GB1589216A

GB1589216A - Bitumen-coating of lightweight aggregate materials

Info

Publication number: GB1589216A
Application number: GB3694576A
Authority: GB
Original assignee: TILCON Ltd
Current assignee: TILCON Ltd
Priority date: 1977-12-06
Filing date: 1977-12-06
Publication date: 1981-05-07

Description

(54) IMPROVEMENTS IN OR RELATING TO THE BITUMEN-COATING OF LIGHTWEIGHT AGGREGATE MATERIALS (71) We, TILCON LIMITED formerly known as Tilling Construction Services Limited, a British Company of Harrogate House. Parliament Street, Harrogate. North Yorkshire, HG1 2RF. do hereby declare the invention for which we pray that a patent.may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: The present invention is concerned with improvements in or relating to the bitumencoating of lightweight aggregate materials.

Expanded perlite has excellent heat insulation properties but in a loose form is difficult to use for insulating roofs and floors.

It is known to produce lightweight bitumen-coated aggregate for use as floor or roof screeding material, and this may by achieved by the in situ mixing of lightweight material, such as expanded perlite particles, with hot bitumen, the resulting coated particles then being spread and compacted to form the screed.

Alternatively, the mixing may be carried out as a factory process. and the bitumen-coated particles delivered from store to the site in suitable containers, such as bags. It is. of course, a pre-requisite of this alternative screeding method that the bagged material should be free-flowing when cold so that it may be easily worked. However, it has been found that such pre-coated materials tend to compact in store and to form agglomerated lumps which are difficult to break up on site.

The invention therefore sets out to improve the free-flowing properties of bitumencoated expanded aggregate material and reduce the density of the compacted material.

The invention therefore provides a method of coating expanded aggregate material with bitumen comprising the steps of coating the material with heated bitument, subjecting the coated material to an accelerated cooling stage, and including the step of mechanically separating the coated material during and after cooling.

The method according to the invention has been found to be particularly beneficial when applied to perlite particles being coated with oxidised bitumen. However. it is envisaged that benefit may also accrue when the invention is applied to aggregate coated with aqueous bitumen emulsion. This use will involve an additional, intervening step of heating the freshly coated aggregate to drive off the water prior to the step of accelerated cooling.

When preparing a mixture of aggregate and oxidised bitumen for subsequent storage it will be found convenient to use between 20 and 100 parts by weight of bitumen to 100 parts by weight of expanded perlite. Perlite is a type of volcanic glass rock containing from 2-5% combined or occluded water. When rapidly heated above a temperature of 1000"C, the perlite ore particles melt and expand to between 4 and 20 times their original volume as the combined water vaporises and forms microscopic cells or bubbles in the heated softened glass. The product is then cooled, classified and collected.

The higher figures in the range of bitumen content quoted above will be applicable where a roofing quality screed is required. a typical figure being 6() parts by weight, whereas the lower figures relate to flooring quality screed, a typical figure being 33.3 parts by weight.

Conveniently, the perlite will be graded between 5 mm to 0.3 mm.

Mixing will take place in any convenient mixer into which the hot bitumen may be sprayed, at a temperature between 150 to 2()00C. Penetration of the bitumen will vary between 10 and 70 according to conditions. All bitumen should comply with the requirements of British Standard 369(): "Test Methods for Bitumens" When the mixing is complete, the coated perlite will then be subjected to an accelerated cooling step to bring the temperature to near ambient. This may be achieved in any convenient manner, for example by passing forced air draughts through the material. This may be done before the material passes through sieve or a series of sieves, for example, of between 19 - 25mm mesh, to remove any large lumps of material or bitumen for re - cycling if required.This sieving step acts to provide the separating action referred to above. The cold material may then be stored. for example, in bags.

The invention will now be described further by way of example with reference to the accompanying drawing. the single figure of which is a diagrammatic side elevation of an apparatus for carrying out the method of the invention.

