GB1577224A

GB1577224A - Cementitious compositions

Info

Publication number: GB1577224A
Application number: GB10811/76A
Authority: GB
Original assignee: Fosroc AG
Current assignee: Fosroc AG
Priority date: 1976-03-17
Filing date: 1976-03-17
Publication date: 1980-10-22
Also published as: DK116077A; ES456929A1; DE2710975B2; NL7702802A; FI770752A; BE852568A; IT1082187B; JPS52128920A; NO770885L; NO144206C; DE2710975A1; FR2344510A1; NO144206B; SE7702791L

Description

(54) CEMENTITIOUS COMPOSITIONS (71) We FOSROC A.C., a Swiss Company, of Gartenstrasse 2, 6300 Zug, Switzerland 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: This invention relates to cementitious compositions containing porous light weight aggregates.

Light weight aggregates tend to be porous and cannot therefore usually be included in cementitious compositions to be pumped because when pressure is applied to compositions containing such aggregates the water in the mix is forced into the pores of the aggregate particles, resulting in a considerable loss of workability of the composition. The loss of workability may result in blockages in the pump, where pressures of the order of 1000 to 4000 kN/m2 may occur.

The absorption of water by the aggregate when the composition is being pumped may be reduced by pre-soaking the aggregate. This requires the use of an expensive vacuum soaking method, which results in a considerable increase in the overall cost of the pumping operation and thus makes it uneconomical in comparison with conventional conveyor placing techniques, which are slower. For these reasons, pumping of light weight aggregate concrete has not previously been practised widely.

Accordingly, the invention provides a pumpable cementitious composition, comprising a hydraulic cement, water, a porous light weight aggregate, a plasticiser, and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption of water by the aggregate when the composition is pumped.

While the proportions of the dispersing agent and gelling agent can vary widely depending upon the light weight aggregate used and the head against which the composition is required to be pumped, the agents preferably each comprise 0.001% to 0.04% by weight of the composition, amounts in the range 0.008% to 0.015% being especially effective.

In this context a non-set retarding dispersing agent is one which will disperse cement particles and will not retard the setting of the cement irrespective of the concentration in which it is used. Such non-set retarding dispersing agents are exemplified by sulphonated melamine formeldehyde, sulphonated polystyrenes and sulphonated naphthalene formaldehyde.

The gelling agent may be of the type exemplified by a water-soluble cellulose derivative, for example methyl cellulose, hydroxy ethyl methyl cellulose, hydroxypropyl methyl cellulose and hydroxy ethyl cellulose.

In this context, a plasticiser is a dispersing agent which, in contrast to the non-set retarding agent, will, if used in high concentration, tend to retard the setting of the cement. Such dispersing agents are exemplified by lignosulphonate and hydroxycarboxylic acid derivatives such as sodium gluconate or sodium heptanoate. A weight ratio of plasticiser to gelling agent to dispersing agent of about 3:1:1 is particularly suitable.

The hydraulic cement may be an ordinary Portland cement, or a sulphate-resisting or rapid-hardening cement. Any commerciallyavailable porous light weight aggregate may be used. Thus, the aggregate may comprise sintered pulverized fuel ash, for example the aggregate available under the Registered Trade Mark LYTAG. Other suitable porous light weight aggregates are clinker, foamed slag, expanded clays, shale or slate, pumice, diatomite, expanded perlite and expanded vermiculite.

The aggregate may be wholly light weight fines, in which the particles have a maximum dimension less than 5 mm, or it may consist partly or wholly of larger particles. Sand may be included in the composition.

The invention also provides a method of pumping a cementitious composition containing a hydraulic cement, water and a porous light weight aggregate, which comprises adding to the composition, before pumping, a plasticiser and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption of water by the aggregate when the composition is pumped.

Preferably the non-set retarding dispersing agent and the gelling agent are added in the form of an admixture, which may be in powder form and may include the plasticiser.

The invention is further illustrated by the following Examples in which all percentages are by weight.

EXAMPLE 1 A concrete mix to be cast into a body of about lm3 in volume was made of the following: 450 kg ordinary Portland cement 740 kg sand (including 6% water by weight) 570 kg "LYTAG" light weight aggregate (in cluding about 12% water by weight) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 g lignosulphonate 310kg water ("LYTAG" is a Registered Trade Mark of Lytag Limited) The components were mixed together to form a wet concrete mix, which was then pumped at a pressure of about 2000 kN/m2 into a mould to form a body of about 1 m3 in volume. The concrete on subsequent testing was found to have adequate compressive strength.

No difficulties were experienced in pumping the composition.

EXAMPLE 2 A concrete mix was prepared from the following, the weights given being those for each cubic metre of the mix prepared: 400 kg ordinary Portland cement 700 kg sand (6% water by weight) 500 kg "LYTAG" light weight aggregate (3.5% water by weight) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 lignosulphonate 260 kg water Some of the water was first poured into a mixing truck and the aggregate, sand and cement were then added, the other components being poured in powder form onto the aggregate, sand and cement as they were introduced into the truck. The remainder of the water was then added and the components thoroughly mixed.

This mix was pumped through a 100 mm internal diameter pipe to a height of 12 to 13 m and over a distance of about 35 m at a rate of 0.7-0.8 m3 per minute. Pumping was contained for a period of 5 hours, during which time approximately 80 to 85 m3 of concrete were pumped, giving an average pumping rate, including waiting time, mixing time and other normal delays, of about 0.27 to 0.28 m3 / minute. This rate is comparable with that obtained with concrete containing ordinary aggregates. The concrete, after pumping, was of high workability and was easily placed and vibrated. Samples of the conrete achieved adequate compressive strength after 28 days' curing.

