (hereinafter "resistive heating") and which remain permanently intact as a structural reinforcement. The invention also pertains to concrete structures containing such components. Figures 1 A, 1 B and C illustrate information published by Antón Schíndler as referenced above. Figure 1A illustrates the compressive strength measured for a concrete mixture cured at three separate temperatures. As can be expected, the heat-cured mixture (20 ° C to 80 ° C) exhibits a significant compressive strength after 10 hours and reaches the maximum compressive strength in 30 hours. The mixture maintained at a low temperature (-1 0 ° C to + 20 ° C) exhibited no compressive strength until after 20 hours and reached maximum strength after about 150 hours. Interestingly, the highest compressive strengths were achieved by samples cured at 20 ° C and at low temperatures (-1 0 ° C to + 20 ° C). This is also illustrated in Figure 1B after the curing time is normalized. Figure 2 represents the results of the tests consistent with the information described in Figures A and 1 B. After 1 0 hours, it is shown that sample 900 that cured at 50 ° C achieves an 800 compressive strength of about 25 MPa (or about 50% or more of the total resistance reached). Sample 901 that cured at 35 ° C reaches a resistance 801 of about 17 to 18 MPa. After 10 hours, the 904 sample that cured at 12.5 ° C has reached a compressed strength 802 of approximately 4 MPa (or less than 10% of the final resistance) and the 903 sample that cured at 5 ° C has reached a negligible compression resistance 803. It will be appreciated that Figure 2 shows that the gain rate in compressive strength reaches the maximum for the 50 ° C sample in about 10 hours. This is particularly noteworthy in view of the fact that the maximum compressive strength achieved by this sample is the lowest 851 of all the samples. The highest measured compression resistance 855 was reached by sample 904. Sample 903 and sample 902 cured at 20 ° C reached 854 measured values of compressive strength near or equal. In addition, the information illustrated in Figure 2 indicates that the maximum 963 resistance gain rate is not reached by the 903 sample at 5 ° C until after 100 hours. Sample 902 of 20 ° C reaches the maximum gain rate of 962 resistance after approximately 65 to 70 hours. Sample 904 of 12.5 ° C reaches the maximum gain rate of 964 resistance after approximately 80 to 90 hours. Therefore, the subject of the invention of this specification includes heating the concrete at the start of curing to achieve a high resistance gain regime, but then letting the concrete cool in such a way that the almost maximum resistance gain regime Hold for each temperature. In a preferred embodiment, the invention includes the ability to vary the heating rate to optimize the temperature control of the concrete during curing. Figure 2B illustrates one embodiment of this variable heating of the concrete for the controlled optimization of the curing regime and the ultimate compressive strength. Therefore, the invention includes the creation of "search" tables for heating regimes to cure different types or the manipulated placement of heating fibers. Figure 2C contains heating and energy information for various fiber types and carbon fiber architectures commercially available. The table lists the results of the tests using a piece of 9.3 square decimeters of base line 2 of 2P50K fiber woven carbon cloth, which consumes 100 watts per 3.05 decimeters, at 5 volts and 20 amps, and reaches 54.5 ° C in 10 minutes. It will be appreciated by persons skilled in the art that the fibers are sorted or calibrated by the number of filaments or braids that make up the fiber. Carbon fiber is typically measured in thousands of filaments, for example, 6 or 12K. Figure 2D illustrates a temperature-to-temperature graph for a 12K braid carbon fiber wire at a specific energy setting. The graph illustrates the ability of a high strength carbon reinforcement material to provide resistive heat. The temperature readings were recorded for an approximate length of 305 meters of carbon circuit, being a length capable of providing heat to a concrete structure of 6.1 meters x 9.15 meters x 0.076 meters. Figure 3A represents test information consistent with the information illustrated in Figure 1C showing that the degree of hydration (curing) is almost equal 971 regardless of the temperature of the concrete. Figure 4A illustrates the typical simple placement of the rebar 210 within a concrete structure 100. The direction of the gravitational force experienced by the trabe is illustrated by the vector arrow 950. An external load in the central section of the structure will place the upper portion 1 12 of the structure in compression and the lower portion 114 in tension, as shown by the vector arrow 955. Steel bars help sustain the stress strain. Figure 4B illustrates a