CA1238038A - Process and plant for the production of cement concrete - Google Patents
Process and plant for the production of cement concreteInfo
- Publication number
- CA1238038A CA1238038A CA000441226A CA441226A CA1238038A CA 1238038 A CA1238038 A CA 1238038A CA 000441226 A CA000441226 A CA 000441226A CA 441226 A CA441226 A CA 441226A CA 1238038 A CA1238038 A CA 1238038A
- Authority
- CA
- Canada
- Prior art keywords
- fine fraction
- cement
- mixing
- aggregates
- fraction
- 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
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28C—PREPARING CLAY; PRODUCING MIXTURES CONTAINING CLAY OR CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28C5/00—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions
- B28C5/003—Methods for mixing
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Structural Engineering (AREA)
- Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
- Artificial Fish Reefs (AREA)
Abstract
19.
Abstract A process for the production of cement-concrete by intimate mixing of aggregates, cement, optional filler, and water in a concrete mixer, wherein the fine fraction of the aggregates is only added into the mixer after the remaining components have been mixed, with the result that the coarse fraction of the aggregates is coated with a paste, consisting of cement, optional filler, and water in which the fine fraction is absorbed.
The addition of the fine fraction is effected successively, controlled by the proportioning means for the fine fraction, preferably by controlled vibration technique. The fine fraction is advantageously added into a zone of the mixer in which the mass consisting of the paste-coated coarse fraction and free-flowing cement paste is moved in a material flow under the influence of an external pressure from the mixing means. In the plant for the realization of the process and comprising a mixing container with proportioning means for the components of the concrete, mixing and discharge means, the proportioning means for the fine fraction of the aggregates is equipped with devices for the control and regulation of the flow of the fine fraction, and is preferably a vibratory feeder.
A homogeneous concrete having excellent strength properties is obtainedwith considerable cement savings.
Abstract A process for the production of cement-concrete by intimate mixing of aggregates, cement, optional filler, and water in a concrete mixer, wherein the fine fraction of the aggregates is only added into the mixer after the remaining components have been mixed, with the result that the coarse fraction of the aggregates is coated with a paste, consisting of cement, optional filler, and water in which the fine fraction is absorbed.
The addition of the fine fraction is effected successively, controlled by the proportioning means for the fine fraction, preferably by controlled vibration technique. The fine fraction is advantageously added into a zone of the mixer in which the mass consisting of the paste-coated coarse fraction and free-flowing cement paste is moved in a material flow under the influence of an external pressure from the mixing means. In the plant for the realization of the process and comprising a mixing container with proportioning means for the components of the concrete, mixing and discharge means, the proportioning means for the fine fraction of the aggregates is equipped with devices for the control and regulation of the flow of the fine fraction, and is preferably a vibratory feeder.
A homogeneous concrete having excellent strength properties is obtainedwith considerable cement savings.
Description
~8~3~
1.
Pr~ces~ and Plant ~or the Produc~ion o~ Cemen-t - Concr~t~
The invention presen-ted relates to a process for the production of cement-concrete by intimate mixing of aggrega-tes, cement, optional filler, and water in a concrete mixer by which the Eine fraction of the aggrega-te material is only added aE~er the remaining components have been mixed, with the result that the coarse f raction of -the aggrega~e rnaterial is coated wi-th a paste consis-ting of cement, optional filler, and water, in which the fine fraction is absorbed.
A process oE this nature is described in the SE patent specification No.
770005~9, publication No. 415 3~9 with the same inventor as the present application, and assigned to the present applicant. This patent specification represents a fundamental breach wi-th tradi-tional concrete mixing techn;ques, according to which the en-tire aggregate quallti-ty is normally added into the concrete mixer, including both the coarse fraction (normally stone materials with particle si~es of 32 - ~ mm) and the fine fraction (sand ~vith particle sizes up to ~ mm) toge-the- with -the cement and mixed for a certain period of time before water is added. It also occurs that aggregates, water and cement are added in the sequence mentioned or alternatively that water and cemen-t are mixed into a paste which is then added to the aggregates.
The process according to the above SE patent specifica-tion with the speciic purpose to produce a cement-concre-te mass with an elevated filler content, low cement content and an ele~ated con-tent of coarse aggregates (stone), was based on the hypothesis -tha-t if the coarse fraction of the aggregates was first added to the mixer and thereafter cement, filler and water in the form o a paste, or one after the other, part of the produced filler-containing cement pas-te would coat the particles contained in the coarse fraction oF the aggregates, while the remaincler would form a free-flowing paste, and when the fine frac-tion c~f the aggregates is thereafter added by continued mixing -the particles of the fine fraction would be absorbed and encapsula-ted in the paste, c oating the .
'' 3~@113~
1.
Pr~ces~ and Plant ~or the Produc~ion o~ Cemen-t - Concr~t~
The invention presen-ted relates to a process for the production of cement-concrete by intimate mixing of aggrega-tes, cement, optional filler, and water in a concrete mixer by which the Eine fraction of the aggrega-te material is only added aE~er the remaining components have been mixed, with the result that the coarse f raction of -the aggrega~e rnaterial is coated wi-th a paste consis-ting of cement, optional filler, and water, in which the fine fraction is absorbed.
A process oE this nature is described in the SE patent specification No.
770005~9, publication No. 415 3~9 with the same inventor as the present application, and assigned to the present applicant. This patent specification represents a fundamental breach wi-th tradi-tional concrete mixing techn;ques, according to which the en-tire aggregate quallti-ty is normally added into the concrete mixer, including both the coarse fraction (normally stone materials with particle si~es of 32 - ~ mm) and the fine fraction (sand ~vith particle sizes up to ~ mm) toge-the- with -the cement and mixed for a certain period of time before water is added. It also occurs that aggregates, water and cement are added in the sequence mentioned or alternatively that water and cemen-t are mixed into a paste which is then added to the aggregates.
The process according to the above SE patent specifica-tion with the speciic purpose to produce a cement-concre-te mass with an elevated filler content, low cement content and an ele~ated con-tent of coarse aggregates (stone), was based on the hypothesis -tha-t if the coarse fraction of the aggregates was first added to the mixer and thereafter cement, filler and water in the form o a paste, or one after the other, part of the produced filler-containing cement pas-te would coat the particles contained in the coarse fraction oF the aggregates, while the remaincler would form a free-flowing paste, and when the fine frac-tion c~f the aggregates is thereafter added by continued mixing -the particles of the fine fraction would be absorbed and encapsula-ted in the paste, c oating the .
'' 3~@113~
2.
particles of the coarse fraction. The fine fraction particles will increase -the viscosi-ty of -the paste, which is high as i-t is, due to the filler conten-t, bu-t the pas-te will remain liquid. It was assumed that the cornpressive s-trength and the workability of -the concrete would be increased, with an increasinO quanti~y of fine fraction incorporated in the cemen-t paste during the mixing.
By -the process described in the pa-tent specification it should also be possi~le to reduce the water/cemen-t ratio in rela-tion to the conven-tional dry mixing process with unchanged quan-tities of aggregates and cement, as a considerable quantity of filler was used.
I-t is a well-known fact tha-t the water/cernent ratio, indica-ting the weight proportion between water and cement in a given concrete rnix, is of vital impor~ance Eor the s-trength qualities of the concrete, and a reduced water/cement ra-tio would -therefore also be desirable.
1~ The dr~wings of the patent speciEic~tion, showing the resul-ts of tests on a laboratory scale with concre-te mixes each of 13 kg seem -to confirm that the adding of filler and the changed mixing sequence provicled the alleged improvements of the s-tren"th qualities of the concre-te. This was, however, largely conditional on the addition of filler.
