Poaceae fibres and building products

Abstract

Chemically modified unpyrolyzed Poaceae fibres having a length of less than 200 mm advantageously comprised between 2 and 100 mm, such as between 2 and 10 mm, said fibres having a water content of less than 40% by weight, and being treated with a treating aqueous dispersion comprising less than 1% by weight of surface treating mixture comprising at least a silanol terminated polydimethylsiloxane, as well as an amino coupling agent.

Claims

1. Chemically modified unpyrolyzed ageing resistant fibers selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, said fibers having a length comprised between 2 and 100 mm, said ageing resistant fibers having a water content of less than 20% by weight, said ageing resistant fibers having a coating obtained by contacting initial fibers with a treating aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising (a) OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, and (b) an amino coupling agent, and drying said initial fibers contacted with the said treating aqueous dispersion; whereby said coating of said ageing resistant fibers comprises at least (a) aminosilane bound to silicon atoms present in said ageing resistant fibers and (b) polydimethylsiloxane bound to aminosilane group via a silanol group, whereby the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of said surface treating mixture is comprised between 5:1 and 20:1, wherein said ageing resistant fibers keeping during a storage period for 6 months in an air environment having a temperature of about 20° C. and a relative humidity of 50%, an alkali resistance in a 1 N NaOH solution for at least 28 days of more than 92%, in which said ageing resistant fibers after complete burning at 600° C. have an ash characterised by a SiO.sub.2 weight content comprised between 41% and 70% and a K.sub.2O weight content comprised between 4% and 24%, while the SiO.sub.2+K.sub.2O weight content of said ash is comprised between 68% and 85%.

2. The ageing resistant fibers of claim 1, in which in dry form, 98% by weight of said ageing resistant fibers have a length comprised between 2 and 10 mm.

3. The ageing resistant fibers of claim 1, in which said amino coupling agent is an amino silane coupling agent.

4. The ageing resistant fibers of claim 1, in which said amino coupling agent is an aminoethyl aminopropyl trimethoxysilane.

5. The ageing resistant fibers of claim 1, in which said surface treating mixture further comprises a polyethylene glycol ether.

6. The ageing resistant fibers of claim 5, in which said polyethylene glycol ether is a polyethylene glycol trimethylnonyl ether.

7. The ageing resistant fibers of claim 1, in which said treating aqueous dispersion comprises an alcohol.

8. The ageing resistant fibers of claim 7, in which said alcohol is ethanol.

9. The ageing resistant fibers of claim 1, wherein said ageing resistant fibers comprise Miscanthus fibers, whereby, before being treated with said treating aqueous dispersion, said Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterized by a SiO.sub.2 content higher than 30% by weight, whereby said fresh Miscanthus fibers after being treated with said treating aqueous dispersion and after being dried, are treated fibers enriched in silicon, so that, after complete burning at 600° C., the ash of said treated fibers enriched in silicon comprises more than 40% by weight SiO.sub.2.

10. The ageing resistant fibers of claim 1, in which said ageing resistant fibers comprise Miscanthus fibers, whereby, before being treated with said treating aqueous dispersion, said Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterised by a SiO.sub.2 content higher than 30% by weight, whereby said fresh Miscanthus fibers after being treated with said treating aqueous dispersion and after being dried, are treated fibers enriched in silicon, so that, after complete burning at 600° C., the ash of said treated fibers enriched in silicon comprises from 55 to 70% by weight SiO.sub.2.

11. The ageing resistant fibers of claim 10, in which before being treated with said treating aqueous dispersion, said Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterized by a SiO.sub.2 content comprised between 30 and 40% by weight.

12. The ageing resistant fibers of claim 1, in which said ageing resistant fibers have a TFSAI (MW) and (V) in 1N NaOH solution of more than 1.1 after at least 7 days soaking.

13. The ageing resistant fibers of claim 1, which comprises in dry matter less than 2% by weight of fibers or particles with a size or length of less than 2 mm.

14. The ageing resistant fibers of claim 1, in which in dry form, more than 98% by weight of said ageing resistant fibers have a length comprised between 2 mm and 6 mm.

