JPS60210554A - Hydraulic cement admixing agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to hydraulic cement admixtures. More specifically, it suppresses the decline in fluidity of hydraulic cement mixtures such as concrete, mortar, or paste over time,
This invention relates to a hydraulic cement admixture that has improved workability and workability, as well as high water-reducing properties and improved quality.

Concrete or mortar is obtained by mixing cement water, sand, gravel, and admixtures as necessary. When cement and water come into contact, cement particles become fluid over time due to chemical and physical effects. This will impede workability and construction efficiency. This phenomenon is generally called concrete slump loss or mortar flowdown.

The first step in improving the quality of concrete or mortar is to mix it with as little unit water as possible.

So-called high-performance water reducing agents, such as naphthalene sulfonic acid formalin high condensate salt or melamine resin sulfonic acid polymarin condensate salt, have high water reducing ability and can significantly reduce the unit water amount. However, the slump loss over time is extremely large, and although it can be used for high-strength secondary concrete products that use large amounts of additives, it cannot be used in ready-mixed concrete factories.
Currently, OAE agents such as resinates and AE water reducers such as lignin sulfonates are used, and the water reduction rate of the former is 5 to 5.
8%, and the latter is about 10-13%.

Concrete slump loss is due to durability issues such as limited conveyance time of agitator vehicles, waiting time at the pouring site, quality changes due to temporary suspension of pump pressure, poor workability, unfilled concrete, occurrence of cold joints, etc. Causes disorders of sexual decline. In addition, in factories for secondary products such as concrete piles and balls, many problems arise in terms of workability and quality, such as limited molding time and poor compaction.

Therefore, the slump loss of concrete over time is an important problem that must be solved in ready-mixed concrete factories, concrete secondary product factories, and others, and the same applies to mortar.

In particular, ready-mixed concrete plants are forced to increase the amount of water and cement per unit due to the decline in aggregate quality, and the most important issue is the development of admixtures that have high water-reducing properties and no slump loss. ing.

The following several methods are known as conventional methods for preventing slump loss in concrete. In other words, (a) A method of increasing the unit water volume of concrete.

(b) Method by post-addition of liquid or granular concrete admixture.

(c) Method by repeated addition of concrete admixture.

(d) A method involving the addition or combination of a setting retarder.

Method (a) above is a method of increasing the unit water volume of concrete by starting mixing to account for slump loss up to pouring, and is the easiest way to suppress slump loss, but in terms of concrete quality, strength There is an economical disadvantage in that durability is reduced due to cracking due to deterioration or drying shrinkage, and the amount of cement per unit is increased in order to obtain a predetermined strength.

Method (b) is a temporary improvement measure to prevent slump loss, and is not an essential preventive measure. Particularly in concrete with a small unit water content aimed at high quality, it tends to promote slump loss after addition. Moreover, the complication of post-addition is unavoidable. In addition, in the case of granular admixtures, dispersibility of cement particles is obtained by gradually melting, which is a method to prevent slump loss, but the time from mixing to casting varies from time to time.
It is difficult to control its dissolution rate, and if it remains partially undissolved in concrete, it poses problems in terms of strength and durability.

Method (c) involves re-adding the admixture at the time of slump loss, and although it does not completely prevent the problem, it can be said to be an effective means. However, there are economical disadvantages such as the workability of repeated addition and an increase in the absolute amount added.

Method (d) attempts to maintain fluidity by delaying the setting time by using setting retarders such as oxycarboxylic acid salts, lignin sulfonates, and dextrin humates alone or in combination with high-performance water reducing agents. However, it does not necessarily prevent slump loss, and if it is added in excess, there is a great risk of causing accidents such as poor curing and reduced strength.

The conventional slump loss prevention methods described above have problems with concrete quality, workability, and economic efficiency, or are temporary slump loss prevention measures, and cannot be said to be practical methods of prevention.

In order to solve the problems of the conventional technology, the inventors of the present invention have conducted intensive research and found that it has high water-reducing properties, maintains fluidity for a long time, and does not cause setting delay or other adverse effects on quality and workability. The present invention has been achieved by discovering an admixture for suppressing slump loss in hydraulic cement formulations that does not cause slump loss.