The mixing process, dealt with in the patent specification has, however, never been applied in practice. On the basis of the promising laboratory test, test runnings on an industrial scale were initiated in a Swedish concrete factory under application of the existing, well-tested mixing plants and concrete recipes, however, with an altera-tion oE the adding sequence in accordance with the teachings of the patent specification, meaning tha-t the fine fraction of the aggregate was added after the mixing of the remaining componen-ts. However, it proved impossible -to absorb the entire sand quantity homogeneously in the cement paste.
Local drainings of the cement paste were observed, and even with long mixing times a heterogeneous concrete was produced~ showing no ~;~3~3~3
particles of the coarse fraction. The fine fraction particles will increase -the viscosi-ty of -the paste, which is high as i-t is, due to the filler conten-t, bu-t the pas-te will remain liquid. It was assumed that the cornpressive s-trength and the workability of -the concrete would be increased, with an increasinO quanti~y of fine fraction incorporated in the cemen-t paste during the mixing.
By -the process described in the pa-tent specification it should also be possi~le to reduce the water/cemen-t ratio in rela-tion to the conven-tional dry mixing process with unchanged quan-tities of aggregates and cement, as a considerable quantity of filler was used.
I-t is a well-known fact tha-t the water/cernent ratio, indica-ting the weight proportion between water and cement in a given concrete rnix, is of vital impor~ance Eor the s-trength qualities of the concrete, and a reduced water/cement ra-tio would -therefore also be desirable.
1~ The dr~wings of the patent speciEic~tion, showing the resul-ts of tests on a laboratory scale with concre-te mixes each of 13 kg seem -to confirm that the adding of filler and the changed mixing sequence provicled the alleged improvements of the s-tren"th qualities of the concre-te. This was, however, largely conditional on the addition of filler.
The mixing process, dealt with in the patent specification has, however, never been applied in practice. On the basis of the promising laboratory test, test runnings on an industrial scale were initiated in a Swedish concrete factory under application of the existing, well-tested mixing plants and concrete recipes, however, with an altera-tion oE the adding sequence in accordance with the teachings of the patent specification, meaning tha-t the fine fraction of the aggregate was added after the mixing of the remaining componen-ts. However, it proved impossible -to absorb the entire sand quantity homogeneously in the cement paste.
Local drainings of the cement paste were observed, and even with long mixing times a heterogeneous concrete was produced~ showing no ~;~3~3~3
3.
improvement of the strength qualities. lt was -thus impossible to render probal~le to skilled persons that the sug~ested change of th~ mixing sequence, -the introduc~ion of which in itself demanded great efforts to overcome very rooted prejudices, had any future.
The present invention rests on ~he surprising realization that to achieve the results aspired in -the patent specifica-tion it is necessary to overcome not only one but two prejudices, and further the adding of filler is not obligatory for the achievement of good strength quali~ies.
As proved by the mentioned, unsuccess-ful tests, and as it will appear from the examples, mentioned below, it is namely not adequate to chanOe only the sequence in which the individual components of the cement-concrete mass are added. It is of vital importance for the homo~geneous absorption of the particles of -the fine fraction during -the mixing process in-to the free-flowin~g cement paste and in-to the part of the paste, coating the coarse particles, that the particles are not as usual added at a time over the shor-test possible period of tirn~ to star-t the mixing process, bu-t on thecontrary that they are added successively in a controlled flow of materials which can be provided by the applica tion of a proportioning means for the fine fraction. The process according to the invention is therefore characterized in -that the addition oE the fine traction is effected successively, controlled by the proportioning means for the fine fraction.
As it will appear from the following test results it is in this way possible to produce a particularly homogeneous concrete wi-th an essential reduction of -the mixing time, wi-th a thus achieved reduction of the energy consumption and wear on the rnixer, also due to the coating effect, brought about by the cement paste under -the adding of the fine fraction.
The concre-e, produced in accordance with the process of the invention, shows in addition to the improved homogeneity a reduced tendency -to separa-tion, and the concrete shows no sign of accumulations of free washed stones, the so-called "stone-nests", as all stones are neatly -, ~3~3~3
improvement of the strength qualities. lt was -thus impossible to render probal~le to skilled persons that the sug~ested change of th~ mixing sequence, -the introduc~ion of which in itself demanded great efforts to overcome very rooted prejudices, had any future.
The present invention rests on ~he surprising realization that to achieve the results aspired in -the patent specifica-tion it is necessary to overcome not only one but two prejudices, and further the adding of filler is not obligatory for the achievement of good strength quali~ies.
As proved by the mentioned, unsuccess-ful tests, and as it will appear from the examples, mentioned below, it is namely not adequate to chanOe only the sequence in which the individual components of the cement-concrete mass are added. It is of vital importance for the homo~geneous absorption of the particles of -the fine fraction during -the mixing process in-to the free-flowin~g cement paste and in-to the part of the paste, coating the coarse particles, that the particles are not as usual added at a time over the shor-test possible period of tirn~ to star-t the mixing process, bu-t on thecontrary that they are added successively in a controlled flow of materials which can be provided by the applica tion of a proportioning means for the fine fraction. The process according to the invention is therefore characterized in -that the addition oE the fine traction is effected successively, controlled by the proportioning means for the fine fraction.
As it will appear from the following test results it is in this way possible to produce a particularly homogeneous concrete wi-th an essential reduction of -the mixing time, wi-th a thus achieved reduction of the energy consumption and wear on the rnixer, also due to the coating effect, brought about by the cement paste under -the adding of the fine fraction.
The concre-e, produced in accordance with the process of the invention, shows in addition to the improved homogeneity a reduced tendency -to separa-tion, and the concrete shows no sign of accumulations of free washed stones, the so-called "stone-nests", as all stones are neatly -, ~3~3~3
-4 ~
surrounded by cement paste~ The concrete liberates only a reduced quantity of water before and after vibration in which way bleeding on the concrete surface and thus strength reduction are avoided. Moreover, -the compressive strength measures show a reduced standard strength deviation compared to concrete produced accord-ing to the normal process. Due to the improved homogen-eity of the concrete and the demonstrated reduced standard deviation of strength it will also by the process according to the invention be possible to reduce the cement content in a given concrete mix, while maintain-ing the strength values.
That the disadvantages, experienced by the reproduction of the SE patent on an industrial scale can be eliminated just by controlling the material flow of the fine fraction may seem obvious in retrospect. However, it is important to keep in mind that such a control constitutes a funda-mental breach with the concrete mixing techniques of several decades, resting on the opinion tha-t the mixer does the work for which reason the components of the batch should be added as quickly as possible in order t~o start up the mixing process.
Without the intention to accuse the concrete technolo-gists of being more conservative than skilled persons within other fields, it appears that the inventions within the concrete field have in latest years principally con-centrated on improving the effectiveness of the mecha-nical part of the mixing process, or on varying the grain size distribution of the fine fraction, or on adding special admixtures to produce improved products.
That it should be possible to perfect the process, rejected by skilled persons, according to Danish patent specification No. 7700052-9, published as publi_ation No.
415 347 on September 29, 1980, merely by modifying the proportioning means for the fine fraction, thus to ~38~3~3 -4a-achieve control with the material flow, must be considered, highly to exceed the expectations of the skilled persons.
