WO2006011690A1

WO2006011690A1 - Exfoliation

Info

Publication number: WO2006011690A1
Application number: PCT/KE2005/000013
Authority: WO
Inventors: A. Shariff Mehboob
Original assignee: REGIONAL MINING Ltd
Current assignee: REGIONAL MINING Ltd
Priority date: 2004-07-27
Filing date: 2005-06-14
Publication date: 2006-02-02
Anticipated expiration: 2007-01-27

Abstract

Admixtures are materials added to cement during its manufacture; for example, Gypsum is used as a retardant, Pulverized fuel ash and silica fumes are added in significant amount >10% of cement content. Today in most industrialised countries admixture usage accounts for 50% of the concrete. Hence the additive used in set proportions gave the cement various attributes of: - (1) Fire proofing; - (2) Sound deadening; - (3) Insulation; - (4) Colour; - (5) Non-toxicity.

Description

DESCRIPTION

EXFOLIAΗON

When vermiculite is heated suddenly to temperatures ranging from 300° C to 800⁰C a rapid generation of steam is released and separation of the structural layers occurs in the direction perpendicular to the cleavage plane.

Differential thermal analysis curves of vermiculite generally show three principal endothermic peaks, corresponding to the expulsion of inter-layer water and a further two peaks due to the disruption of the structure by loss of hydroxyl ions. The above results of exfoliation can also be achieved by treating the mineral with hydrogen peroxide.

After the exfoliation there is generally an increase in the bulk volume, eight to twelve times its original. The mineral generally attains certain attributes that when combined with other products, the attributes are accentuated. Hence the attributes are due to;-

(1) Unreactivity (2) Sintering temperatures of 1150° - 125O⁰C

(3) Cation exchange capacity : 50 - 150 m/100g

(4) Specific heat : 0.20 - 0.26 Kcal/Kgk

Thus when the mineral is combined with Portland cement in specific volumetric ratios, the cement can acquire Fire resistance, Light weightedness, Insulation capabilities and Sound deadening attributes. PORTLAND CEMENT

There are two types of cement products manufactured based on the type of constituents used which are:-

1) Ordinary Portland cement (OPC)

2) Pozzolanic Portland cement (PPC)

1. Ordinary Portland Cement (OPC)

This type of cement tends to have two main constituent. These are

a) Gypsum - 5% by weight b) Clinker - ranging from 95% to 75% by weight.

„ By virtue of its strength, the cement is used in building of bridges and buildings that require high strengths.

Pozzolanic Portland Cement (PPC)

This type of cement tends to have three main constituent. These are

a) Gypsum - 5%by weight - b) Clinker - minimum of 60% by weight c) Pozzolanic - maximum of 35% by weight The constituents :-

a) Gypsum

This is a naturally occurring mineral which is used as a retardant in cement manufacture. It generally slows the pace of reaction when the cement is 5 combined with water.

b) Pozzolanic

This is also a natural occurring mineral which is used as an additive in cement. Manufactured according to internally set standards, it should not exceed 35% by weight. It reduces the quantity of alkaline elements and -_|_Q heat generation during combination of cement with water. Hence reducing the occurrence of cracks and breakages during cement setting; internally averting weakness in the cement.

c) Clinker

This is an admixture of various minerals formed under intense temperature ₁₅ and pressure and is the main constituent that gives the cement its strength, considering it has binding abilities.

In order for us to prove the fire resistance abilities in cement, we had to conduct experiments by mixing various proportions of vermiculite to 0 pozzolanic, maintaining set proportions of Gypsum and Clinker, in order to maintain the strength and conditions set for cement manufacture. As per the results in table A (see appendix) the higher the percentage of Mica used (above 30%), the greater the strength of the cement is reduced. Hence after increasing the surface area of the proportions mixed to a range of 4500 - 5300 units and also increasing the proportion of Clinker between 70% - 85%, the desired results of strength were achieved within a stipulated 2 day and 7 day period.

In table B (see appendix), the level of alkali metals were analysed and an inverse relationship was observed between the percentile increase of Mica to the prescence of detectable alkali metals. Hence the less the alkali metal available, the less likelihood of salt formation thus reducing the formation of any cracks and weakening of the concrete strength.

The magnesium-oxide level was detected to be higher than the standard of 5%. Normally any value above the standard, should cause an expansivity of 10mm in a bath of water at 100⁰C for a period of 1 hr, but despite volume of magnesium being above 5% standard, the vermicuiite cement exhibited no significant expansivity (if any, it was within the stipulated standard of below 10mm). As shown in Table C (see appendix), we draw to the tentative conclusion that the magnesium did not participate in any reaction.