The present invention is based on the general formula, 1 CH2=C(11 C-Ni1-R2-5011 , X is H
or an alkali metal or NH4 or an organic base) from 100 to 15 mol%.

General formula, 3 ■ CH2=C(21 C-NH-A 1 (However, in the formula, Ra is H or a lower alkyl group, A is H
or 1002011) from 0 to
85 mol%.

General formula, 4 ■ CR2= C(31 ■ -OY 1 (However, in the formula, R4 is H or a lower alkyl group, Y is H
or an alkali metal or a compound represented by N) 14 or an organic base) from 0 to 85 mol%.

The intrinsic viscosity obtained by polymerizing (3 of INNaα aqueous solution)
The present invention provides a hydraulic cement admixture characterized in that it contains as an essential component a water-soluble polymer having a (at 0°C) of 0.05 to 2.0 dl/g.

Examples of the compound represented by the above general formula (1) include 2-acryloylamino-2-methylpropanesulfonic acid, 2-
Acrylocruaminoethanesulfonic acid, 3-methacryloylaminopropanesulfonic acid, etc., with the general formula (2
Examples of the compound represented by formula (3) include acrylamide and methacrylamide, and examples of the compound represented by general formula (3) include acrylic acid, methacrylic acid, and salts thereof.

The amount of the hydraulic cement admixture of the present invention is preferably in the range of 0.05 to 1.5% by weight based on cement solid content. The hydraulic cement admixture may be added to the mixing water of the cement composition, or may be added after the cement composition is mixed.

Furthermore, the dry powder of the water-soluble polymer, which is the hydraulic cement admixture of the present invention, can be premixed with cement and then kneaded.

Further, the curing method after casting after addition and mixing or after molding may be the usual air drying, underwater, steam, or autoclave curing.

The target cements include hydraulic cements such as various portland cements, mixed cements, fly ash cements, and special cements.

In addition, if necessary, it may be used in combination with an AE agent such as a resin acid salt, an AE water reducing agent such as a lignin sulfonate, a high performance water reducing agent such as a naphthalene sulfonic acid formalin high condensate salt, and a curing accelerator, It can also be used in combination with a setting retarder or an expanding agent.

Next, the method for producing a water-soluble polymer in the present invention involves polymerizing a compound represented by the general formula (11) in the presence of a radical initiator and, if necessary, a polymerization regulator. It can be obtained by copolymerizing the compounds shown in , (2) and (3).It can also be synthesized by synthesizing the base polymer by a conventional method and then converting the functional group by a polymer reaction. .

Next, general formula +11. The molar ratio of compounds represented by +21 and (3) will be described.

The compound represented by general formula (1) contains 100 to 15 mol% (
If it is less than 15 mol%, the dispersibility of cement particles will be poor and the unit water amount in the cement composition will increase. In other words, the water reduction rate increases significantly,
It cannot be used as a fluidizing water reducing agent.

General formula +21. (The compound represented by 31 is 0 to 85 mol% (preferably 10 to 75 mol%), and has the general formula (
When the amount of the compound represented by 2) is 85 mol % or more, the water reduction rate decreases and the stability of slump over time is poor. Moreover, if the compound represented by the general formula (3) exceeds 85 mol %, it may exhibit a setting retarding effect on the cement mixture, leading to a decrease in initial strength.

lN of the water-soluble polymer which is the hydraulic cement admixture of the present invention
Na0i! The intrinsic viscosity (η) of an aqueous solution at 30°C is 0
．． It is preferable that the intrinsic viscosity is in the range of 0.05 to 2.0, and if the intrinsic viscosity is less than 0.05 or exceeds 2.0, the fluidizing effect of the hydraulic cement admixture will not be exerted immediately after addition to the cement composition. First, the water reduction rate decreases, and the stability of slump over time becomes poor.

By adding the hydraulic cement admixture of the present invention to a cement mixture, it is possible to obtain a high water reduction rate that could not be obtained with conventional AE agents and AE water reducers, without any retarding effect, and even at high temperatures. , it becomes possible to maintain slump stability for a long time.

