FR2726550A1 - PROCESS FOR IMPLEMENTING CONCRETE BY SLIDING FORMWORK - Google Patents

Abstract

The subject of the invention is a process for obtaining a concrete structure by the sliding formwork technique, in which a water-reducing agent and at least one natural water-soluble polysaccharide and an acrylic polymer are added to the concrete before forming by sliding formwork. water-soluble, the proportion by weight of water-reducing agent relative to the polysaccharide and / or to the polymer being between 90:10 and 99.9: 0.1. Concrete has a thixotropic structure that allows it to flow when flow is needed and to stiffen when rigidity is needed. The concrete formed by slipforming according to this process has relatively low ventilation.

Description

The present invention relates to the use of concrete by

  sliding formwork as well as the additives used in this process.

  The sliding formwork technique, in which a concrete structure of uniform cross section is produced continuously by means of a movable formwork, is commonly used today to manufacture various concrete objects, such as continuous gutters, walls, chimneys and coatings. of tunnels. The concrete used with this technique must have a very low slump, of the order of 2 to 5 cm (measured according to standard ASTM C 143), so that, when the formwork

  advance, the concrete formed keeps its shape until it has hardened.

  The problem with this type of concrete is that, of course, it does not flow and is therefore difficult to manufacture and transport to where it is needed. The addition of conventional fluidizing agents such as lignosulfonates, carboxylates, BNS and melamine sulfonate-formaldehyde condensates, has the effect of improving the flow but destroys the property which is precisely

  sought for sliding formwork.

  It has been proposed to add a fluidizing agent to the concrete at the time of manufacture and then to add thereto, on the formwork site, a polymeric substance, for example an absorbent polymer or carboxymethylcellulose so as to allow setting concrete work by sliding formwork. This process introduces a problem

  that of the air entrainment.

  Therefore, there is an obvious need in this industry for a technique for making concrete sufficiently fluid for manufacture and transport, but rigid enough to be

  successfully used with sliding formwork.

  However, it has been noted that the use of certain materials makes it possible to satisfy these apparently contradictory requirements. Consequently, the present invention provides a process for obtaining a concrete structure by the sliding formwork technique, in which a water-reducing agent and at least one natural water-soluble polysaccharide and / or are added to the concrete before forming by sliding formwork. a water-soluble acrylic polymer, the proportion by weight of water-reducing agent relative to the polysaccharide and / or to the

  polymer being in the range of 90:10 to 99.9: 0.1.

  By "natural water-soluble polysaccharide" is meant here any water-soluble polysaccharide of natural origin. Highly modified polysaccharides such as modified starches and modified celluloses are not taken into account, as are relatively low molecular weight polysaccharides which are known to be water-reducing agents for cement-based mixtures (water-soluble polysaccharides natural must have high molecular weights, preferably at least 10,000 (weight average molecular weight). A particularly useful category of materials consists of water-soluble gums, polymeric materials which, in a suitable solvent or swelling agent, form highly viscous dispersions or gels with a low dry matter content. This type of material is well described in "Encyclopaedia of Chemical Technology Kirk-Othmer, 4th edition (Wiley-Interscience, 1992), Vol 4 page 928", of which citation is for reference. Preferred gums are e xanthan, carob gum, sodium alginate and X-carrageenan, but other gums such as koraya, guar, pectin, [3-1,3-glucan and

  3-1,4-glucan can also be used.

  The water-reducing agent suitable for the present invention can be chosen from the wide range of products of this kind known in the current state of the art. By way of examples, mention may be made of P3-naphthalene sulfonate-formaldehyde condensates, melamine sulfonate-formaldehyde condensates and polycarboxylates,

  preferred materials being lignosulfonates and sugar alcohols.

  The term "sugar alcohols" denotes the alcohols obtained by hydrogenation of saccharides. Although the sugars can be monosaccharides or disaccharides, they are preferably polysaccharides, and more preferably starches. Among the suitable saccharides, mention may be made of starch hydrolysates (particularly desirable), celluloses, cellulose hydrolysates, as well as hemicelluloses and hemicellulose hydrolysates. Other materials are, for example, maltitol, mannitol and xylitol, as well as hydrogenated oligosaccharides, in particular those of the type described in US Pat. No. 4,073,658, the citation of which is given by way of reference. Examples of suitable commercial materials include "D-Sorbit" and "PO-20" from Towa Kasei and "SE-100" from Nikken Kagaku. The water-soluble acrylic polymers which can be used in the present invention include all the materials of this type known in the current state of the art, suitable materials including polyacrylic acid, copolymers of acrylamide and sodium acrylate, copolymers acrylamide, sodium acrylate and acrylamide-2,2-dimethylethane sulfonate sodium salt, as well as aminoalkyl- (meth) acrylate and acrylamide copolymers, the particularly preferred materials being sodium polyacrylate , polyacrylamide and partially hydrolyzed polyacrylamide. The use of other polymers, such as polyvinyl alcohol, polyethyleneimine, polydiallylamine and

