CA1240827A - Lightweight aggregate - Google Patents
Lightweight aggregateInfo
- Publication number
- CA1240827A CA1240827A CA000462751A CA462751A CA1240827A CA 1240827 A CA1240827 A CA 1240827A CA 000462751 A CA000462751 A CA 000462751A CA 462751 A CA462751 A CA 462751A CA 1240827 A CA1240827 A CA 1240827A
- Authority
- CA
- Canada
- Prior art keywords
- pellets
- lime
- process according
- siliceous material
- granules
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
A B S T R A C T:
LIGHTWEIGHT AGGREGATE
Lightweight aggregate for use in the building industry is produced by pelletising or granulating pulver-ised fuel ash or other siliceous material with a binder comprising lime in an amount less than 5% by weight based on the weight of the mixture of lime and siliceous material and curing the pellets or granules at a temp-erature within the range of from 35°C to 100°C in an atmosphere saturated with water vapour. The amount of lime added as binder is preferably within the range of from 1 to 4.5% by weight and curing temperature is pre-ferably within the range of from 50 to 85°C. Preferably the pelletising process is also carried out at an elevated temperature within the range of from 35°C to 100°C.
LIGHTWEIGHT AGGREGATE
Lightweight aggregate for use in the building industry is produced by pelletising or granulating pulver-ised fuel ash or other siliceous material with a binder comprising lime in an amount less than 5% by weight based on the weight of the mixture of lime and siliceous material and curing the pellets or granules at a temp-erature within the range of from 35°C to 100°C in an atmosphere saturated with water vapour. The amount of lime added as binder is preferably within the range of from 1 to 4.5% by weight and curing temperature is pre-ferably within the range of from 50 to 85°C. Preferably the pelletising process is also carried out at an elevated temperature within the range of from 35°C to 100°C.
Description
~` ~z~oa27 LIGHTWEIGHT ~GGR$GAT~
This invention relates to lightweight aggregates for use in the building industry and more especially in the 'manufacture of building blocks.
It has been proposed to make a lightweight aggregate by pelletising pulverised fuel ash or other siliceous material 1n the presence of lime or cement. It has hitherto heen thought that the amount of lime or cement required must amount to at least 5~ based on the weight of the mixture of cement or lime and siliceous material and normally at least 7~, if the pellets and the blocks produced from them are to have adequate strength.
This invention'is based on the observation that .
amounts of lime considerably less than the 5~ required by the prior art can be used to produce pellets Qr granules of conside,rable strength if after formation the pellets or granules are cured at a temperature within the range of 35 C to 100Cj and preferab]y the process for the production of the pellets or granules is carried out at an ,' elevated temperature. The strength of pellets, for example, produced using 2% of lime (calculated as CaO) in admixture with fly ash, after curing for 24 hours at 70C
have a `strength equivalent to similar pellets produced using 5~ of cement in admixture with fly ash, cured for the same period.
~ . .;~, .
. _ _ _ . .. . _ .. . _. . . .... .. ..
~Z~a~1827 -- 2 ~
The invention provides a process for the manufacture of lightwei~ht aggregate which is suitable for use in the building industry which comprises blending a siliceous material with a binder comprising quicklime and/
s or hydrated lime in an amount less than 5% (calculated as CaO) based on the total dry weight o siliceous material and binder, forming the blend into granules or pellets, if necessary or desired with the additlon of waterrand curing or hardening the pellets or granules by main~aining them at a temperature within the range of from 35C to : ~ looc in an atmosphere saturated with water vapour.
Preferably during the manufacture of the pellets or granules an elevated temperature within the range of from 35C to 100 C is maintained and a particular advantage of the invention is that by use of hot ~uel ash or other siliceous material direct from! for example, a power station and/or by utilizing the heat of slaking of quicklime, the process can be made self-sufficient in energy.
- 20 The amount of lime added as, or forming part of, the blnder is preferably between 4.5 and 1% by weight, (expressedas calcium oxide) based on the dry weight of lime -plus siliceous material. Water may be added to the blend in an~ amount necessary to give the consistency required ~5 for the chosen granule or pellet making process.
The pellets or granules may be hardened before further processing or they may be processed, for example by .
. . . ~ . . .
-` ~2~ 2~
~ 3 ~
:
moulding to a desired shape, before hardening and then allowed to harden as a processed mass The hardening or curing temperature is preferahly in the range of irom 50C to 85C and a similar range of temperature is preferably used in the pelletislng or granule making process.
The lightweight aggregate according to the invention is in the form of pellets or granules which may be produced for example by extrusion or by pelletising, either wet or dry. Preferably in any wet process hydrated lime is used which is produced by slaking quicklime substantially almost immediately before the lime is used in the process. When a dry pclletising process is used, the siliceous material may be mixed with quicklime and water sprayed thereon to slake the lime.
If desired, accelerators and~or dispersers may be added to the blend, such materials being known in the art.
Ac~elerators that can be used are for example, calcium chloride and sodium hydroxide.