The importance of this simple modification is better unders-tood by a closer observation of the very mixing process. By the prevalent dry mixing 3~
surrounded by cement paste~ The concrete liberates only a reduced quantity of water before and after vibration in which way bleeding on the concrete surface and thus strength reduction are avoided. Moreover, -the compressive strength measures show a reduced standard strength deviation compared to concrete produced accord-ing to the normal process. Due to the improved homogen-eity of the concrete and the demonstrated reduced standard deviation of strength it will also by the process according to the invention be possible to reduce the cement content in a given concrete mix, while maintain-ing the strength values.
That the disadvantages, experienced by the reproduction of the SE patent on an industrial scale can be eliminated just by controlling the material flow of the fine fraction may seem obvious in retrospect. However, it is important to keep in mind that such a control constitutes a funda-mental breach with the concrete mixing techniques of several decades, resting on the opinion tha-t the mixer does the work for which reason the components of the batch should be added as quickly as possible in order t~o start up the mixing process.
Without the intention to accuse the concrete technolo-gists of being more conservative than skilled persons within other fields, it appears that the inventions within the concrete field have in latest years principally con-centrated on improving the effectiveness of the mecha-nical part of the mixing process, or on varying the grain size distribution of the fine fraction, or on adding special admixtures to produce improved products.
That it should be possible to perfect the process, rejected by skilled persons, according to Danish patent specification No. 7700052-9, published as publi_ation No.
415 347 on September 29, 1980, merely by modifying the proportioning means for the fine fraction, thus to ~38~3~3 -4a-achieve control with the material flow, must be considered, highly to exceed the expectations of the skilled persons.
The importance of this simple modification is better unders-tood by a closer observation of the very mixing process. By the prevalent dry mixing 3~
5.
process the water content in -the cement pas-te is increased during the m;xing from zero by water feeding start-up to the final value, corresponding to the requested water/cement ra-tio. During the mixing the concrete -thus passes from a dry to a we-t stage.
Contrary to this from the beginning of the adding of the fine fraction, the cement paste has the pre-de-terminated water content, and a~l the cemen-t particles are preground and possibly ac-tivated by the mixing wi-th the coarse fraction. By the successive adding of the fine fraction water is bound by the formation of water meniscus between the fine grains. By this the viscosity of the paste and the volume of fines in the mix are increased. Thus, during the mixing process the concrete passes from a wet to a less wet stage.
The qualities of the concrete mass, such as homogenei-ty and workabili-ty increase with increasing fine fraction volume which contributes to the above improved quali-ties of the ready concrete.
1, .
A particularly appropriate adding of -the fine Eraction is achieved by controlled vibration technique, more precisely by the application of a so-called vibratory feeder.
Such vibratory feeders have a wide field of applica-tion within the most diversi:Eied lines of material handlin~" from the transportation of granulated su~ar in sugar factories to the charging of pelle ts in blast furnaces.
The application of a vibratory feeder in the process according to the invention permits an especially effective control with -the material flow of the fine fraction whic'n can be adjusted according to requirements.
An investigation of differen-t types of concrete mixers has proved that the optimum mixirllg process and the best concre-te mass is achieved if the fine fraction is added in a zone oF the mixer in which the mass, including the paste-coated coarse fraction and ~he free-flowing cemen-t paste is moved , . ,.
3~
process the water content in -the cement pas-te is increased during the m;xing from zero by water feeding start-up to the final value, corresponding to the requested water/cement ra-tio. During the mixing the concrete -thus passes from a dry to a we-t stage.
Contrary to this from the beginning of the adding of the fine fraction, the cement paste has the pre-de-terminated water content, and a~l the cemen-t particles are preground and possibly ac-tivated by the mixing wi-th the coarse fraction. By the successive adding of the fine fraction water is bound by the formation of water meniscus between the fine grains. By this the viscosity of the paste and the volume of fines in the mix are increased. Thus, during the mixing process the concrete passes from a wet to a less wet stage.
The qualities of the concrete mass, such as homogenei-ty and workabili-ty increase with increasing fine fraction volume which contributes to the above improved quali-ties of the ready concrete.
1, .
A particularly appropriate adding of -the fine Eraction is achieved by controlled vibration technique, more precisely by the application of a so-called vibratory feeder.
Such vibratory feeders have a wide field of applica-tion within the most diversi:Eied lines of material handlin~" from the transportation of granulated su~ar in sugar factories to the charging of pelle ts in blast furnaces.
The application of a vibratory feeder in the process according to the invention permits an especially effective control with -the material flow of the fine fraction whic'n can be adjusted according to requirements.
An investigation of differen-t types of concrete mixers has proved that the optimum mixirllg process and the best concre-te mass is achieved if the fine fraction is added in a zone oF the mixer in which the mass, including the paste-coated coarse fraction and ~he free-flowing cemen-t paste is moved , . ,.
3~
6.
in a material flow under the influence of an external pressure from the rnixing means in such a way that the material Elow is pressed together and -the par~icles thus under rolling pressed against each other. By the successive adding oE the particles of the fine fraction into the material flow -these are drawn into the flow, and due to the pressure between the particles of the coarse frac~ion and the individual movernents of the p~rticles, brought about by the mixing means, the particles of the fine fraction are "ground" into the paste coating of the coarse particles.
Considering this it will be especially advantageous to design the mixing means and arrange the curve path described so as to establish high and low pressure zones in the concrete mass during the mixing process. This can e.g. be achieved by the applica tion of a stationary mixing pan in which the mixing shovels are driven in pairs in a planetary movement.
The successive adding oE the Eine fraction is advantageous~y adjusted so in relation to the rotation ot the mixing means that the fine fraction added does not meet previously added fine fraction material~ not yet absorbed in the paste, which would then form a double layer of fine fraction which i-t would be difficult homogeneously to work into the mass.
Despite the Iact tha-t the application of fillers, contrary to the SE patent specification No. 415 349, is not obligatory for the process in accordance with the invention it may be desirable -to add filler, among other things to be able to adjust the viscosity of the cement paste. Such an adjustment could be carried out by measuring means for -the de-termination of the viscosity of the paste, connected to the proportioning means for the filler.
It is pointed out that the designation "filler" is here used in the widest ~of the word, and not only with the meaning fine fraction material with particle sizes srnaller than l/4 mm, but also covering mineral admixtures such e.g. as silica, fly ash, puzzolanes etc., and in addition more special admixtures such as colours and inactive fillers such as fineground quartz etc. The filler materials are normally added together with the cement and/or used for later adjustrnents.
~38~3~
Any admix-ture for the productis~n of concrete may be used in -the process according to the invention, both l. Physically active admixtures such as plas-ticisers, both normal and superplasticisers9 and air-entrainin~ admixtures, such as tensides, reducing the surface tension of the water by the formation of bubbles, and 2~ Chemically active admixtures such as accelerators or retarders for the reaction be-tween wa-ter and cement The adding of these admix-tures will normally be effected wi-th the las-t part of the water before the adding of the fine fraction which will enabie -the cement to react wi-th water on its surface.
It has also -turned out tha-t to produce a concre-te wi-th op-timurn qualities -the coarse frac-tion of the aggregates can with advantage be moistened with part of -the water before cement, op-tional filler, and the remaining water quantity is added. It is also important to establish a suitable pre-mixing time before successively adding the fine fraction. Hereby the qualities of the cement paste and thus the workabili ty of the mass is improved.
The invention further relates to a plant for the production of cement concre-te and of a na-ture comprising a mixing container ~vith proportioning means for the components of the concrete mass, mixing means and discharge means, and the plant is characterized in that the propor-tioning means for the fine fraction of the aggregates is equipped with devices for the control and regulation of the flow of the fine fraction.
