fiberglass materials. Fiberglass Reinforcement for Corrosion Resistant Offshore Concrete Structures

The article talks about what properties fiberglass has and how applicable it is in construction and in everyday life. You will find out what components are needed to make this material and their cost. The article provides step-by-step videos and recommendations for the use of fiberglass.

Since the discovery of the rapid petrification effect epoxy resin under the action of an acid catalyst, fiberglass and its derivatives began to be actively introduced into household products and machine parts. In practice, it replaces or supplements the exhaustible Natural resources- metal and wood.

What is fiberglass

The principle of operation, which is the basis of the strength of fiberglass, is similar to reinforced concrete, and in terms of appearance and structure, it is closest to reinforced layers modern "wet" finishing of facades. As a rule, a binder - a composite, gypsum or cement mortar - tends to shrink and crack, not holding the load, and sometimes not even maintaining the integrity of the layer. To avoid this, a reinforcing component is introduced into the layer - rods, meshes or canvas.

The result is a balanced layer - the binder (in dried or polymerized form) works in compression, and the reinforcing component works in tension. From such layers based on fiberglass and epoxy resin, you can create three-dimensional products, or additional reinforcing and protective elements.

fiberglass components

Reinforcing component*. For the manufacture of household and auxiliary building elements, three types of reinforcement material are commonly used:

1. Fiberglass mesh. This is a fiberglass mesh with a cell from 0.1 to 10 mm. Since epoxy mortar is an aggressive environment, impregnated mesh is highly recommended for products and building structures. The grid cell and the thread thickness should be selected based on the purpose of the product and the requirements for it. For example, for reinforcing a loaded plane with a fiberglass layer, a mesh with a cell from 3 to 10 mm, a thread thickness of 0.32-0.35 mm (reinforced) and a density of 160 to 330 g / cu. cm.
2. Fiberglass. This is a more advanced type of fiberglass base. It is a very dense mesh made of "glass" (silicon) filaments. It is used to create and repair household products.
3. Fiberglass. It has the same properties as the material for clothing - soft, flexible, pliable. This component is very diverse - it differs in tensile strength, thread thickness, weaving density, special impregnations - all these indicators significantly affect the final result (the higher they are, the stronger the product). Main indicator- density, ranging from 17 to 390 g / sq. m. Such a fabric is much stronger than even the famous military cloth.

* The described types of reinforcement are also used for other works, but their compatibility with epoxy resin is usually indicated in the product passport.

Table. Prices for fiberglass (on the example of Intercomposite products)

Astringent. This is an epoxy solution - a resin mixed with a hardener. Separately, the components can be stored for years, but in a mixed form, the composition hardens from 1 to 30 minutes, depending on the amount of hardener - the more it is, the faster the layer hardens.

Table. The most common resin grades

Popular hardeners:

1. ETAL-45M - 10 c.u. e./kg.
2. XT-116 - 12.5 cu e./kg.
3. PEPA - 18 c.u. e./kg.

Additional chemical component can be called a lubricant, which is sometimes applied in order to protect surfaces from the penetration of epoxy (for lubricating molds).

In most cases, the master studies and selects the balance of components on his own.

How to use fiberglass in everyday life and in construction

In private, this material is most often used in three cases:

• for rod repair;
• for inventory repair;
• for strengthening structures and planes and for sealing.

Repair of fiberglass rods

This will require a fiberglass sleeve and a high-strength resin grade (ED-20 or equivalent). The technical process is described in detail in this article. It is worth noting that carbon fiber is much stronger than fiberglass, which means that the latter is not suitable for repairs. percussion instrument(hammers, axes, shovels). At the same time, it is quite possible to make a new handle or handle for inventory from fiberglass, for example, the wing of a walk-behind tractor.

Useful advice. Fiberglass can improve your tool. Wrap the handle of a working hammer, axe, screwdriver, saw with impregnated fiber and squeeze it in your hand after 15 minutes. The layer will ideally take the shape of your hand, which will noticeably affect the ease of use.

Inventory repair

The tightness and chemical resistance of fiberglass make it possible to repair and seal the following plastic products:

1. Sewer pipes.
2. Construction buckets.
3. Plastic barrels.
4. Rain tides.
5. Any plastic parts of tools and equipment that do not experience heavy loads.

Repair with fiberglass - step by step video

The "home-made" fiberglass has one indispensable property - it is accurately processed and holds rigidity well. This means that a hopelessly damaged plastic part can be restored from canvas and resin, or a new one can be made.

Strengthening building structures

Fiberglass in liquid form has excellent adhesion to porous materials. In other words, it adheres well to concrete and wood. This effect can be realized when installing wooden jumpers. The board, on which liquid fiberglass is applied, acquires an additional 60-70% strength, which means that a board twice as thin can be used for a jumper or crossbar. If reinforced with this material door frame, it will become more resistant to loads and distortions.