Preferably the siliceous material used in the process is pulverised fly ash direct from a power station, for example at a temperature of say 65 to 70 C. The entrained heat in such fuel ash provides much of the heat which is desirable during the pelletislng operation and this may be supplemented as indicated above by utilizing the heat of slaking of quicklime in addition to which hot air which inherently derives from the hot ash may provide a heated atmosphere for curing the pellets.
. . .
The process of the invention ~part from its economic advantages provides a further advantage arising from the use of lime as binder, namely that the pellets or granules are much more resilient than those based on cement. This factor reduces breakage during handling and facilitates inter-particle binding and it also allows large moulded masses of the pellets or granules to be cut into desired smaller masses, for example, using a vibrating wire cutter.
Although the invention has basically been described with reference to the use of pulverised fly ash, any pulverised fuel ash can be used in the process, as indeed can any siliceous material in pulverised form providing that it will react with the lime to form hydrated calcium silicates.
The invention will now be described in greater detail by way of example with reference to the accompanying drawings of which the ~hree figures are flow diagrams showing those variations of the process according to the invention.
As shown in Fig. 1 of the drawings, pulverised fly ash from a storage silo l at a power station at a temperature of say 65C to 75C is transferred by insulated pipelinè 2 or insulated tanker to a classifier 3 where it is graded as to size. The graded fly ash which is still at a temperature of 65C to 70C is then passed to a blender 4 where it is mixed with hydrated lime from a .
-_ 5 _ storage tank 5 and thence to a peIletiser 6.
Following pelletising the pellets are passed toa curing silo 7 into which, if extxa heat is needed, is fed the used hot air from the classiEier 3. After curing at a temperature of 70C for 24 hours or so to allow full reaction between the lime and the siliceous material the pellets are either transported away of passed to a building block producing plant 8 in which the pellets are mlxed with cement and~or lime and, if desired, more fly ash, as binder, and formed into blocks.
~ s shown in Fig. 2 the process is basically the same as that of Fig. 1 except that instead of hydrated lime being fed to blender ~, quicklime in silo 9 is slaked in slaker 10 and the hot milk of lime is ed through line 11 to the pelletiser.
Fig. 3 shows a modification of the process of Fig. 2 in which the pellets from pelletiser 6 are fed to block forming plant 12 after which the green blocks are cut into smaller units at 13 and then passed to a hardening ~o unit 14.
. .
1 , ,, ~, .
This invention relates to lightweight aggregates for use in the building industry and more especially in the 'manufacture of building blocks.
It has been proposed to make a lightweight aggregate by pelletising pulverised fuel ash or other siliceous material 1n the presence of lime or cement. It has hitherto heen thought that the amount of lime or cement required must amount to at least 5~ based on the weight of the mixture of cement or lime and siliceous material and normally at least 7~, if the pellets and the blocks produced from them are to have adequate strength.
This invention'is based on the observation that .
amounts of lime considerably less than the 5~ required by the prior art can be used to produce pellets Qr granules of conside,rable strength if after formation the pellets or granules are cured at a temperature within the range of 35 C to 100Cj and preferab]y the process for the production of the pellets or granules is carried out at an ,' elevated temperature. The strength of pellets, for example, produced using 2% of lime (calculated as CaO) in admixture with fly ash, after curing for 24 hours at 70C
have a `strength equivalent to similar pellets produced using 5~ of cement in admixture with fly ash, cured for the same period.
~ . .;~, .
. _ _ _ . .. . _ .. . _. . . .... .. ..
~Z~a~1827 -- 2 ~
The invention provides a process for the manufacture of lightwei~ht aggregate which is suitable for use in the building industry which comprises blending a siliceous material with a binder comprising quicklime and/
s or hydrated lime in an amount less than 5% (calculated as CaO) based on the total dry weight o siliceous material and binder, forming the blend into granules or pellets, if necessary or desired with the additlon of waterrand curing or hardening the pellets or granules by main~aining them at a temperature within the range of from 35C to : ~ looc in an atmosphere saturated with water vapour.
Preferably during the manufacture of the pellets or granules an elevated temperature within the range of from 35C to 100 C is maintained and a particular advantage of the invention is that by use of hot ~uel ash or other siliceous material direct from! for example, a power station and/or by utilizing the heat of slaking of quicklime, the process can be made self-sufficient in energy.
- 20 The amount of lime added as, or forming part of, the blnder is preferably between 4.5 and 1% by weight, (expressedas calcium oxide) based on the dry weight of lime -plus siliceous material. Water may be added to the blend in an~ amount necessary to give the consistency required ~5 for the chosen granule or pellet making process.
The pellets or granules may be hardened before further processing or they may be processed, for example by .
. . . ~ . . .
-` ~2~ 2~
~ 3 ~
:
moulding to a desired shape, before hardening and then allowed to harden as a processed mass The hardening or curing temperature is preferahly in the range of irom 50C to 85C and a similar range of temperature is preferably used in the pelletislng or granule making process.
