3. Fire action on materials

Fire is an energetic manifestation that constantly accompanies human activity; therefore, the emerging risk must be assumed.

Fire develops strongly exothermic chemical reactions, starting when oxidizer and combustible are in a sufficient energetic state (activation energy). The combustible includes substances that are not in their maximum oxidation state; in general, any material containing carbon and/or hydrogen can be oxidized and therefore be combustible. The most important oxidizer is air, which is composed in its fifth part by oxygen; during combustion, the other components remain unchanged (except at very high temperatures) and accompany the products of combustion in the fumes. Part of the energy released in the reaction is dissipated, generating an increase in the temperature of the medium and the remainder is transferred to the reaction products providing the activation energy for the process to continue; if this is not enough, the combustion stops.

The knowledge of the physicochemical theory of combustion has allowed the development of products and systems of defense against fires. Nevertheless, the losses occasioned continue to be one of the greatest tragedies of modern civilization. Taking into account the current technology of fire-retardant treatments (impregnation, coatings, etc.), it is important to mention the generic concept of "passive protection against fire," in which the efficiency is independent of human activity.

The research and development studies are thus significant to reduce the combustibility of materials and the speed of propagation of the flame front as well as to keep during the conflagration the mechanical properties of structures based on either combustible and noncombustible materials. The design of the constructions also plays a very important role.

The true magnitude of the fire problem is remarkable when considering the human and material losses occurring year after year. Thus, for example, 25% of the deaths caused by fire are due to people remain trapped inside buildings; the majority of victims are younger than 10 or older than 70 years. Considering accident deaths, those caused by the fire action are only surpassed by the car crashes.

With regard to economic losses, they reach in many countries a value nearly to 0.25% gross national product. Fire generates significant problems in civil constructions, ships, offshore structures and industrial plants; in many cases, the use of both untreated materials and conventional coatings contribute to the fire spreading.

Often, there are also significant indirect losses of difficult evaluation such as the decrease of income by the total or partial interruption of the activity of a company, the decrease in customers, the increase of replacement costs of installations and equipment, and so on. It is estimated that out of every five companies that have had a major fire, four of them disappear within three years of the incident.

In relation to cultural heritage and historical buildings, material losses are remarkable. For example, the Argentinian Theater of La Plata (Buenos Aires, Argentina) was completely destroyed by a fire and the Theater della Scala (Venice, Italy) was seriously affected by another conflagration, in the decades of the 70 and 90 of the previous century, respectively.

3. Fire action on materials

10 New Technologies in Protective Coatings

emerging risk must be assumed.

combustion stops.

human activity.

surpassed by the car crashes.

within three years of the incident.

conventional coatings contribute to the fire spreading.

Fire is an energetic manifestation that constantly accompanies human activity; therefore, the

Fire develops strongly exothermic chemical reactions, starting when oxidizer and combustible are in a sufficient energetic state (activation energy). The combustible includes substances that are not in their maximum oxidation state; in general, any material containing carbon and/or hydrogen can be oxidized and therefore be combustible. The most important oxidizer is air, which is composed in its fifth part by oxygen; during combustion, the other components remain unchanged (except at very high temperatures) and accompany the products of combustion in the fumes. Part of the energy released in the reaction is dissipated, generating an increase in the temperature of the medium and the remainder is transferred to the reaction products providing the activation energy for the process to continue; if this is not enough, the

The knowledge of the physicochemical theory of combustion has allowed the development of products and systems of defense against fires. Nevertheless, the losses occasioned continue to be one of the greatest tragedies of modern civilization. Taking into account the current technology of fire-retardant treatments (impregnation, coatings, etc.), it is important to mention the generic concept of "passive protection against fire," in which the efficiency is independent of

The research and development studies are thus significant to reduce the combustibility of materials and the speed of propagation of the flame front as well as to keep during the conflagration the mechanical properties of structures based on either combustible and noncombustible materials. The design of the constructions also plays a very important role.