Sealing

Another method of application is the sealing of stationary containers. Reservoirs, stone tanks, pools, covered with fiberglass from the inside, acquire all the positive properties of plastic utensils:

• insensitivity to corrosion;
• smooth walls;
• continuous monolithic coating.

At the same time, the creation of such a coating will cost about 25 USD. e. per 1 sq. m. Real tests of products of one of the private mini-factories speak eloquently about the strength of products.

On the video - fiberglass testing

Of particular note is the possibility of repairing the roof. With a properly selected and applied epoxy compound, slate or tile can be repaired. With its help, you can simulate complex translucent structures made of plexiglass and polycarbonate - canopies, Street lights, benches, walls and much more.

As we found out, fiberglass is becoming a simple and understandable repair and construction material that is convenient to use in everyday life. With a developed skill, you can create interesting products from it right in your own workshop.

In foreign construction, of all types of fiberglass, the main application is translucent fiberglass, which is successfully used in industrial buildings in the form of sheet elements of a corrugated profile (usually in combination with corrugated sheets of asbestos cement or metal), flat panels, domes, spatial structures.

Translucent enclosing structures serve as a replacement for labor-intensive and inefficient window blocks and skylights of industrial, public and agricultural buildings.

Translucent barriers found wide application in walls and roofs, as well as in elements of auxiliary structures: sheds, kiosks, fences of parks and bridges, balconies, flights of stairs and etc.

In cold enclosures industrial buildings FRP corrugated sheets are combined with asbestos cement, aluminum and steel corrugated sheets. This makes it possible to use fiberglass in the most rational way, using it as separate inclusions in the roof and walls in quantities dictated by lighting considerations (20-30% of the total area), as well as fire resistance considerations. Fiberglass sheets are attached to the girders and fachwerk with the same fasteners as sheets of other materials.

Recently, in connection with the reduction in prices for fiberglass and the production of a self-extinguishing material, translucent fiberglass began to be used in the form of large or continuous areas in the enclosing structures of industrial and public buildings.

Standard sizes of corrugated sheets cover all (or almost all) possible combinations with profiled sheets made of other materials: asbestos-cement, clad steel, corrugated steel, aluminum, etc. accepted in the US and Europe. Approximately the same range profile sheets from vinyl plastic (Merley company) and plexiglass (ICA company).

Simultaneously with translucent sheets, consumers are also offered complete sets of their fastening parts.

Along with translucent fiberglass in last years in a number of countries, rigid translucent vinyl plastic, mainly in the form of corrugated sheets, is also becoming more widespread. Although this material is larger than fiberglass, sensitive to temperature fluctuations, has a lower modulus of elasticity and, according to a number of data, is less durable, it nevertheless has certain prospects due to a wide raw material base and certain technological advantages.

Domes fiberglass and plexiglass are widely used abroad due to high lighting characteristics, low weight, relative ease of manufacture (especially plexiglass domes), etc. They are produced in a spherical or pyramidal shape of a round, square or rectangular shape in plan. in the USA and Western Europe predominantly single-layer domes are used, while in countries with a colder climate (Sweden, Finland, etc.) they are double-layer with an air gap and a special device for draining condensate, made in the form of a small gutter along the perimeter of the supporting part of the dome.

Scope of translucent domes - industrial and public buildings. Dozens of firms in France, England, the USA, Sweden, Finland and other countries are engaged in their mass production. Fiberglass domes are typically available in sizes 600 to 5500 mm, And from plexiglass from 400 to 2800 mm. There are examples of the use of domes (composite) significantly large sizes(to 10 m and more).

There are also examples of the use of reinforced vinyl domes (see chapter 2).

Translucent glass-reinforced plastics, which until recently were used only in the form of corrugated sheets, are now beginning to be widely used for the manufacture of large-sized structures, especially wall and roof panels. standard sizes capable of competing with similar designs made from traditional materials. Only one American company, Colwall, produces three-layer translucent panels up to 6 m, applied them in several thousand buildings.

Of particular interest are the developed fundamentally new translucent panels of the capillary structure, which have an increased thermal insulation capacity with high translucency. These panels are made of a thermoplastic core with capillary channels (capillary plastic), glued on both sides with flat sheets of fiberglass or plexiglass. The core is essentially a translucent honeycomb with small cells (0.1-0.2 mm). It contains 90% solid and 10% air and is made mainly of polystyrene, less often - plexiglass. It is also possible to use polycarbonate - a thermoplastic of increased fire resistance. The main advantage of this translucent construction is its high thermal resistance, which results in significant savings in heating costs and prevents condensation even when high humidity air. An increased resistance to its concentrated, including shock loads, should also be noted.

The standard dimensions of capillary structure panels are -3X1 m, but they can be produced up to 10 m and width up to 2 m. On fig. 1.14 shows a general view and details of an industrial building, where panels of a capillary structure with a size of 4.2X1 are used as light fences for the roof and walls m. The panels are laid along the long sides on V-shaped gaskets and joined from above with the help of metal linings on the mastic.

