Abstract:
System and method for reinforcing structures includes basalt textile ( 20 ) connected to surfaces of the structure ( 100 ) with fiber anchors ( 30 ). Textile spreads forces and increases ductility of structure. Textile may connect multiple structural elements together, including walls, floors, columns, beams, and roofs. Textile is covered with mortar ( 50 ) customized to match color and texture of structure by use of locally obtained grit, aggregate, or colorant. Basalt fiber textile is preferred to avoid degradation of textile from alkaline components of mortar ( 50 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates in general to reinforcing structures and more particularly to materials for strengthening existing structures without substantial change to the appearance of the structures. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many existing buildings throughout the world are in need of reinforcement to help them resist damage by earthquake, violent storms, acidic atmosphere, vibrations due to vehicle traffic, or similar threats. Many older buildings, especially, were designed to handle large compressive forces but are not resistant to lateral forces. 
         [0003]    Buildings that are not resistant to sudden lateral force need to be reinforced for the safety of people who live or work in, or visit the building. Some buildings have considerable historical or artistic value and must be protected from disasters and environmental deterioration for their own sakes. 
         [0004]    Some methods exist for reinforcing existing buildings. One that is used all over the world is wrapping a structure with fiberglass textile that is impregnated with epoxy. This method is taught in different forms in U.S. Pat. Nos. 5,043,033, 5,649,398, and 5,657,595. A means of connecting different components of a structure using ductile fiber anchors is taught in U.S. Pat. No. 7,207,149 and incorporated herein by reference. 
         [0005]    The methods of U.S. Pat. Nos. 5,043,033, 5,649,398, and 5,657,595 are effective and can be performed with little intrusion on the occupants and visitors of the building being reinforced. A disadvantage to these methods is that they use some specialized materials that are not readily available in all locations. As a result, the materials are shipped from centralized distribution centers, sometimes to remote locations that are difficult to reach. The shipping and round transportation of heavy materials adds significantly to the cost of the project. 
         [0006]    Another disadvantage of the wrapping methods is that the materials readily available on the market are not good matches in color and texture with old buildings. There are many buildings all over the world that are constructed of native stone, brick from local clay, or that are coated with plaster made with local minerals. As a result, the materials of the methods mentioned above, such as epoxy and fiberglass, may not match the color or texture of a given building. 
         [0007]    Yet another disadvantage to the method discussed above is that some of the materials, particularly epoxy, are less fire resistant than conventional stone, brick, or plaster construction. It is desirable that a method for increasing a building&#39;s strength should also increase its fire-resistance, or at least not degrade it. 
         [0008]    To avoid the disadvantage of the flammability of epoxy or other organic polymers, the textile could be coated with an inorganic hardenable paste such as mortar. However, this leads to a different disadvantage, which is that inorganic mortars are alkaline and tend to degrade ordinary fiberglass. Special alkaline-resistant glass textile is available, but is quite expensive. This has discouraged the use of glass textile with mortar for reinforcement of structures. Graphite carbon or aramid fiber textiles would be compatible with mortar, but these textiles are also very expensive and not widely available in all countries. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is a system of materials and methods for reinforcing structures using some locally derived materials. The system includes a textile wrap attached to the structure with fiber anchors and a finishing layer of mortar made with grit and aggregate that was obtained from sources in the vicinity of the structure being reinforced. 
         [0010]    The textile is composed of fibrous basalt, which is resistant to alkaline and compatible with inorganic mortar. The textile is typically an open-weave fabric that is strong and ductile. The fabric is attached to the structure in a ductile manner, such as with fiber anchors as taught in U.S. Pat. No. 7,207,149. The fiber anchors are preferably also created from basalt fiber. 
         [0011]    A mortar finishing material is mixed, beginning with a hardenable liquid matrix, such as slurry of calcined mineral particles that harden to create a solid mortar after being mixed with water. Grit, aggregate, or both are added to the hardenable liquid matrix. The grit or aggregate add color and texture to the mortar finishing material. 
         [0012]    The reinforcing system is intrinsically fire resistant and does not increase the fire risk to a structure. 
         [0013]    By using grit and aggregate that are mined or quarried locally, it is often possible to match the color and texture of the original building very well. The final appearance of the reinforced structure is relatively unchanged from the original, possibly historic, appearance. Further, the ability to use local mineral materials saves money on shipping material to a remote location. 
         [0014]    Utilizing local minerals for the mortar finishing material is made possible by the use of basalt fiber textile and fiber anchors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a top plan view, partly cut away, of the reinforcement system of the present invention, as used to strengthen a wall of a building. 
           [0016]      FIG. 2  is a sectional view, taken on line  2 - 2  of  FIG. 1 . 