The apparatus illustrated in the drawing consists of a mixer 10 having a perforated pipe fitted with spray nozzles which extend thereacross. Perlite is introduced into the mixer chamber through a hopper 14 and heated bitumen under pressure is forced evenly and as a spray out through the nozzles in pipe 12. thus coating the perlite particles. The mixer, which is of known type, includes two contra-rotating shafts fitted with paddles for mixing the perlite/bitumen mixture and an extractor fan (not shown) removes bitumenous fumes and vapours. After the perlite has been coated, a trap door 18 in the base of the mixer is opened and the coated perlite allowed to fall under the influence of gravity down a chute 20 to the input of a cooler 22.A compressor fan introduces cooling air into the cooler to accelerate the cooling of the hot coated perlite, the temperature of which on entry is normally about 120"C.

The cooler consists basically of a rotatably mounted cylindrical housing. Lifting fins within the cooler feed coated perlite from the cooler input towards an output thereof where a vertical elevator 26 is disposed. During the passage of the coated perlite through the cooler, water from a cooling water spray bar 28 is applied to the cooler housing to accelerate cooling of the coated perlite. At the same time, lengths of chain, which are fixed at one end and mounted inside the cooler, serve to break down any large lumps of material which may be present. The cooler may be alternatively of the known fluidised bed type.

The vertical elevator 26 lifts the cooled perlite to the level of a storage hopper. A vibrating sieve or series of sieves 29 are mounted on the inlet to the hopper and takes out any remaining large lumps not broken down in the cooler. The coated perlite then falls down into the hopper and is removed for bagging from a gated opening 30.

Examples of the types and quantities of perlite and bitumen used are set out in the following examples.

Example 1 150 kg of expanded perlite having a density of 130kg/m was introduced into the mixer and 80kg of bitumen grade R85/4() in accordance with B.S 3235 sprayed on, giving the mixture a mix ratio of 65% expanded perlite. The temperature of the bitumen was 200"C.

Example 2 150 kg of expanded perlite having a density of 130kg/m was introduced into the mixer and 65kg of bitumen at 1C)OOC sprayed on. The bitumen was graded 100/10 in accordance with B.S 3235 and the mixture had a mix ratio of 70% expanded perlite.

The sieve analysis of the expanded perlite used in both the above examples is as given in the following table: Sieve Size Percentage by (Microns) weight passing 4750 9() - I 100 2500 55 - Xt) 1200 25 - 5() 6()() 10 - 30 300 0 - 2() It has been found that satisfactorv results may be obtained with a perlite density lying within the range 100 - 17()kg/m-;.

WHAT WE CLAIM 1S:- 1. A method of coating expanded ag,gre,gate material with bitumen comprising the steps of coating the material with heated bitumen, subjecting the coated material to an accelerated cooling stage. and including the step of mechanically separating the coated material during and after cooling.

2. A method as claimed in claim 1 in which the bitumen comprises oxidised bitumen.

3. A method as claimed in claim 1 in which the bitumen comprises an aqueous bitumen

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

When the mixing is complete, the coated perlite will then be subjected to an accelerated cooling step to bring the temperature to near ambient. This may be achieved in any convenient manner, for example by passing forced air draughts through the material. This may be done before the material passes through sieve or a series of sieves, for example, of between 19 - 25mm mesh, to remove any large lumps of material or bitumen for re - cycling if required. This sieving step acts to provide the separating action referred to above. The cold material may then be stored. for example, in bags.

The invention will now be described further by way of example with reference to the accompanying drawing. the single figure of which is a diagrammatic side elevation of an apparatus for carrying out the method of the invention.