  polyvinyl imidazole, associated with the acrylic polymers described above

  on it, can improve the viscosity and

thixotropy.

  The materials to be used in the present invention may be added separately to the concrete mixture, but they are preferably added together, in the form of a single admixture. Consequently, the present invention describes a slip-form adjuvant which consists of a mixture of a water-reducing agent and a natural water-soluble polysaccharide and / or a water-soluble acrylic polymer in the ratio of 90:10 to 99.9: 0.1 by weight in the preparation. When the content of polysaccharide and / or water-soluble acrylic polymer is less than 0.1%, the concrete is fluid but it sags. When the content is greater than 10%, the opposite occurs: the concrete does not collapse, but it

lack of fluidity.

  It is possible to use more than one type of each of the components in the adjuvant of the present invention. It is also possible to use both a natural polysaccharide and a water-soluble acrylic polymer. In this case, the proportion of natural polysaccharide relative to the acrylic polymer can vary within wide limits (depending on the nature of the materials present), but it is

  typically around 20: 1 to 30: 1 by weight.

  The materials can be added to the concrete either separately or together in the form of a single admixture, in sufficient quantity for the concrete to have the desired flow under the effect of vibration and the absence of desired sag under the effect of its own weight when vibration is stopped. In other words, the concrete must have a sufficient degree of thixotropy. This value is naturally variable, depending on the exact nature of the concrete and the use made of it. As a general rule, the quantity required is 0.1 to 5% of the weight of the cement for all the materials (when added separately) or for the additive (when the materials are added in a combined form), but there may be cases where it is necessary to add a quantity outside these limits. The process and the additive according to the present invention can be used with conventional equipment and techniques. They make it possible to manufacture a cement-based mixture with the fluidity required for production, handling and installation in a sliding formwork. Furthermore, it presents a thixotropy which

  allows it to resist sagging due to its own weight.

  there is no excessive air entrainment and ease of set up

  workmanship as well as durability are improved.

  The present invention is further illustrated by the examples.

non-limiting below.

  1. Preparation of mortars Series of mortars and concretes are prepared from the following premixes: (a Mortar Proportion Proportion Unit content (kg) water / cement sand / cement Water Cement Fine aggregate

0.451 2.29 677 1500 3441

  Unit content (kg) Proportion Proportion Water Cement Aggregate Aggregate water / cement sand coarse fine aggregate 0.451 4-5.0 158 350 803 1000r The raw materials used are as follows: Fine aggregate: Quarry sand Oi River System (specific gravity =

2.60; fineness module = 2.76).

  Coarse aggregate: Crushed greywacke Ohme (specific gravity =

2.65; maximum dimension = 20 m).

  Cement: Ordinary Portland cement (specific gravity = 3.16;

  lange in equal parts of cements manufactured by Onoda companies,

Sumitomo and Mitsubishi).

  To some of these mortars and concretes, various water-reducing agents, natural polysaccharides and water-soluble acrylic polymers are added. These products, as well as the proportions of s15 used in mortars and concretes, are shown in Table 1. The various materials are as follows: Hydrorductive agents

  "SAL" - Water-reducing agent: Sugar alcohols (Sorbit D-

  manufactured by Towa Kasei) and PO-2 (manufactured by the same company)

  mixed in a ratio of 9: 1 by weight.

