Concrete aggregate

Details Concrete aggregate Concrete aggregate

2001-11-28

2004-10-12

Koslow, C. Melissa (Department: 1755)

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

C106S624000, C106S700000, C106S705000, C106SDIG001

Reexamination Certificate

active

06802896

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a method of forming a lightweight fly ash aggregate together with the resultant fly ash aggregate. The invention further relates to various aspects of the method of forming the lightweight fly ash aggregate including methods of forming fly ash slurry, briquettes, or lightweight fly ash particles.
BACKGROUND OF THE INVENTION
Sintered pelletised fly ash aggregates have been commercially produced in several industrialised countries such as the UK, USA, Japan, India and North Europe. The manufacturing process of these aggregates requires pelletising a mixture of the fly ash and water before sintering the pellets at temperatures above 1200° C. This process produces light spherical aggregate with a high proportion of voids. The manufacture of sintered pelletised aggregate from fly ash requires a high degree of control during the production processes. The experience of the present applicants with this type of lightweight aggregate has been with the UK produced aggregate that is called LYTAG. This experience has shown large variations in the size and quality of the aggregate. Such variations have resulted, as expected, in inconsistency with the final product, namely the concrete. Since it is structural concrete that is ultimately the subject of interest, it is imperative that the produced aggregate should be of high quality and consistent characteristics. This is particularly the case when such aggregates are to be used in important structures such as off-shore platforms.
In Australia, there is no production of fly ash aggregates by any method. This is in spite of the fact that most of the power industry in this country is from coal sources, and that fly ash itself is produced abundantly. Investigations have been conducted using the LYTAG sintered pelletised fly ash in high-strength concrete production and it was capable of producing concrete with compressive strength of 70 MPa. Nevertheless, consistency and repeatability of the strength values and workability levels, even under the strictest laboratory conditions were not high. The reason for this drawback was the inconsistency in the lightweight aggregate that was used. The inconsistency was manifested mainly in the water absorption capacity, hardness, and size distribution. Moreover, producing high strength lightweight concrete required a very large quantity of ordinary portland cement. This should be discouraged as much as possible because cement manufacture is an industry that causes significant damage to the environment through its very high demand of energy and its emission of very large amounts of carbon dioxide. Thus, it was previously understood that in order to produce high performance concrete from LYTAG, a substantial amount of cement must be used. This is quite defeating to at least the environmental reasons for which the lightweight aggregate concrete was originally envisaged.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of forming a lightweight fly ash aggregate, said method comprising the steps of:
blending fly ash together with a plasticiser and a reduced quantity of water to produce a fly ash slurry;
heating the fly ash slurry to effectively dry the slurry from which a fly ash briquette is derived; and
crushing the fly ash briquette to provide the lightweight fly ash aggregate.
Preferably the method further comprises the step of sizing the fly ash aggregate according to a predetermined particle size range.
According to another aspect of the present invention there is provided a method of forming a fly ash slurry, said method comprising blending fly ash together with a plasticiser and a reduced quantity of water to produce the fly ash slurry.
Preferably the plasticiser is a superplasticiser.
Preferably the volume (1) of the plasticiser to the weight (kg) of the fly ash is between about 0.1 to 5%. More preferably the reduced volumetric quantity (1) of water to the weight (kg) of the fly ash is less than about 35%.
According to yet another aspect of the invention there is provided a method of forming a fly ash briquette, said method comprising the steps of:
heating a fly ash slurry at between about 40 to 110° C. to effectively cure the slurry from which the fly ash briquette is derived; and
firing the fly ash briquette at around 1300° C.
Preferably the curing of the slurry is effected at a controlled level of humidity, for example at approximately 37% relative humidity. More preferably the slurry is cured for an extended period of between about one (1) to four (4) days.
Generally the method also comprises the step of compacting or compressing the slurry prior to curing.
According to a further aspect of the invention there is provided a method of forming lightweight fly ash particles, said method comprising crushing a fly ash briquette to provide the lightweight fly ash particles.
Generally the step of crushing the fly ash briquette provides said fly ash particles having irregular or angular shapes. It is understood that the irregular or angular shapes of the fly ash aggregate improves its interlocking with the mortar-paste matrix of concrete and thus the strength of the concrete.
Preferably the method further comprises the step of sizing the fly ash particles according to a predetermined particle size range. More preferably the sizing is effected by screening of the fly ash particles. Generally the predetermined particle size range covers fly ash particles of a size from between about 75 &mgr;m to 30 mm.
According to yet a further aspect of the invention there is provided a lightweight fly ash aggregate for concrete production, said aggregate being of a relatively low water absorption capacity.
Preferably the relatively low absorption capacity as measured over 24 hours is less than 10%. More preferably the absorption capacity is between 2 to 5%.
Preferably the lightweight fly ash aggregate is of a predetermined particle size range. More preferably the predetermined particle size range covers fly ash particles of a size from about 75 &mgr;m to 30 mm. Generally the particle size range is between 0.075 mm (75 &mgr;m)to 12 mm.


REFERENCES:
patent: 2724656 (1955-11-01), Gunzelmann
patent: 4504320 (1985-03-01), Rizer et al.
patent: 4701222 (1987-10-01), Kobayashi et al.
patent: 4741782 (1988-05-01), Styron
patent: 4770831 (1988-09-01), Walker
patent: 5211750 (1993-05-01), Smith
patent: 5350549 (1994-09-01), Boyle
patent: 5374307 (1994-12-01), Riddle
patent: 5584895 (1996-12-01), Seike
patent: 5665290 (1997-09-01), Koslowski
patent: 5669969 (1997-09-01), Meade et al.
patent: 5704972 (1998-01-01), Ivkovich
patent: 5766338 (1998-06-01), Weber
patent: 6054074 (2000-04-01), Wu
patent: 6068803 (2000-05-01), Weyand
patent: 6277189 (2001-08-01), Chugh
patent: 2273629 (2000-01-01), None
patent: 2318115 (1998-04-01), None
patent: 2330138 (1999-04-01), None
patent: 98-148153/14 (1998-02-01), None
patent: 80724C/46 (1980-11-01), None
patent: 30444K/13 (1983-02-01), None
patent: 84-197622/32 (1984-06-01), None
patent: 7-206491 (1985-08-01), None
patent: 84-24958/38 (1986-08-01), None
patent: 89-237632/33 (1989-07-01), None
patent: 98-280314/25 (1998-04-01), None
patent: 98-514998/44 (1998-08-01), None
patent: 99-258722/22 (1999-03-01), None
patent: 2000-142344/13 (2000-01-01), None
patent: 2000-313679 (2000-11-01), None
patent: 2001-544329/61 (2001-06-01), None
patent: 84-034686/06 (1984-01-01), None

Affiliated with

Also associated with

Rating

Concrete aggregate does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Concrete aggregate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Concrete aggregate will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3324913