15. The ageing resistant fibers of claim 1, in which after complete burning at 600° C., the ash of treated fibers corresponds to 3 to 4% by weight of dried treated fibers before their burning, said ash being characterised by a SiO.sub.2 weight content comprised between 57% and 70% and by a SiO.sub.2+K.sub.2O weight content comprised between 70% and 78%.

16. The ageing resistant fibers of claim 1, in which said ageing resistant fibers comprise treated Miscanthus fibers, in which after complete burning at 600° C., the ash of said treated fibers corresponds to 3 to 3.2% by weight of dried treated fibers before their burning, said ash being characterised by a SiO.sub.2 weight content comprised between 57% and 60% and by a SiO.sub.2+K.sub.2O weight content comprised between 70% and 78%.

17. A dry binder mix which is ready to use after addition of water, said mix comprising at least (A) a silicon containing hydraulic binder and (B) chemically modified unpyrolyzed ageing resistant fibers selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, said ageing resistant fibers having a length comprised between 2 and 100 mm, said ageing resistant fibers having a water content of less than 20% by weight, said ageing resistant fibers having a coating obtained by contacting initial fibers with a treating aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising (a) OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, and (b) an amino coupling agent, and drying said initial fibers contacted with said treating aqueous dispersion; whereby said coating of said ageing resistant fibers comprises at least (a) aminosilane bound to silicon atoms present in said ageing resistant fibers and (b) polydimethylsiloxane bound to aminosilane group via a silanol group, whereby the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of the surface treating mixture is comprised between 5:1 and 20:1, wherein said ageing resistant fibers keeping during a storage period for 6 months in an air environment having a temperature of about 20° C. and a relative humidity of 50%, an alkali resistance in a 1 N NaOH solution for at least 28 days of more than 92%, in which said ageing resistant fibers after complete burning at 600° C. have an ash characterised by a SiO.sub.2 weight content comprised between 41% and 70% and a K.sub.20 weight content comprised between 4% and 24%, while the SiO.sub.2+K.sub.2O weight content of said ash is comprised between 68% and 85%.

18. The mix of claim 17, in which in dry form, more than 98% by weight of said ageing resistant fibers have a length comprised between 2 mm and 10 mm.

19. The mix of claim 17, in which said amino coupling agent is aminoethyl aminopropyl trimethoxysilane.

20. The mix of claim 17, in which said ageing resistant fibers are chemically modified unpyrolyzed Miscanthus fibers, whereby, before being treated with said treating aqueous dispersion, said Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterised by a SiO.sub.2 content higher than 30% by weight, whereby said fresh Miscanthus fibers after being treated with said treating aqueous dispersion and after being dried, are treated fibers enriched in silicon, so that, after complete burning at 600° C., the ash of the treated fibers enriched in silicon comprises from 55 to 70% by weight SiO.sub.2.

21. The mix of claim 20, in which before being treated with said treating aqueous dispersion, the Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterised by a SiO.sub.2 content comprised between 30 and 40% by weight.

22. The mix of claim 17, in which in dry form, more than 98% by weight of said ageing resistant fibers have a length comprised between 2 mm and 6 mm.

23. The mix of claim 17, in which after complete burning at 600° C., the ash of said ageing resistant fibers corresponds to 3 to 4% by weight of dried chemically unpyrolyzed fibers before their burning, said ash being characterised by a SiO.sub.2 weight content comprised between 57% and 70% and by a SiO.sub.2+K.sub.2O weight content comprised between 70% and 78%.

24. The mix of claim 1, in which said ageing resistant fibers are chemically modified unpyrolyzed Miscanthus fibers, in which after complete burning at 600° C., the ash of said ageing resistant fibers corresponds to 3 to 3.2% by weight of said dried chemically modified unpyrolyzed fibers before their burning, said ash being characterised by a SiO.sub.2 weight content comprised between 57% and 60% and by a SiO.sub.2+K.sub.2O weight content comprised between 70% and 78%.

25. A building product comprising at least a part or layer comprising a hardened silicon containing hydraulic binder containing chemically modified unpyrolyzed ageing resistant fibers selected from the group consisting of Miscanthus like species, Pennisetum species, Zea species and mixtures thereof, wherein said ageing resistant fibers having a length comprised between 2 mm and 100 mm, said ageing resistant fibers having a water content of less than 20% by weight, said ageing resistant fibers having a coating obtained by contacting initial fibers with a treating aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising (a) OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, and (b) an amino coupling agent, and drying said initial fibers contacted with said treating aqueous dispersion; whereby said coating of said ageing resistant fibers comprises at least (a) aminosilane bound to silicon atoms present in the fibers and (b) polydimethylsiloxane bound to aminosilane group via a silanol group, whereby the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of said surface treating mixture is comprised between 5:1 and 20:1, the said ageing resistant fibers keeping during a storage period for 6 months in an air environment having a temperature of about 20° C. and a relative humidity of 50%, an alkali resistance in a 1 N NaOH solution for at least 28 days of more than 92%, in which said ageing resistant fibers after complete burning at 600° C. have an ash characterised by a SiO.sub.2 weight content comprised between 41% and 70% and a K.sub.20 weight content comprised between 4% and 24%, while the SiO.sub.2+K.sub.2O weight content of said ash is comprised between 68% and 85%.

26. The building product of claim 25, whereby said hardened silicon containing hydraulic binder is a calcium based hydraulic binder.

27. The building product of claim 26, in which before hardening, said calcium based hydraulic binder is mixed with water comprising less than 0.5% by weight of a mixture comprising (a) a polydiethoxysiloxane, and (b) a silane compound selected from the group consisting of butyl triethoxysilane, octyl triethoxysilane and mixture thereof.

28. The building product of claim 27, in which said polydiethoxysiloxane is selected from the group consisting of fluoro alkyl polydiethoxysiloxanes, whereby the alkyl group comprises 1 to 10 carbon atoms.

29. The building product of claim 25, in which said amino coupling agent is aminoethyl aminopropyl trimethoxysilane.

30. The building product of claim 25, in which said ageing resistant fibers are chemically modified unpyrolyzed Miscanthus fibers, whereby, before being treated with the treating aqueous dispersion, said Miscanthus fibers are selected from fresh Miscanthus fibers having after complete burning at 600° C. an ash characterised by a SiO.sub.2 content comprised between 30% and 40% by weight, whereby said fresh Miscanthus fibers after being treated with said treating aqueous dispersion and after being dried, are treated fibers enriched in silicon, so that, after complete burning at 600° C., the ash of said chemically modified unpyrolyzed Miscanthus fibers corresponds to 3 to 3.2% by weight of said dried chemically modified unpyrolyzed Miscanthus fibers before their burning, said ash of said dried chemically modified unpyrolyzed Miscanthus fibers being further characterised by a SiO.sub.2 weight content comprised between 55% and 60% and by a SiO.sub.2+K.sub.20 weight content comprised between 70% and 78%.

31. The building product of claim 25, in which in dry form, more than 98% by weight of said ageing resistant fibers have a length comprised between 2 mm and 10 mm.

32. A method for the preparation of a building product, said method comprising at least the steps of: (1) mixing together at least (A) chemically modified unpyrolyzed ageing resistant fibers selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, said ageing resistant fibers having a length comprised between 2 and 100 mm, said ageing resistant fibers having a water content of less than 20% by weight, said ageing resistant fibers having a coating obtained by contacting initial fibers with a treating aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising (a) OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, and (b) an amino coupling agent, and drying said initial fibers contacted with said treating aqueous dispersion; whereby said coating of said ageing resistant fibers comprises at least (a) aminosilane bound to silicon atoms present in said ageing resistant fibers and (b) polydimethylsiloxane bound to aminosilane group via a silanol group, whereby the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of said surface treating mixture is comprised between 5:1 and 20:1, wherein said ageing resistant fibers keeping during a storage period for 6 months in an air environment having a temperature of about 20° C. and a relative humidity of 50%, an alkali resistance in a 1 N NaOH solution for at least 28 days of more than 92%, in which said ageing resistant fibers after complete burning at 600° C. have an ash characterised by a SiO.sub.2 weight content comprised between 41% and 70% and a K.sub.2O weight content comprised between 4% and 24%, while the SiO.sub.2+K.sub.2O weight content of said ash is comprised between 68% and 85%, (B) a hardenable calcium containing hydraulic binder, and (C) water, to form a hardenable fibers containing mixture; and (2) hardening said hardenable fibers containing mixture at a temperature greater than 20° C.