  "LSA" - Lignosulfonate Natural polysaccharides "XG" - Xanthan gum "LBG" - Carob gum 2s "ALA" - Sodium alginate "CGN" -; - carrageenan Water-soluble acrylic polymers "PA-l" - Sodium polyacrylate (weight weight average molecular weight 220,000) "PA-2" - Sodium polyacrylate (weight average molecular weight 50,000) "PAA" - Polyacrylamide (weight average molecular weight

1,000,000)

  "HPAA" - Partially hydrolyzed polyacrylamide (weight average molecular weight 1,000,000)

Table 1

  Ftchant Type of component and proportions in the mixture (% by weight) Agent Polysaccharide Natural hydroreductive polymer, water-soluble acrylic Type% Type% T

A SAL 95.00 XG 5.0

B LSA 95.00 XG 50 -

C LSA 66.50 XG 5.0

SAL 28.50

D LSA 66.50 LBG 5.0

SAL 28.50

E LSA 66.50 ALA 5.0

SAL 28.50

F ISA 66.50 CN 5.0

SAL 28.50 I

G -__, - LSA68,60 PA- 1,

SAL 29.40

: --H ELSA 69.30 PA-2 1.0

SAL 29.70

1 LSA 69.60 PAA 0.5

SAL 29.90

J LSA 69.80 HPAA 0.3

SAL 29.90

K LSA 68.20 XG 2.50 HPAA 0.1

SAL 29.20

L LSA 9000 XG 10.00 -

M LSA 99.90 XG 0.10

N LSA 85.00 XG 15.00

LSA 9 995 XG 0.05

P LSA 99.95, HPAA 0.05

  -P-13- 1 - "r W 2) Mortar and concrete test methods l0 2.1) Mortar In order to assess the fluidity of the mixed mortar according to the mixing ratios above, the slump and l flow, while vibration and resistance to deformation make it possible to evaluate thixotropy and fluidity.

  tests are summarized in Table 2.

  a) Fluidity Sagging and flow are measured using an Abrams cone (steel, upper internal diameter 50 mm, lower internal diameter 150 mm, height 150 mm) used in the slump test method. polymer cement mortar. * Subsidence: according to Japanese industrial standard JIS A * Flow: the condition for spreading the flow of the

mortar is measured.

  b) Fluidity at vibration The mortar is poured into the Abrams cone then the latter is lifted and the mortar is subjected to vibrations by means of a rod vibrator (frequency: 2700 vibrations per minute) and the time is measured necessary for the spreading of the mortar to reach 300 mm. This time

  s15 is indicated in Table 2 below with "T300".

  c) Resistance to deformation (having the effect of preventing

sagging due to dead weight).

  The mortar is shaped by vibration in a cylindrical mold 10 cm in diameter and 20 cm high, then the deformations of the mortar in the vertical direction and in the direction

  horizontal after immediate release are measured.

  d) Thixotropy A subjective evaluation is made based on the fluidity at vibration and the resistance to deformation of the mortar. The mortars are noted as follows: A (good): the conditions of fluidity at vibration and resistance

  to the deformation are both good.

  B (bad): either the fluidity condition at vibration, or the

  deformation resistance condition is bad.

  2.2) Concrete The slump is measured to assess the fluidity of the concrete with the mixing proportions indicated above and the air content is measured to assess the air entrainment. In addition, the fluidity at vibration and the resistance to deformation are evaluated, as well as the thixotropy of concrete, on the basis of the two characteristics of fluidity at vibration and resistance to deformation. Finally, we measure the compressive strength at 28 days and we carry out an evaluation

  visual appearance of the surface texture of hardened concrete.

  The results of these tests are summarized in Table 3.

  a) Fluidity: Measured according to JIS A 1101 b) Air entrainment: Measured according to JIS A 1128 c) Fluidity at vibration: The concrete is poured into the Abrams cone then the latter is Tevé and the concrete is subjected to vibrations using a rod vibrator (frequency: 10,000 vibrations per minute) and time is measured

  necessary so that the spread of the concrete reaches 600 mm.

  d) Resistance to deformation: The concrete is shaped by vibration in a cylindrical mold 20 cm in diameter and 40 cm high, then the concrete deformations in the vertical direction and in the horizontal direction

  after immediate release are measured.

  e) Thixotropy A subjective evaluation is made based on the fluidity at vibration and the resistance to deformation of the concrete. Concretes are noted as follows: A (good): the conditions of fluidity at vibration and resistance

  to the deformation are both good.

  B (bad): either the fluidity condition at vibration, or the

  deformation resistance condition is bad.

  f) Compressive strength: According to JIS A 1118, JIS A 1132 g) Visual examination The appearance of the surface texture of hardened concrete is assessed by

visual examination.