Preferably the propor~ioning means for the fine fraction is a vibratory feeder, providing a very accurate control with the proportioning and which can be adjusted to provide different proportionin~ periods, in accordance with the composition and qualities of the concrete mass in question.
-I, `f,l " ~3~33~3 8.
If diesired, the proportioning rnearls can be adap-ted to ~dd the fine fraction on more than one zone of the mixer. ~ t~is can be achieved by the application of -two or more proportioning means or by a turnable proportioning device.
e~ ~7~J,~ ~ .f ~b S In the,li~ of the process according to the invention in which filler is used for the adjustment of the viscosity of the cement paste, the plant may also include means for the determination of the viscosity of the cemen t pas-te, connected to the proportionin g means for the filler and control the filler flow.
In order to achieve a particularly effective mixing of the fine fraction i~
is of great importance that the material flow in the mixer is under the influence of an external pressure from the mixing means, thus es-tablishing high and low pressure zones in the concrete mass, and tha-t the Eine fraction is ~dded in a high pressure zone. In addition -to the fact that the pressure can be increased or reduced in the pressure ~one by an increasecl or reduced material flow of fines, the mixin~ means of the plan-t are primarily designed so as to establish al-ternating high and low pressure zones which can further be supported by adapting the mixing means to move in a curved path,e.~.3a planetary movement.
The invention can be applied in the production of any type of concrete for varyin~ purposes and with varying stren~th qualities. A person skilled in the art will be able to determine the optimum mixing process -for a given type of concrete by varying the components of the mass, the grain sizes of the aggrega-tes, the types of cement, different admixtures, mixing time etc.
Comparative Tests on a Laboratory Scale In order to document the importance of a successive adding of -the fine fraction of the aggrega-te materials (sand 0 - 4 mm) tests were carried out in a laboratory pan mixer wi-th four shovels and two side scrapers by which 3 the pan and the shovels rotated in the opposite directions. The used basic mix had the composi-tion:
~3~138 9.
Rapid cement 325 kg/cbm Wa-ter 150 kg/cbm W/C ratio 0.46 Aggregates:
Sand 0 - 4 mm 650 kg/cbm Stone 4 - 16 mm 1260 kg/cbm The following tests were carried out:
Reproduction of SE Patent No. 415 349 S~one and half of the water were mixed for 5 s. to moisten the stone material. Hereafter cement and the remainder of the water, con~aining a plasticiser, were added, and the mix was pre-mixed for 20 s. Hereafter the sand yuantity was added at a time, and the mixing was continued for 65 s. Total mixing -time 90 s.
II Process Accordin~ to the Invention (long pre-mixing time).
Stone, water, containing a plasticiser, and cement were mixed as under I. Hereafter sand was added over a pe~iod o:E 20 s., and -the mixing was continued for 45 s. Total mixing time 90 s.
On termination of -the mixing the following determinations were madeo II
Air content 1,2% 1,3%
Slump Slump (Vebe~ 4 s. 2,5 s.
Mix 1 was homogeneous and had a workabili-ty, expressecl by a Vebe measure of 4 s.
.-, ~' .
2~3~
10.
Mix 11 was also homogeneous and demonstrated an improved workability, expressed by a Vebe measure of 2,5 s.
Of both types of concrete cylinders were cast which were used for early compressive strength determina-tions according to standard DS 423, 1 and 2 days after completed mix, respectively.
The results of the compressive strength tests appear from the b~
-tabl~. By way of comparison,standard values for concretetproduced with the same type of rapid cemen~ according to the traditional mixing technique, are usedO
Compressive Stren~th A/l Pa Period 1 II Stand. Values 21 h 11.6 13 (24 h) 22 h 10.6 44 h 30.1 23 ~4~ h) 45 h 29.3 From the above table it is seen that test Il shows improved- early strength values, not least if the time differences are taken into account. It is assumed that the differences would be even more significant if a mixer providing high and low pressure zones had been used.
Comparative Tests on an Industrial Scale .
The tests have bee~ run wi-th a very experienced Danish manufacturer of concrete with his existing 1500 1 SK~KO mixer for the production of ready-mixed concrete.
The mixer is a pan mixer, operating on the basis of the counter-current mixing principle, by which the mixing is effected in a fixed pan by means of 4 shovels, driven in pairs by a planetary gear box. In addition the mixer is equipped with 2 off side scrapers, incorporated with the purpose to lead .
3~
11.
the concrete to the most active mixing zone. The speed of the side scrapers is approx. hal~ the speed oE the shovels. This specific cou~r-A current mixing principle makes the concrete mass mov$ ~. one round per each 10 - 12 s. and brings about the effect that high and low pressure zones are continuously developed in the concrete mass.
~he below concrete recipes have been selected for the tests, according to the standard mixing procedure and -to the new mixing procedure.
1) 15 MN/M_ Concrete Cement (Portiand) 230 kg Water 165 1 Sand (0 - 4 mm) 717 kg Gravel (4 - 8 mm3 200 kg Gravel (8- 16 mm) 818 kg Air-en-training admix 53 g 2) 30 MN/M_ Concrete Cement (Portland) 330 kg Water 165 1 Sand (0 - 4 mm) 66~ kg Gravel (4 - 8 mm) 200 kg Gravel (8 - 1~ rnm3 789 kg Air-entraining admix 60 g Pipe Concrete Cement (Portlarid~ 346 kg ~/ater 131 1 ; 25 Sand (0 - 4 mm) 760 kg Gravel (4 - 8 mm) 285 kg Gravel (8 - 16 mm) 855 Icg ~L23~
The below described proportioning cycle has been applied:
A. Standard Mixing Procedure The stone fractions 4 - 8 and 8 - 16 mm and the sand were added a-t a time. AEter a dry-mixing period of 5 s. wa~er was added over a period of 20 s., and after 15 s. mixing time ~he cement was added. The total adding lasted approx. 30 s., and hereafter -the batch was mixed for approx. 30 s.
The total mixing time was -thus 60 s.
New Mixing Procedure, Accordin~ to the Invention The stone fractions 4 - 8 and 8 -16 mm were added all at a time together LO with the water. After a 5 s. moisturing the cement proportioning was started and lasted for approx. 15 s., whereafter -the batch was mixed for another 10 s. (paste mixing time). Then sand was added successively over a period o-f 15 s. by means of a SKAKO vibratory feeder. To reach the same total mixing time -the batch was ready-mixed for another 15 s., but the concrete was homogeneous already after 5 s. ready mixing.
In addition to the visual observations 3 cylinder cores were -taken from each mix, all each of 1 cbm.
The cylinder cores were s-tored in a water bath for 14 days at ~ constant temperature of 21 C. The results achieved are listed in the below tables.
All three test runnings indicate that an essential increase of the average strength by the process according to the invention was achieved and that the standard devia~ion of strength and the variation coefficient was reduced.
This clearly demonstrates that by the process according to the invention considerable cement savings can be achieved, compared -to the standard mixing procedure, re-taining the same s-trength values.