33. The method of claim 32, which further comprises the step of: shaping said hardenable fibers containing mixture to form a shaped hardenable fibers containing mixture, before hardening said shaped hardenable fibers containing mixture at a temperature comprised between 100° C. and 250° C. and under a pressure of 3×10.sup.5 and 20×10.sup.5 Pa for at least 60 minutes.

34. A method for preparation of chemically modified unpyrolyzed ageing resistant fibers selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, said ageing resistant fibers having a length comprised of between 2 mm and 100 mm, said ageing resistant fibers having a water content of less than 20% by weight, said ageing resistant fibers having a coating obtained by contacting initial fibers with a treating aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising (a) OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, and (b) an amino coupling agent, and drying said initial fibers contacted with said treating aqueous dispersion down to a water content of less than 20% by weight; whereby said coating of said ageing resistant the fibers comprises at least (a) aminosilane bound to silicon atoms present in said ageing resistant fibers and (b) polydimethylsiloxane bound to aminosilane group via a silanol group, whereby the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of the surface treating mixture is comprised between 5:1 and 20:1, wherein said ageing resistant fibers keeping during a storage period for 6 months in an air environment having a temperature of about 20° C. and a relative humidity of 50%, an alkali resistance in a 1 N NaOH solution for at least 28 days of more than 92%, in which said ageing resistant fibers after complete burning at 600° C. have an ash characterised by a SiO.sub.2 weight content comprised between 41% and 70% and a K.sub.20 weight content comprised between 4% and 24%, while the SiO.sub.2+K.sub.2O weight content of said ash is comprised between 68% and 85%, said method comprising at least the following steps: determining, after complete burning at 600° C., an average SiO2 content of the ash of at least one sample of fresh fibers containing plant parts from plants selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, intended to be harvested, in case the determined average SiO.sub.2 content of said ash of said at least one sample of fresh fibers containing plant parts from plants selected from the group consisting of Miscanthus species, Pennisetum species, Zea species and mixtures thereof, is greater than 30% by weight, harvesting fresh fibers containing plant parts; cutting said fresh fibers containing plant parts into plant fibers with a length comprised between 2 mm and 100 mm; drying said cut plant fibers at a temperature of less than 75° C., so as to obtain dried plant fibers with a water content of less than 20% by weight; treating said dried plant fibers with an aqueous dispersion comprising less than 1% by weight of a surface treating mixture comprising OH terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000, an aminosilane coupling agent, and a polyethylene glycolether, in which the weight ratio between said OH-terminated silanol terminated polydimethylsiloxane having a molecular weight comprised between 200 and 1000 and said amino silane coupling agent of the surface treating mixture is comprised between 5:1 and 20:1, so as to obtain humid coated plant fibers; drying of said humid coated plant fibers for obtaining said ageing resistant fibers with a water content of less than 20% by weight.

35. The method of claim 34, which comprises a step of cutting said fresh fibers into cut plant fibers with a length of less than 10 mm, and a step for removing from said cut plant fibers, said cut plant fibers with a length of less than 2 mm, so as to obtain cut plant fibers characterised by a weight content of fibers with a length of 2 mm to 10 mm greater than 98%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a partial perspective view of an embodiment of a noise insulating and fire-resistant wall of the invention;

(2) FIG. 2 is a partial cross section view of the wall of FIG. 1, and

(3) FIG. 3 is a schematic view showing fibres of the invention attached the one to the other by a hydraulic binder.

DESCRIPTION OF EXAMPLES AND EMBODIMENTS

(4) 1. Preparation of Miscanthus Fibres of the Invention, as Preferred Poaceae Fibres

(5) Before harvesting Miscanthus plant (Miscanthus sinensis species), the silicon content and water content thereof were controlled.