  A (good): void-free state and smooth surface B (normal): state in which a low incidence of air voids is observed, but the appearance is acceptable C (bad): state in which the voids air and gravel

  visible are clearly visible, the appearance is unacceptable.

  3) Results of the tests 3.1) Mortar The results of the tests on the mortar are summarized in Table 2. In Table 2, tests n 1 to 13 are examples according to the present invention, tests n 14 to 16 are examples given by way of comparison in which only a water-reducing agent is added to the mortar, tests 17 and 18 are l0 examples given by way of comparison in which only a natural polysaccharide or a water-soluble acrylic polymer is added to the mortar, tests n 19 to 21 are examples given by way of comparison in which the proportions of water-reducing agent and of natural polysaccharide or of water-soluble acrylic polymer s15 added to the mortar are outside the limits

  mentioned above, and the results of these tests are provided.

O10

Table 2

  Additive Fluidity Fluidity Resistance to Eval.

cement vibrated thixo-

  deformation tropie Es- Type Dosage Aff. Flow T300 (s) X 2) y 3) sai (Cx%) (cm) (mm) (m (mm) no m Exem 1 A 0.55 8.0 127 28 80 85 A -pie

2 B 0.55 8.1 127 28 82 86 A

3 C 0.55 8.1 129 27 80 85 A

4 D 0.55 8.0 127 27 79 86 A

E 0.55 8.1 128 26 80 84 A

6 F 0.55 8.0 127 26 80 84 A

7 G 0.50 8.0 128 27 79 84 A

8 H 0.50 8.0 127 26 80 85 A

9 I 0.50 8.0 128 26 82 85 A

J 0.50 8.1 128 27 80 85 A

1 K 0.50 8.0 127 26 80 85 A

12 L 0.70 7.5 123 31 70 79 A

13 M 0.50 8.5 131 23 83 86 A

  Exem 14 SAL 0.50 8.1 128 27 120 114 B - a 15 LSA 0.45 8.0 128 26 122 113 B com title 16 LSA 0.35 8.0 127 25 123 115 B par SAL 0 , 15 -sound

17 XG 0.01 2.0 104 75 55 78 B

18 HPAA 0.01 1.4 106 73 49 75 B

19 N 0.80 4.7 112 56 71 78 B

O 0.50 4.7 112 56 71 78 B

21 P 0.50 4.5 112 54 72 78 B

  Notes: 1) The dosage of the cement additive is expressed as a percentage in

  weight relative to the weight of cement in terms of solids.

  2) Deformation in the horizontal direction 3) Deformation in the vertical direction As the results given in Table 2 show, the following effects can be observed in cases where the mortar uses the cement additive of the sliding formwork technique according to the

present invention.

  a) Fluidity In tests 1 to 13 (examples according to the present invention), equivalent fluidities are obtained, as clearly shown by the

  comparison with tests no. 14 to 16 (comparison examples).

  On the other hand, tests no 17 and 18 both give poor fluidity. b) Fluidity at vibration l0 Tests n 1 to 13 (examples according to the present invention) and tests n 14 to 16 (comparison examples), with almost identical fluidities, reveal good fluidities at vibration. On the other hand, tests 17 to 21 (comparison examples) all reveal

  poor vibration fluidities.

  c) Resistance to deformation The deformations in the horizontal direction (X) and in the vertical direction (Y) in tests n 1 to 13 (examples according to the present invention) are small compared to those of tests n 14 to 16 ( comparison examples), which indicates almost identical values of fluidity and of fluidity at vibration and excellent values of resistance to deformation are obtained. The deformations obtained in tests n 1 to 13 (examples according to the present invention) are slightly larger compared to those of tests n 17 to 21 (comparison examples) which have

  poor fluidity and vibration fluidity values.

  d) Evaluation of the Thixotropy Tests 1 to 13 (examples according to the present invention) show good thixotropies. On the other hand, in tests no. 14 to 16 (comparison examples), although the values of fluidity at vibration are excellent, the values of resistance to deformation

  are bad and the thixotropies are lower.

  3.2) Concrete The results of tests of tests no 22 and 23 (examples according to the present invention), of test no 24 (comparison example) in which only a water-reducing agent is added to the concrete, and tests no 25 and 26 (comparison examples) in which only a natural polysaccharide or a water-soluble acrylic polymer is

  added to concrete, are presented in Table 3.