The lightweight aggregate according to the invention is in the form of pellets or granules which may be produced for example by extrusion or by pelletising, either wet or dry. Preferably in any wet process hydrated lime is used which is produced by slaking quicklime substantially almost immediately before the lime is used in the process. When a dry pclletising process is used, the siliceous material may be mixed with quicklime and water sprayed thereon to slake the lime.
If desired, accelerators and~or dispersers may be added to the blend, such materials being known in the art.
Ac~elerators that can be used are for example, calcium chloride and sodium hydroxide.
Preferably the siliceous material used in the process is pulverised fly ash direct from a power station, for example at a temperature of say 65 to 70 C. The entrained heat in such fuel ash provides much of the heat which is desirable during the pelletislng operation and this may be supplemented as indicated above by utilizing the heat of slaking of quicklime in addition to which hot air which inherently derives from the hot ash may provide a heated atmosphere for curing the pellets.
. . .
The process of the invention ~part from its economic advantages provides a further advantage arising from the use of lime as binder, namely that the pellets or granules are much more resilient than those based on cement. This factor reduces breakage during handling and facilitates inter-particle binding and it also allows large moulded masses of the pellets or granules to be cut into desired smaller masses, for example, using a vibrating wire cutter.
Although the invention has basically been described with reference to the use of pulverised fly ash, any pulverised fuel ash can be used in the process, as indeed can any siliceous material in pulverised form providing that it will react with the lime to form hydrated calcium silicates.
The invention will now be described in greater detail by way of example with reference to the accompanying drawings of which the ~hree figures are flow diagrams showing those variations of the process according to the invention.
As shown in Fig. 1 of the drawings, pulverised fly ash from a storage silo l at a power station at a temperature of say 65C to 75C is transferred by insulated pipelinè 2 or insulated tanker to a classifier 3 where it is graded as to size. The graded fly ash which is still at a temperature of 65C to 70C is then passed to a blender 4 where it is mixed with hydrated lime from a .
-_ 5 _ storage tank 5 and thence to a peIletiser 6.
Following pelletising the pellets are passed toa curing silo 7 into which, if extxa heat is needed, is fed the used hot air from the classiEier 3. After curing at a temperature of 70C for 24 hours or so to allow full reaction between the lime and the siliceous material the pellets are either transported away of passed to a building block producing plant 8 in which the pellets are mlxed with cement and~or lime and, if desired, more fly ash, as binder, and formed into blocks.
~ s shown in Fig. 2 the process is basically the same as that of Fig. 1 except that instead of hydrated lime being fed to blender ~, quicklime in silo 9 is slaked in slaker 10 and the hot milk of lime is ed through line 11 to the pelletiser.
Fig. 3 shows a modification of the process of Fig. 2 in which the pellets from pelletiser 6 are fed to block forming plant 12 after which the green blocks are cut into smaller units at 13 and then passed to a hardening ~o unit 14.
. .
1 , ,, ~, .
Claims (9)
1. A process for the manufacture of lightweight aggregate for use in the building industry which com-prises blending a siliceous material with a binder com-prising quick lime and/or hydrated lime in an amount less than 5% (calculated as CaO) based on the total dry weight of siliceous material and binder, forming and blend into granules or pellets, if necessary or desired with the addition of water, and curing or hardening the pellets or granules by maintaining them at a temp-erature within the range of from 35°C to 100°C in an atmosphere saturated with water vapour.
2. A process according to Claim 1, wherein during manufacture of the pellets or granules the temperature is maintained within the range of from 35°C to 100°C.
3. A process according to Claim 2, wherein the pellets or granules are manufactured from siliceous material that retains heat from its method of product-ion.
4. A process according to Claim 3, wherein the siliceous material at least partially consists of hot fuel ash.
5. A process according to Claim 1, wherein the siliceous material is pulverised fly ash.
6. A process according to Claim 1, wherein the amount of lime added as binder is within the range of 1 to 4.5% by weight, calculated as CaO (based on the dry weight of lime plus siliceous material).
7. A process according to Claim 1, wherein the hardening or curing temperature is within the range of from 50°C to 85°C.
8. A process according to Claim 1, wherein the pellets are processed by moulding to form building materials before they hardened or cured and are then hardened or cured as a processed mass.
9. A process according to Claim 1, wherein the pellets or granules are produced by a wet process and the binder comprises lime produced by slaking quick lime which is then immediately used in the process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000462751A CA1240827A (en) | 1984-09-10 | 1984-09-10 | Lightweight aggregate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000462751A CA1240827A (en) | 1984-09-10 | 1984-09-10 | Lightweight aggregate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1240827A true CA1240827A (en) | 1988-08-23 |
Family
ID=4128675
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000462751A Expired CA1240827A (en) | 1984-09-10 | 1984-09-10 | Lightweight aggregate |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1240827A (en) |
-
1984
- 1984-09-10 CA CA000462751A patent/CA1240827A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |