CA1130953A

CA1130953A - Coating for protecting structures, more particularly from fire and heat

Info

Publication number: CA1130953A
Application number: CA353,399A
Authority: CA
Inventors: Jean-Charles Daussan; Gerard Daussan; Andre Daussan
Original assignee: Daussan SAS
Current assignee: Daussan SAS
Priority date: 1979-06-05
Filing date: 1980-06-05
Publication date: 1982-09-07
Also published as: SG54585G; EP0029833B1; DE3068671D1; IT1144046B; WO1980002685A1; HK24786A; IT8048881A0; EP0029833A1

Abstract

Abstract of the Disclosure The invention relates to a coating for protecting structures against fire and heat, comprising refractory particles coated with a cement and at least an inorganic compound adapted to provide the coating with a number of molecules of water of crystallization larger than that normally obtained with the cement alone, the relative amount of said inorganic compound being comprised between 1.5 and 20%. The coating is useful for protection against fires.

Description

~3~953 The present invention relates to a coating for protecting struc-tures, more particularly against fire and heat.
The word "coating" is used hereinafter in its strlct sense, thus excluding all solid materials, such as br;ck and perpend-stone having suffi-cient strength to be used for the fabrication of ma~or construction works.
The word "structures" is used hereinafter mainly to indicate walls, ceilings, roofing, doors and frames of dwellings or industrial or agricultural buildings, garages and hangers made with metal beams, joists and pillars, trusses which are solid, perforated, or in ~he form of lattices, partitions, panels made of plastic or expanded materials, false ceilings and the suspen-sion-sections thereof, fire-resistant shields, ventilation shafts, smoke and flre conduits, pipelines, more particularly pipelines for petroleum products and the like inflammable materials.
In the following speciication, the word "structures" will also be used to cover floating structures such QS ships, storage tanks for inflammable products such as petroleum and chemical products, casings of hydraulic or atomic turbines, atomic reactors and the like.
~ or the purpose of protecting the foregoing structures from the effects of fire and heat, general use has already been made of asbestos pro-ducts, ceramic fibre products, and rock-wool or glass fibre products, possibly coated with an inorganic or organic binder.
~ mong the binders most commonly used for coating the aforesaid fibres etc., special mention may be made of the following: ordinary cements of the "Portland" type, magnesia cements, plaster, aluminum monophosphate and chlorophosphate, and phosphatic binders.
The density ofthese P~re-resistant products is between 0.3 and 1.2.
Light prodllcts, having a density of between 0.3 and 0.4 usually have a base of mineral fibres such as rock-wool, basalt wool, or blast furnace-slag wool, _ 1 - '~' ~L3~

mixed with ordinary"Portland" type cement in a ratio of between 40 and 50%
of cement to between 50 and 70% of fibre. The resistance of these products to heat is mediocre and they provide relatively little thermal insulation.
They rarely resist fire for more than sixty or ninety minutes, unless they are compacted or compressed to a density of up to about 0.9, with a protection thickness greater than or equal to 30 mm.
Fire-resistant products of greater density, i.e. between about 0.9 and 1.2, are generally in the form of a projectable mud having a base of plas-ter, ordinary cement or magnesia cement, containing refractory particles and fibres.
These latter products resist fire better and also have a better thermal-insulation coefficient than the lower-density products mentioned above.
~lowever, none of the above referred to known fire-resistant pro-ducts withstands a temperature of more than 800-900C. In fack, they lose their cohesion at these temperatures, since the inorganic binder disintegrates into a powder. As a result of this, the fire-resistant product becomes de-tached from the surface to which it was applied, leaving the surface ~mpro-tected against the effects of fire and heat.
Known products also have the disadvantage of heating up quickly when exposed to heat, thus rapidly reaching the heat-threshold at which they are no longer able to perform their protective function.
It is the main purpose of the invention to overcome the foregoing disadvantages.
According to the present invention there is provided a coating for protecting structures against fire and heat, comprising refractory particles coated with a cement and at least an inorganic compound adapted to provide the coating with a number of molecules of water of crystallisation larger than . , .