(6) The harvesting was operated in April, when the plant had a water content of less than 15% by weight and a SiO.sub.2 content in the ash (of plant completely burn at 600° C.) of more than 35% by weight. The so harvested Miscanthus fibres had a high weight carbon content, such content measured on dry matter was greater than 40% by weight (such as between 45 and 55%), meaning Miscanthus plants are good CO.sub.2 sequester.

(7) The harvested Miscanthus plant were during the harvesting cut in fibres with a weight average length of about 5 mm Particles and fibres with a size of less than 2 mm were removed from the fibres. The harvested and cut Miscanthus plant is preferably not submitted to a grinding step.

(8) The cut Miscanthus fibres were placed in a mixing trommel associated to a spray system for spraying on the Miscanthus fibres an aqueous composition containing: 0.5% by weight alcohol (ethanol) 0.5% by weight of OH terminated silanol terminated polydimethylsiloxane with an average molecular weight comprised between 200 and 500; 0.05% by weight aminoethyl aminopropyl trimethoxysilane; and 0.1% by weight polyethylene glycol trimethylnonyl ether.

(9) Said treatment is operated at room temperature (20° C.) and at atmospheric pressure (1 bar).

(10) The amount of aqueous dispersion added was sufficient so that the treated Miscanthus fibres had a SiO.sub.2 content in the ash (after complete burning at 600° C.) of more than 45%, such as more than 55%.

(11) After complete burning at 600° C., the ash composition of the so treated fibres was the following: Ash content: about 3.2% of the weight of the treated Miscanthus fibres before burning Silicon content (as SiO.sub.2): about 57-58% by weight Potassium content (as K.sub.2O): about 18-20% by weight Phosphor content (as P.sub.2O.sub.5): about 5% by weight Calcium content (as CaO): about 5% by weight Magnesium content (as MgO): about 5% by weight

(12) The treated Miscanthus fibres (referenced as Misc. Fib. in the examples) were dried (with hot air at 60-80° C.) so that their water weight content was less than 10% (comprised between 5 and 8% by weight).

(13) The treated Miscanthus fibres (Misc. Fib.) were stored in an open room with a relative humidity level of 50% and a temperature of 20° C.

(14) After one month storage, no insect attacks, nor fungus development were observed. It seems that the treatment of Miscanthus fibres provided to the fibres some extra properties against insects and fungus development. After 6 months storage and even after one year storage, no insect attacks, nor fungus development were observed.

(15) Some of the treated Miscanthus fibres were further milled into a powder (with micro fibres) with a size of less than 1 mm, such as comprised between 100 and 500 μm. Said powder was stored in closed container.

(16) After two months storage, as well after 1 year storage, no fungus development was observed on the powder, although untreated Miscanthus powder is an excellent medium for the growth of fungi and bacteria.

(17) Coated Miscanthus fibres (as preferred example of fibres of the invention) and fresh Miscanthus fibres (not provided with the coating) have been tested according to Norm EN 350 in order to measure the durability of the fibres against fungi. After two months testing, the weight reduction for the coated fibres of the invention was less than 5% (with respect to the weight of the coated fibres before testing), while said weight reduction for the fresh cut fibres (not coated) was higher than 20% (with respect to the weight of the fresh cut fibres before testing). According to said norm EN 350, the fibres of the invention (coated Miscanthus fibres) have a durability level of 1 on a scale of 1 to 5, meaning substantially no weight loss after a six months testing period.

(18) The so achieved chemically modified Miscanthus fibres of the invention with a weight average length of about 5 mm, as well as in powder form, had polyvalent silicon content of more than 1% by weight, a Zero-Span Stability Ratio in 1N NaOH (for up to 28 days) of more than 92%, and a treated fibre alkaline resistance, as well as a stability improvement ratio (TFSAI (V) and (MW)) of more than 1.1 (after soaking time of 28 days in 1N NaOH).

(19) In the same way, as further preferred examples of Poaceae fibres, fibres from Pennisetum-like species (such as Pennisetum purpureum, also known as Elephant grass, Pennisetum clandestinum also known as Kikuyu grass), and Zea-like species (such as Zea mays species, Zea mexicana species) were treated in similar way than for the Miscanthus fibres.

