FR2528822A1 - Mouldings for use in building etc. - made from natural earths mixed with geo-polymer binder contg. free sodium oxide or potassium oxide - Google Patents

Abstract

A mixt. is made contg. ferruginous-, lateritic-, mediterranean-, tropical-, and/or equatorial- earths. The mixt. is pressed into an object with a desired shape, e.g. a brick, and is then placed immediately in a non-ventilated chamber, at an ambient temp. below 45 deg.C, for setting or hardening by alkaline geopolymerisation, esp. using min. 2 h at 25 deg.C, or min 1 day at 40 deg.C. The alkaline geopolymerisation is pref. obtd. using a mixt. of clay contg. by wt. either 0.5-5% of free active Na2O, or 0.7-7% of free active K2O. Bricks etc. can be made which set and harden at a low temp. below 45 deg.C.

Description

The present invention relates to the use of ferruginous soils,
lteritics, ferrallitics, or associates encountered primarily
in the Mediterranean, tropical and equatorial regions, and
geologically equivalent regions of the earth, for man
use bricks or other objects that can be used in the building. We
uses the chemical consolidation reaction by constitution of a
Binder of the Geopolymer type obtained by reaction between the different constituents of these sols with at least one alkaline reagent producing
MaO or K20 free, then a hardening at room temperature, in
less than 450C.

These soils, which are generally referred to as the very "laterite", are rich in iron and aluminum sesquioxides such as goethite, hematite, gibbsite, and boemite.
general, based on hydrated alumino-silicates of the SiO 2 / Al 2 O 3 type = 2
(kaolinitic type) or SiO2 / A1203 = 4 (montmoritic type) or more.

In the regions of the globe where these soils are found, it is
general quite difficult to manufacture bricks by the methods of
traditional cooking, at high temperature to 9000C-11000C. The
The simplest method is simply to take these soils and
dry them in the air. This is the technique of the pisé, and the brick
dry in the sun, heavily used in most countries
Africa. A more elaborate process is to mix these soils with
artificial cement of the Portland type, and to make blocks or
bricks by hydraulic connection. The results start to be
satisfactory for quantities of cement not less than 400-450
kg s per m3, usually 500kgs per m3.We proposed to react
"laterite" soils with lime Ca (OH2), either using the
technique of the silico-limestone reaction in an autoclave, for example in
extrapolating the process described in French Patent No. 1,501,753 and
its certificate of addition No 2,092,936, that is to say according to
humid oven at 970C as described by T. RINGSHOLT and TC

HANSEN in the review "Ceramic Bulletin" Vol. 57, No. 5 (1978), page
150: Lateritic soil as a raw material for Building Blocks. In the
cited French patents, a material containing less than 50% is used
in weight of clay matrix, and 30% by weight of lime is added,
that is to say about 60% by weight relative to the clay matrix.

In the oven oven at 97 ° C., for a laterite soil containing
about 30% by weight of kaolinitic clay is added 17% by weight of lime, also about 60% by weight relative to the clay matrix. The products made in an autoclave are silico-aluminates of the CSH type, while the firing in a humid oven at 970 ° C. would result in the formation of a hydrated tricalcium aluminate of the C3AH6 type. The results obtained vary for compressive strength from 25 MPa for C3AH6 to 90 MPa for CSH.

Instead of using lime Ca (OH) 2, the clays can be reacted with caustic soda which produces free Na2O. Thus, German Patent No. 600,327 of May 28, 1932, describes a method of manufacturing objects from a clay reacted with caustic soda.
NaOH, with firing between 1500C and 500 ° C. The chemical constitution of this clay was: loss on ignition 8.25 / SiO 2: 51.55 / Fe 2 O 3: 8.55 / Al 2 O 3: 20.60 / MgO: 2.75 / Na2O: 5.20 / K20: 5.20 / SO3
: 1.35, ie a clay of the SiO 2 / Al 2 O 3 type equal to or greater than 4. The studies carried out by the Applicant show that when the SiO 2 / Al 2 O 3 molar ratio is greater than 2, the product of the reaction with caustic soda is on the one hand a silico-aluminate of the type of geopolymers Poly (sialate) called hydroxysodalite (Na 2 O, Al 2 O 3, 2SiO 2, 8H 2 O), with on the other hand important formation of sodium silicate. However, this sodium silicate migrates towards the surface, mobilizes a large part of free Na2O available for the poly (sialate) formation reaction, so that the products produced according to this system are not stable to water, in their entirety. .

As described in the publication "Preparation of Low Temperature Sodalite and Neosane from Phyllitic Minerals" French Group Bulletin of Clays, Volume XXII, pp. 5-16 (1970), by H.