~ ~3~ 3 that normally obtained with the cement alone, the relative amount of said inorganic compound being cornprised between 1.5 and 20%.
The coating for protecting structures, more particularly against fire and heat, comprises refractory particles coated with an inorganic binder or cement.
According to the present invention, the said coating also contains at least one inorganic compound imparting thereto, or forming, during the setting thereof, a number of molecules of water of crystallization higher than that normally obtained with the binder alonc.
Inorgallis binders, or cements, form, as they set, moLecules of water of crystallization. Thanks to the presence in the coating of the above-mentioned inorganic compound, the number of the said molecules of water of crystalLizat:ion is incroased in the hardened coating.
Experience has shown the surprising result, that the above-mentioned inorganic compound increases considerably the protection against fire obtained with the coating.
It has actually been found that a coating of this kind, when exposed to heat or fire, heats up much less rapidly than known coatings; the larg0r the ;~
number of molecules of water of crystallization contained in the coating, the lower the average velocity of temperature increase.
Without restricting the present invention to this explanation, it is believed that this characteristic is due to the fact that the release of the ..
. ~ .

: -~3~ 5~
water of crystallization requires the application of a considerable amount of heat, the effect of which is to keep the temperature of the coating to a low value of between 100 and 200C as long as the water of crystallization has not been released.
Moreover, the cracking and disintegration of the coating mentioned above are due precisely to this release of the water of crystallization formed during the setting of the inorganic binder in the presence of water.
Experts in this field have thus hitherto been discouraged from in-creasing the amount of water of crystallization in the coating, as proposed by the present invention, out of fear of accelerating or increasing crackingand disintegration of ~he coating.
Accordlng to the preferred version of the present invention, the coating also contains a sufficient proportion of flux particles to assure s~porficial calcination of the reEractory particles at a temperature substan-~lally be~ween 850 and 900C.
This calclnation causes the refractory particles to weld together, thus surprisingly maintaining the cohesion of the coating after the inorganic binder has cracked and disintegrated under the effect of fire and heat. This calcination of the particles, brought about by the addition of the Elux, thus 2Q takes over the function performed by the inorganic binder until the disinte-grating temperature is reached.
The above-mentioned temperature range is critical for the following reasons:
- if the calcination takes place above 900C, the coating becomes detached from the supporting surface because the binder loses all of its adhesive power;
- if the calcination takes place below 850C, the cracks which form in the coating well below that temperature are filled up much too soon by ~L3~;i3 fusion of the inorganic particles under the action of the flux; this preventsevacuation of the final fractions of water of crystallization, allowing gas pockets to form in the coating, the bursting of which causes the coating to hecome detached from its supporting surface.
The proportion of 1ux added to the composition is governed mainly by the following parameters:
- the nature and grain-size of the refractory particles; the higher the fusion point and size of the said refractory particles, the larger the amount of flux to be added;
- the nature of the flux; as a general rule the higher the fusion temperature of the refractory particles ~for example magnesia), the lower the required fusion temperature af the flux;
- the temperature at which the blnder disintegrates: the lower this temperature, the higher the amount oE flux to be added, to ensure that the calcination begins at a temperature substantially equal to that at which the binder disintegrates.
The coating according to the present invention may also contain up to about 20% by weight of inflammable carbonaceous material, which may be in t~e form of paper pulp, vegetable flour, dextrine, or a vegetable oil.
Contrary to what might be expected, carbonization of carbonaceous material promotes cohesion of the coating exposed to ire and heat.
It has been found in effect, that carbonization of carbonaceous material causes micro-pores to form within the coating. These micro-pores prevent the formation of larger cracks detrimental to satisfactory adhesion of the coating, since they allow the water of crystallization to escape thus preventing the formation of gas pockets.
~ccording to one advantageous version of the invention, when the inorganic blnder i~ in the form of an aluminous or magnesia cement, the i , . .