In the USSR, fiberglass was found in building structures very limited use (for individual experimental facilities) due to its insufficient quality and limited range

(see chapter 3). Corrugated sheets with a small wave height (up to 54 mm), which are used mainly in the form of cold fences for buildings of "small forms" - kiosks, sheds, light sheds.

Meanwhile, as feasibility studies have shown, the use of fiberglass in industrial construction as translucent wall and roof barriers can give the greatest effect. At the same time, expensive and labor-intensive lamp superstructures are excluded. The use of translucent barriers in public construction is also effective.

Fences made entirely of translucent structures are recommended for temporary public and auxiliary buildings and structures in which the use of translucent plastic fencing is dictated by increased lighting or aesthetic requirements (for example, exhibition, sports buildings and facilities). For other buildings and structures, the total area of ​​light openings filled with translucent structures is determined by lighting design.

TsNIIPromzdaniy, together with TsNIISK, Kharkov Promstroyniiproekt and the All-Russian Research Institute of Fiberglass and Fiberglass, has developed a number of efficient structures for industrial construction. The simplest design is translucent sheets laid along the frame in combination with corrugated sheets of non-transparent
transparent materials (asbestos cement, steel or aluminium). It is preferable to use shear-wave fiberglass in rolls, which eliminates the need to join sheets across the width. At longitudinal wave it is advisable to use sheets of increased length (two spans) to reduce the number of joints above the supports.

Coating slopes in the case of a combination of corrugated sheets of translucent materials with corrugated sheets of asbestos cement, aluminum or steel should be assigned in accordance with the requirements,

Presented to coatings from non-translucent corrugated sheets. When covering entirely from translucent wavy layers, the slopes should be at least 10% if the sheets are joined along the length of the slope, 5% if there are no joints.

The overlap length of translucent corrugated sheets in the direction of the slope of the coating (Fig. 1.15) should be 20 cm with slopes from 10 to 25% and 15 cm with slopes over 25%. In wall railings, the length of the overlap should be 10 cm.

When applying such solutions, serious attention should be paid to the device for attaching sheets to the frame, which largely determine the durability of structures. Corrugated sheets are fastened to the girders with bolts (to steel and reinforced concrete girders) or screws (to wooden girders) installed along the crests of the waves (Fig. 1.15). Bolts and screws must be galvanized or cadmium plated.

For sheets with wave sizes 200/54, 167/50, 115/28 and 125/35, fastenings are placed on every second wave, for sheets with wave sizes 90/30 and 78/18 - on every third wave. All extreme crests of the waves of each corrugated sheet must be fixed.

The diameter of bolts and screws is taken according to the calculation, but not less than 6 mm. The diameter of the hole for bolts and screws should be 1-2 mm More than the diameter of the fixing bolt (screw). Metal washers for bolts (screws) must be bent along the curvature of the wave and provided with elastic sealing linings. The diameter of the washer is taken according to the calculation. In places where corrugated sheets are fastened, wooden or metal linings are installed to prevent the wave from settling on the support.

The joint across the direction of the slope can be bolted or glued. For bolted connections, the overlap length of corrugated sheets is taken not less than the length of one wave; bolt pitch 30 cm. Joints of corrugated sheets on bolts should be sealed with tape gaskets (for example, made of flexible polyurethane foam impregnated with polyisobutylene) or mastics. At adhesive bond the length of the overlap is taken according to the calculation, and the length of one joint is not more than 3 m.

In accordance with the guidelines adopted in the USSR for capital construction, the main attention in research is given to large-sized panels. One of these structures consists of a metal frame, working for a span of 6 m, and corrugated sheets supported on it, working for a span of 1.2-2.4 m .

Double-sheet filling is preferred as it is relatively more economical. Panels of this design with a size of 4.5X2.4 m were installed in an experimental pavilion built in Moscow.

The advantage of the described panel with a metal frame is the ease of manufacture and the use of materials currently produced by the industry. However, more economical and promising are three-layer panels with flat sheet skins, which have increased rigidity, better thermal properties and require minimal metal consumption.

The light weight of such structures allows the use of elements of significant dimensions, however, their span, as well as corrugated sheets, is limited by the maximum allowable deflections and some technological difficulties (the need for large-sized press equipment, sheet joints, etc.).

Depending on the manufacturing technology, fiberglass panels can be glued or integrally molded. Glued panels are produced by glueing flat skins with an element of the middle layer: ribs made of fiberglass, metal or antiseptic wood. For their manufacture, standard fiberglass materials produced by the continuous method can be widely used: flat and corrugated sheets, as well as various profile elements. Glued constructions allow, depending on the need, to vary the height and pitch of the elements of the middle layer relatively widely. Their main disadvantage, however, is the greater number of technological operations compared to integrally molded panels, which makes their production more difficult, as well as the less reliable connection of skins with ribs than in integrally molded panels.

