JPH0155210B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to hydraulic cement admixtures. More specifically, it suppresses the decline in fluidity of concrete, mortar, or paste, which is a hydraulic cement compound, over time and improves its workability and workability. This invention relates to hard cement admixtures. Concrete or mortar is cement,
It can be obtained by mixing water, sand, gravel, and admixtures if necessary, but when cement and water come into contact, the fluidity of cement particles decreases over time due to chemical and physical effects. It becomes an obstacle to workability and construction. 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 salts or melamine resin sulfonic acid formalin condensate salts 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 concrete high-strength secondary products that are used in large amounts, it cannot be used in ready-mixed concrete plants. Currently, water reducing agents are used, and the water reduction rate of the former is about 5 to 8%, and the latter is about 10 to 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 poles, there are problems such as limited molding time, poor compaction, etc.
This causes many problems in terms of quality. Therefore, the slump loss of concrete over time is an important issue 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 factories 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 content of concrete. (b) Method by post-addition of liquid or granular concrete admixture. (c) Method by repeated addition of concrete admixtures. (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 dissolving them, which is a method of preventing slump loss, but the time from mixing to casting varies depending on the situation. 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 oxycarboxylate, lignin sulfonate, and dextrin humate alone or in combination with a high performance water reducing agent. 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 methods for preventing slump loss as described above have problems with concrete quality, workability, and economic efficiency, or are temporary measures to prevent slump loss, and cannot be said to be practical methods for preventing slump loss. 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 has the general formula: (However, in the formula, R ₁ is H or a lower alkyl group,
Compounds 100 to 15 where R ₂ is a linear or branched alkylene group having 1 to 4 carbon atoms, and X is H, an alkali metal, NH ₄ or an organic base
Mol%, general formula, (However, in the formula, R ₃ is H or a lower alkyl group,
A represents H or _-CH2OH ) 0 to 85 mol% of the compound represented by the general formula, (However, in the formula, R ₄ is H or a lower alkyl group,
0 to 85 mol% of a compound represented by H, an alkali metal, _NH4 , or an organic base) whose intrinsic viscosity (at 30°C of a 1N NaCl aqueous solution) is 0.05 to 2.0 dl/g. The present invention provides a hydraulic cement admixture characterized by containing a water-soluble polymer having the following properties as an essential component. As the compound represented by the above general formula (1), 2-
There are acryloylamino-2-methylpropanesulfonic acid, 2-acryloylaminoethanesulfonic acid, 3-methacryloylaminopropanesulfonic acid, etc., and compounds represented by general formula (2) include acrylamide, methacrylamide, etc. Further, examples of the compound represented by the 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. Further, as a method for adding and curing the hydraulic cement admixture, water for mixing the cement composition may be added, or it may be added and mixed after mixing the cement composition.
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 mixed. 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, flyash 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 lignosulfonate, 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 according to the present invention involves polymerizing a compound represented by the general formula (1) in the presence of a radical initiator and, if necessary, a polymerization regulator, or by polymerizing the compound represented by the general formula ( It can be obtained by copolymerizing the compounds shown in 1), (2) and (3). It can also be synthesized by synthesizing a polymer as a base by a conventional method and then converting the functional groups by a polymer reaction. Next, the blending molar ratio of the compounds represented by general formulas (1), (2) and (3) will be described. The compound represented by general formula (1) is 100 to 15 mol%
(preferably 90 to 25 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. That is, the water reduction rate increases significantly and it cannot be used as a fluidizing water reducing agent. Compounds represented by general formulas (2) and (3) are 0 to 85 mol%
(preferably 10 to 75 mol%), and when the compound represented by general formula (2) is 85 mol% or more, the water loss rate decreases and the stability of slump over time is poor. Moreover, if the compound represented by general formula (3) exceeds 85 mol%, it may exhibit a setting retarding effect on the cement mixture, leading to a decrease in initial strength. The intrinsic viscosity (η) at 30°C of the 1N NaCl aqueous solution of the water-soluble polymer that is the hydraulic cement admixture of the present invention is preferably in the range of 0.05 to 2.0 dl/g, and the intrinsic viscosity is preferably less than 0.05 dl/g. if, and
If it exceeds 2.0 dl/g, the fluidizing effect of the hydraulic cement admixture on the cement composition will not be exhibited immediately after addition, the water reduction rate will decrease, and the stability of slump over time will become 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, when pouring concrete that requires a small amount of water per unit, fresh concrete is delivered to the site, where a so-called fluidizing agent is poured into an agitator vehicle, stirred and mixed, and temporarily increased fluidity. Previously, admixtures were pumped and placed, but now it is possible to add, mix, transport, and place admixtures in the same way as conventional AE agents and AE water reducers for ready-mixed concrete, improving pumping performance. This improves work efficiency, eliminates the noise pollution caused by high-speed stirring on site, and maintains the fluidity and stability over time of low water consumption concrete, allowing stable, high-quality concrete to be poured. It became possible to do so. 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 using Examples (parts and percentages are based on weight). Production example 1 Stirring bar, thermometer, reflux condenser,
A 4-neck flask with a capacity of 1 and equipped with a nitrogen inlet tube is charged with 500 g of an aqueous solution of sodium 2-acryloylamino-2-methyl-propanesulfonate having a solid content concentration of 30% and a pH of 8.0. Next, 3.0 g of 2-mercaptoethanol was charged while nitrogen was introduced, and the temperature was adjusted to 40°C.
Dissolve 0.15 g of 2-2'-azobis(2-aminodipropane) hydrochloride in 20 ml 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. The intrinsic viscosity of the thus obtained sodium poly-2-acryloylamino-2-methyl-propanesulfonate measured in 1N NaCl at 30°C was 0.51 dl/g. Production Example 2 In Production Example 1, 2-acryloylamino-2
- Of the aqueous solution of sodium methyl-propanesulfonate, 150g was changed to a 9.3% acrylamide aqueous solution, and further 150g was changed to a 12.3% aqueous sodium acrylate solution with a pH of 8.0, and the amount of 2-mercaptoethanol added was changed to 0.1g. Manufacturing example 1 except what to do
It was synthesized in the same way. The intrinsic viscosity of the obtained copolymer was 1.5 dl/g. Production Example 3 In Production Example 1, 2-acryloylamino-2
A 30% aqueous allylamide solution was used instead of sodium -methyl-propanesulfonate, 5 g of 2-mercaptoethanol was added, and polyacrylamide was obtained by polymerization in the same manner. Add 171 g of 37% formaldehyde and 220 g of acidic sodium sulfite to this polyacrylamide aqueous solution and adjust the pH to 12.0. The resulting mixture was reacted at 50°C for 4 hours to obtain the sodium salt of sulfomethylated polyacrylamide. The intrinsic viscosity of the obtained polymer was 0.09 dl/g
It was hot. Table 1 shows polymers and copolymers (admixtures) synthesized according to the above production example.