Therefore, conventionally, when pouring concrete that requires a small amount of water per unit, fresh concrete is delivered to the site and a so-called fluidizing agent is poured into an agitator truck at the site, where it is stirred and mixed to temporarily increase fluidity. Previously, it was pumped and placed, but now it is possible to add, knead, transport, and place admixtures in the same way as conventional AE agents and AE water reducers for ready-mixed concrete, improving pumping performance. This has improved work efficiency, and there is no noise pollution caused by high-speed agitation on site.
Moreover, it is possible to maintain the fluidity and stability over time of low water content concrete, making it possible to cast stable, high-quality concrete. Furthermore, in the molding and manufacturing of secondary concrete products, it is possible to achieve high quality and improve work efficiency by having a higher water-reducing effect and stable fluidity.

The present invention will be specifically explained below with reference to Examples (parts, %
(indicates weight basis).

Production Example 1 A solid content concentration of 3 was placed in a 4-bottle flask with a capacity of 1β equipped with a stirring bar, thermometer, reflux condenser, and nitrogen inlet tube.
Charge 500 g of a 0%, pH 8.0 sodium 2-acryloylamino-2-methyl-propanesulfonic acid aqueous solution.

Then, without introducing nitrogen, 2-mercaptoethanol 3
．． 0g and adjust the temperature to 40°C.

2-2′-azobis(2-aminodipropane) hydrochloride 0
．． Dissolve 15 g in 20 g of water and add. After a slight induction period, exotherm is observed and the polymerization reaction begins.

The polymerization reaction was continued for 4 hours while controlling the temperature at 60°C. 3 of the thus obtained sodium poly-2-acryloylamino-2-methyl-propanesulfonate.
0℃IN NaCj! The intrinsic viscosity measured inside is 0.51
It was dl/g.

Production Example 2 In Production Example 1, 300 g of the aqueous solution of sodium 2-acryloylamino-2-methyl-propanesulfonate
Production example except that 150g was changed to 9.3% aqueous acrylamide solution, and further 150g was changed to 12.3% aqueous sodium acrylate solution, pH 8.0, and the amount of 2-mercaptoethanol added was 0.1g. It was synthesized in the same manner as 1.

The intrinsic viscosity of the obtained copolymer was 1.5 dl/g.

Production Example 3 In Production Example 1, 30% aqueous acrylamide solution was used instead of sodium 2-acryloylamino-2-methyl-propanesulfonate, 5g of 2-mercaptoethanol was added, and polyacrylamide was obtained by polymerization in the same manner. .

Add 37% borumamide 1 to this polyacrylamide aqueous solution.
71 g, add 220 g of sodium acid sulfite, and
Adjust so that it becomes H12.0.

The resulting mixture was reacted at 50° C. for 4 hours to obtain a sodium salt of sulfomethylated polyacrylamide. The intrinsic viscosity of the obtained polymer was 0.09 di/g.

Table 1 shows polymers and copolymers (admixtures) synthesized according to the above production example.

(Leaving space below) Table 1 General Formula (2) Niacrylamide General Formula (3) Sodium Niacrylate Example 1 The admixtures shown in Table 1 were added to concrete, and changes in slump over time and setting time were measured.

Table 2 shows the concrete formulation.

(Left below) 1007 experiments! The amount of kneading in the trunk type mixer is 501
Weigh out the formulation shown in Table 2 and add all ingredients. Immediately knead for 3 minutes (19r, p, m,)
Discharge the entire amount from the mixer and slump (JISA 1101
), measure the amount of air (JIS 81 to 28). This value is taken as before addition.

Immediately after the measurement, return to the mixer, add the admixture shown in Table 1, mix for 1 to 2 minutes, and slump.

Air Volume and Condensation Time (ASTM (403-797)
measurements were taken. This value is set immediately after addition.

Thereafter, the mixer was subjected to aji-cheating at low speed (10 r, p, m,), and the slump and air amount were measured every 20 minutes to observe changes over time.

The measurement results are shown in Table-3.

(The following is a blank space) As is clear from the measurement results in Table 3, the concrete to which admixtures Nos. 1 to 6 of the present invention were added had good slump stability over time and exhibited high fluidity even after 90 minutes. Moreover, the setting time is the same as that of additive-free concrete (Ikll), indicating that there is no setting delay. On the other hand, Comparative Example No. 7 has the general formula +11. It was confirmed that the mixing molar ratio (%) of f31 was outside the scope of the present invention, the slump increasing effect was weak, the stability over time was poor, and the setting time was delayed by 2 hours or more compared to additive-free concrete.