One-piece molded panels are obtained directly from the original components - fiberglass and a binder, from which a box-shaped element is formed by winding the fiber onto rectangular mandrels (Fig. 1.16). Such elements, even before the binder is cured, are pressed into a panel by creating lateral and vertical pressure. The width of these panels is determined by the length of the box-shaped elements and, in relation to the module of industrial buildings, is assumed to be 3 m.

Rice. 1.16. Translucent one-piece molded fiberglass panels

A - manufacturing scheme: 1 - winding fiberglass filler on mandrels; 2 - lateral compression; 3-vertical pressure; 4-finished panel after extracting the mandrels; b-general view panel fragment

The use of continuous rather than chopped fiberglass for integrally molded panels makes it possible to obtain material in panels with increased values ​​of the modulus of elasticity and strength. The most important advantage of integrally molded panels is also a single-stage process and increased reliability of connecting thin ribs of the middle layer with skins.

At present, it is still difficult to give preference to one or another technological scheme for the manufacture of translucent fiberglass structures. This can be done only after their production is established and data on the operation of various types of translucent structures are obtained.

The middle layer of glued panels can be arranged in various options. Panels with a corrugated middle layer are relatively easy to manufacture and have good lighting properties. However, the height of such panels is limited maximum dimensions waves

(50-54mm), in connection with which BUT)250^250g250 such panels have

Rigidity. More acceptable in this regard are panels with a ribbed middle layer.

When selecting the cross-sectional dimensions of translucent ribbed panels, a special place is occupied by the question of the width and height of the ribs and the frequency of their placement. The use of thin, low and rarely spaced ribs ensures greater light transmission of the panel (see below), but at the same time leads to a decrease in its load-bearing capacity and rigidity. When assigning the spacing of the ribs, one should also take into account the bearing capacity of the skin under the conditions of its operation for a local load and a span equal to the distance between the ribs.

The span of three-layer panels, due to their significantly greater rigidity than that of corrugated sheets, can be increased for roof slabs up to 3 m, and for wall panels - up to 6 m.

Three-layer glued panels with a middle layer of wooden ribs are used, for example, for office premises of the Kiev branch of VNIINSM.

Of particular interest is the use of three-layer panels for the installation of skylights in the roof of industrial and public buildings. The development and research of translucent structures for industrial construction was carried out at TsNIIPromzdaniy together with TsNIISK. Based on comprehensive research
work row interesting solutions anti-aircraft lamps made of fiberglass and plexiglass, as well as experimental facilities.

skylights from fiberglass can be solved in the form of domes or panel structures (Fig. 1.17). In turn, the latter can be glued or integrally molded, flat or curved. Due to the reduced load-bearing capacity of fiberglass, the panels are supported along their long sides on adjacent blind panels, which must be reinforced for this purpose. It is also possible to arrange special support ribs.

Since the section of a panel is usually determined by calculating it from deflections, in some structures the possibility of reducing deflections by appropriate fastening of the panel on supports was used. Depending on the design of such an attachment and the rigidity of the panel itself, the panel deflection can be reduced both due to the development of the support moment and the appearance of “chain” forces that contribute to the development of additional tensile stresses in the panel. In the latter case, it is necessary to provide constructive measures that would exclude the possibility of convergence of the supporting edges of the panel (for example, by attaching the panel to a special frame or to adjacent rigid structures).

A significant reduction in deflection can also be achieved by giving the panel a three-dimensional shape. Curvilinear vaulted panel performs better than flat panel on static loads, and its shape helps to better remove dirt and water from the outer surface. The design of this panel is similar to that adopted for the translucent coating of the pool in Pushkino (see below).

Skylights in the form of domes, usually rectangular in shape, are arranged, as a rule, double, given our relatively harsh climatic conditions. They can be installed separately

4 A. B. Gubenko

Domes or be interlocked on the roof slab. So far, only organic glass domes have found practical application in the USSR due to the lack of fiberglass the right quality and sizes.

In the roof of the Moscow Palace of Pioneers (Fig. 1.18), above the lecture hall, it is installed in increments of about 1.5 m 100 spherical domes with a diameter of 60 cm. These domes illuminate an area of ​​about 300 m2. The design of the domes rises above the roof, which provides them better cleaning and discharge of rainwater.

In the same building, a different design was used above the winter garden, which consists of triangular packages glued together from two flat sheets of organic glass, laid on a spherical steel frame. The diameter of the dome formed by the spatial frame is about 3 m. Organic glass bags were sealed in the frame with porous rubber and sealed with U 30 mastic. Warm air that accumulates in the dome space prevents condensation from forming on the inner surface of the dome.

Observations of the organic glass domes of the Moscow Palace of Pioneers have shown that seamless translucent structures have undeniable advantages over prefabricated ones. This is explained by the fact that the operation of a spherical dome, consisting of triangular packages, is more difficult than seamless domes of small diameter. The flat surface of double-glazed windows, the frequent arrangement of frame elements and sealing mastic make it difficult for water to drain and blow off dust, and in winter they contribute to the formation of snow drifts. These factors significantly reduce the light transmission of structures and lead to a violation of the seal between the elements.