prestressed concrete structure 100. Steel wires 211 exert a compression force (vector arrow 970) on the concrete in the lower portion 114. This compression force deflects the expansive tension illustrated in Figure 4A by the vector arrow 955. The compression force is placed on each end of the structure 1 16, 117, using the fittings 212 for the tensioned steel wire. Figure 5 represents a typical concrete formation arrangement used in the construction of sloping walls. The concrete 100 is shown partially filled within a panel formation array defined by the perimeter shapes 310. Support blocks 320 are positioned to provide lateral support to the shapes 310 and to enable the shapes to resist the concrete casting forces without distorting the desired geometry. Reinforcing steel wires 210 are shown in a typical configuration. Because concrete panels constructed using this construction technique should be given sufficient time to reach a less than full level of curing before tilting in position, additional reinforcing steel should be added to resist tilting stresses . The concrete construction typically uses shapes, such as those shown in Figure 5, to keep the viscous concrete, uncured in the intended manner during fixing and hardening. The forms are then removed frequently. The rebar, as shown in Figure 4 above, is typically installed at the desired location within the shapes prior to emptying the uncured concrete. Due to the high density and viscosity of the concrete, it is necessary that fas forms and rebar have sufficient strength to maintain the intended placement. The fiber circuits, matter of this invention, can also be installed before the casting of the concrete. Although the fibers can be carbon or other high strength material, it is necessary that the movement of the concrete during the emptying does not displace the circuit. It will be appreciated that the fiber circuits can be secured to the shapes, rebar or other components. This can be done by winding or similar methods. In some applications, it may be desirable for the circuits to be placed in a tensioned frame so that the separation of the circuits, and hence the heat dispersion by engineering, is not altered. This method can be similar to the installation of steel reinforcement in prestressed concrete. The engineering and design of the circuit installation can also incorporate the placement of electrical power connection components. In Figure 6, an array for concrete wall formation with heating members 250 (fiber circuits) is shown to replace the steel reinforcements shown in Figure 5. The members 250 communicate with the penetrating electrical contacts 460. through the forms 310 to allow connection with a power supply (not shown). Based on the actual tensile properties needed in the finished structure, the heating members are designed to provide structural reinforcement as well. Figures 6 and 7 describe the heating element 250 as a wire or fiber that can be easily coiled and manipulated at the site. In this embodiment, the heating element 250 is supplied in this cylindrical profile or as a rope with other possible modes being a "C" channel, rectangular or any other designed customary form specific for the application and requirements of the place. Such an alternative arrangement is shown in Figure 8. The heating element 250 may comprise a plurality of high resistance electrically conductive fibers (e.g., fibers or carbon filaments) that can be impregnated with a resin matrix capable of making them rigid with the application of heat. A suitable resin matrix is Dion 6694 vinyl ester combined with an RD 1070 thickening agent from Reichhold Chemicals. In order to provide an extended shelf life, a latent starter package is used that allows 30 days shelf life at cold storage temperatures. A catalyst packet consumption with this objective is a concentration of 1% by weight of both Trigonox 29-B75 and Trigonox 21 available from Akzo Nobel. The impregnation of the resin takes place off-site and the heating members are shipped to the site of the installation. The members of conductive components of this invention are variously described as fibers or circuits of electrically conductive fibers. It will be appreciated that this term includes elongated materials, incriminating, but not limited to, wires, rods, fibers, filaments, staple fibers, emboiled or stapled fibers. In another embodiment, the heating member 250 is impregnated with a thermoplastic resin matrix or mixed with thermoplastic fibers. This arrangement offers unlimited shelf life and remains malleable until the heat generated during the concrete curing process sets the combination of thermoplastic resin or fiber. Once cooled, the heating member becomes rigid providing a structural reinforcement in the finished concrete structure 10. In yet another embodiment, the heating members are supplied in a previously rigidized form.