【table】

[Table] Example 1 Add the admixtures shown in Table-1 to concrete,
Changes in slump over time and condensation time were measured. Table 2 shows the concrete formulation.

[Table] In the experiment, the mixing amount was 50 in a tilting mixer.
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 (JIS
A1101) and air volume (JIS A1128). 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, slump,
The air volume and condensation time (ASTM (403-79T)) were measured. These values were taken immediately after addition. After that, the mixer was agitated at low speed (10 rpm), and the slump and air volume were adjusted every 20 minutes. Measurements were taken to observe changes over time. The measurement results are shown in Table 3.

【table】

[Table] *Additional amount: Converted to cement solid content Concrete temperature: 25 to 26℃
As is clear from the measurement results in Table 3, the concretes 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. Furthermore, the setting time was the same as additive-free concrete (No. 11), indicating that there was no setting delay. On the other hand, Comparative Example No. 7 has the general formula (1),
The molar ratio (%) of (3) is outside the scope of the present invention,
Slump increasing effect is weak, stability over time is poor,
Furthermore, it was confirmed that the setting time was delayed by more than 2 hours compared to additive-free concrete. In No. 8, the compounding molar ratio (%) of general formula (1) was outside the scope of the present invention, and like No. 7, the slump increasing effect and stability over time were poor. No. 9 is the admixture of the present invention No. 2
It has the same molar ratio as , but the intrinsic viscosity is 2.65.
dl/g, so there was no setting delay, but no slump increasing effect was obtained. No. 10 is a homopolymer of 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 The concrete formulation is shown in Table-4.

[Table] Based on the formulation shown in Table 4, ready-mixed concrete was produced at a ready-mixed concrete factory by mixing for 45 seconds with a forced mixing mixer (the admixture was included in the mixing water). This was transferred to a track agitator, and the slump and air amount immediately after were measured.Then, the track agitator was continuously agitated at a low speed (2 rpm) to measure the slump and air amount over time. The measurement results are shown in Table-5.

[Table] Unit water volume of additive-free concrete Concrete temperature: 28 to 30℃
As is clear from Table 5, normal AE concrete (No. 13) and AE water-reduced concrete (No. 14) are 90
Although stability over time can be seen with a slump of 16 cm or more after minutes, the water loss rate is small at 6.9% and 11.9%, respectively. Moreover, Comparative Examples No. 15 and No. 16 are polymers (admixtures) outside the scope of the present invention, and both lack slump stability over time. On the other hand, the present invention No. 17 and No. 18 have 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%, which cannot be obtained with conventional ready-mixed concrete. It was confirmed that slump stability and high water reduction rate, that is, high quality ready-mixed concrete could be obtained. Example 3 Changes in slump over time and compressive strength (JIS
A1108) measurements were carried out. The concrete formulation is shown in Table 6, and the measurement results are shown in Table 7.

[Table] The materials used were the same as those in Table 2 of Example 1. The mixing method was the same as in Example 2.

[Table] As is clear from the measurement results, invention Nos. 19 and 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,
Comparative Example No. 21 is the combination with an admixture other than the present invention,
No. 22 is the one that only contains a high-performance water reducer. No.21
No. 22 is inferior in both slump stability and compressive strength, and No. 22 has no problems in terms of strength, but the slump deteriorates significantly over time. In this way, the admixture of the present invention can maintain stable fluidity in concrete with a low water-cement ratio, so-called high-strength concrete.
It becomes possible to produce high-strength concrete as a secondary concrete product or cast-in-place at a ready-mixed concrete factory.

Claims (1)

[Claims] 1 General formula, (However, in the formula, R ₁ is H or a lower alkyl group,
Compounds 100 to 15 where R ₂ is a linear or branched alkylene group having 1 to 4 carbon atoms, and X is H, an alkali metal, NH ₄ or an organic base
Mol%, general formula, (However, in the formula, R ₃ is H or a lower alkyl group,
A represents H or _-CH2OH ) 0 to 85 mol% of the compound represented by the general formula, (However, in the formula, R ₄ is H or a lower alkyl group,
Y represents H or an alkali metal or _NH4 or an organic base) having an intrinsic viscosity (at 30°C of a 1N NaCl aqueous solution) of 0.05 to 2.0 dl/g obtained by polymerizing 0 to 85 mol% of a compound represented by A hydraulic cement admixture characterized by containing a water-soluble polymer as an essential component.