           [0017]      FIG. 3  is a top plan view of the reinforcement system of the present invention, as used to strengthen an expansion joint of a structure. 
           [0018]      FIG. 4  is a sectional view, taken on line  4 - 4  of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  is a top plan view of the reinforcement system  10  of the present invention, partly cut away.  FIG. 2  is a sectional view of reinforcement system  10 , taken on line  2 - 2  of  FIG. 1 , as used to strengthen a structure  100 , for example a wall  110  of a building. 
         [0020]    Reinforcement system  10  include alkaline-resistant textile  20  stretched over wall  110 . Textile  20  is attached to wall  110  with a plurality of fiber anchors  30 . A mortar  50 , containing mineral products preferably obtained in the same geographic region as structure  100 , is spread over textile  20  and fiber anchors  30 . 
         [0021]    Textile  20  is preferably a lightweight, mesh fabric, woven or knit of suitable ductile, strong, and alkaline resistant fibers such as basalt. Conventionally, structures have been reinforced with fabrics made of glass fibers. Ordinary glass fabric must be covered with a protective finishing material that is pH neutral, that is, neither strongly alkaline nor acidic. Many alkaline or acidic materials, including cementitious materials such as mortar and concrete, degrade glass and weaken it. For this reason, structural reinforcing systems that include glass fiber fabric also typically include a finishing layer of epoxy or polyurethane, which are substantially neutral. 
         [0022]    Of course, other alkaline-resistant fibers with good ductility and high tensile strength may be used to create textile  20  in place of basalt. The choice of specific fiber for textile  20  may be made for each application based upon availability, strength, and cost. Basalt is found to be the preferred material at this time, but other materials may become available in the future. 
         [0023]    Test results show that system  10  greatly increases the load-bearing ability of wall  110  even if the weave of textile  20  includes openings as wide as three or four inches across, although 1 inch across is a more typical size. A plain or twill weave with square or rectangular openings has been found to be convenient to apply and to provide sufficient strength and ductility. Textile  20  is typically woven from yarns or bundles consisting of many individual thin filaments of basalt fiber. 
         [0024]    Textile  20  is stretched over surfaces of various structural elements of a structure  100  to be reinforced. Panels of textile  20  may be wrapped over interior or exterior corners so as to connect different walls  110 , or to connect a wall  110  to a ceiling, or other combinations as appropriate. Textile  20  may be temporarily attached to wall  110  by suitable clips, staples, or adhesive. 
         [0025]    In the case of structures  100  that are built of fragile materials, or that have been damaged by weathering or environmental degradation, it is preferable that the mesh opening size be small, such as 0.5 inch across. 
         [0026]    Many types of structural element can be reinforced by using textile  20  to connect walls  110  to floors or ceilings, columns or beams to ceilings, roofs to walls  110 , and so on. 
         [0027]    The next step in the reinforcement method is to permanently attach textile  20  to wall  110  or other structure using suitable ductile connecting means, such as a plurality of fiber anchors  30 , as are well known in the art. Fiber anchors  30  are created by boring a hole through an opening in textile  20  and into the underlying wall  110 . A length of fiber roving, preferably also composed of fibrous basalt, is inserted into the borehole with a free end extending above textile  20 . 
         [0028]    A backfill material, such as grout or polymeric adhesive, is pushed or injected into the borehole. The free end of the roving is attached to the outer surface of wall  110  and over textile  20 , such as with adhesive or mortar. The backfill material retains the roving within the borehole such that fiber anchor  30  forms a sort of large pin attaching textile  20  to wall  110 . Fiber anchor  30  is the most preferred ductile connecting means for system  10  because fiber anchor  30  spreads forces over a broad area and so is unlikely to pull out from wall  110  as a mechanical fastener might, or pull off a section of wall  110  as a surface adhesive might. 
         [0029]    The final process is to cover textile  10  and fiber anchors  30  with a mortar finish coat  50 . Mortar finish coat  50  covers textile  20  so that it will not be damaged by weather, or snagged. Mortar  50  contacts and adheres to the original surface of wall  110  through the openings of the weave of textile  20 , embedding textile  20  and helping spread any large lateral forces such as from earthquake or wind. Mortar  50  mechanically holds textile  20  in place near wall  110  but cannot entirely take the place of ductile connection means such as fiber anchors  30 . 
         [0030]    Mortar finish coat  50  is largely for creating a uniformly textured and colored surface for the reinforced wall  110 . Conventional epoxy and glass fiber textile reinforcement typically gives a structure a smoother texture and slightly hazy coloration. Although the epoxy can be covered with paint of other finish, mortar is not advised due to possible degradation of the glass fiber. 
         [0031]    Mortar finish coat  50  works well for replicating the appearance of original concrete, stucco, or plaster walls  110 . With additional modeling and coloring work, mortar finish  50  can even replicate the appearance of historical stone or brick walls  110 . 