Here, the members are largely handled as traditional reinforcing steel (rebar) with the exception of the provision of a means to communicate electrical power to the members. Stiffness in this mode may be the result of a thermoplastic or thermoplastic resin matrix combined with carbon fibers. Figure 7 shows a cross-sectional view of one embodiment of an electrical connection as seen in Figure 6 along lines A-A. In this view, the assembly of electrical contacts 460 comprises a fastening apparatus 470 for the carbon fiber heating member 250. This interface carries electrical energy from an external power supply (not shown) through the contact 469. This member has an externally threaded portion for accepting a fastener. The fastener rod 468 has a thinned section 411 where, after the concrete is cured and the forms are stripped, the rod can be easily detached and removed within the conical area formed by the depression forming shoe 410. In a typical wall forming operation, the shapes 310 are assembled to define the perimeter of the structure 100. The circuit 250 of heating fibers, which are an object of this invention, are disposed within the cavity defined by the shapes. Figure 9 shows one such arrangement. The arrangement is dictated by the necessary amount of heating energy to accelerate the curing process as well as by the mechanical properties of the finished wall or wall. Because a section of the wall cured using the described method will achieve a greater degree of curing in a shorter time frame, the actual reinforcement requirements can be reduced to accommodate the wall in position. In Figure 9, the heating members (fiber circuit) are arranged in a continuous mode wherein electrical contact is required only in two locations 472A and 472B. This mode also facilitates the simultaneous curing of several panels or wall structures by connecting the panels in series or parallel circuits. Figure 9A is a cross-sectional illustration along the axis A-A of the structure of Figure 9. Figure 9A illustrates the orientation of the multi-layer fiber reinforcement circuit 250 within the section. Illustrated are also the components 310, 320 of the section shape and the ratio of the concrete section to the ground 199 during curing. Figure 10 illustrates a cross-sectional view of another embodiment wherein multiple circuits 250A, 250B, 250C are installed within a concrete section 100. The circuits are placed at different depths and may have different directional orientation. The orientation and composition of the circuits can be manipulated to create a greater reinforcement in the lower portion 114 of the structure than in the upper level 2. The orientation will be beneficial as the structure rises from one end, represented by the vector arrow 960, using the opposite end as a fulcrum. 910. Figure 10B illustrates a single fiber reinforcement circuit path 250 of the invention wherein the orientation of the fibers is increased in a third direction through the thickness of the structure 1 1 1. The fibrous composite circuits, of course, can be oriented in conjunction with another non-energized fiber reinforcing material to supply heat for the curing process. It may be desirable to selectively heat portions of the uncured concrete in order to achieve rapid setting and hardening, while allowing other portions of the uncured concrete to cure more slowly (and thus, possibly achieve a higher final compression strength) . Figure 1 1 A illustrates a concrete structure in which one or more circuits 250 of electrically conductive fibers are installed proximate the outer perimeter of the shape 310. This circuit allows the concrete 100 to be heated after pouring, thus accelerating the setting of concrete next to the forms. The setting of concrete along the perimeter will allow forms 310, 320 to be removed and reused more quickly than would otherwise be possible. The remaining concrete can advance through a slower curing cycle. Figure 1 1 B illustrates a cross-sectional view along the axis AA shown in Figure 1 1A of the fiber circuits installed adjacent to the perimeter of the concrete structure adjacent to the shapes 310, 320. Electrical power can be supplied to the circuit by means of the components 472A, 472B connectors. It will be appreciated that the carbon fiber braid is electrically conductive and disperses heat rapidly. Since the concrete has a low thermal conductivity, it may be desirable to improve the heat dispersion within the concrete (forming the matrix surrounding the carbon fiber braid) by increasing the dispersion (and therefore the number) of carbon fibers electrically conductive that create circuits within the concrete. The greater dispersion of the heating circuits will facilitate a more uniform temperature inside the concrete. Accordingly, Figure 11 C illustrates a cross-sectional view of a concrete structure containing an increased number of circuits 250 of separate fibers. It is intended that the circuits be relatively evenly dispersed within the concrete matrix 100. Unlike the prior art placement of the reinforcement rebar, the fiber circuits are both placed within the upper 1 12 and lower 1 14 portions of the concrete structure and close to the 31 0 forms. The fibers may be tensioned between the component shapes 310 or by similar means in order that the fibers do not move during the casting of the concrete. It will be appreciated that concrete is a dense and relatively viscous material. In another embodiment, the fibers can be fixed to the rebar to provide a quick installation and minimize the deformation during the casting of the concrete. This embodiment is discussed further in conjunction with Figures 13 and 13A. Figure 1 1 D illustrates an embodiment of the invention wherein the electrically conductive components 250 (fiber