~3~3~ ~
t~ FETE MIXING TEST 1 SKAKOA/S
STRENGTH 15 MN/M2 SLUMP 6-lO W/C O . 8 STANDARG MIXING PPO[ESS = NEW MIXING PROCESS `
AVERAGE STRENGT~I SLUMP AVERAGE 5TRENGT~ AVEI?AG STREriGT 1 SLUrJ.P AvERAGE STRENGl NO. O; 3 SAMPLES PER CONVERTED TO OF 3 SAMPLE5 PER rONVERTED TO
ltlX SLUMP ~ MIX 5LUMP 8 14 17.3 8 17.3 19.4 ~0.5 20.3 - - - --20.3 6 19.3 23.0 6 21.8 - - -21 15.1 9 15.5 21.3 10 22.2 - -24 15.9 ~ 16.3 20.8 8 20.8 - - -27 15.6 4.5 1~.0 16.4 l3.5 18.0 28 16.1 5.5 - 15.3 19.~ 5 - 18.3 19.5 5 18.0 18.1 10 19.0 - - - - - -32 18.1 7 17.6 22 2 - 7 21.6 IMN/M21 AVE.RAG_RErJGTH: _ 17.1 AvERAaE sTllrNGT~ 20 3 . AVERAGE STRENGTH INCREASE FROM "A" Ta "El" 18.6 %
STANDARO DEVIATION S~ \/(Xl- ml2 1 Ix -In)2 ,,,,,,,, : S~= 1. 74 MN/M S~- 1.64 MN/M2 VARIATION KOEFFICIENT V_~ X 100 1%1 0-2 % v~ 8.1 %
CALC. CEMENT SAVING ~; = K 1 V/C - 0.5 ) SAVING ~ 26 KG ~ 10.4 %
.. .. . ~ .. . . . ~
DATE a3-0~,-06 _ _ NAME F FRANDSEN
:"
~ -3L23~
_ . .
~ONCRETE MIXING TEST 2 SKAKOA/s _ST ?ENGTH 30 MNjMi ~ SLUMP 6-10 ~ ~ ,/~ 0.5 ~
STA,`IOARD MIXINGPROCESS _ ~ NEW MIXING PROCESS ~
AVERAGE STRENGTH SLUl-tP AVERAGE STRENGT AVERAGE STRE~GT SLUMP AVERAGE STRENGT
NO. OF 3 SAMPLES PER EONVERTED TO OF 3 SAMPLE5 PER I O~JVERTED TO
~IX sLuMpa rlx _ SLUMP~
~6 30.9 5 29.3 33.2 5.5 33.2 .
8 32.3 7 31.5 36.4 6.5 36 0 19 31.~ 8 ~ 31.4 34.0 10 35.4 29.~ 8 29.4 30.3 10.5 31 7 _ 22 27. ~ 9 28.3 33.5 6 31.8 38.4 6 36.8 32.6 13 36.5 _ .
29 38.0 4 34.1 1 37.1 5 3~.3 31 35.9 5 34.2 36.0 6 34.5 MN/M2] AVERAGE STRENGTH 31.9 AVERAGE STRENGTH 3~1.2 _ . . - . .
AVERAGESTRENGTHINCREASE FROM "A" TO "El" 7.2 %
STANDARD DEVlATlD;3 5= ~
SA= 2 . 94 MN/M S~ 1 . 85 MN/~2 . ' VARIAT!ON KOEFFICIENT v~QQ 1%1 y~ 9.2 % ~ 5.4 %
CALC.CEMENT SAYING 6 -K~ V/C -0.5 ~
SAVlNb, 2a KG ~
DATE: 83-0~-06 _ _ NAME: F.FRANDSEN
' ~.~3~
_ ~
S TRENG rH Pipe concrete . ~ /C - 38 SrANDARD MIXING PROCESS ~.W ~ I ~b `R~
_ A _ _ __3 -AVERAGE STRENGT~I 5LUMP AVERAGE 5TRE~GT AVERAGE STRENGT 5LU~P AVERAGE ST2E11GT~
NO OF 3 SAMPLES PER EON~fERTEU TO OF 3 SAMPLES PER rONVERTED TO
. MIX SLUMP u MIX SLUMP a IV 42.1 O _ 47.4 O
_ . _ V ~3.4 O . 46.8 O
_ VI 4 4.2 O _ 48.1 O
_ l VI:I: 44 . 6 O _ 48 . 9 O
~ _ IX 46 . 3 O _ 4 7 . 7 O
_ l _ X 45.9 O _ 48.6 O
_ _ .__ .
XI 4 5 .1 O _ 50 . 6 O
_ _ __~ . __ XII 4 1 . 1 O _ 46 . 4 O
_ _ _ MN/M2I AVERAGE STRENGTH __ 4 4 . 1 AVERAGE STRENGTH. 4 8 .1 AVERAGE STRENGTH INCREASE FROM "A" TO "B": 9.1 /1-STANDARD DEVIATION S= V~=~
SA_ 1 . 8 MN/M Sa= .1 3 MN/M~
v~E~ ~ s x loo 10/ l V~= 4.1 % Vil 2.7 %
.
~A~L CEMENT SAVI~'TG ~; - K ( V/C ~ 0.5 ) SAVIN5 ~ 26 KG ~ 6 ~ 8 YO
~ _ . _ . . .
')ATE 83-0l.-06 NAME F. FRANDSEN_ _ .
. ~i ,,
in a material flow under the influence of an external pressure from the rnixing means in such a way that the material Elow is pressed together and -the par~icles thus under rolling pressed against each other. By the successive adding oE the particles of the fine fraction into the material flow -these are drawn into the flow, and due to the pressure between the particles of the coarse frac~ion and the individual movernents of the p~rticles, brought about by the mixing means, the particles of the fine fraction are "ground" into the paste coating of the coarse particles.
Considering this it will be especially advantageous to design the mixing means and arrange the curve path described so as to establish high and low pressure zones in the concrete mass during the mixing process. This can e.g. be achieved by the applica tion of a stationary mixing pan in which the mixing shovels are driven in pairs in a planetary movement.
The successive adding oE the Eine fraction is advantageous~y adjusted so in relation to the rotation ot the mixing means that the fine fraction added does not meet previously added fine fraction material~ not yet absorbed in the paste, which would then form a double layer of fine fraction which i-t would be difficult homogeneously to work into the mass.
Despite the Iact tha-t the application of fillers, contrary to the SE patent specification No. 415 349, is not obligatory for the process in accordance with the invention it may be desirable -to add filler, among other things to be able to adjust the viscosity of the cement paste. Such an adjustment could be carried out by measuring means for -the de-termination of the viscosity of the paste, connected to the proportioning means for the filler.
It is pointed out that the designation "filler" is here used in the widest ~of the word, and not only with the meaning fine fraction material with particle sizes srnaller than l/4 mm, but also covering mineral admixtures such e.g. as silica, fly ash, puzzolanes etc., and in addition more special admixtures such as colours and inactive fillers such as fineground quartz etc. The filler materials are normally added together with the cement and/or used for later adjustrnents.
~38~3~
Any admix-ture for the productis~n of concrete may be used in -the process according to the invention, both l. Physically active admixtures such as plas-ticisers, both normal and superplasticisers9 and air-entrainin~ admixtures, such as tensides, reducing the surface tension of the water by the formation of bubbles, and 2~ Chemically active admixtures such as accelerators or retarders for the reaction be-tween wa-ter and cement The adding of these admix-tures will normally be effected wi-th the las-t part of the water before the adding of the fine fraction which will enabie -the cement to react wi-th water on its surface.
It has also -turned out tha-t to produce a concre-te wi-th op-timurn qualities -the coarse frac-tion of the aggregates can with advantage be moistened with part of -the water before cement, op-tional filler, and the remaining water quantity is added. It is also important to establish a suitable pre-mixing time before successively adding the fine fraction. Hereby the qualities of the cement paste and thus the workabili ty of the mass is improved.
The invention further relates to a plant for the production of cement concre-te and of a na-ture comprising a mixing container ~vith proportioning means for the components of the concrete mass, mixing means and discharge means, and the plant is characterized in that the propor-tioning means for the fine fraction of the aggregates is equipped with devices for the control and regulation of the flow of the fine fraction.