In No. 8, the compounding molar ratio (%) of the general formula (11) was outside the scope of the present invention, and as with Positive 7, the slump increase effect and stability over time were poor. Although they had the same blending molar ratio, the intrinsic viscosity was 2.65 dl/g, so although there was no setting delay, no slump increasing effect was obtained.

Nlll0 is a homopolymer represented by the general formula (3), which has a weak dispersion ability for cement particles and a small slump increasing effect. Moreover, it became clear that the setting delay was extremely large, and it was confirmed that the admixture of the present invention is an effective admixture only within the blending molar ratio (%) and intrinsic viscosity range.

Example 2 Table 4 shows the concrete formulation.

(The following is a blank space) Based on the formulation shown in Table 4, ready-mixed concrete was produced by mixing for 45 seconds using a forced mixing mixer at ready-mixed concrete factory G (the admixture was included in the mixing water). Transfer this to the trunk agitator, measure the slump and air volume immediately after, and then turn the trunk agitator at low speed (2r, p,
n+, ), and the slump and air amount over time were measured.

The measurement results are shown in Table-5.

(Margin below) As is clear from Table 5, normal AE concrete-1-(
11kl13), AE water-reduced concrete (14)
Although stability over time can be seen with the lamp entering after 90 minutes of 16a++ or more, the water reduction rate is small at 6.9% and 11.9%, respectively.

Comparative example Nn15. Na16 is a polymer (admixture) outside the scope of the present invention, and both lack slump stability over time.

On the other hand, the present invention Nn17. m18 has good slump stability over time, equivalent to additive-free concrete with a large unit water volume, and concrete with a water reduction rate of 14.9% and 18.8%, and has slump stability that cannot be obtained with conventional ready-mixed concrete. and high water reduction rate, i.e. high quality ready-mixed concrete 1
It was confirmed that .

Example 3 Changes in slump over time and compressive strength (JIS A1108
) was measured.

The formulation of Concrete 1 is shown in Table 6, and the measurement results are shown in Table 7.

As is clear from the measurement results, the present invention 11h19.20
It can be seen that it shows a stable slump over time even when used in combination with a commercially available high performance water reducing agent. On the other hand, the comparative example floor 21
is used in combination with an admixture other than the present invention, and Company 22 is a product in which a high performance water reducing agent is added alone. No. 21 has poor slump stability and compressive strength, and No. 22 has no problems in terms of strength, but the slump has decreased significantly over time.

In this way, the admixture of the present invention can maintain stable fluidity in concrete with a low water-to-cement ratio, so-called high-strength concrete, and can improve the on-site casting height in secondary concrete products or fresh concrete L fields. It becomes possible to manufacture high-strength concrete.

Applicant Kajima Corporation ＼Ill', 1□h□), f Continued on page 1 0 Inventor Hiroshi Ueno @ Inventor Tatsuo Kojima 0 Inventor Hiroshi Takimoto @ Inventor Hori 1) Hiroshi 18 Yanagifuro-cho, Nishiiri Nisujime-kami, Imaide-yotsuji-cho, Kamigyo-ku, Kyoto City
9 171-19 Nojicho, Kusatsu City

Claims (1)

[Claims] General formula, 1 CR2=C(11 C-N11-R2-3Oa alkylene group, X is H
or an alkali metal or NH4 or an organic base) from 100 to 15 mol%. General formula, 3゜3 C)+2 = CT21 C-NH-^ 1 (However, in the formula, R8 is H or a lower alkyl group, A is H
or -C) represents 120+1) is 0
~85 mol%. General formula, 4 CH2=C(31 -OY 1 (in the formula, R4 is H or a lower alkyl group, Y is H
Intrinsic viscosity (INNaC1! at 30°C of aqueous solution) obtained by polymerizing 0 to 85 mol% of a compound represented by alkali metal or NH4 or an organic base)
is 0.05 to 2. A hydraulic cement admixture characterized by containing a water-soluble polymer having Oa/g as an essential component.