circuit) are used in conjunction with the rebar 210. The rebar is placed within the lower portion 14 of the structure. The fiber circuits 250 are placed relatively uniformly throughout the matrix 100. Figure 1 1 D also illustrates the use of carbon heat conducting fibers or the like within the concrete matrix 105 similar to the teaching of the patents of US Nos. 5,308,696 and 5,685,902. Carbon fibers, which are thermally conductive, are used in this invention to facilitate uniformly uniform heating of the concrete. Figure 12 illustrates a cross-sectional view along the CC axis of the structure incorporating the embodiment illustrated in Figure 1 1 D. The carbon fiber strands 250 within the concrete matrix 100 are interconnected by means of the components 252 to form a fiber circuit having connection components 472A, 472B that can be used with a separate power supply (not shown). Also illustrated is rebar 210 and concrete forming component 310. Figure 13 illustrates the winding of the fiber circuit 250 around the rebar 210. It will be appreciated that the rebar, which is made of a ferrous metal, is electrically isolated from the electrically conductive fiber. This isolation can be achieved by various means, including the use of coated fiber, or by placing non-conductive separators between the fiber and the rebar (not shown). The use of rebar in this manner has the advantage of rapidly minimizing the distortion of fiber placement during concrete casting. Figure 14 illustrates a modality of the fiber circuit, that is, the conductive component, taught by the invention. It will be appreciated by those skilled in the art that carbon fibers having a high tensile strength are not very elastic, having a low voltage ratio to the fault. In order to maintain a tensile strength and electrical conductivity, a multi-layered braid can be fabricated with the inner layers having different fiber orientation. Although the orientation of the fibers can be measured or specified in various ways, the angle? (hereinafter "braid angle") of the intersecting fibers forming the braid. Figure 14 illustrates a multi-layered braid having an outer layer 250C, an intermediate layer 250B and an inner layer 250A. The outer layer 250C is constituted by two fibers A, B braided together and intersecting at a selected angle braid. When subjected to an external force pulling in the axial direction 270 (vector arrow 955), the braid angle decreases and the length of the braided fiber increases. The diameter of the braid can also decrease. The next braided fiber inner layer, which has a larger braid angle 2, has the ability to elongate in response to an external axial load. The next layer, which has a larger braid angle? 3, can also be lengthened. The modality of a braid component with multiple layers is not limited to three layers. In addition, the sequence of the placement of the layers can be altered, the inner layers having successively smaller braid angles. In addition, the fiber layers of the braid can be separated by other layers of braid that do not carry load. These unloaded braid layers can facilitate the movement of the other braid layers relative to other braids or the surrounding concrete. Similarly, design requirements such as wind loading, opening and crimping supports can be easily met with the addition of a limited amount of high strength carbon fiber support members. It will be appreciated that for wall panels fabricated either on-site or manufactured in a central, controlled location, the center of the panel will experience compressive forces and stress forces will be concentrated on the external surfaces. Therefore, it will be advantageous to have a greater reinforcement in the external portions of the wall or the wall. It will be appreciated that for a uniform and controlled heat distribution, however, not all fiber reinforcement needs to be energized with electric current. A slower curing of the concrete matrix in the central section 120 may also have the advantage that the highest compression strength is reached at the exact location where such higher compressive strength will be beneficial. The selective placement of reinforcements near the outer surface of the wall is suggested in Figure 13 where the rebar 210 is concentrated closer to the surfaces without any rebar in the center. The fiber circuit 250 can be used to maintain the orientation of the rebar after the wall panel is raised to a vertical position. Figure 15 illustrates a wall panel formed in a horizontal plane; similar to the structure illustrated in Figure 13. The fiber circuit 250 is wound around the rebar 210 placed next to each side of the panel wall 1, 12, 14. The heating will result in faster set and hardening of the outer portions 12, 14 of the structure. The inner section 120 is not subject to significant heat and will therefore cure (harden and harden) more slowly. Figure 15A illustrates the wall panel after it has been erected. The placement of the reinforcement 215 relevant to the changed load vectors is also illustrated. It will be appreciated that as the wall panel is raised from one end 17 in the direction shown by the vector arrow 960, the upper portion of the wall surface 12 will be in compression as shown by the vector arrow 970. The opposite side 14 of the panel will be in tension as shown by the vector arrow 955. Figure 15A illustrates the wall panel erected vertically by the end 116. When in this position, the downward load, the vector arrow 960, will produce an expansive outward force next to the lower wall section 116, as shown by the vector arrow 980. The rebar is reinforced by the advanced curing of the heated sections of the external wall of the structure, as well as by means of complementary lateral support bands 215 that hold the repair 210 in a fixed position.