~13~53 above-mentioned inorganic compound is preferably selected from one of the following compounds or mlxtures thereof: hydrated sodium carbonate, sodium metasilicate, and alkali metal or alkaline-earth me~al phosphate.
These compounds, when added to conventional cements, ~ormJ during the setting of the latter a number of molecules of water of crystalllzation distinctly higher than that formed by the cement alone.
Other characteristics and advantages of the invention appear in the following description thereof.
When the inorganic binder used is a magnesia cement, the composition 10 by weight of the coating according to the invention is preferably as follows:

magnesia cement ~magnesia chloride or magnesia sulphate with added magnesia): 20 to 80%
perlite and/or vermiculite and/or fillite: 10 to 0%
calcium borate: O to 10%
synthetic fibres: 60 to 0%
carbonaceous materials (wood flour) O to 4%
iron oxiaes: O to 2.2%
fluorspar: O to 4%

compound introducing water of crystallization (hydrated sodium carbonate and/or sodium meta-silicate and/or alkali metal or alkaline-earth metal phosphate 10 to 1.8%.
A few examples of coating compounds having a magnesia cement base are given below.

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~34~3 Example I
magnesia chloride: 30%
magnesia: 38.5%
perlite: 7%
synthetic fibres: 2%
calcium borate: 10%
wood flour 2%
iron oxide: 0.~%
. sodium metasilicate 10%.
~x. II Ex. IIIEx IV
magnesia sulphate: 31% 31% 34%
magnesia: 33% 33% 37.5%
perlite: 0% 15% 0%
synthetic ibres: 0% 0.5% 0%
calcium borate: 10% 5% 10%
wood flour: 4-5% 4% 4-5%
fluorspar 4% 4% 4%
sodium metasilicate: 10% 7.5% %

hydrated sodium carbonate and/or alkali metal or alkaline-earth 2n metal phosphate % % 10%
When coatings of this kind are exposed to heat or fireJ they behave ~n the following manner:
The internal temperature of the coating, instcad of increasing in the form of a continually growing curve, as would be expected, remains con-stant, for a period generally of several hours, at a temperature between 100 and 200C. This imparts to the coatings according to the invention extremely advantageous fire and heat-resistant properties.
The said temperature level cannot possibly be attributed to thermal : - 7 -~'.

;

insulation provided by the compon0nts o the coating; it is believed that it is due to the presence, with~n the coating, of an appreciable quantity of water of crystallization.
The release of this water of crystallization in fact requires the application of an amount of heat correspondina to the binding energy of water molecules and 540 kcal~kg to transform this free water into steam. Further-more, water released in the form of steam adds moisture ~o the atmosphere which aids in extinguishing the fire.
The temperature level at which this release of water occurs persists until all of the water of crystallization has been evaporated. Thus the time during which the temperature TemainS at this level is proportional to the amount of water of crystallization in the coating.
Cracking of the coa~ing, due to disintegration of the inorganic binder~ begins before all of the water of crystallization has been released.
At thls stage, the inorganic binder, which has now lost all oE the physical properties of a binder, is no longer capable of providing cohesion of the coat-ing. This is when calcination of the refractory particles occurs and assures a certain amount of cohesion, preventing the coating from becoming a dust.
Thanks to the fluxes (calcium borate and fluorspar)J the calcination b~gins at a temperature substantially between 850 and 900C, as a result the coating according to the invention provides protection against heat and fire up to temperature generally ln excess of 1200C.
The coating obtained with the composition according to Example I is ~ery hard and adheres very well to all supports, including glass. It should not, howsverJ be exposed to weathering. When exposed to fire, the temperature of these coatings remains constant at about 100C for between thirty minutes and six hours ~depending on their thickness), due to the water of crystalliza-tion they contain. Moreover, calcination of the inorganic particles ~perlite ~.`