Light engineering tests of these coatings gave good results. It was found that the illumination from natural light of a horizontal area at the floor level of the lecture hall is almost the same as when artificial lighting. Illumination is almost uniform (fluctuation 2-2.5%). Determining the effect of snow cover showed that with a thickness of the latter 1-2 cm the illumination of the room drops by 20%. At positive temperatures, the fallen snow melts.

Anti-aircraft domes made of plexiglass were also used in the construction of a number of industrial buildings: the Poltava diamond tool plant (Fig. 1.19), the Smolensk processing plant, the laboratory building of Noginsky scientific center Academy of Sciences of the USSR, etc. The designs of domes in these objects are similar. Dimensions of domes in length 1100 mm, in width 650-800 mm. The domes are double-layered, the support cups have inclined edges.

Rod and other supporting structures fiberglass is used relatively rarely, due to its insufficiently high mechanical properties (especially low rigidity). The scope of these structures is of a specific nature, associated mainly with special operating conditions, such as the requirement for increased corrosion resistance, radio transparency, high transportability, etc.

Relatively big effect gives application fiberglass structures exposed to various aggressive substances that quickly destroy conventional materials. In 1960, for the manufacture of corrosion-resistant fiberglass structures, only
about $7.5 million was spent in the USA (the total cost of translucent fiberglass plastics produced in the USA in 1959 is about $40 million). Interest in corrosion-resistant fiberglass structures is explained, according to firms, primarily by their good economic performance. Their weight

Rice. 1.19. Organic glass domes on the roof of the Poltava diamond tools plant

A - general view; b - design of the support unit: 1 - dome; 2 - condensate collection chute; 3 - frost-resistant sponge rubber;

4 - wooden frame;

5 - clamping metal clamp; 6 - apron made of galvanized steel; 7 - waterproofing carpet; 8 - compacted slag wool; 9 - metal support cup; 10 - plate heater; 11 - asphalt screed; 12 - dumping from granular

Slag

Much less steel or wooden structures, they are much more durable than the latter, are easy to build, repair and clean, can be made on the basis of self-extinguishing resins, and translucent containers do not need water gauge glasses. So, a serial tank for aggressive environments with a height of 6 m and diameter 3 m weighs about 680 kg, while a similar steel container weighs about 4.5 t. Weight of chimney diameter 3 m and height 14.3 mu intended for metallurgical production, is 77-Vio of the weight of a steel pipe with the same bearing capacity; although a fiberglass pipe cost 1.5 times more to manufacture, it is more economical than steel
noah, since, according to foreign firms, the service life of such structures made of steel is calculated in weeks, from of stainless steel- for months, similar structures made of fiberglass are operated without damage for years. So, a pipe with a height of 60 meters and a diameter of 1.5 m operating for the seventh year. Earlier installed pipe made of stainless steel lasted only 8 months, and its manufacture and installation cost only half the price. Thus, the cost of the fiberglass pipe paid off after 16 months.

An example of durability in an aggressive environment are also fiberglass containers. Such a container with a diameter and height of 3 l, intended for various acids (including sulfuric), with a temperature of about 80 ° C, is operated without repair for 10 years, having served 6 times longer than the corresponding metal one; only one repair cost for the last one over a five-year period is equal to the cost of a fiberglass tank.

In England, Germany and the USA, containers in the form of warehouses and water tanks of considerable height have also found wide distribution (Fig. 1.20).

Along with the indicated large-sized products, in a number of countries (USA, England), pipes, air duct sections and other similar elements intended for operation in aggressive environments are mass-produced from fiberglass.

Basic concepts
Fiberglass - a system of glass threads bound by thermoplastics (irreversible hardening resins).

Strength Mechanisms - Adhesion between single fiber and polymer (resin) adhesion depends on the degree of cleaning of the fiber surface from the sizing (polyethylene waxes, paraffin). The sizing is applied at the manufacturer of fibers or fabrics to preserve the prevention of delamination during transport and technological operations.

Resins - polyester, are characterized by low strength and significant shrinkage during hardening, this is their minus. Plus - fast polymerization unlike epoxides.

However, shrinkage and rapid polymerization cause strong elastic stresses in the product and over time the product warps, warping is insignificant, but on thin products it gives unpleasant glare of a curved surface - see any Soviet body kit for VAZs.

Epoxies - hold their shape much more accurately, are much stronger, but more expensive. The myth about the cheapness of epoxides is due to the fact that the cost of domestic epoxy resin is compared with the cost of imported polyester. Epoxies also benefit from heat resistance.

The strength of fiberglass - in any case depends on the amount of glass by volume - the most durable with a glass content of 60 percent, however, this can only be obtained under pressure and at temperature. AT "cold conditions, it is difficult to obtain durable fiberglass.
Preparation of glass materials before gluing.