(20) Ash content and ash composition of said treated further examples of Poaceae fibres were the following: Ash content: more than about 3.1-3.3% of the weight of the treated Poaceae fibres before burning at 600° C. Silicon content (as SiO.sub.2): about 57-60% by weight for Pennisetum purpureum and Pennisetum clandestinum species, and about 65 to 70% for the Zea mays species and the Zea mexicana species. Potassium content (as K.sub.2O): about 9-10% by weight for Pennisetum species and about 4-5% by weight for the Zea species Calcium content (as CaO): about 8-11% by weight Magnesium content (as MgO): less than about 3% by weight

(21) The so treated fibres belonging to the Poaceae family had similar storage property and stability properties, as for the treated Miscanthus fibres.

(22) When treating fresh Miscanthus fibres only with aminosilane or only with OH terminated silanol terminated polydimethylsiloxane, the so treated Miscanthus fibres had reduced storage property. It seems that the said combination amino silane with OH terminated silanol terminated polydimethylsiloxane has a synergistic effect on the storage, enabling to keep or maintain mechanical and chemical property of the fibre for storage period of more than 6 months and even more than 1 year.

(23) 2. Examples of Use of Treated Poaceae Fibres Such as Miscanthus Fibres, Pennisetum Fibres and Zea Fibres in Building Products

(24) The herebelow disclosed examples is described specifically with treated Miscanthus fibres.

(25) A. Bricks or Panels

(26) A1. Concrete Blocks or Bricks

(27) For the preparation of said blocks, various hydraulic binders can be used. However, alumino silicate rich hydraulic binders are preferred. The hardening can be operated at room temperature and atmospheric pressure, but is advantageously operated at a temperature of 100° C. to 200° C. (such as 150° C.-180° C.) and under pressure, so as to accelerate the hardening of the bricks. The hardening time can vary, but can be highly reduced when using temperature of 150° C.-180° C.

(28) A first hydraulic binder (given as example only, referenced as H.B. 1 in the example) was achieved by dry mixing 15 kg Portland cement, 15 kg quick lime, 70 kg silica sand and 100 g alumina powder.

(29) Said first hydraulic binder will be mixed with about 60 litres water per 100 kg binder.

(30) A second hydraulic binder was a mix of 30% by weight of Portland cement (average composition comprising by weight: 11% Ca.sub.3Al.sub.2O.sub.5; 66% Ca.sub.3SiO.sub.5; 13% Ca.sub.2SiO.sub.4 and 3.7% SO.sub.3) and sulfo alumino cement (average composition comprising by weight: 10.4% Ca.sub.2SiO.sub.4; 64.2% Ca.sub.4(AlO.sub.2).sub.6SO.sub.4; 2.4% CaO,7Al.sub.2O.sub.3; 2.9% CaSO.sub.4).

(31) Said second hydraulic binder will be mixed with about 100 litres water per 100 kg binder.

(32) A first aqueous siloxane/silane dispersion or emulsion (referenced as Disp 1) for improving the water repellence of the product was prepared by mixing together: 3 parts by weight of polysiloxane with units having the following average empirical formula: CH.sub.3Si(OC.sub.2H.sub.5).sub.0.8O.sub.1.1, with an average molecular weight of 600-700 g and a kinetic viscosity of about 20 mm.sup.2/s (dynamic viscosity of less than 20 mPa.Math.s), 60 parts by weight of isooctyltriethoxysilane, 20 parts by weight isobutyltriethoxysilane, 0.5 part by weight ethanol, water for achieving in total 100 parts by weight. Said first siloxane/silane dispersion is intended to be added to the water at a rate of 0.5 kg per 100 kg water to be mixed with the hydraulic binder.