Using the teaching of this invention, a concrete slab of 55.8 square meters reached a temperature of 48.9 ° C after ten minutes using a 5 kW generator. In this demonstration, conductive insulating fibers were dispersed every 15.24 centimeters in rebar with 8 ohms per meter. Approximately 305 meters of carbon fiber were used. Although specific embodiments have been illustrated and described, numerous modifications are possible without departing from the spirit of the invention, since the scope of protection is limited only by the scope of the appended claims. This specification should be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It should be understood that the forms of the invention shown and described herein are taken as currently preferred embodiments. As already stated, various changes can be made in the form, size and arrangement of the components or adjustments made in the steps of the method without departing from the scope of this invention. For example, elements equivalent to those illustrated and described herein may be substituted and certain aspects of the invention may be used independently of the use of other aspects, as will be apparent to one skilled in the art after having the benefit of this description of the invention. Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in light of this specification.

Claims (67)

1. CLAIMS 1. A method for curing concrete that uses at least one electrically conductive circuit within the uncured concrete by energizing the circuit with electrical energy to positively heat the circuit for at least a portion of the concrete cure time.
2. 2. The method of claim 1, wherein the concrete is heated by the circuit for at least a portion of the curing time of the concrete.
3. 3. The method of claim 2, wherein the concrete is heated to a first temperature and then the electrically modified energy in a controllable manner before the completion of curing.
4. 4. The method of claim 3, wherein the amount of electrical energy is modified to achieve an intended rate of compression strength gain of the concrete during curing.
5. The method of claim 1, wherein the circuit is constituted by electrically conductive non-metallic material.
6. 6. The method of claim 1, wherein the circuit is constituted, at least partially, by carbon.
7. The method of claim 1, wherein the circuit contains carbon fibers.
8. The method of claim 7, wherein the carbon fiber is selected from a group consisting of 2P50K, 1 P6K, 2P6K, 3KUNI, 6P12KCL and 3P1 KTIAX.
9. 9. The method of claim 7, wherein the carbon fiber is a 1 2K carbon fiber tow.
10. The method of claim 7, wherein the carbon fiber is a 24K carbon fiber tow. eleven .
11. The method of claim 7, wherein the carbon fiber is a 48K carbon fiber tow.
12. The method of claim 7, wherein the carbon fiber is a 80K carbon fiber tow.
13. The method of claim 7, wherein the carbon fiber is a carbon fiber tow of 96K.
14. The method of claim 7, wherein the circuit contains thermally responsive filaments blended with 12K carbon fiber.
15. The method of claim 7, wherein the carbon fiber is coated with a non-electrically conductive material.
16. 16. The method of claim 1, wherein the coating is a polymer.
17. 17. The method of claim 1, wherein the coating is a textile.
18. 18. The method of claim 1, wherein the thermally responsive filaments contain nylon 6 and carbon fiber 12K.
19. 9. The method of claim 14, wherein the thermally responsive filaments contain nylon 12 and carbon fiber. 12K.
20. The method of claim 14, wherein the thermoplastic fiber is polyethylene and carbon fiber 12K. twenty-one .
21. The method of claim 14, wherein the thermoplastic fiber is polypropylene and 12K carbon fiber.
22. 22. The method of claim 14, wherein the thermoplastic and carbon fiber circuit can be installed in a concrete form, energized with electrical energy and prior to the introduction of uncured concrete.
23. 23. The method of claim 7, wherein the circuit contains carbon fiber with a tensile strength of at least 900 MN / m2.
24. 24. A method for heating concrete by placing an electrically conductive circuit inside the concrete before curing and placing the circuit in electrical communication with an external power source to resistively heat the circuit.
25. 25. A method for curing concrete comprising: a) placing at least one electrically conductive circuit within a concrete shape; b) add uncured concrete to the form; c) connecting the circuit to a source of electrical energy to resistively heat the circuit, and d) using resistive heat to raise the temperature of the uncured concrete.
26. 26. The method of claim 25, further comprising coated electrically conductive fibers.
27. 27. A method for curing concrete containing additives that respond to heat comprising energizing electrically conductive circuits within uncured concrete to resistively heat the circuit within the concrete.
28. 28. The method of claim 25, where the concrete contains polymer additives.
29. 29. The method of claim 25, wherein the concrete contains additives that respond to heat to activate a hydration reaction by means of interlaminar heating.