Since the process consists in gluing the fibers together with resins, the requirements for the glued fibers are exactly the same as in the gluing processes - thorough degreasing, removal of adsorbed water by annealing.

Degreasing, or removal of the sizing, can be done in BR2 gasoline, xylene, toluene, and their mixtures. Acetone is not recommended due to the binding of water from the atmosphere and "getting wet» fiber surface. As a degreasing method, annealing at a temperature of 300-400 degrees can also be used. In amateur conditions, this can be done as follows - a fabric rolled into a roll is placed in a blank from a vent pipe or a galvanized drainpipe and heated with a spiral from an electric stove placed inside the roll, you can use a hair dryer to remove paint and etc.

After annealing, glass materials should not lie in the air, since the surface of the glass fabric absorbs water.
The words of some "craftsmen"about the possibility of gluing without removing the dressing cause a sad smile - it would never occur to anyone to glue glass over a layer of paraffin. Tales about what de "resin dissolves paraffin" is even funnier. smear the glass with paraffin, rub it and now try to stick something to it. Draw your own conclusions))

Pasting.
The release layer on the matrix is ​​the best polyvinyl alcohol in water, applied by spray and dried. Gives a slippery and elastic film.
Special waxes or silicone-based waxes can be used, but always make sure that the solvent in the resin does not dissolve the release layer by trying it on something small first.

When gluing, lay layer on layer by rolling with a rubber roller, squeezing out excess resin, remove air bubbles by piercing with a needle.
Be guided by the principle - excess resin is always harmful - resin only glues glass fibers, but is not a material for creating shapes.
if detail high precision, such as a hood cover, it is desirable to introduce a minimum of hardener into the resin and use heat sources for polymerization, for example infrared lamp or household "reflector».

After hardening, without removing from the matrix, it is very desirable to warm up the product evenly - especially at the stage "gelatinization» resin. This measure will relieve internal stresses and the part will not warp over time. Regarding warping - I'm talking about the appearance of glare and not about changing sizes, dimensions can change by only a fraction of a percent but at the same time give strong glare. Pay attention to plastic body kits made in Russia - none of the manufacturers "bothers The result is summer, stood in the sun, in winter a couple of frosts and ... everything is crooked ... although the new one looked great.
In addition, with the constant action of moisture, especially at the places of chips, the fiberglass begins to crawl out, and gradually wetting with water, it simply fringes, water sooner or later penetrating into the thickness of the material peels off the glass threads from the base (glass absorbs moisture very strongly
in a year.

The sight is more than sad, well, you see such products every day. what is made of steel and what is made of plastic can be seen immediately.

By the way, prepregs sometimes appear on the market - these are sheets of fiberglass already coated with resin, it remains to put it under pressure and heat it - they will stick together into a beautiful plastic. But the manufacturing process is more complicated, although I have heard that prepregs are coated with a resin layer with a hardener and get excellent results. didn't do it myself.

These are the basic concepts about fiberglass, the matrix should be made in accordance with common sense from any suitable material.

I use dry plaster "Rotband» it is processed perfectly, keeps the size very accurately, after drying from water it is impregnated with a mixture of 40 percent epoxy resin with a hardener - the rest is xylene, after the resin has cured, such forms can be polished or. very strong and excellent size.

How to peel the product from the matrix?
for many, this simple operation causes difficulties, up to the destruction of the form.

It is easy to peel off - in the matrix, before gluing, make a hole or several, seal it with thin tape. after manufacturing the product, blow compressed air into these holes in turn - the product will peel off and be removed very easily.

Again, I can tell you what I use.

Resin - ED20 or ED6
hardener - polyethylenepolyamine aka PEPA.
Thixotropic additive - Aerosil (at adding it, the resin loses its fluidity and becomes jelly-like, very convenient) is added according to the desired result.
Plasticizer - dibutyl phthalate or castor oil, about a percent - a quarter of a percent.
Solvent - orthoxylene, xylene, ethyl cellosolve.
filler in resin for surface layers - aluminum powder (hides fiberglass)
fiberglass - asstt, or glass wool.

Auxiliary materials - polyvinyl alcohol, silicone vaseline KV
very useful thin polyethylene film as a separating layer.
useful - vacuum the resin after stirring to remove the bubbles.

I cut the fiberglass into the necessary pieces, then fold it, put it in a pipe and ignite the whole thing with a tubular heating element placed inside the roll, the night is calcined - so convenient.

Yes, and here's more.
Do not mix epoxy resin with a hardener in one container in an amount of more than 200 grams. heat up and boil in no time.

Express control of the results - on a test piece when breaking the glass threads should not stick out - a plastic break should be similar to a plywood break.
break any plastic from which the body kit is made or pay attention to broken ones - solid shag. This is the result "no» bonds of glass with polymer.

Well, little secrets.
it is very convenient to fix devects such as scratches or sinks - put a drop of epoxy on the sink, then stick tape on top, as usual (ordinary, transparent), smooth the surface by highlights with your fingers or applying something elastic, after hardening, the adhesive tape peels off easily and gives a mirror surface. No processing is required.

