PileMedic® is an innovative product by QuakeWrap, Inc. perfect for repair, strengthening and encapsulation of underwater steel, concrete and wood or timber piles.
A large number of structures in coastal regions or crossing waterways are supported on piles. These piles are commonly made of concrete or wood. Additionally, steel piles are often encountered in certain structures such as offshore oil platforms. The adverse environment introduced by seawater, high humidity/high temperature, and dry-wet cycles causes rapid deterioration of these structures. The most severe conditions are found in the splash zone area which encompasses the portion of the pile between the low and high tide water levels. The high concentration of chloride ion in seawater allows it to penetrate and reach the steel even in high-quality concrete. As a result, the passive layer that normally protects steel is destroyed making corrosion of reinforcing or prestressing steel inevitable.
Since corroded steel occupies a larger volume, it causes lateral forces on the surrounding concrete that far exceed the tensile strength of concrete. This results in cracking and spalling of the cover concrete. The deterioration of concrete and the loss of cross sectional area of the reinforcing steel results in reduction in capacity of the piles. Repairs often require creating a formwork around the pile and filling it with grout or concrete to enlarge the section, thereby increasing its load-carrying capacity. The wet marine environment combined with access difficulties are not suitable for use of formwork made with wood or steel. In the last twenty years, Glass Fiber Reinforced Polymer (GFRP) jackets have become a material of choice for formwork in marine construction. In many cases, these forms are used as stay-in-place forms.
PILEMEDIC LAMINATESRepair and strengthening of structures by external bonding of FRP products was introduced by the author in the late 1980s. The technique, known as wet layup, includes saturating fabrics of carbon or glass with resin in the field and applying them to the surface of beams, columns, walls, slabs, pipes, etc. By the next day when the FRP is cured, it forms an impervious sheet that is 2-3 times stronger than steel. This technique has seen worldwide acceptance and growth in the last two decades for repair of buildings and bridges. While new advances have been made to develop resins that cure underwater, repair of piles with this technology is not very efficient. Among the major disadvantages is the fact that wet layup systems can be applied to smooth surfaces. For deteriorated underwater piles, the forming of the surfaces requires construction of coffer dams, adding significant expense to the project. It is therefore preferred to use FRP forms which create a shell around the pile, allowing the annular space to be filled with grout. The author has recently developed a new form of FRP called PileMedic® that offers major advantages for repair of piles. Sheets of glass or carbon fabric are impregnated with resin in the manufacturing plant and pressed together under high pressure and heat to produce very thin laminates. Laminates with thickness of ¼ inch or higher have been available for years and are fairly easy to manufacture. However, PileMedic® laminates vary in thickness between 0.010 to 0.025 inches. The development of a process and specially-designed equipment to allow construction of such uniform thin sheets is not a trivial matter. Depending on the design requirements, the laminate may include multiple layers of uniaxial or biaxial carbon and glass fabrics. Typical laminate rolls are less than 0.025 inch thick X 4-ft wide X 300-ft long (Fig. 2). The higher quality control of the manufacturing process allows production of laminates with tensile strength higher than 150,000 psi. By mixing and orienting the fibers in different directions, laminates with infinite number of strength and stiffness characteristics can be produced. In the field, the laminates are cut to desired size and wrapped around the pile to create a multilayered shell of any desired size. The annular space between the shell and the pile is filled with grout or resin. A moisture-insensitive resin that cures in water is applied to the laminate as it is wrapped onto itself to create this free-standing shell.
GFRP jackets are lightweight and moisture tolerant and have been used extensively for underwater pile repair. A handful of manufacturers supply the majority of the products used in north America. These products are typically constructed of two half shells made out of fiberglass that are bolted or glued together or held together with external straps to form a jacket around the pile. In some cases, the connection may be a tongue and groove type that gets filled with epoxy in the field. There are also other forms where the two half shells are supplied as U-shapes where the sides are overlapped and bonded together in the field with epoxy or screws to create a solid rectangular or square shell.
All existing pile jackets require advance planning for the contractor to order the right size jacket for the project. Often times the jackets are available in standard sizes only. This leads to large annular spaces between the jacket and the pile which is unattractive and adds to the weight and cost of the grout or resin that is needed to fill the annular space. The jackets are also bulky, resulting in higher shipping and storage costs. From a structural engineering point of view, the vertical seam along the jacket whether glued or bolted in the field introduces a plane of weakness that minimizes the confining pressure offered by the jacket.
To overcome these shortcomings, PileMedic® Laminates were invented.
Need more information? Contact our engineers!