EXAMPLE 3 A concrete mix was prepared from the following, the weight being those for each cubic metre of the mix prepared: 375 kg ordinary Portland cement 770kg sand 520 kg "LYTAG" light weight aggregate (pumping grade) 218 kg water (excluding water absorbed by the aggregate on mixing) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 g lignosulphonate The mix was pumped through a 100 mm internal diameter pipe through a distance of 31 m without difficulty.

COMPARA TIVE EXAMPLE A concrete mix was prepared as in Example 1, but excluding the melamine sulphonate/ formaldehyde condensate, the cellulose ether and the lignosulphonate. An attempt was made to pump the mix at a pressure of about 2000 kNlm2 but blockages occurred in the pump due to loss of workability of the mix, and continuous pumping of the material was not possible.

WHAT WE CLAIM IS: 1. A pumpable cementitious composition, comprising a hydraulic cement, water, a porous light weight aggregate, a plasticiser, and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption ol watet by the aggregate when the composition is pumped.

2. A composition according to claim 1, in which the plasticiser is present in an amount by weight greater than that of the non-set retarding dispersing agent and gelling agent together.

3. A composition according to claim 2, in which the plasticiser, the non-set retarding dispersing agent and the gelling agent are present in a weight ratio of 3:1:1.

4. A composition according to any preceding claim, in which the non-set retarding dispersing agent and the gelling agent each comprise 0.001% to 0.04% by weight of the composition.

5. A composition according to claim 4, in which the non-set retarding dispersing agent and the gelling agent each comprise 0.008% to 0.015% by weight of the composition.

6. A composition according to any preceding claim, in which the light weight aggregate comprises sintered pulverized fuel ash.

7. A composition according to any preceding claim, which also comprises sand.

8. A pumpable cementitious composition

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. light weight aggregate, which comprises adding to the composition, before pumping, a plasticiser and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption of water by the aggregate when the composition is pumped. Preferably the non-set retarding dispersing agent and the gelling agent are added in the form of an admixture, which may be in powder form and may include the plasticiser. The invention is further illustrated by the following Examples in which all percentages are by weight. EXAMPLE 1 A concrete mix to be cast into a body of about lm3 in volume was made of the following: 450 kg ordinary Portland cement 740 kg sand (including 6% water by weight) 570 kg "LYTAG" light weight aggregate (in cluding about 12% water by weight) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 g lignosulphonate 310kg water ("LYTAG" is a Registered Trade Mark of Lytag Limited) The components were mixed together to form a wet concrete mix, which was then pumped at a pressure of about 2000 kN/m2 into a mould to form a body of about 1 m3 in volume. The concrete on subsequent testing was found to have adequate compressive strength. No difficulties were experienced in pumping the composition. EXAMPLE 2 A concrete mix was prepared from the following, the weights given being those for each cubic metre of the mix prepared: 400 kg ordinary Portland cement 700 kg sand (6% water by weight) 500 kg "LYTAG" light weight aggregate (3.5% water by weight) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 lignosulphonate 260 kg water Some of the water was first poured into a mixing truck and the aggregate, sand and cement were then added, the other components being poured in powder form onto the aggregate, sand and cement as they were introduced into the truck. The remainder of the water was then added and the components thoroughly mixed. This mix was pumped through a 100 mm internal diameter pipe to a height of 12 to 13 m and over a distance of about 35 m at a rate of 0.7-0.8 m3 per minute. Pumping was contained for a period of 5 hours, during which time approximately 80 to 85 m3 of concrete were pumped, giving an average pumping rate, including waiting time, mixing time and other normal delays, of about 0.27 to 0.28 m3 / minute. This rate is comparable with that obtained with concrete containing ordinary aggregates. The concrete, after pumping, was of high workability and was easily placed and vibrated. Samples of the conrete achieved adequate compressive strength after 28 days' curing. EXAMPLE 3 A concrete mix was prepared from the following, the weight being those for each cubic metre of the mix prepared: 375 kg ordinary Portland cement 770kg sand 520 kg "LYTAG" light weight aggregate (pumping grade) 218 kg water (excluding water absorbed by the aggregate on mixing) 204 g sulphonated melamine formaldehyde condensate 204 g hydroxyethyl cellulose 592 g lignosulphonate The mix was pumped through a 100 mm internal diameter pipe through a distance of 31 m without difficulty. COMPARA TIVE EXAMPLE A concrete mix was prepared as in Example 1, but excluding the melamine sulphonate/ formaldehyde condensate, the cellulose ether and the lignosulphonate. An attempt was made to pump the mix at a pressure of about 2000 kNlm2 but blockages occurred in the pump due to loss of workability of the mix, and continuous pumping of the material was not possible. WHAT WE CLAIM IS:

1. A pumpable cementitious composition, comprising a hydraulic cement, water, a porous light weight aggregate, a plasticiser, and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption ol watet by the aggregate when the composition is pumped.

7. A composition according to any preceding claim, which also comprises sand.

8. A pumpable cementitious composition

according to claim 1, substantially as described with reference to any of Examples 1, 2 and 3.

9. A method of pumping a cementitious composition containing a hydraulic cement, water and a porous light weight aggregate, which comprises adding to the composition, before pumping, a plasticiser and sufficient of both a non-set retarding dispersing agent and a gelling agent to reduce the absorption of water by the aggregate when the composition is pumped.

10. A method according to claim 9, in which the non-set retarding dispersing agent and the gelling agent are added in the form of an admixture.

11. A method according to claim 10, in which the admixture is added in powder form.

12. A method according to claim 10 or 11, in which the admixture includes the plasticiser.

13. A method of pumping a cementitious composition according to claim 9, substantially as described with reference to any of Examples 1,2 and 3.