The solvent reduces the strength of the plastic and causes shrinkage in the finished product.
its use should be avoided whenever possible.
aluminum powder is added only to the surface layers - it reduces shrinkage very much, the grid characteristic of plastics does not appear to me later, the amount is up to the consistency of thick sour cream.
Epoxies are processed worse than polyesters and this is their disadvantage.
the color after adding aluminum powder is not silvery but gray-metallic.
ugly in general.

The metal mount glued into the plastic should be made of aluminum alloys or titanium - because. A very thin layer is applied to the embedded product silicone sealant, and fiberglass, previously well annealed, is pressed against it. The fabric should stick but MUST NOT soak through. after 20 minutes, this cloth is wetted with SOLVENT-FREE resin and the remaining layers are glued onto it. this is "combat "technology as a silicone sealant, we used the Soviet KLT75 compound, vibration, heat-resistant, frost-resistant, resistant to salt water. Preparation of a surface of metal - Aluminium alloy wash in clean solvent. pickle in a mixture of washing soda and washing powder, heating the solution to a boil, if possible in a weak alkali, for example, a 5% solution of caustic potash or sodium, dry with heat. warm up to 200-400 degrees. After cooling, glue as soon as possible.

Fiberglass reinforcement occupies an increasingly strong position in modern construction. This is due, on the one hand, to its high specific strength (the ratio of strength to specific gravity), on the other hand, high corrosion resistance, frost resistance, low thermal conductivity. Structures where fiberglass reinforcement is used are non-conductive, which is very important to exclude stray currents and electroosmosis. Due to the higher cost compared to steel reinforcement, fiberglass reinforcement is mainly used in critical structures that are subject to special requirements. Such structures include offshore structures, especially those parts of them that are in the zone of variable water level.

CORROSION OF CONCRETE IN SEAWATER

The chemical effect of sea water is mainly due to the presence of magnesium sulfate, which causes two types of concrete corrosion - magnesia and sulfate. In the latter case, a complex salt (calcium hydrosulfoaluminate) is formed in the concrete, which increases in volume and causes concrete cracking.

Another strong corrosion factor is carbon dioxide, which is released by organic substances during decomposition. In the presence of carbon dioxide, insoluble compounds that determine strength are converted into highly soluble calcium bicarbonate, which is washed out of concrete.

Seawater acts most strongly on concrete directly above the top of the water. When water evaporates, a solid residue remains in the pores of concrete, formed from dissolved salts. The constant flow of water into concrete and its subsequent evaporation from exposed surfaces leads to the accumulation and growth of salt crystals in the pores of concrete. This process is accompanied by expansion and cracking of concrete. In addition to salts, surface concrete experiences the effects of alternate freezing and thawing, as well as moistening and drying.

In the zone of variable water level, concrete is destroyed to a somewhat lesser extent, due to the absence of salt corrosion. The underwater part of concrete, not subjected to the cyclic action of these factors, is rarely destroyed.

The paper gives an example of the destruction of a reinforced concrete pile pier, the piles of which, 2.5 m high, were not protected in the zone of a variable water horizon. A year later, the almost complete disappearance of concrete from this zone was discovered, so that the pier was supported by one reinforcement. Below the water level, the concrete remained in good condition.

The possibility of manufacturing durable piles for offshore structures lies in the use of surface fiberglass reinforcement. In terms of corrosion resistance and frost resistance, such structures are not inferior to structures made entirely of polymer materials, and they are superior in strength, rigidity and stability.

The durability of structures with external fiberglass reinforcement is determined by the corrosion resistance of fiberglass. Due to the tightness of the fiberglass shell, concrete is not exposed to the environment and therefore its composition can only be selected based on the required strength.

GRP REINFORCEMENTS AND ITS TYPES

For concrete elements where fiberglass reinforcement is used, the design principles of iron concrete structures. The classification according to the types of fiberglass reinforcement used is similar. Reinforcement can be internal, external and combined, which is a combination of the first two.

Internal non-metallic reinforcement is used in structures operated in environments that are aggressive to steel reinforcement, but not aggressive to concrete. Internal reinforcement can be divided into discrete, dispersed and mixed. Discrete reinforcement includes individual rods, flat and spatial frames, meshes. It is possible to combine, for example, individual rods and meshes, etc.

The simplest type of fiberglass reinforcement are rods of the required length, which are used instead of steel ones. Not inferior to steel in strength, fiberglass rods are significantly superior to them in corrosion resistance and therefore are used in structures in which there is a risk of reinforcement corrosion. It is possible to fasten fiberglass rods into frames using self-latching plastic elements or by tying.

Dispersed reinforcement consists in introducing chopped fibers (fibers) into the concrete mixture with stirring, which are randomly distributed in concrete. By special measures it is possible to achieve a directional arrangement of the fibers. Concrete with dispersed reinforcement is commonly referred to as fiber reinforced concrete.
In the case of an aggressive environment to concrete, external reinforcement is an effective protection. At the same time, external sheet reinforcement can simultaneously perform three functions: power, protective and the function of formwork during concreting.