The apparatus illustrated in the drawing consists of a mixer 10 having a perforated pipe fitted with spray nozzles which extend thereacross. Perlite is introduced into the mixer chamber through a hopper 14 and heated bitumen under pressure is forced evenly and as a spray out through the nozzles in pipe 12. thus coating the perlite particles. The mixer, which is of known type, includes two contra-rotating shafts fitted with paddles for mixing the perlite/bitumen mixture and an extractor fan (not shown) removes bitumenous fumes and vapours. After the perlite has been coated, a trap door 18 in the base of the mixer is opened and the coated perlite allowed to fall under the influence of gravity down a chute 20 to the input of a cooler 22.A compressor fan introduces cooling air into the cooler to accelerate the cooling of the hot coated perlite, the temperature of which on entry is normally about 120"C.

The cooler consists basically of a rotatably mounted cylindrical housing. Lifting fins within the cooler feed coated perlite from the cooler input towards an output thereof where a vertical elevator 26 is disposed. During the passage of the coated perlite through the cooler, water from a cooling water spray bar 28 is applied to the cooler housing to accelerate cooling of the coated perlite. At the same time, lengths of chain, which are fixed at one end and mounted inside the cooler, serve to break down any large lumps of material which may be present. The cooler may be alternatively of the known fluidised bed type.

The vertical elevator 26 lifts the cooled perlite to the level of a storage hopper. A vibrating sieve or series of sieves 29 are mounted on the inlet to the hopper and takes out any remaining large lumps not broken down in the cooler. The coated perlite then falls down into the hopper and is removed for bagging from a gated opening 30.

Examples of the types and quantities of perlite and bitumen used are set out in the following examples.

Example 1

150 kg of expanded perlite having a density of 130kg/m was introduced into the mixer and 80kg of bitumen grade R85/4() in accordance with B.S 3235 sprayed on, giving the mixture a mix ratio of 65% expanded perlite. The temperature of the bitumen was 200"C.

Example 2

150 kg of expanded perlite having a density of 130kg/m was introduced into the mixer and 65kg of bitumen at 1C)OOC sprayed on. The bitumen was graded 100/10 in accordance with B.S 3235 and the mixture had a mix ratio of 70% expanded perlite.

The sieve analysis of the expanded perlite used in both the above examples is as given in the following table: Sieve Size Percentage by (Microns) weight passing

4750 9() - I 100

2500 55 - Xt)

1200 25 - 5() 6()() 10 - 30

300 0 - 2() It has been found that satisfactorv results may be obtained with a perlite density lying within the range 100 - 17()kg/m-;.

WHAT WE CLAIM 1S:- 1. A method of coating expanded ag,gre,gate material with bitumen comprising the steps of coating the material with heated bitumen, subjecting the coated material to an accelerated cooling stage. and including the step of mechanically separating the coated material during and after cooling.
2. A method as claimed in claim 1 in which the bitumen comprises oxidised bitumen.
3. A method as claimed in claim 1 in which the bitumen comprises an aqueous bitumen

emulsion.
4. A method as claimed in any one of claims 1 to 3 in which the expanded aggregate material is perlite.
5. A method as claimed in any one of claims 1 to 3 in which the ratio of bitumen to perlite lies in the range 20 to 100 parts by weight bitumen to 100 parts by weight of perlite.
6. A method as claimed in claim 5 in which the perlite is graded essentially between 5mm ot 0.3mm.
7. A method as claimed in any one of claims 1 to 6 in which the step of coating the material with bitumen comprises spraying hot bitumen onto the material.
8. A method as claimed in claim 7 in which the hot bitumen is at a temperature between 150 to 2200C.
9. A method as claimed in any one of claims 1 to 8 in which the accelerated cooling step comprises passing a forced air draught through the coated material in a rotary or fluidised bed cooler before the material passes over a sieve. or a series of sieves, to remove any agglomerates of material or bitumen.
10. A method as claimed in claim 9 which additionally comprises passing the coated material through a rotary cooler and causing cooling water to be sprayed onto the rotary cooler.
11. A method of coating expanded aggregate material with bitumen substantially as herein described with reference to and as illustrated in the accompanying drawings.
12. Coated expanded aggregate material whenever produced by the method of claim 1.