DE2710975B2 - Pumpable concrete mix - Google Patents

Description

The invention relates to pumpable concrete mixes.i, the porous, lightweight aggregates (aggregates) contain.

Lightweight aggregates (aggregates) tend to be porous and can therefore usually not be added to cementitious mixtures to be pumped, since when pressure is applied to mixtures containing such aggregates (aggregates) the water in the mixture is forced into the pores of the aggregate particles, resulting in a leads to a considerable deterioration in the processability of the mixture. This deterioration in processability can lead to the pump blocking if pressures of 1000 to 4000 kN / m ² occur.

The absorption of water by the aggregates when pumping the mixture can be prevented by pre-watering the Aggregates are reduced. However, this requires the use of an expensive vacuum washing process, which leads to a considerable increase in the overall costs of the pumping process and this in turn Makes it uneconomical compared to conventional slower conveying techniques. For these reasons the pumping of concrete containing lightweight aggregates has not yet been widely used found.

The invention now relates to a concrete mix as characterized in the claims Kind, whereby the additive combination contained in the concrete mix leads to a reduction of the Leads to water absorption through the aggregate.

Although the amounts of component a and b depending on the lightweight surcharge and the amount to which the concrete mix to be pumped can vary over a wide range, so their respective share in the Mixture preferably 0.001 to 0.04% by weight and in particular 0.008 to 0.015% by weight.

Component a, the dispersant, disperses the cement particles, but does not delay the hardening (setting) of the cement regardless of the concentration tration in which it is used. Examples of such Dispersants include: sulfonated melamine formaldehyde, sulfonated polystyrenes and sulfonated naphthalene formaldehyde.

Component b, the gelling agent, is typically a water-soluble cellulose derivative, e.g. B. methyl cellulose, Hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose or hydroxyethyl cellulose.

Component c serves as a plasticizer for the concrete and is typically a dispersant,

which, when used in high concentration, tends to increase the hardening (setting) of the cement. Examples of such plasticizers include lignosulfonates and hydroxycarboxylic acid derivatives such as Sodium gluconate or sodium heptanoate. A weight ratio of plasticizer is particularly suitable to gelling agent to dispersing agent of about 3: 1: 1.

The water cement (hydraulic cement) can be an ordinary portland cement or a sulfate-resistant

i (i be ger or quick setting cement. Everyone im Commercially available porous, lightweight aggregate can be used. So can the aggregate be sintered, pulverized fuel ash, such as B. under the trade name "LYTAG" im

ü Commercially available aggregate. Others suitable Porous, lightweight aggregates are slag (clinker), foamed slag (foamed slag), expanded Slate, pumice stone, diatomite, expanded perlite, and expanded vermiculite.

mi The aggregate can be made entirely of lightweight Abrasion, the particles having a maximum size of less than 5 mm, or partly or entirely consist of larger particles. Sand can be added to the concrete mix.

• Ti The invention also relates to a method for Production of a pumpable concrete mixture, which is characterized in that the mixture is before pumping sufficient to reduce water absorption by the aggregate under pressure

μ Amounts of the previously described additive combinations from components a, b and c (dispersants, gelling agents and plasticizers) are added. Components a (dispersant) and b (gelling agent) are preferably in the form of a mixture

M added, which can be preformed in Pu! '.

The invention is to be explained in more detail below with the aid of examples; all percentages are based on weight.

example 1

A concrete mix for pouring into a cavity of about 1 m ^{1 was} prepared from the following components:

450 kg of ordinary portland cement
740 kg sand (water content 6%)
570 kg »LYTAG«, lighter
(Water content about 12%)

Aggregate

204 g sulfonated melamine formaldehyde condensate

204 grams of F-hydroxyethyl cellulose

592 grams of lignosulfonate

310 kg of water

(»LYTAG« is a trade name of the company

Lytag Limited and is made from powdered ash with

a low content of carbon and sulphate)

The components were mixed together to form a wet concrete mix which was then pumped into a mold ^{at a pressure of about 2000 kN / m 2} to form a 1 m ^{3 body.} Tests carried out afterwards showed that the concrete had good compressive strength. Pumping the mixture was no problem.

Example 2

A concrete mixture was produced from the following components, the specified weights being used for the production of 1 m ^{3 of} mixture:

400 kg of ordinary portland cement

700 kg sand (6% water)

5Λ) kg »LYTAG«, lightweight aggregate (3.5% water)

204 g sulfonated melamine formaldehyde condensate 204 g of hydroxyethyl cellulose 592 grams of lignosulfonate 260 kg of water

Some of the water was first placed in a mixing vat and then the aggregate, sand and cement were added. The others Components were poured in powder form onto the aggregate, sand and cement and into the Mixing tub introduced. Then the remaining water was added, and the components were thoroughly mixed.

This mixture was through a pipe with an internal diameter of 100 mm to a height of 12 to 13 m and over a distance of 35 m with a throughput of 0.7 to 0.8 mV min. pumping The pumping was continued for 5 hours, pumping about 80 to 85 m ^{3 of} concrete. The average pumping rate including waiting time, mixing time and other normal

The delays were about 0.27 to 0.28 mVmin. This delivery rate is comparable to that obtained with concrete containing ordinary aggregates. After pumping, the concrete was good Processable and could easily be placed and jogged

ίο be. Samples of this concrete achieved a good one Compressive strength after curing for 28 days.

Example 3

A concrete mixture was produced from the following components, the specified amounts by weight being used for each 1 m ^{3 of} mixture:

375 kg of ordinary Portland cement 770 kg of sand ^J 520 kg of "LYTAG", lightweight aggregate

(pumping grade) 218 kg of water (excluding that from the aggregate

when mixing absorbed water) 204 g sulfonated melamine formaldehyde condensate "'204 g of hydroxyethyl cellulose 592 grams of lignosulfonate

The mixture went through with no difficulty Pipe with an inside diameter of 100 mm pumped over) o a distance of 31 m.

Comparative example

A concrete mix was prepared as described in Example 1, with the difference that none sulfonated melamine formaldehyde condensate, no cellulose ether and no lignosulfonate were used. Attempts were made to pump the mixture at a pressure of about 2000 kN / m ² , but due to the deteriorated processability of the mixture,

clogged the pump and continuous pumping of the material was not possible.

Claims (5)

Patent claims: 1. Pumpable concrete mix, which is essentially a water cement, water and porous contains lightweight aggregate and, if necessary, sand, characterized that it also contains an additive combination that consists of the components a) sulfonated melamine formaldehyde, sulfonated Polystyrenes, sulfonated naphthalene formaldehyde or mixtures thereof, b) water-soluble cellulose derivative, such as methyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose, Hydroxyethyl cellulose or mixtures thereof and c) lignosulfonates and / or hydroxycarboxylic acid derivatives, such as sodium gluconate and sodium heptanoate consists. 2. Concrete mix according to claim 1, characterized in that component c) is larger Amount is present as the sum of components a) and b). 3. Concrete mix according to claim 2, characterized in that the weight ratio of Components a), b) and c) is 1: 1: 3. 4. Concrete mix according to claim 1 to 3, characterized in that they are each 0.001 to 0.04 Contains percent by weight of components a) and b). 5. Concrete mix according to claim 4, characterized in that they are each 0.008 to 0.015 Contains% by weight of components a) and b).