30. 30. A method for controllably initiating the curing of concrete by placing additives to the uncured concrete and at least one electrical circuit that can be heated in a resistive manner that is capable of supplying sufficient activation heat energy for curing .
31. 31 The method of claim 30, wherein the additives are selected from a group consisting of polymers and catalysts that respond to heat.
32. 32. A method for heating a concrete surface using at least one electrically conductive circuit installed within the concrete prior to the completion of curing and energizing the circuit with electrical power to resistively heat the circuit.
33. 33. A method to reinforce concrete by placing an electrically conductive circuit containing fibers with a tensile strength of at least 900 MN / m2 within the concrete.
34. 34. A concrete structure containing at least one electrically conductive circuit installed prior to the completion of concrete curing.
35. 35. The concrete structure of claim 32, wherein the circuit can be energized before the concrete cures.
36. 36. The concrete structure of claim 35, wherein the circuit is heated resistively to increase the temperature of a surface of the structure.
37. 37. The structure of claim 32, wherein the circuit can be energized during the curing of the concrete.
38. 38. A concrete object comprising: a) at least one electrically conductive circuit within the concrete; and b) means for connecting the circuit to an external electrical power source.
39. 39. The object of) to claim 38 further comprising the rebar.
40. 40. The object of claim 39, wherein the circuit is attached to the rebar.
41. 41 The object of claim 40, wherein the attached circuit is electrically insulated from the rebar.
42. 42. The object of claim 38, wherein the circuit is wrapped around the rebar.
43. 43. The concrete object of claim 38, wherein the electrically conductive circuit is tensioned prior to the placement of uncured concrete.
44. 44. The concrete object of claim 38, wherein the circuit is placed within the object in a manner to provide structural strength.
45. 45. A concrete object comprising: a) at least one first surface; b) at least one electrically conductive circuit inside the concrete; c) means for energizing the circuit to produce resistive heat to raise the temperature of the first surface.
46. 46. A concrete object containing at least one electrically conductive circuit constituted by braided carbon fibers.
47. 47. The concrete object of claim 46, wherein the braided carbon fibers are oriented at varying angles.
48. 48. The concrete object of claim 46, wherein the circuit comprises carbon fibers in multiple braided layers.
49. 49. A concrete structure containing at least one electrically conductive circuit comprising fibers with a thermally responsive resin.
50. 50. The concrete structure of claim 49, wherein the thermally responsive resin is also cured at the time the concrete is cured.
51. 51 A concrete object containing an electrically conductive material that can be connected to a source of electrical energy for heating.
52. 52. A concrete material that contains an electrically conductive material that can be connected to a source of electrical energy to produce heat within the concrete structure.
53. 53. The object of claim 52, wherein the electrically conductive material is connected to the power source with a bus bar component.
54. 54. A concrete structure containing an electrical circuit consisting of conductive fibers with a tensile strength of at least 900 M N / m2.
55. 55. A concrete structure that contains an electrical circuit made up of mechanically wound carbon fibers.
56. 56. A concrete structure containing an electrical circuit comprising consolidated bundles of carbon having a first end and a second end joined to at least one busbar.
57. 57. The busbar of claim 56 is the electrical contact point through which electric power is conducted to generate sufficient resistive heat to activate a hydration reaction? inside the concrete.
58. 58. A concrete structure that contains an electrical circuit constituted by carbon fibers mechanically consolidated by tissue.
59. 59. A concrete structure that contains an electrical circuit constituted by mechanically consolidated carbon fibers by stitch bonding.
60. 60. A concrete structure containing an electrical circuit constituted by carbon fibers mechanically consolidated by tissue points.
61. 61 A concrete structure that contains an electrical circuit constituted by carbon fibers mechanically consolidated by braiding.
62. 62. A concrete structure containing at least one electrically conductive circuit installed within the concrete prior to the completion of concrete curing and which can be energized after curing to provide radiant heat from the concrete.
63. 63. The structure of claim 38 is a wall or wall.
64. 64. The structure of verification 38 is a floor.
65. 65. The structure of claim 38 is a roof.
66. 66. The floor of claim 38 can serve as the heated pouring pan to radially heat the concrete structure formed thereon.
67. 67. The heated pouring slab to cure the walls, ceilings, pre-emptied parts, had pre-emptied and pre-stressed beams and concrete covers.