(33) A second aqueous siloxane/silane dispersion or emulsion (referenced as Disp 2) for improving the water repellence of the product was prepared by mixing together: 1 part by weight of polysiloxane with units having the following average empirical formula: (CH.sub.3).sub.1.2Si(OC.sub.2H.sub.5).sub.1.8O.sub.0.5, with an average molecular weight of 900-1000 g and a viscosity of about 20 mm.sup.2/s (dynamic viscosity of less than 20 mPa.Math.s), 1 part by weight of polysiloxane with units with the empirical formula: NH.sub.2(CH.sub.2).sub.5Si(OC.sub.2H.sub.5).sub.0.8O.sub.1.1 with an average molecular weight of 600-700 g and a kinetic viscosity of about 20 mm.sup.2/s and a dynamic viscosity of less than 20 mPa.Math.s, 1 part by weight of polysiloxane with units having the average empirical formula (CF.sub.3(CF.sub.2).sub.5).sub.1.2Si(OC.sub.2H.sub.5).sub.1.8O.sub.0.5 with an average molecular weight of about 900-1000 g and a kinetic viscosity of about 20 mm.sup.2/s and a kinetic viscosity of less than 20 mPa.Math.s, 70 parts by weight of N-octyltriethoxysilane, 0.5 part by weight ethanol, and water for achieving in total 100 parts by weight.

(34) Said second siloxane/silane dispersion is intended to be added to the water at a rate of 0.5 kg per 100 kg water to be mixed with the hydraulic binder.

(35) The dry binder will be mixed with the treated miscanthus fibres. The weight rate of Miscanthus fibres/dry binder is 10%, 25%, 50%.

(36) After said dry mixing, water (with or without added siloxane/silane dispersion) is added progressively to the mix of binder-miscanthus fibres.

(37) The following table gives composition of manufactured bricks, as well as details of processing steps.

(38) TABLE-US-00001 Misc. Time Brick Fib H.B. Disp Water Hours Temp Press. No. kg 1/2 0/1/2 liter or days ° C. 10.sup.5 Pa 1 100 1 0 60 28 days room room 2 100 1 1 60 12 hours 180 10 3 100 1 2 60 12 hours 180 10 4 100 2 0 100 28 days room room 5 100 2 1 100 12 hours 180 10 6 100 2 2 100 12 hours 180 10 7 50 1 1 130 12 hours 180 10 8 50 2 2 160 12 hours 180 10 9 200 2 2 160 12 hours 180 10 Misc. Fib: quantity of treated Miscanthus fibres with a length (average in weight) of about 5 mm added per 100 kg hydraulic binder H.B.: hydraulic binder H.B. 1 or H.B. 2 Disp 0: No dispersion added Disp 1: first dispersion added at a rate of 0.5 kg per 100 kg or liter water. Disp 2: second dispersion added at a rate of 0.5 kg per 100 kg or liter water Water: volume water added per 100 kg binder Time: hardening time in days or hours Temp: temperature for the hardening (room = room temperature or 20° C.) Press: pressure during the hardening (room = atmospheric pressure)

(39) The bricks (in the shape of cube of 10 cm edge) were shaped in a cubic mould, the lateral sides thereof and the bottom thereof were provided with a thin layer of hydraulic binder without Miscanthus fibres of about 0.5 cm. After completing the filing of the mould, a top layer of hydraulic binder without Miscanthus fibres was added.

(40) After hardening and cooling, the bricks were tested. It was observed that the bricks had the followings properties: good thermal insulation, good acoustic insulation, lightweight material, good fire resistance, low water/humidity absorption, compressive strength of more than 2.5 MPpa good resistance against insects/fungi attacks (especially when using Disp ½)
A.2 Panels

(41) Panels were shaped by using the mix of bricks 2, 3 and 5 to 9.

(42) A first layer of the mix hydraulic binder/water/disp 1 or 2 was deposited on a fabric or tissue or a porous paper sheet. Said first layer had a thickness of 2 to 5 mm.

(43) On said bottom layer, a layer (with a thickness comprised between 1 and 5 cm) of the mix 2, 3 and 5 to 9 was deposited.

(44) Thereafter a top coat was deposited with the mix hydraulic binder/water/disp 1 or 2.

(45) The so shaped panel was put in an oven at a temperature of 180° C. for 12 hours.

(46) After hardening and cooling, the panels had the followings properties: good thermal insulation, good acoustic insulation, lightweight material, good fire resistance, low water/humidity absorption, compressive strength of more than 2.5 MPa good resistance against insects/fungi attacks (especially when using Disp ½)

(47) The miscanthus fibres can be used as filler in concrete, and can be added to hydraulic binder with sand, water and aggregates. The content of treated miscanthus fibres with respect to the weight content of hydraulic binder will depend of the desired properties.

