CS263391B1 - The method of concrete mixture production - Google Patents

Abstract

In today's practice, the turbochargers are added to the concrete mixer, along with the mixing water, for the concrete mixer to the concrete mixer before being emptied on site. According to the invention, a substantial higher fluidity is achieved or a lower dose of the additive can be used by the addition of a fluidizer 10 to 300 seconds after addition of the mixing water or a portion thereof. At the same time, the swelling effect is not rapidly lost, but is maintained for the time required to transport and process the mixture.

Description

The invention relates to a process for the production of a concrete mixture with the addition of a fluidizer.

To improve the workability of the concrete mixture, additives reducing the viscosity of the cement paste and consequently increasing the flowability of the concrete mixture are used. These additives are referred to as plasticizers or fluidizers or superplasticizers. The best known substances with this action are lignin sulphonates, formaldehyde condensates with sulphonated naphthalene, phenol, melamine, but also other substances and combinations thereof.

In practice, these additives are added, in accordance with generally known recommendations, to the mixing water dosed into the concrete mixer in the manufacture of concrete mix (see Ha example Proceedings US1 Rationalizing the production of concrete mixes by chemical additives for concrete, 1984, p. 10). the guarantor was TAZUS Praha spólu with MSv ČSR).

In the case of concrete with a long distribution distance and therefore a long transport time, they are sometimes added at the site of the concrete mixer before the concrete mixer is emptied. In doing so, it aims to eliminate the loss of workability, which occurs relatively quickly when the plasticized concrete is delivered. However, the liquefaction effect of the additives added for a longer time after mixing the concrete mixture is less (see Superplasticizing Admixtures in Concrete, Report of the Joint Working Party of the Cement Admixtures Association and the Cement and Concrete Association, 1976, p. 16).

Surprisingly, it has now been found that the liquefaction effect of the additive addition can be increased up to several times if the additive is not added by the prior art mixing water in the production of the concrete mixture, but only after adding the mixing water or a part thereof. 180 seconds after adding the mixing water to the cement or cement and aggregate. Further prolongation of this time no longer has a positive effect and at times above 300 seconds the efficiency decreases.

Accordingly, according to the invention, a plasticized or liquefied concrete mixture is produced in that the cement is first contacted with the mixing water or part thereof and only after a period of not less than 10 seconds and not longer than 300 seconds, preferably after 60 to 180 seconds. adds a dripping additive.

The enhancement of the effect achieved according to the invention is apparent from the exemplary embodiments. A mixture of Portland cement and standard sand with v / c 0.45 was produced, to which they were added in a different batch of fluidizer at different times from the time of addition of the mixing water. The fluidity after preparation of the mixture as well as the repeated fluidity of the same, maturing after a further 20 minutes, were determined. The flowability was measured by a standard method such as spillage of the mixture on the shaker. In the tables, the liquefaction expressed as a% of the spillage value of the mixture without additive is achieved.

Example 1

Liquefaction of the mixture by addition of lignin sulphonate

Additive added 0.15% 0.30% 0.45%

after adding water after production after production after production sec immediately ¹ zaa / 20 * immediately for 20 ' immediately. za 20 0 11 6 21 2 35 8 30 22nd 10 30 32 120 30 30 44 48 53 61 360 25 23 42 59 41 48 Fifteen minutes 0 1 23 26 32 32

It can be seen from the results that by the method according to the invention, it is possible to add 3 times less liquid flow to the same liquefaction.

Achieve up to 3-fold flow at low dose, 2-fold at medium dose and 50% higher at high dose.

While the addition of the additive to the water, the flowing effect quickly disappears with time, according to the invention it was the same after 20 minutes and at higher doses even higher than immediately after mixing. This is significant because the concrete mixture compacts after a certain time from production. At the same time, the results show that a very short as well as a very long time between the addition of water and the additive is not appropriate and the desired effect is not achieved.

The same conclusions also follow from the next example.

Example 2

Liquefaction of the mixture by the addition of naphthalene condensate

Additive added to < 0.30% 0.45% after addition of water after manufacture

sec immediately for 20 ' immediately for 20 ' immediately for 20 ' 0 6 3 24 25 30 21 27 Mar: 40 74 46 60 36 26 52 42 83 78 180 48 34 75 57 79 81 360 34 30 33 12 57 59 Fifteen minutes 25 26 15 Dec 10 41 43

Example 3

Liquefaction of the mixture by addition of melamine condensate

Additive added after the addition of water sec 0.15% 0,30% after production immediately after 20 ' 0.45% immediately after 20 ' immediately for 20 ' 0 13 4 18 13 31 ³⁰ 18 8 58 47 60 32 20 May 76 180 57 47 126 360 46 50 Fifteen minutes 46 40

The results of the examples show that it is a highly efficient and technically undemanding method. It is natural that the effect achieved also depends on the composition of the concrete mixture and its components and thus may be higher or lower in specific cases. The optimum time should be determined experimentally for a specific mixture, and it is also influenced by other factors of production - such as the capacity of the concrete mixing plant and the limited mixing time for these capacity factors. Addition of the additive for example up to 180 seconds after the addition of the mixing water can be utilized without changing the mixing time in the mixer, for example by adding the additive after this time to the mixer. Adding times in tens of seconds directly to the concrete mixer.

Similar to the manufacture of concrete mixtures, the process of the invention can be used in the manufacture of mortar mixes, cement-bentonite mixtures and other cementitious binders freshly flowed by the addition of flowing additives.

Claims (1)

OBJECT OF THE INVENTION Process for producing a concrete mixture with the addition of a flowing additive characterized in that the additive is added 10 to 300 seconds expediently 30 to 180 seconds after the addition of the mixing water or part thereof.