FIRE RESISTANCE

Various ratios of vermiculite and modules made were added in the standard cement of Pozzolana Portland cement (PPC). These modules were subjected to temperatures of 900⁰C and HOO⁰C for a period of 4 hours and observations were made after every one hour. Thus within a period of two hours, the vermiculite cement exhibited discontinued cracks and change of coloration to a lighter goldish-brown hue. Though feasibility was evident, compaction of the modules were also evident.

But the control module of PPC after a period two hours exhibited cracks and disjointment, both cross sectionally and longitudinally.

Under HOO⁰C the results were markedly identical to those at 900⁰C, only that the cross section of the control exhibited continous cracks and total deformity

Hence we can tentatively conclude that vermiculite or mica was the main cause of resistance in the cement to higher temperatures affecting the structure since it was the only additive used in the test. Hence the attribute of fire resistance was proved.

The mineral has a refractive index of 1.6, giving the final product a pearly lustre and goldish brown hue, instead of a dull grayish coloration consistent with all Portland cement. A Block of 9 inch width mortars were made, one control and two with

vermiculite of 10% to 15% in proportion. Heat was then subject to one

face of the block. For a period of lhour, the blocks constituting

vermiculite, the opposite face did not show any rise in temperature, but

5 the Normal Portland -pozzolana cement block the temperature- rose

steadily. Hence indicating transmission of the heat in the p.p.c .

The golden colour was generally visible in the cement constituting

vermiculate by virtue of the golden colour of the vermiculate, which was

/ o determined by the temperature range during its beneficiation

Claims

WHAT IS CLAIMED 1) The cement composition of A + B + C + D = 100% by weight Where; A = Clinker B = Gypsum C = Pozzolana D= Vermiculite 2) A cement composition according to claim (1) wherein; a) D is a percentage range increase of 5% - 30% by weight b) C is a percentage range decrease of 5% - 30% by weight in relation to D c) A is not less than 65% nor more than 80% by weight 3) The cement composition of; A + B + D = 100% Where; A = Clinker B = Gypsum D = Vermiculite 4) A cement composition according to claim (3) Wherein; A = is not less 65% by weight nor more than 90% by weight D = is in the range of 5% to 30% by weight 5) Cement composition as in any one of claims 1 to 4 for use in fire resistance 6) Cement composition as in any one of claims 1 to 4 for use in insulation 7) Cement composition as in any one of claims 1 to 4 for use in sound deadening 8) Cement composition as in any one of claims 1 to 4 for its goldish-brown hue. 9) Cement composition as in any one of claims 1 to 4 for its non-reactivity 10) Cement composition as in any one of claims 1 to 4 for use as a light weight plaster. 11) The process of making the cement composition of any of the preceding claims comprising the following steps: - a) Mixing A, B, C and D in ratios by weight b) Grinding the admixture to attain an SSA range of 4300 to 5300 <* /, units. 12)The process for preparing D for use in making cement composition of any of the preceding claims 1 to 10 comprises of the following steps :- STEPS: a) Extracting the raw material from a suitable explored area using basic mining methods. b) Grinding the raw material to reduce the size (surface Q area) to a range from 16mm to 0.5mm. c) Emplacing the crushed raw material in a furnace and subjecting it to a range of temperatures from 9000C to 2000C. d) The crushed raw material shall exfoliate 8 to 12 times its 5 volume in the process of releasing water as a by-product. e) The crushed raw material can also be exfoliated by subjecting it to a hydrogen peroxide chemical. f) The exfoliation material attains:-

(1) Fireproofing abilities _Q

(2) Sound deadening abilities

(3) Non-reactivity

(4) Insulation

(5) Light gold-brownish hue

APENDIX TABLE A.

STRENGTH Isoluble. Residue 2days 7 days S.S.A SETTING TIME

INITIAL FINAL < 35% 10 N/m^α 24 Nlrn > 4500 40m 600m MICA Pozzo lana Clinker

23.51 10.68 21.11 4867 210 345 10% 10% 75%

H 15.2 17.73 27.58 45.67 248 318 5% 10% 80%

10.69 16.7 30.48 4506 220 290 10% 5% 80%

12.84 11.72 24.6 4504 257 332 15% 5% 75%

NB. GYPSUM HAS A 5% PROPORTION IN SETS G. H. I. J.

APPENDIX

TABLE B

SET Ha,fi% Mg 0% Aψ₃% Si 0_χ% Si O₃ % K₁O % Ca 0 % Fo₂O₅ % TOTAL Loi

G 1.09 6.7 7.95 31.47 2.54 0.77 42.45 4.52 97 0

H 0.78 5.62 6.45 28.04 3.24 0.68 50.1 3.78 99 0

I 0.5 8.06 5.91 25.39 3.71 0.62 51.1 3.76 99 0

J 0.46 9.49 6.11 26.22 3.01 0.62 50.07 3.97 100 0

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