(48) Specific examples of panel of the invention are noise insulating and fire resistant walls, as disclosed in FIGS. 1 and 2.

(49) The noise insulating wall 1 of FIG. 1 comprises three distinct porous layers 10,11,12 containing coated Miscanthus fibres of the invention, each layer having a thickness of at least 6 cm, as well as a wood covering 15.

(50) The outer layer 12 containing coated Miscanthus fibres is provided with vertical protuberances 12A, whereby said porous layer has an outer developed are of 2 to 3 m.sup.3 per planar square meter. Said porous layer 12 had a maximal thickness of 10 cm, while the protuberance had a thickness of about 4 cm.

(51) The porous layers 10,11,12 have different coated Miscanthus content. The layer 10 (directed towards the wood covering 15) comprised 15-20% by weight coated Miscanthus fibres and has a density of about 1600-1800 kg/m.sup.3.

(52) The porous layer 12 comprised 45-55% by weight coated Miscanthus fibres and has a density of about 600-800 kg/m.sup.3.

(53) The intermediate porous layer 11 comprised 25-35% by weight coated Miscanthus fibres and has a density of about 800-1000 kg/m.sup.3.

(54) The layers were attached the one with the other by connecting elements, such as glue points or lines 20. The open inner channels of the porous layers are communicating the one with the other forming an inner open web. Air can flow from channels of a porous layer into channels of another adjacent porous layer.

(55) The intermediate porous layer 11 is placed with respect to the end porous layers 10,12 so as to define on one vertical edge of the panel a vertical groove 16, and on the opposite vertical edge of the panel, a vertical protuberance 17. The vertical protuberance 17 is adapted for being inserted within the vertical groove of an adjacent noise insulating panel.

(56) FIG. 2 is a cross section view of the noise insulating wall of FIG. 1.

(57) FIG. 3 is a partial schematic view of coated Miscanthus fibres which are attached together by a hardened calcium containing hydraulic binder, such as a binder containing hydrated lime (the binder advantageously also containing some silicon).

(58) The coated Miscanthus fibres 30 are substantially completely coated with a silane containing coating 31 as disclosed here above. The cement comprising binder 32 covers only partly the coated miscanthus fibres 30, whereby an open web is formed between the fibres and within the inner channels 32 of the fibres.

(59) According to another possible embodiment, the binder is selected to form a MDF panel. The glue comprises a resin glue, which is curable or hardenable at room temperature or at temperature above room temperatures, such as at a temperature comprised between 50 and 150° C. The resin glue can possibly be a resin comprising urea-formaldehyde compounds.

(60) B. Plastic Product Charged with Treated Miscanthus Fibres and/or Powder

(61) The treated miscanthus fibres were dried in a rotating drum (with air circulation at a temperature below 70° C.) so as to reduce its free water content to less than 5% by weight (such as less than 1% by weight). After drying, the fibres can possibly be partly ground into a powder form (size of less than 100 μm).

(62) The polymer was melted and mixed with the miscanthus powder and/or fibres, so as to achieve a substantially uniform dispersion of the miscanthus powder and/or fibres in the melted polymer.

(63) The said melted polymer can thereafter be injected or extruded or can be transformed into pellets or granules ready for use in an extruder or injection apparatus.

(64) The polymer is for example polyethylene, polypropylene, PVC, polystyrene, silicon, copolymers, etc.

(65) The Miscanthus powder and/or fibres weight content within the plastic can range as example from 5 to 50% with respect to the weight of the polymer.

(66) The fibres can be is required first transformed into aggregates. While not being necessary, the fibres of the invention can be further treated with a mineralizator, especially dry treated with a mineralizator (such as stone dust, hydrated lime (high specific surface area 30 m.sup.2/g), etc.)

(67) As further examples of treated Poaceae fibres and powders in bricks, panels and plastics, the treated Miscanthus fibres were replaced by treated fibres from Pennisetum-like species (such as Pennisetum purpureum, also known as Elephant grass, Pennisetum clandestinum also known as Kikuyu grass), and treated Zea-like species (such as Zea mays species, Zea mexicana species), as well as a mixture of such Poaceae fibres.