BESSON, S. CAILLERE, S. HENIN, R.PROST, the clay materials that react well with soda hydroxysodalite Poly (sialate) formation are: kaolinite, halloysite, clays SiO2 / Al203 = 2 type montmorionnite, pyrophyllite, muscovite, SiO2 / Al203 clays = 4 or greater than 4 producing a sodium silicate that must be removed. The best seems to be obtained with kaolinite, as can be seen in the Soviet Patent No. 19.3335 of the Bulletin of Inventions No. 6.1967 and reported in the publication: "uncooked materials based on kaolin, for the apparent surfaces of buildings in Stroitelnye materialy ne10, 1970, page 22 by LG BERG, BA DEMIDENKO et al. With a molar ratio of Na 2 O / Al 2 O 3 equal to 0.6, ie approximately 19% relative to the weight of the kaolin matrix, a material having a compressive strength of 100 MPa is obtained after firing at 1500 ° C. for 4 hours. This way of working is however only valid for small thicknesses, indeed experience shows that cooking at this temperature, for objects thicker than 10 mm, leads. free Na20 migration from the inside to the outside of the object. These objects have skin, extremely hard but an interior made of clay that has not reacted and is destroyed with water.

 The method according to the invention is an unexpected development of the method of manufacturing objects for buildings, French Patent Application No. 80.203.86. It makes it possible to obtain the hardening of soils and clays at ordinary temperature or at most at a temperature equal to 45 ° C. In the traditional methods of manufacturing cooked bricks, the most delicate phase of manufacture is drying. Generally, this drying is carried out in the open air, with a well ventilated atmosphere to allow the moisture present in the clay mixture to evaporate without causing any crack. This drying phase is generally carried out at first to temperature generally below 45 ° C. Then the bricks are dried at higher temperature and put in cooking.

In the process described by the French patent application No. 80.203.86 and which is particularly suitable for raw materials coming from ferruginous, lateritic, tropical or equatorial soils, the hardening is carried out using an alkaline reagent. .

 It is first done by drying the soil to eliminate the maximum amount of water and facilitate the grinding. The alkaline reagent is added as a powder, usually accompanied by a mineral additive to correct the clay nature of the soil, and the soil + alkaline reagent mixture is ground to powder, for example in a hammer mill. This powder mixture can be stored for a long time if necessary. It is then moistened in a kneader, in order to obtain a semi-plastic paste, the amounts of water depending exclusively on the nature of each soil. This semi-plastic mixture is then allowed to mature for at least 24 hours, preferably at least 48 hours at a temperature below 450C, in an enclosed area.

After maturation the object is made to the press, for example to make a brick. This raw brick is then placed in an unventilated oven, preferably humidified, at a temperature of between 70 ° and 95 ° C., preferably 85 ° C., for at least one hour, preferably 2 hours. to a transformation or degradation of the aluminosilicates into sodium silico-aluminate gels which are the precursors of the polycondensation of the Poly (sialate) geopolymers of the hydroxysodalite.Na20 free type is thus fixed and no longer migrates.The products obtained after this parboiling already have acceptable mechanical characteristics to make bricks.When the clay matrix is of the type
If / 02 / A1203 = 2, the products cured at 85 ° C, are water-stable and can be used as they are in the building, the sodium silico-aluminates being fixed, the products can be subjected to posterior thermal, at higher temperatures.

 It was noted, however, that the optimum of the characteristics was obtained for firing temperatures between 370 ° C. and 5000 ° C., for at least one hour, preferably for 2 to 3 hours, depending on the thickness of the product.

Instead of placing the raw brick, as previously described directly in an unventilated oven heated to 85 ° C, it was inadvertently left in this unventilated oven for 3 days at a temperature of 25 ° C. The material had hardened and it was immersed in water. Unexpectedly, the brick did not deform.

This fact is all the more surprising since, as a rule, un-pressed semi-plastic powder mixtures which have been left (matured) for about 3 to 4 days in a plastic bag, at an ambient temperature of about 25 ° C., these semi-solid mixtures -plastic can be compressed to make a brick, but this brick is not stable with water just after pressing.It seems therefore that the phase of maturation at room temperature has a totally different action on the kinetics of geopolymerisation'des argillaceous materials, depending on whether the clays were compressed or not.An explanation of this phenomenon could be the change in alkali concentration, intermiclllll water in the clay, that is to say an identical phenomenon or close to During the unconfined phase, the alkaline reagent migrates and occupies certain free A1 / OH3 functional groups located on the outer surface of the clay a large quantity of intermicellar water. The compression brings the crystallites closer together, expels part of the free-cellular water which is free and is lodged in the macropores. We then witness the possibility of geopo-lyxerization reaction according to the following scheme ::

Clay <SEP> (OH) 3 <SEP> Na + <SEP> OH "
<tb><SEP> ~~~~~~~~~~~~ <SEP> Clay <SEP> (OH) <SEP> 4
<tb><SEP> K <SEP> OH <SEP> (Na +)
<tb><SEP> (K +)
<tb> Clay <SEP> (OH) <SEP> 4 <SEP> + <SEP> q (OH) <SEP> Clay <SEP> - <SEP> Clay-O-Clay <SEP> + <SEP> H20
<tb><SEP> (Na +) <SEP> (Na +) <SEP> (Na +) <SEP> (Na +)
<tb><SEP> (K +) <SEP> (K +) <SEP> (K +) <SEP> (K +)
<Tb>
The following examples help to better understand the inventi
and illustrate the different manufacturing possibilities. The
clay material used in these examples belongs to the category
kaollnic lateritic clays. He is known as
"Flint d'OlliAre", located in the south of France, near Provence
deposits of bauxite.This material contains between 20 and 40%
weight of kaolinite, for 5 to 15% of goethite, 5 to 15% of gibbsite and
20 to 40% quartz and other rock materials. IT corresponds to the
classification of clays of "laterite" type.