Preferably the propor~ioning means for the fine fraction is a vibratory feeder, providing a very accurate control with the proportioning and which can be adjusted to provide different proportionin~ periods, in accordance with the composition and qualities of the concrete mass in question.
-I, `f,l " ~3~33~3 8.
If diesired, the proportioning rnearls can be adap-ted to ~dd the fine fraction on more than one zone of the mixer. ~ t~is can be achieved by the application of -two or more proportioning means or by a turnable proportioning device.
e~ ~7~J,~ ~ .f ~b S In the,li~ of the process according to the invention in which filler is used for the adjustment of the viscosity of the cement paste, the plant may also include means for the determination of the viscosity of the cemen t pas-te, connected to the proportionin g means for the filler and control the filler flow.
In order to achieve a particularly effective mixing of the fine fraction i~
is of great importance that the material flow in the mixer is under the influence of an external pressure from the mixing means, thus es-tablishing high and low pressure zones in the concrete mass, and tha-t the Eine fraction is ~dded in a high pressure zone. In addition -to the fact that the pressure can be increased or reduced in the pressure ~one by an increasecl or reduced material flow of fines, the mixin~ means of the plan-t are primarily designed so as to establish al-ternating high and low pressure zones which can further be supported by adapting the mixing means to move in a curved path,e.~.3a planetary movement.
The invention can be applied in the production of any type of concrete for varyin~ purposes and with varying stren~th qualities. A person skilled in the art will be able to determine the optimum mixing process -for a given type of concrete by varying the components of the mass, the grain sizes of the aggrega-tes, the types of cement, different admixtures, mixing time etc.
Comparative Tests on a Laboratory Scale In order to document the importance of a successive adding of -the fine fraction of the aggrega-te materials (sand 0 - 4 mm) tests were carried out in a laboratory pan mixer wi-th four shovels and two side scrapers by which 3 the pan and the shovels rotated in the opposite directions. The used basic mix had the composi-tion:
~3~138 9.
Rapid cement 325 kg/cbm Wa-ter 150 kg/cbm W/C ratio 0.46 Aggregates:
Sand 0 - 4 mm 650 kg/cbm Stone 4 - 16 mm 1260 kg/cbm The following tests were carried out:
Reproduction of SE Patent No. 415 349 S~one and half of the water were mixed for 5 s. to moisten the stone material. Hereafter cement and the remainder of the water, con~aining a plasticiser, were added, and the mix was pre-mixed for 20 s. Hereafter the sand yuantity was added at a time, and the mixing was continued for 65 s. Total mixing -time 90 s.
II Process Accordin~ to the Invention (long pre-mixing time).
Stone, water, containing a plasticiser, and cement were mixed as under I. Hereafter sand was added over a pe~iod o:E 20 s., and -the mixing was continued for 45 s. Total mixing time 90 s.
On termination of -the mixing the following determinations were madeo II
Air content 1,2% 1,3%
Slump Slump (Vebe~ 4 s. 2,5 s.
Mix 1 was homogeneous and had a workabili-ty, expressecl by a Vebe measure of 4 s.
.-, ~' .
2~3~
10.
Mix 11 was also homogeneous and demonstrated an improved workability, expressed by a Vebe measure of 2,5 s.
Of both types of concrete cylinders were cast which were used for early compressive strength determina-tions according to standard DS 423, 1 and 2 days after completed mix, respectively.
The results of the compressive strength tests appear from the b~
-tabl~. By way of comparison,standard values for concretetproduced with the same type of rapid cemen~ according to the traditional mixing technique, are usedO
Compressive Stren~th A/l Pa Period 1 II Stand. Values 21 h 11.6 13 (24 h) 22 h 10.6 44 h 30.1 23 ~4~ h) 45 h 29.3 From the above table it is seen that test Il shows improved- early strength values, not least if the time differences are taken into account. It is assumed that the differences would be even more significant if a mixer providing high and low pressure zones had been used.
Comparative Tests on an Industrial Scale .
The tests have bee~ run wi-th a very experienced Danish manufacturer of concrete with his existing 1500 1 SK~KO mixer for the production of ready-mixed concrete.
The mixer is a pan mixer, operating on the basis of the counter-current mixing principle, by which the mixing is effected in a fixed pan by means of 4 shovels, driven in pairs by a planetary gear box. In addition the mixer is equipped with 2 off side scrapers, incorporated with the purpose to lead .
3~
11.
the concrete to the most active mixing zone. The speed of the side scrapers is approx. hal~ the speed oE the shovels. This specific cou~r-A current mixing principle makes the concrete mass mov$ ~. one round per each 10 - 12 s. and brings about the effect that high and low pressure zones are continuously developed in the concrete mass.
~he below concrete recipes have been selected for the tests, according to the standard mixing procedure and -to the new mixing procedure.
1) 15 MN/M_ Concrete Cement (Portiand) 230 kg Water 165 1 Sand (0 - 4 mm) 717 kg Gravel (4 - 8 mm3 200 kg Gravel (8- 16 mm) 818 kg Air-en-training admix 53 g 2) 30 MN/M_ Concrete Cement (Portland) 330 kg Water 165 1 Sand (0 - 4 mm) 66~ kg Gravel (4 - 8 mm) 200 kg Gravel (8 - 1~ rnm3 789 kg Air-entraining admix 60 g Pipe Concrete Cement (Portlarid~ 346 kg ~/ater 131 1 ; 25 Sand (0 - 4 mm) 760 kg Gravel (4 - 8 mm) 285 kg Gravel (8 - 16 mm) 855 Icg ~L23~
The below described proportioning cycle has been applied:
A. Standard Mixing Procedure The stone fractions 4 - 8 and 8 - 16 mm and the sand were added a-t a time. AEter a dry-mixing period of 5 s. wa~er was added over a period of 20 s., and after 15 s. mixing time ~he cement was added. The total adding lasted approx. 30 s., and hereafter -the batch was mixed for approx. 30 s.
The total mixing time was -thus 60 s.
New Mixing Procedure, Accordin~ to the Invention The stone fractions 4 - 8 and 8 -16 mm were added all at a time together LO with the water. After a 5 s. moisturing the cement proportioning was started and lasted for approx. 15 s., whereafter -the batch was mixed for another 10 s. (paste mixing time). Then sand was added successively over a period o-f 15 s. by means of a SKAKO vibratory feeder. To reach the same total mixing time -the batch was ready-mixed for another 15 s., but the concrete was homogeneous already after 5 s. ready mixing.
In addition to the visual observations 3 cylinder cores were -taken from each mix, all each of 1 cbm.
The cylinder cores were s-tored in a water bath for 14 days at ~ constant temperature of 21 C. The results achieved are listed in the below tables.
All three test runnings indicate that an essential increase of the average strength by the process according to the invention was achieved and that the standard devia~ion of strength and the variation coefficient was reduced.
This clearly demonstrates that by the process according to the invention considerable cement savings can be achieved, compared -to the standard mixing procedure, re-taining the same s-trength values.