~3~5~
or vermiculite), brought about by the fluxes ~calcium bora~e and fluorspar), allo~s the coating to remain cohesive up to temperatures well above 1000C.
Coatings in accordance with Examples II, III and IV are preferably used for finishing layers applied to existing coatings, such as mineral or asbestos sheets, for the purpose of improving mechanical properties.
It is also possible to obtain, with a magnesia cement, a coating having good acoustical-insulating properties, with substantical resistance to fire, by modifying the composition as follows:

magnesia chloride or magnesia sulphate with added magnesia: 26 to 60%

. perlite and/or vermiculite in grains of between 0 and 5 mm in diameter: 15 to 38%
. calcium borate and/or calcium carbonate3 to 0%
synthetic fibres: 28 to 0%
wood flour: 4 to 0%
fluorspar: 4 to 0.5%

sodium metasilicate and/or hydrated sodium carbonate and/or alkali metal or alkalin-earth metal phosphate: 20 to 1.5%
When the inorganic binder used is an aluminous cement of the Port-land type ~ordinary cement or NF 45 R white cement), the composition by weight of the coating according to the addition is as follows:
aluminous and/or Portland cement: 30 to 62%

inorganic particles ~for example perlite and/or vermiculite: 25 to 10%
carbonaceous materials: 0 to 2%
~ . cement-setting retardants or accelerators0 to 2%
.:
- . fluxes: 0 to 3.5%

. mineral and/or organic fibres: 40 to 0.5%

~ . compounds contributing or ~orming .- the water of crystallization: 5 to 20%.

~: _ g _ ,.

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1~30953 A few exa~ples of coating compounds having an aluminous or Portland I cement ~ase are given ~elow: ~.
Example V
. Portland cement: 29%
: . aluminous cement: 16% ~ :
fluorspar: 5%
. silica: 20% :
hydrated alumina: 20%
sodium metasilicate or alkali metal ::
or alkaline-earth metal phosphate: 10%
: 10 Ex. VIEx. VII
aluminous cement: 62% 50%
perlite: 10% 15%
vermiculite: 0% 10%
synthetic fibres: 0.5% 0.5%
~ood flour: 4% ~%
. fluorspar: 3.5% 2.5%
-~ . hydrated sodium`carbonate and/or alkali metal or alkaline-earth 17 5o~
metal phosphate: 20% . O
- Ex. VIII Ex IX
. aluminous cement: 20% 17%
~ Portland cemen~: 37% 29%
quick lime: 18% 14%
perlite: 20% 18%

2% 2%
:: . fluorspar:
- . ~ood flour: 3% 3%
hydrated sodium carbonate and/or : alkali metal or alkaline-earth 18%
metal phosphate:
, '''`'' - 10-:-~
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Ex. X Ex. XI Ex. XII
aluminous cement: 17.5% 0% 57.45%
Portland cement: 32% 58% 0%
quick or slaked lim0: 26.5% 0% 0%
perlite: 16% 5% 10%
vermiculite: 0% 10% 0%
synthetic -fibres: 0.5% 0.5% 0% ;-1uorspar: 3.5% 3.5% 3-5%
cement-setting retardants or accelerators: 0% 1% 0.045%
. wood flour: 4% 2% 4%
hydrated calcium carbonate and/or alkali metal or alkaline-earth metal phosphate: 0% 20% 0%
calcium carbonate: 0% 0% 25~
Coatings obtained with compositions according to Examples V to XII
are not as hard as those obtained with compositions according to Examples 1 to IV. They adhere well to plaster, cement and iron. Ater exposure to ire, they do not adhere quite as well as coatings with a magnesia-cement base, but the~ have better flre-resistance, due to the excellent calcination between the inorganic particles.
- 20 In this respect, the coating according to Example XII has the best performance.
Coatings according to Examples V to XIT may be exposed to weathering.
' Coatings according to Examples V to IX are best for delaying the in-crease in temperature during a fire since, during setting, they retain a maximal quantity of water of crystallization.
In the case o ordlnary Portland-type cements, slag cements, fused monocalcium-aluminate cements, artificial silicate tri- and boro-calcium ~ ' - 11 - ' '~', , ' .~' ' ' '~
~ ' ~3~

cements, and refractory cements having a high alumina content, the addition of the compound which provides the water of crystallizationJ especially in the case of alkali metal carbonate,accelerates appreciably the setting of these cements, which is a disadvantage when the coatings are b0ing appLied.
The Applicant has found that this disadvantage may be overcome b~
adding to the coating composition a setting-retardant consisting of borax ~sodium tetraborate) or boric acid.
In this connection, Exampl0 XIII is as follows:
. cement as specified above: 57%