If external reinforcement is not enough to absorb mechanical loads, additional internal reinforcement is used, which can be either fiberglass or metal.
External reinforcement is divided into continuous and discrete. Solid is a sheet structure that completely covers the concrete surface, discrete - mesh-type elements or individual strips. Most often, one-sided reinforcement of the tensioned face of a beam or slab surface is carried out. With one-sided surface reinforcement of the beams, it is advisable to place the bends of the reinforcement sheet on the side faces, which increases the crack resistance of the structure. External reinforcement can be arranged both along the entire length or surface of the bearing element, and in separate, most stressed areas. The latter is done only in those cases when it is not required to protect the concrete from the effects of an aggressive environment.

EXTERNAL GRP REINFORCEMENT

The main idea of ​​structures with external reinforcement is that the hermetic fiberglass shell reliably protects the concrete element from the effects of the external environment and, at the same time, performs the functions of reinforcement, perceiving mechanical loads.

There are two ways to obtain concrete structures in fiberglass shells. The first one involves the manufacture of concrete elements, their drying, and then encasing in a fiberglass shell, by means of multilayer winding with glass material (fiberglass, glass tape) with layer-by-layer resin impregnation. After polymerization of the binder, the winding turns into a continuous fiberglass shell, and the entire element into a pipe-concrete structure.

The second is based on the pre-fabrication of the fiberglass shell and its subsequent filling with a concrete mixture.

The first way to obtain structures, where fiberglass reinforcement is used, makes it possible to create a preliminary transverse compression of concrete, which significantly increases the strength and reduces the deformability of the resulting element. This circumstance is especially important, since the deformability of pipe-concrete structures does not allow to take full advantage of a significant increase in strength. Preliminary transverse compression of concrete is created not only by the tension of the glass fibers (although quantitatively it makes up the bulk of the effort), but also due to the shrinkage of the binder during polymerization.

GRP REINFORCEMENT: CORROSION RESISTANCE

The resistance of glass-reinforced plastics to aggressive media mainly depends on the type of polymer binder and fiber. When internal reinforcement of concrete elements, the resistance of fiberglass reinforcement should be evaluated not only in relation to external environment, but also in relation to the liquid phase in concrete, since hardening concrete is an alkaline environment in which the commonly used aluminoborosilicate fiber is destroyed. In this case, the fibers must be protected with a layer of resin or fibers of a different composition should be used. In the case of non-wetted concrete structures, glass fiber corrosion is not observed. In wetted structures, the alkalinity of the concrete environment can be significantly reduced by using cements with active mineral additives.

Tests have shown that fiberglass reinforcement has resistance in an acidic environment by more than 10 times, and in salt solutions by more than 5 times higher than the resistance of steel reinforcement. The most aggressive for fiberglass reinforcement is an alkaline environment. The decrease in the strength of fiberglass reinforcement in an alkaline environment occurs as a result of the penetration of the liquid phase to the fiberglass through open defects in the binder, as well as through diffusion through the binder. It should be noted that the nomenclature of starting materials and modern technologies The production of polymeric materials makes it possible to regulate the properties of the binder for fiberglass reinforcement in a wide range and obtain compositions with extremely low permeability, and therefore minimize fiber corrosion.

GRP REINFORCEMENTS: APPLICATION IN REPAIR OF REINFORCED CONCRETE STRUCTURES

Traditional methods of strengthening and recovery reinforced concrete structures quite laborious and often require a long shutdown of production. In the case of an aggressive environment after repair, it is required to create protection for the structure against corrosion. High manufacturability, short curing time of the polymer binder, high strength and corrosion resistance of external fiberglass reinforcement predetermined the expediency of its use for strengthening and restoring the load-bearing elements of structures. The methods used for this purpose depend on design features repaired items.

GRP REINFORCEMENTS: ECONOMIC EFFICIENCY

The service life of reinforced concrete structures under the influence of aggressive environments is sharply reduced. Replacing them with fiberglass eliminates the cost of overhauls, losses from which increase significantly when a shutdown of production is required for the time of repair. Investments in the construction of structures where fiberglass reinforcement is used are much higher than those for reinforced concrete. However, after 5 years they pay off, and after 20 years the economic effect reaches twice the cost of erecting structures.

LITERATURE

1. Corrosion of concrete and reinforced concrete, methods of their protection / V. M. Moskvin, F. M. Ivanov, S. N. Alekseev, E. A. Guzeev. - M.: Stroyizdat, 1980. - 536 p.
2. Frolov N.P. Fiberglass fittings and fiberglass concrete structures. - M.: Stroyizdat, 1980.- 104p.
3. Tikhonov M.K. Corrosion and protection of marine structures made of concrete and reinforced concrete. M.: Publishing House of the Academy of Sciences of the USSR, 1962. - 120 p.