~3~3~ ~
t~ FETE MIXING TEST 1 SKAKOA/S
STRENGTH 15 MN/M2 SLUMP 6-lO W/C O . 8 STANDARG MIXING PPO[ESS = NEW MIXING PROCESS `
AVERAGE STRENGT~I SLUMP AVERAGE 5TRENGT~ AVEI?AG STREriGT 1 SLUrJ.P AvERAGE STRENGl NO. O; 3 SAMPLES PER CONVERTED TO OF 3 SAMPLE5 PER rONVERTED TO
ltlX SLUMP ~ MIX 5LUMP 8 14 17.3 8 17.3 19.4 ~0.5 20.3 - - - --20.3 6 19.3 23.0 6 21.8 - - -21 15.1 9 15.5 21.3 10 22.2 - -24 15.9 ~ 16.3 20.8 8 20.8 - - -27 15.6 4.5 1~.0 16.4 l3.5 18.0 28 16.1 5.5 - 15.3 19.~ 5 - 18.3 19.5 5 18.0 18.1 10 19.0 - - - - - -32 18.1 7 17.6 22 2 - 7 21.6 IMN/M21 AVE.RAG_RErJGTH: _ 17.1 AvERAaE sTllrNGT~ 20 3 . AVERAGE STRENGTH INCREASE FROM "A" Ta "El" 18.6 %
STANDARO DEVIATION S~ \/(Xl- ml2 1 Ix -In)2 ,,,,,,,, : S~= 1. 74 MN/M S~- 1.64 MN/M2 VARIATION KOEFFICIENT V_~ X 100 1%1 0-2 % v~ 8.1 %
CALC. CEMENT SAVING ~; = K 1 V/C - 0.5 ) SAVING ~ 26 KG ~ 10.4 %
.. .. . ~ .. . . . ~
DATE a3-0~,-06 _ _ NAME F FRANDSEN
:"
~ -3L23~
_ . .
~ONCRETE MIXING TEST 2 SKAKOA/s _ST ?ENGTH 30 MNjMi ~ SLUMP 6-10 ~ ~ ,/~ 0.5 ~
STA,`IOARD MIXINGPROCESS _ ~ NEW MIXING PROCESS ~
AVERAGE STRENGTH SLUl-tP AVERAGE STRENGT AVERAGE STRE~GT SLUMP AVERAGE STRENGT
NO. OF 3 SAMPLES PER EONVERTED TO OF 3 SAMPLE5 PER I O~JVERTED TO
~IX sLuMpa rlx _ SLUMP~
~6 30.9 5 29.3 33.2 5.5 33.2 .
8 32.3 7 31.5 36.4 6.5 36 0 19 31.~ 8 ~ 31.4 34.0 10 35.4 29.~ 8 29.4 30.3 10.5 31 7 _ 22 27. ~ 9 28.3 33.5 6 31.8 38.4 6 36.8 32.6 13 36.5 _ .
29 38.0 4 34.1 1 37.1 5 3~.3 31 35.9 5 34.2 36.0 6 34.5 MN/M2] AVERAGE STRENGTH 31.9 AVERAGE STRENGTH 3~1.2 _ . . - . .
AVERAGESTRENGTHINCREASE FROM "A" TO "El" 7.2 %
STANDARD DEVlATlD;3 5= ~
SA= 2 . 94 MN/M S~ 1 . 85 MN/~2 . ' VARIAT!ON KOEFFICIENT v~QQ 1%1 y~ 9.2 % ~ 5.4 %
CALC.CEMENT SAYING 6 -K~ V/C -0.5 ~
SAVlNb, 2a KG ~
DATE: 83-0~-06 _ _ NAME: F.FRANDSEN
' ~.~3~
_ ~
S TRENG rH Pipe concrete . ~ /C - 38 SrANDARD MIXING PROCESS ~.W ~ I ~b `R~
_ A _ _ __3 -AVERAGE STRENGT~I 5LUMP AVERAGE 5TRE~GT AVERAGE STRENGT 5LU~P AVERAGE ST2E11GT~
NO OF 3 SAMPLES PER EON~fERTEU TO OF 3 SAMPLES PER rONVERTED TO
. MIX SLUMP u MIX SLUMP a IV 42.1 O _ 47.4 O
_ . _ V ~3.4 O . 46.8 O
_ VI 4 4.2 O _ 48.1 O
_ l VI:I: 44 . 6 O _ 48 . 9 O
~ _ IX 46 . 3 O _ 4 7 . 7 O
_ l _ X 45.9 O _ 48.6 O
_ _ .__ .
XI 4 5 .1 O _ 50 . 6 O
_ _ __~ . __ XII 4 1 . 1 O _ 46 . 4 O
_ _ _ MN/M2I AVERAGE STRENGTH __ 4 4 . 1 AVERAGE STRENGTH. 4 8 .1 AVERAGE STRENGTH INCREASE FROM "A" TO "B": 9.1 /1-STANDARD DEVIATION S= V~=~
SA_ 1 . 8 MN/M Sa= .1 3 MN/M~
v~E~ ~ s x loo 10/ l V~= 4.1 % Vil 2.7 %
.
~A~L CEMENT SAVI~'TG ~; - K ( V/C ~ 0.5 ) SAVIN5 ~ 26 KG ~ 6 ~ 8 YO
~ _ . _ . . .
')ATE 83-0l.-06 NAME F. FRANDSEN_ _ .
. ~i ,,
Claims (13)
1. A process for the batch-wise production of cement-concrete by intimate mixing of aggregates including a coarse fraction and a fine fraction, cement, optional filler, and water in a concrete mixer with proportioning means for the components of the concrete mass, mixing means, and discharge means wherein the fine fraction of the aggregates is added to and absorbed in a premixture of the remaining components, wherein the coarse fraction of the aggregates is coated with a paste, consisting of cement, optional filler, and water, wherein the process further comprises gradually increasing the volume of the fine fraction of aggregates in the premixture by successive addition of the fine fraction of the aggregates by the proportioning means for the fine fraction to effect a gradual decrease in the water/solid content of the resulting mixture, and wherein the addition of the fine fraction is adjusted in relation to rotation of a mixing means so as to prevent the fine fraction from meeting previously added fine fraction not yet absorbed in the premixture.
2. A process according to claim 1, wherein the addition of the fine fraction to the premixture is effected by controlled vibration of a fine portion aggregate propor-tioning means.
3. A process according to claim 1, wherein the fine fraction is added into a zone of the mixer in which the mass consisting of the paste-coated coarse fraction and free-flowing cement paste is moved in a material flow under the influence of an external pressure from the mixing means.
4. A process according to claim 3, wherein the external pressure on the material flow is so exerted that the added particles of the fine fraction are immediately absorbed in the material flow.
5. A process according to claim 1, including adjusting the viscosity of the paste-covered coarse fraction by the addition of a filler material.
6. A process according to claim 5, wherein the adjustment is carried out by a measuring means connected to a proportioning means for the filler.
7. A process according to claim 1, including wetting the coarse fraction of the aggregates by part of the water before the cement, optional filler, and the remaining water are added to form a premixture, and before the adding of the fine fraction.
8. A plant for producing cement concrete from cement, water, and coarse and fine aggregates and comprising a mixing container, proportioning means for the components of the concrete mass, the container including mixing means and discharge means wherein the proportioning means for the fine fraction of the aggregates includes means for the control and regulation of the flow of the fine fraction to gradually increase the volume of the fine fraction in the mixture effecting a gradual decrease in the water/solid content of the resulting mixture, and to adjust the addition of the fine fraction in relation to rotation of a mixing means so as to prevent the fine fraction from meeting previously added fine fraction not yet absorbed in the premixture.
9. A plant according to claim 8, wherein the proportioning means for the fine fraction is a vibratory feeder.
10. A plant according to claim 9, wherein the mixing container includes plural mixing zones and the proportioning means includes means to add the fine fraction in more than one zone of the mixer.
11. A plant according to claim 8, wherein the mixing means are movable in a curved path so as to establish high and low pressure zones in the concrete mass.
12. A plant according to claim 8, wherein the proportioning means for the filler is connected to means for the determination of the filler content and the viscosity of the cement paste.