. a powder charge ~perlite, vermiculite, expanded glass spheres and mixtures thereof): 15%
fluxes (colemanite and/or fluorspar): 5%

hydrated sodium carbonate ~water o crystallization): 20%
borax and/or boric acid: 3%.
When a coating of this kind 25 mm in thickness is exposed to a tem-peratur~ of 1050C ~as measured on one of its surfaces), after 60 minutes the temperature on the other surface scarcely reaches 110C.
The composition starts to set only 10 minutes after the constituants have been mixed.
In the case of magnesia cementsJ the setting time depends upon the fire-loss of the magnesia used therein. The setting time is optimal when the magnesia fire-loss is about 12-13%. Otherwise the setting is often too slow.
The Applicant has found that this disadvantage may be overcome by adding, to the composition of a magnesia cement containing any kind of magne-- sia, quick and/or slaked lime as a setting accelerator.
This is rapresented in Example XIV below:

.-:

~.~.3~S3 magnesia cement Cmagnesia chloride and/or sulphate with added magnesia~: 72%
perlite and~or vermiculite and/o~ expanded glass spheres and/or expanded polystyrene: 15%
carbonaceous materials (wood flour or the like): 3%
fluxes ~fluorspar and/or eolemanite): 5%
quick and/or slaked lime: 5%.
A composition of this kind begins to set after about 15 minutes.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coating for protecting structures against fire and heat, com-prising refractory particles coated with a cement and at least an inorganic compound adapted to provide the coating with a number of molecules of water of crystallisation larger than that normally obtained with the cement alone, the relative amount of said inorganic compound being comprised between 1.5 and 20%.

2. A coating according to claim 1, characterized in that it also contains particles of flux in an amount sufficient to ensure superficial cal-cination of the refractory particles at a temperature substantially between 850 and 900°C.

3. A coating according to claim 1, the cement consisting of an alum-inous or magnesia cement, characterized in that the said inorganic compound is selected from the following chemical compounds and mixtures thereof: hy-drated sodium carbonate, sodium metasilicate, and alkali metal or alkaline-earth metal phosphate.

4. A coating according to claim 3, characterized in that it has the following weight composition:

. magnesia cement (magnesia chloride and/or sulphate with added magnesia): 20 to 80%
. perlite and/or vermiculite and/or fillite: 10 to 0%
. calcium borate 0 to 10%
. synthetic fibres: 60 to 1%
. carbonacous materials (wood flour): 0 to 4%

. iron oxide: 0 to 0.2%
. fluorspar: 0 to 4%
. compound contributing water of crystallization (hydrated sodium carbonate and/or sodium meta-silicate and/or alkaline or alkaline-earth phosphate: 10 to 1.8%

5. A coating according to claim 3, characterized in that it has the following weight composition:
. magnesia chloride and/or sulphate, with added magnesia: 26 to 60%
. perlite and/or vermiculite in grains of between 0 and 5 mm in diameter: 15 to 38%
. calcium borate and/or calcium carbonate: 3 to 0%
. synthetic fibres: 28 to 0%
. wood f:Lour: 4 to 0%
. fluorspar: 4 to 0.5%
. sodium metasilicate and/or hydrated sodium carbonate and/or alkaline or alkaline-earth phosphate: 20 to 1.5%

6. A coating according to claim 3, characterized in that it has the following weight composition:
. aluminous cement and/or Portland cement: 30 to 62%
. inorganic particles (e.g. perlite, vermiculite): 25 to 10%
. carbonaceous materials: 0 to 2%
. cement-setting retardants or accelerators: 0 to 2%
. fluxes: 0 to 3.5%
. mineral and/or organic fibres: 40 to 0.5%
. compounds contributing or forming the water of crystallization: 5 to 20%

7. A coating according to claim 3 or 6, the cement being an ordinary cement, a monocalcium-aluminate cement, a silicate tri- and bi-calcium cement, or a refractory cement having a high alumina content, characterized in that it contains sodium tetraborate and/or boric acid as a cement-setting retardant.

8. A coating according to claim 3, the cement being a magnesia cem-ent, characterized in that it contains quick and/or slaked lime as a cement-setting accelerator.