         [0032]    Mortar  50  is customized to suit the structure to be reinforced. Typically, mortar  50  is based on a matrix of hardenable paste, such as ductile concrete. Uncured ductile concrete may be termed a slurry, that is, a mixture of solid particles suspended in a liquid, with sufficient viscosity or surface tension that the particles remain suspended for a long time and yield a mixture that can be handled like a liquid or paste. 
         [0033]    Ductile concrete is not typically used as a finish coat for homes, historical buildings, or other structures where appearance is important but a modern “industrial” look is not desired. However, it is a strong, ductile material that is less likely to crack under lateral forces than standard concrete. 
         [0034]    Other matrix materials such as organic polymers or other inorganic cementitious materials may also be used to create mortar  50 . 
         [0035]    Generally, building materials such as stone, brick, and adobe are not transported farther than necessary. As a result, structures in a given country or geographic area tend to have distinctive appearances. To customize mortar  50 , it is preferred that mineral materials are used that are similar to those used for the structure originally. 
         [0036]    In the case of historical buildings, it is often desirable to determine the components of the original materials, such as by microscopic examination or chemical analysis. 
         [0037]    For example, many older public buildings in the American Midwest are of the tan stone call Indiana limestone. In the American Southwest, many historical buildings are of adobe bricks, which vary in color depending upon the iron content of the local clay. 
         [0038]    Thus, to reinforce a structure in the Midwest it might be appropriate to incorporate ground limestone into mortar  50  to produce a smooth tan surface on the reinforced structure. In the Southwest, adobe clay or ground sandstone might be added to mortar  50  to make it resemble brick or stone. 
         [0039]    Mineral materials obtained locally may include sand, clay, gravel, ground stone, or mineral colorants. Although the minerals used for customized mortar finish coat  50  are described herein as locally obtained, it is to be understood that the mineral materials are to be obtained preferably from the same source as the materials of the original structure. For example, if an historical structure in Indonesia was built originally of imported Italian marble, it may be aesthetically desirable to obtain material from the same quarry in Italy to customize mortar  50  if reinforcing the structure in Indonesia. 
         [0040]    An alternative embodiment of reinforcing system  10  is illustrated in  FIGS. 3 and 4 .  FIG. 3  is a top plan view of reinforcement system  10 , as used to strengthen an expansion joint  122  of a structure, such as a bridge  120 .  FIG. 4  is a sectional view; taken on line  4 - 4  of expansion joint  122  of  FIG. 3 . 
         [0041]    Expansion joint  122  is a design feature of bridge  120 . It is a gap of a few inches width, left between sections of bridge  120  to allow for thermal expansion of the bridge material. The gap of expansion joint  122  is typically filled to provide a smooth surface for traffic. 
         [0042]    The filling of expansion joint  122  must be of a material that is ductile and will not interfere with the function of expansion joint  122 . The alternative embodiment of reinforcing system  10  as illustrated in  FIGS. 3 and 4  has been found to be a low cost and very effective way of dressing expansion joint  122 . 
         [0043]    Expansion joint  122  has been created with a recess  125  to be filled to provide a smooth upper surface. To fill expansion joint  122  using system  10  of the present invention, a first layer of mortar  50  is laid into recess  125 , filling recess  125  approximately halfway. Next, a strip of textile  20 , as described above, is laid over mortar  50 . A second layer of mortar  50  is poured or spread over textile  20  to fill recess  125  to the desired level. Mortar  50  may be textured as desired or left in the as-applied state. Fiber anchors  30  are typically not required for this embodiment of system  10 . 
         [0044]    It may be noted that reinforcement system  10 , as practiced for reinforcing structures such as buildings, may be optionally installed similarly to the method of filling expansion joints  122 . That is, a first layer of mortar  50  may be spread on the original wall  110  of the structure, then textile  20  attached over the first layer of mortar  50 . Fiber anchors  30  are preferably still employed as detailed above. Fiber anchors  30  are preferably installed after the first layer of mortar  50 . A second layer of mortar  50  is applied over textile  20  and fiber anchors  30 , then finished, also as described above. 
         [0045]    This method of practicing the present invention is especially useful in the case of buildings that are constructed of fragile materials, or that have been weakened by weather, degradation by pollution, or earthquakes. Another precaution taken in the case of fragile buildings is to create a borehole for fiber anchor  30  that is deeper than is typically used for a strong matrix such as undamaged concrete. 
         [0046]    Although particular embodiments of the invention have been illustrated and described, various changes may be made in the form, composition, construction, and arrangement of the parts herein without sacrificing any of its advantages. Therefore, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense, and it is intended to cover in the appended claims such modifications as come within the true spirit and scope of the invention.