13. A process for the batch-wise production of cement-concrete by mixing of coarse and fine aggregates, cement, and water in a concrete mixer, said process comprising the steps of:
a) adding cement, water, and coarse aggregates in a predetermined proportion to form a premixture;
b) mixing the premixture in a concrete mixer to coat the coarse aggregates with a paste including cement and water;
c) gradually adding fine aggregates to the premixture after the coarse aggregates have been coated and while continuing to mix the materials until a homogeneous mixture of all of the materials has been achieved, to effect a gradual decrease in the water/solid content of the resulting mixture; and d) adjusting the addition of the fine aggregates, i.e. the fine fraction, in relation to rotation of a mixing means so as to prevent the fine fraction from meeting previously added fine fraction not yet absorbed in the mixture.
a) adding cement, water, and coarse aggregates in a predetermined proportion to form a premixture;
b) mixing the premixture in a concrete mixer to coat the coarse aggregates with a paste including cement and water;
c) gradually adding fine aggregates to the premixture after the coarse aggregates have been coated and while continuing to mix the materials until a homogeneous mixture of all of the materials has been achieved, to effect a gradual decrease in the water/solid content of the resulting mixture; and d) adjusting the addition of the fine aggregates, i.e. the fine fraction, in relation to rotation of a mixing means so as to prevent the fine fraction from meeting previously added fine fraction not yet absorbed in the mixture.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8206489A SE8206489D0 (en) | 1982-11-15 | 1982-11-15 | PROCEDURE AND DEVICE FOR CEMENT CONCRETE PREPARATION |
SE8206489-0 | 1982-11-15 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1238038A true CA1238038A (en) | 1988-06-14 |
Family
ID=20348590
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000441226A Expired CA1238038A (en) | 1982-11-15 | 1983-11-15 | Process and plant for the production of cement concrete |
Country Status (12)
Country | Link |
---|---|
EP (1) | EP0126105B1 (en) |
JP (1) | JPS59502017A (en) |
AU (1) | AU574655B2 (en) |
CA (1) | CA1238038A (en) |
DE (1) | DE3366672D1 (en) |
ES (2) | ES8501725A1 (en) |
FI (1) | FI842744A (en) |
GR (1) | GR79036B (en) |
IT (1) | IT1174795B (en) |
PT (1) | PT77660B (en) |
SE (1) | SE8206489D0 (en) |
WO (1) | WO1984001918A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE502752C2 (en) * | 1994-04-19 | 1995-12-18 | Gunnar Ohlson | Process for the preparation of tough cement concrete |
CN110577390B (en) * | 2019-10-25 | 2022-01-18 | 四川信敏绿色新建筑材料科技有限公司 | Concrete preparation process |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR992896A (en) * | 1944-09-23 | 1951-10-24 | Concrete improvements | |
FR1049272A (en) * | 1950-02-08 | 1953-12-29 | Concrete mixing process and concrete mixer allowing the realization | |
CH490946A (en) * | 1967-06-08 | 1970-05-31 | Huther & Co | Roller mixer for the production of mix, in particular concrete |
US3812076A (en) * | 1973-02-20 | 1974-05-21 | Grace W R & Co | Method of adding small amounts of solid particulate admixtures to hydraulic cement compositions |
LU81524A1 (en) * | 1979-07-17 | 1981-02-03 | Arbed | METHOD FOR PRODUCING COLLOID MORTAR AND PRODUCT OBTAINED ACCORDING TO THIS METHOD |
-
1982
- 1982-11-15 SE SE8206489A patent/SE8206489D0/en unknown
-
1983
- 1983-08-15 IT IT49338/83A patent/IT1174795B/en active
- 1983-11-11 GR GR72950A patent/GR79036B/el unknown
- 1983-11-14 DE DE8383903538T patent/DE3366672D1/en not_active Expired
- 1983-11-14 JP JP58503667A patent/JPS59502017A/en active Pending
- 1983-11-14 PT PT77660A patent/PT77660B/en not_active IP Right Cessation
- 1983-11-14 ES ES527247A patent/ES8501725A1/en not_active Expired
- 1983-11-14 EP EP83903538A patent/EP0126105B1/en not_active Expired
- 1983-11-14 WO PCT/DK1983/000107 patent/WO1984001918A1/en active IP Right Grant
- 1983-11-14 AU AU22602/83A patent/AU574655B2/en not_active Ceased
- 1983-11-15 CA CA000441226A patent/CA1238038A/en not_active Expired
-
1984
- 1984-07-09 FI FI842744A patent/FI842744A/en not_active Application Discontinuation
- 1984-08-31 ES ES535577A patent/ES8602560A1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
JPS59502017A (en) | 1984-12-06 |
DE3366672D1 (en) | 1986-11-13 |
GR79036B (en) | 1984-10-02 |
ES535577A0 (en) | 1985-12-01 |
ES527247A0 (en) | 1984-12-01 |
EP0126105A1 (en) | 1984-11-28 |
PT77660A (en) | 1983-12-01 |
ES8602560A1 (en) | 1985-12-01 |
IT8349338A0 (en) | 1983-08-15 |
SE8206489D0 (en) | 1982-11-15 |
FI842744A0 (en) | 1984-07-09 |
ES8501725A1 (en) | 1984-12-01 |
AU2260283A (en) | 1984-06-04 |
FI842744A (en) | 1984-07-09 |
AU574655B2 (en) | 1988-07-14 |
PT77660B (en) | 1986-03-18 |
IT1174795B (en) | 1987-07-01 |
WO1984001918A1 (en) | 1984-05-24 |
EP0126105B1 (en) | 1986-10-08 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5203629A (en) | Method for modifying concrete properties | |
US7470338B2 (en) | Process for forming dense layers in a gypsum slurry | |
JP4780888B2 (en) | Additive for enhancing hydration of calcined gypsum | |
JPH11501002A (en) | How to make foam gypsum products | |
KR20070111476A (en) | Process for manufacturing sound absorbing cement tile | |
CA1238038A (en) | Process and plant for the production of cement concrete | |
Karl et al. | Foamed concrete—mixing and workability | |
RU2044714C1 (en) | Method of preparing raw mixture for building articles | |
CN108501210A (en) | A kind of the fiber dispersion mill and fiber dispersing method of organic fibre reinforced compsite | |
RU2131856C1 (en) | Concrete mix and method of its preparation | |
GB2035990A (en) | Fibre Containing Water- Hardenable Masses | |
Von Berg et al. | Fresh mortar and concrete with fly ash | |
SU1364617A1 (en) | Method of preparing fiber-reinforced concrete mix | |
JP3736990B2 (en) | Continuous kneading equipment for powdery hydraulic materials | |
CN108249803A (en) | Hydration heat of cement controlled material and preparation method thereof under a kind of cryogenic conditions | |
CN213725943U (en) | Limestone and anthracite mixing stirring device | |
SU922095A1 (en) | Method for preparing concrete mixes | |
RU2132315C1 (en) | Method of foam-concrete mixture producing | |
US7067003B2 (en) | Use of dunder in concrete compositions | |
SU1296555A1 (en) | Method for preparing building mixture | |
JPS5910886B2 (en) | Concrete manufacturing method using a laminated pan type mixer | |
SU1096250A1 (en) | Method for preparing mortar mix | |
JPS599854Y2 (en) | Two-stage concrete mixing equipment using a variable speed mixer and a two-stage discharge water meter | |
SU675029A1 (en) | Method of preparing mortar | |
Hua et al. | Thin sand concrete plate of high resistance in traction |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
MKEX | Expiry |