Example I:
The following mixture is produced: To 1 kg of flint containing 5% of moisture, 10% by weight of Geopoly KA reagent and 7% by weight of water are added. Geopoly reagent
KA commercialized by the company CORDI SA / France, contains 30% by weight
K20 free, active at low temperature, ie the mixture
thus achieved contains 2.9% of active free K20. We pour the mixture
in a waterproof plastic bag and let it ripen for 24
hours, at room temperature 25 ° C. This mixture is then tested for
following way: we shape small rings using a mold,
known in the ceramic profession, to make the rings of
fusion of ceramics cooked at high temperature.These rings weigh
10 grams, and can give excellent indications on the
physical and mechanical properties. One ring of 10 grams is made with the matured mixture for 24 hours and quenched in water immediately. The ring disintegrates instantly. Several rings of 10 grams are made with the same mixture, matured for 24 hours, and stored in a sealed plastic bag at room temperature. Every 24 hours a ring will be placed in water to note the moment when it will not disintegrate any more. In parallel, the mixture always kept in its waterproof bag, will also be tested, by the making of a ring.

With the reagent Geopoly KA of this Example I, the ring becomes stable with water after 48 hours, while the mixture remained in the bag, disintegrates, even after one month of storage.

Example I1:
According to the technique described in Example I, a new mixture comprising 6% by weight of Geopoly NA reagent of the Company is produced.
CORDI SA / France. Geopoly NA reagent contains 33XO of free active Na2O, ie 2% by weight of free active Na2O, in the mixture. After a 24-hour maturation, the ring-making operation is repeated as described in Example I. The ring becomes stable with water also after 48 hours, while the mixture remains in the bag, disintegrates, even after a month of storage.

 The progression in time of the mechanical strengths of the samples made according to examples I and II is then measured, the rings remaining in a sealed plastic bag: the compressive strength is measured.

Compressive strength
Geopoly KA Geopoly NA after 3 days 4.1 MPa 4.8 MPa after 15 days 7.9 MPa 8.5 MPa after 45 days 7.7 MPa 8.4 MPa
The rings obtained with the mixtures of Examples I and II are placed at different temperatures to determine the kinetics of the curing and polycondensation of the water-stable poly (sialate).

At 40 ° C, the rings containing either Geopoly NA or Geopoly KA are water-stable after 24 hours, whereas at 50 ° C the reaction becomes very fast, since this stability is already acquired at 2 hours 30 minutes. The critical threshold seems to be around 45 ° C.

 The invention therefore makes it possible to manufacture, at room temperature, less than 450 ° C., objects, bricks or similar materials, stable with water, from soils or clay materials belonging to the categories ferruginous, lateritic, ferralitic soils, or associates.

The geopolymerization reaction of the preferred kaolinitic argillaceous material is used with alkaline caustic reagents.

 the amount of alkaline reagent required to obtain a water-stable brick depends on the mineralogical nature of the soils and clay materials. Experience shows that good results are obtained for mixtures containing between 0, 5% and 5% by weight, preferably between 1.0% and 3.5% by weight of Na 2 O, or between 0.7% and 7% by weight, preferably between 1.5% and 4.5% by weight of K20.

 The sealed plastic bag in which were placed the rings in Examples 1 and 2, is actually a non-ventilated enclosure, in which there is no drying. This enclosure can have all dimensions, it being understood, that a control of the ambient humudity, will be necessary, to ensure the progress of the alkaline geopotymérisation.

 Of course, various modifications may be made by those skilled in the art to the process and compositions which have just been described by way of example, without departing from the scope of the invention.

Claims (6)

claims:  1) Method of manufacturing objects for the building using ferruginous, lateritic, ferrallitic, Mediterranean, tropical, equatorial soils, by alkaline geopolymerization, characterized in that the object is manufactured by pressing and then placed immediately in an unventilated chamber, at room temperature, lower, at 45 ° C. 2) Process according to 1 characterized in that the object obtained by pressing is placed immediately, for at least 2 days, in a non-ventilated enclosure, at room temperature of 25 "C. 3) Method according to 1, characterized in that the object obtained by pressing is placed immediately, for at least 1 day in a non-ventilated enclosure, at room temperature of 40 "C. 4) Process according to any one of claims 1, 2 or 3, characterized in that said alkaline geopolymerization is obtained with a mixture of clay soil containing between 0.5% and 5% by weight of free active Na2O. 5) Process according to any one of claims 1, 2 or 3, characterized in that said alkaline geopolymerization is obtained with a clay mixture containing between 0.7% and 7% by weight of free active K20. 6) Product in all forms and in any dimensions obtained according to any one of claims 1, 2, 3, 4 or 5.