Table 3

  Additive Causes Fluid- Cement resistance Fluidity -ment Examination dity

  air resistance visual vibrated deformation Eval.

to the mix-

  Es- Type Dosagel) Lowers pressure! Time X 2) Y 3) tropie sai (Cx / o) in air (kgf / cm-) flow. (mm) (mm) no (% _ Example 22 C 0.55 8.0 4.5 465 A 59 78 A

23 K 0.50 8.5 4.6 467 B 32 60 76 A

  Example 24 LSA 0.35 8.5 4.3 453 A 26 78 135 B as SAL 0.15 compa25 XG 0.01 2.5 2.0 454 C 72 52 65 B reason 26 HPAA 0.01 2, 5 2.5 450 C 71 52 63 B Notes: 1) The dosage of the cement additive is expressed as a percentage by weight relative to the weight of

cement in terms of solids.

  2) Deformation in the horizontal direction 3) Deformation in the vertical direction As shown in tests n 22 and 23 in Table 3, the following effects can be observed for the case where the concrete uses the cement additive of the technique of sliding formwork according to

present invention.

  a) Fluidity Excellent fluidity values substantially of the same order of magnitude as in test 24 (comparison example) are obtained in tests 22 and 23 (examples according to the present invention). On the other hand, the values of fluidity are lower in the

  two tests no 25 and 26 (comparison examples).

  b) Air entrainment property Air entrainment properties of substantially the same order of magnitude as in test 24 (comparison example) are obtained in tests 22 and 23 (examples according to the present invention) . No excessive air entrainment properties were observed. c) Resistance to compression The values of resistance to compression obtained in tests 22 and 23 (examples according to the present invention) are higher than those obtained in tests n 24 to 26 (examples of comparison). d) Visual examination It is observed that the appearance of the surface textures is excellent in test No. 22 (example according to the present invention) and in test 24 2s (comparison example). Slight air voids are observed on the surface in test No. 23 (example according to the present invention) but to a degree which does not pose any problem. However, the results of

  tests 25 and 26 (comparison examples) are very poor.

  e) Vibration fluidity Tests 22 and 23 (examples according to the present invention) and test 24 (comparison example) give excellent values of vibration fluidity. On the other hand, tests n 25 and 26 (comparison examples) give results of fluidity at the

poor vibration.

  f) Resistance to deformation All the deformations, with the exception of those of test No. 24 (comparison example) are reduced and acceptable, which indicates

  excellent resistance to deformation.

  g) Evaluation of the Thixotropy Tests No. 22 and 23 (examples according to the present invention) give good thixotropies. On the other hand, in test No. 24 (comparison example), although the fluidity at vibration is excellent, the resistance to deformation is poor and the thixotropy is lower. Although tests 25 and 26 (comparison examples) give excellent values of resistance to compression, the fluidity at vibration is poor, which gives a

lower thixotropy.

Claims (8)

  1. Method for obtaining a concrete structure by the sliding formwork technique, in which a water-reducing agent and at least one natural water-soluble polysaccharide and / or a water-soluble acrylic polymer are added to the concrete before forming by sliding formwork. proportion by weight of water-reducing agent relative to the polysaccharide and / or to the   polymer being in the range of 90:10 to 99.9: 0.1.   2. Method according to claim 1, characterized in that the water-reducing agent is chosen from the group consisting of   lignosulfonates and sugar alcohols.   3. Method according to claim 2, characterized in that the sugar alcohol is an alcohol obtained from a polysaccharide, preferably a starch.   4. Method according to any one of claims 1 to 3,   characterized in that the natural water-soluble polysaccharide is chosen   among the group of water-soluble gums.   5. Method according to claim 4, characterized in that the gum is chosen from the group consisting of gum   xanthan, carob gum, sodium alginate and X-   carrageenan. 6. Method according to claim 4, characterized in that the gum is chosen from the group consisting of koraya gum,   guar gum, pectin, J3-1,3-glucan and 3,1,4-glucan.   7. Method according to any one of claims 1 to 6,   characterized in that the water-soluble acrylic polymer is chosen from the group consisting of sodium polyacrylate,   polyacrylamide and partially hydrolyzed polyacrylamide.   8. Sliding co-forming adjuvant consisting of a mixture of a water-reducing agent and a natural water-soluble polysaccharide and / or a water-soluble acrylic polymer in the proportion of   : 10 to 99.9: 0.1 by weight in the preparation.