The true magnitude of the fire problem is remarkable when considering the human and material losses occurring year after year. Thus, for example, 25% of the deaths caused by fire are due to people remain trapped inside buildings; the majority of victims are younger than 10 or older than 70 years. Considering accident deaths, those caused by the fire action are only

With regard to economic losses, they reach in many countries a value nearly to 0.25% gross national product. Fire generates significant problems in civil constructions, ships, offshore structures and industrial plants; in many cases, the use of both untreated materials and

Often, there are also significant indirect losses of difficult evaluation such as the decrease of income by the total or partial interruption of the activity of a company, the decrease in customers, the increase of replacement costs of installations and equipment, and so on. It is estimated that out of every five companies that have had a major fire, four of them disappear

In relation to cultural heritage and historical buildings, material losses are remarkable. For example, the Argentinian Theater of La Plata (Buenos Aires, Argentina) was completely As a consequence of the spectacular fires in historic and massive concurrence buildings, many countries adopted regulations for the control of materials flammability. The latter led to developments of intrinsically fire-resistant materials, retardant treatments, and a large number of test methods to evaluate the reaction to fire of the materials. It is also important to mention that for many years now, insurance companies have found that the way to deal with fire is through the prevention and the use of fire-proofing materials.

Stability of construction materials. The fire action on construction materials is significant; thus, for example, calcareous collapses rapidly by dilation and by contraction during drying.

Concerning the concrete, it exhibits satisfactory response to high temperatures if perfectly anchored. For its part, reinforced concrete presents adequate behavior up to 300–330C if its aggregates are small in size; the iron framework begins to lose resistance when reaching a critical temperature of 500–550C.

As regards gypsum, it is gradually dehydrated above 120C and up to 180C, loosing cohesion at 700–800C.

The load-bearing iron and steel structures (made by forging or rolling) are plastically deformed by the action of heat, essentially when the pressure leads to lose their static equilibrium; at approximately 500C, these materials halve their structural strength.

Wood and wood products were widely used in the construction of historic buildings; in spite of behaving like combustible materials and to be vulnerable in cases of fire, in general they display a considerable fire resistance (small decrease of area attributable to the low thermal conductivity of the superficially formed carbonaceous layer). Untreated wood begins to burn at 300C but that treated with suitable fire retardants does not release so much smoke (the gases are nontoxic and non-combustible). The losses in cases of conflagration are always lower than in the constructions with iron and other metals and, once the origin of the fire has been eliminated, the wood is characterized by exhibiting a behavior corresponding to a self-extinguishing material.

All the abovementioned values have a singular meaning, since the average temperature of the fire ranges usually between 700 and 800C.

Fire spreading. The speed of propagation of the flames plays a preponderant role in the advance of the fire front; as mentioned, the toxicity of gases and fumes is a significant variable. The room propagation involves the three forms of heat transfer (convection, radiation, and conduction): in the interior of a building, by conduction through the walls when the thermal insulation is reduced or by convection when there are open stairs while between adjacent buildings by radiation through the openings, doors, and windows.

It is worth mentioning that in the buildings under construction, expansion, or demolition, the probability of fire is particularly high during (i) the heating, welding, and cutting processes; (ii) the transport of flammable liquids and materials; and (iii) the use of electrical equipment with precarious installations.

Total thermal load and fire load. It is significant to determine the degree of risk and adequate security measures, particularly for civil buildings designed to permanently or transiently accommodate a large number of people (schools, libraries, hospitals, hotels, restaurants, auditoriums, theaters, cinemas, shops, etc.) and industrial units built to store and/or manufacture products, equipment, and appliances (petrochemicals, automotive terminals, medical laboratories, sawmills, etc.).

The total combustion risk of a building is calculated by considering the caloric content of the building (fire load including the building itself) and the enthalpy level of the content (fire load involving human lives and properties). The Pourt method was developed from the value of fire load and is widely used to determine the total risk of buildings; the fire charge density, calculated by dividing the fire load by the building surface, is also a widely considered variable.

Performance of coatings in fire. Coatings in particular and coating systems in general play welldefined actions against fire action [7–19]; they may


Testing methods. The analysis of the current regulations in the world indicates the existence of a great number of tests of different characteristics to determine the reaction, the resistance, and the stability against fire of the constructive elements. The results depend on the type and shape of the specimen, the intensity and time of action of the external energy source, and so on.

Figure 2. Left, panel without treatment and right, film of intumescent coating, both after the fire action.

The main variables considered include the size and position of specimen, the type and magnitude of energy source, the way and rate of heating, the duration of test, and valued indices; the fire performance varies according to the method applied.

In many occasions, the abovementioned is a technological barrier for the export/import of either fire retardants or treated materials. A political decision must be taken to impose common test methods at least at the regional or continental level, resulting in adequate reproducibility, that is, that in the case of operators working in different laboratories or in the same laboratory at different times, achieve comparable individual results (low dispersion of the mean value) by using the same method on an identical material.
